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  • Column liquid chromatography  (119)
  • RFLP  (50)
  • kinetics
  • Springer  (205)
  • Institute of Physics
  • 1995-1999
  • 1990-1994  (205)
  • 1940-1944
  • 1993  (205)
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  • 1995-1999
  • 1990-1994  (205)
  • 1940-1944
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  • 1
    ISSN: 1572-879X
    Schlagwort(e): Fischer-Tropsch synthesis ; reaction activation barrier ; carbon chain growth and termination ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A method is established, by which the difference of the reaction activation barriers of carbon chain growth and termination in Fischer-Tropsch (FT) synthesis can be determined from experiments. A FT synthesis is carried out on Fe/Zn catalyst. We apply the method to analyze the experimental result and obtain the difference of reaction activation barriers of carbon chain growth and termination of α-olefins on the catalyst.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 49 (1993), S. 110-117 
    ISSN: 1420-9071
    Schlagwort(e): Polymerization ; sickle hemoglobin ; sickle cell disease ; kinetics ; thermodynamics ; polymer domains ; nucleation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The polymerization of sickle hemoglobin occurs by the same mechanisms in solutions and in cells, and involves the formation of 14 stranded fibers from hemoglobin molecules which have assumed a deoxy quaternary structure. The fibers form via two types of highly concentration-dependent nucleation processes: homogeneous nucleation in solutions with hemoglobin activity above a critical activity, and heterogeneous nucleation in similarly supersaturated solutions which also contain hemoglobin polymers. The latter pathway is dominant, and creates polymer arrays called domains. The individual polymers bend, but also cross-link, and the resulting mass behaves as a solid. The concentration of polymerized hemoglobin increases exponentially unless clamped by rate limiting effects such as oxygen delivery.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Biodegradation 4 (1993), S. 163-170 
    ISSN: 1572-9729
    Schlagwort(e): factorial analysis ; kinetics ; methane ; methanotrophs ; nutrients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effect of different mineral nutrients on the kinetics of methane biodegradation by a mixed culture of methanotrophic bacteria was studied. The substrate factors examined were ammonia, iron, copper, manganese, phosphate, and sulphide. The presence of iron in the growth medium had a strong effect on the yield coefficient. Yield coefficients up to 0.49 mg protein per mg methane were observed when iron was added at concentrations of 0.10–5.0 mg/l. Iron addition also increased the maximum methane utilization rate. The same effect was observed after addition of ammonium to a medium where nitrate was the only nitrogen source. The observed Monod constant for methane utilization increased with increasing concentration of ammonia. This shows that ammonia is a weak competitive inhibitor as observed by other researchers. Relatively high levels of both ammonia (70 mg/l) and copper (300 µg/l) inhibited the methane degradation, probably due to the toxic effect of copper-amine complexes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Aquatic sciences 55 (1993), S. 103-111 
    ISSN: 1420-9055
    Schlagwort(e): iron(III) (hydr)oxide ; fulvic acid ; iron redox cycling ; dissolution ; surface reactivity ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The kinetics of conversion of iron(III) (hydr)oxides to ferrous iron mediated by fulvic acid have been investigated in order to improve the understanding of the redox cycling of iron at the oxic-anoxic boundary in natural waters. Under the conditions similar to natural waters, fulvic acid is able to reduce the iron(III) (hydr)oxide. The kinetics of the reaction depend on the reactivity of iron(III) (hydr)oxides and the reducing power of the fulvic acid. The rate of reaction is 60 nm/h obtained under following conditions: total concentration of Fe(III) 1.0 × 10−4 M, pH 7.5, fulvic acid 5 mg/L. The rate is considered as a net result of reduction and oxidation in the 〉 FeIII-OH/Fe(II) “wheel” coupled with fulvic acid. In a real natural water system, reductants other than fulvic acid may be of importance. The results obtained in the laboratory, however, provide evidence that the Fe(OH)3(s)/Fe(II) redox couple is able to act as an electron-transfer mediator for the oxidation of natural organic substances, such as fulvic acid by molecular oxygen either in the absence of microorganisms or as a supplement to microbial activity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell reports 12 (1993), S. 293-297 
    ISSN: 1432-203X
    Schlagwort(e): Lycopersicon esculentum ; Genetic marker ; Intraspecific genetic map ; DNA polymorphism ; Isozyme ; RFLP ; RAPD
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The existing molecular genetic maps of the tomato, Lycopersicon spp, are constructed based on isozyme and RFLP polymorphisms between tomato species. These maps are useful for certain applications but have few markers that exhibit sufficient polymorphisms for intraspecific analysis and manipulations within the cultivated tomato. The purpose of this study was to investigate the relative potential of RAPD technology, as compared to isozymes and RFLPs, to generate polymorphic DNA markers within cultivated tomatoes. Sixteen isozymes and 25 RFLP clones that were known to detect polymorphism between L. esculentum and L. pennellii, and 313 random oligonucleotide primers were examined. None of the isozymes and only four of the RFLP clones (i.e., 16%) revealed polymorphism between the cultivated varieties whereas up to 63% of the RAPD primers detected one or more polymorphic DNA fragments between these varieties. All RAPD primers detected polymorphism between L. esculentum and L. pennellii genotypes. These results clearly indicate that RAPD technology can generate sufficient genetic markers exploiting sequence differences within cultivated tomatoes to facilitate construction of intraspecific genetic maps.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell reports 12 (1993), S. 457-461 
    ISSN: 1432-203X
    Schlagwort(e): Rice (Oryza sativa) ; Genetic Marker ; Genetic Map ; Integrated Linkage Map ; RFLP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Application of genetic linkage maps in plant genetics and breeding can be greatly facilitated by integrating the available classical and molecular genetic linkage maps. In rice, Oryza sativa L., the classical linkage map includes about 300 genes which correspond to various important morphological, physiological, biochemical and agronomic characteristics. The molecular maps consist of more than 500 DNA markers which cover most of the genome within relatively short intervals. Little effort has been made to integrate these two genetic maps. In this paper we report preliminary results of an ongoing research project aimed at the complete integration and alignment of the two linkage maps of rice. Six different F2 populations segregating for various phenotypic and RFLP markers were used and a total of 12 morphological and physiological markers (Table 1) were mapped onto our recently constructed molecular map. Six linkage groups (i.e., chr. 1, 3, 7, 9, 11 and 12) on our RFLP map were aligned with the corresponding linkage groups on the classical map, and the previous alignment for chromosome 6 was further confirmed by RFLP mapping of an additional physiological marker on this chromosome. Results from this study, combined with our previous results, indicate that, for most chromosomes in rice, the RFLP map encompasses the classical map. The usefulness of an integrated genetic linkage map for rice genetics and breeding is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 231-235 
    ISSN: 1432-1041
    Schlagwort(e): Carbamazepine ; kinetics ; population pharmacokinetics ; bioavailability ; controlled release ; non-linear model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The absorption properties of a conventional tablet of carbamazepine (T) and a controlled release form of carbamazepine (TCR) have been compared using a nonlinear mixed effect model (NONMEM). Plasma carbamazepine concentration data were obtained from an open, steady-state, crossover bioavailability study in which 494 measurements were obtained from 13 patients, with an equal number of samples per patient for each dosage form. The pharmacokinetic model used was a one-compartment open model with first-order absorption and elimination. The objective function was used as a measure of the goodness of fit of the model to the data. Body weight was an important determinant of carbamazepine clearance (CL) but not volume of distribution (V). Accounting for the interindividual variability in volume of distribution did not significantly influence the objective function. Including different rates of absorption (ka) for the two dosage forms resulted in a significant improvement in the objective function, as well as reducing the interindividual variability in the rate of absorption. Adding a parameter for relative bioavailability (f) of TCR improved the objective function statistically, but an unrealistic value for V was obtained, and the absorption and elimination rates appeared to be transposed in the classical “flip-flop” manner. Fixing V to the value obtained before introducing f did not change the objective function and permitted estimation of f without the confounding influence of excessive parameters. The final population parameter estimates (standard error of estimate) were: CL, 0.0522 (0.0019) l·h−1·kg−1; V, 63.7 (FIXED)l; kaT, 0.312 (0.064) h−1; kaTCR, 0.149 (0.016) h−1; f, 1.01 (0.0326); variance (additive) in CL, 0.291 (0.083) (l·h−1·kg−1)2; residual intrasubject error variance (additive), 0.572 (0.082) (mg·l−1)2. The 95% confidence interval of the extent of absorption (f) of 93.6%–107.4% was well within the generally accepted range of ±20%, while the rate of absorption of Tegretol CR was significantly slower than that of Tegretol, as expected for a controlled release product.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 39 (1993), S. 15-20 
    ISSN: 1572-8943
    Schlagwort(e): alloys ; high-temperature sulphidation ; kinetics ; new thermobalane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird ein neue Apparat zur Untersuchung der Hochtemperatur-Sulfidierung von Metallen in H2/H2S Atmosphare beschrieben. Der Unterschied zwischen diesem Apparat und dem fruher benutzten, besteht im Gasdosierungsystem. Wasserstoff reagiert teilweise mit Schwefel, was eine stabile Zusammensetzung des Gasgemisches beim niedrigen Schwefeldampfdruck sichert. Gewichtsmessungen von Metallen und Legierungen konnen in diesem System bei Temperaturen von 1073 bis 1473 K mit einer Genauigkeit von 10−6 g ausgefuhrt werden.
    Notizen: Abstract A new thermogravimetric apparatus for studying the kinetics of metal sulphidation in a H2/H2S gas mixture is described. The main difference between this device and other equipment is the application of hydrogen to obtain a H2/H2S mixture at suitable sulphur partial pressures at a total mixture pressure of 1 atm. The use of the carrier gas allows the measurement of sulphidation kinetics under dynamic conditions and consequently over a much wider pressure range of sulphur vapour, down to 10−12 atm.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 39 (1993), S. 65-74 
    ISSN: 1572-8943
    Schlagwort(e): electrical conductivity ; hydrazone complexes ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Bei zwei verschiedenenpH-Werten wurden die Zn-, Cd- und Hg-Komplexe von Isatinisonicotinoylhydrazon hergestellt. Diese wurden thermisch untersucht (TG, DTG, DTA) und die Gleichstromleitfähigkeit von gepreßten Pulverproben als eine Funktion der Temperatur untersucht. Sowohl für die Liganden als auch für die Komplexe wurden die Aktivierungsenergien (ΔE) berechnet, wobei sich für die Liganden niedrigere Werte ergaben. Man fand, daß die Größe von ΔE durch die Art des Metalles und denpH-Wert bei der Herstellung beeinflußt wird.
    Notizen: Abstract The complexes of Zn, Cd and Hg of isatin isonicotinoyl hydrazone were prepared at two differentpHs. Their thermal studies (TG, DTG and DTA) have been made and the DC electrical conductivity of compressed powder samples as a function of temperature was investigated. The activation energies (ΔE) were calculated for the ligand and the complexes which showed that the ligand has a lower value of ΔE than the complexes. The magnitude of ΔE was found to be affected by the nature of the metal and thepH of preparation.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 39 (1993), S. 75-86 
    ISSN: 1572-8943
    Schlagwort(e): chlorination ; kinetics ; WO3+CCl4 reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Mittels Thermogravimetrie wurde die Chlorierungskinetik von alkaliversetztem (K und Li) Wolframtrioxid untersucht, wobei CCl4 als Chlorierungsreagens fungierte. Die Reaktivität der modifizierten Proben wurden mit der von reinem WO3 verglichen. Für die reinen und für die alkaliversetzten Proben wurden ähnliche scheinbare Aktivierungsenergien gefunden. Der Zusatz von Kalium verursacht jedoch eine starke Abnahme der ursprünglichen Reaktionsgeschwindigkeit, während oberflächiges Lithium keinen Effekt zeigt. Während der Chlorierung wurde eine ständige Senkung der linearen Reaktionsgeschwindigkeit für beide Proben festgestellt, was mit Rückhalteeffekten von oberflächigen Nebenprodukten und Alkalizusätzen erklärt wird. Zur Beschreibung der isothermen TG-Kurven wurde ein entsprechendes kinetisches Modell angenommen, welches auf einer monoton steigenden Inhibition dieser Proben basiert. Die auf der Grundlage dieses Modelles berechnete Kurve stimmt recht gut mit den experimentellen Ergebnissen überein.
    Notizen: Abstract The chlorination kinetics of alkali-added (K and Li) tungsten trioxide were studied by thermogravimetry, using gaseous CCl4 as chlorinating agent. The reactivity of the modified samples was compared to the results on the chlorination of pure WO3. Similar apparent activation energies were found for the pure and alkali-added samples. However, potassium additive resulted in a strong decrease of the initial reaction rate, while surface lithium has no influence on it. During the chlorination a continuous decrease of the linear reaction rate was observed for both samples, which was explained by retarding effects of surface by-products and alkali additives. For describing the isothermal TG curves an appropriate kinetic model, based on the monotonously increasing inhibition of these species was assumed. The curve calculated with this model fits well to the experimental results.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 39 (1993), S. 229-238 
    ISSN: 1572-8943
    Schlagwort(e): epoxy resins ; kinetics ; thermal stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Vernetzungsreaktionen der Epoxidharze Tetraglycidyl-diamino-diphenyl-methan (TGDDM) und Tetraglycidyl-methylen-bis(o-toluidin) (TGMBT) unter Verwendung von Diaminodiphenylsulfon (DDS), Diaminodiphenylmethan (DDM) und Diethylentriamin (DETA) als Vernetzungsmittel wurden kinetisch mittels DSC untersucht. Die dynamischen Scans im Temperaturbereich 20°–300°C wurden analysiert, um unter Anwendung einiger empirischer Gleichungen die Aktivierungsenergie und die Reaktionsordnung des Vernetzungsprozesses zu ermitteln. Die Aktivierungsenergie der einzelnen Epoxy-Systeme liegt im Bereich 71.9–110.2 kJ·mol−1. An der ausgehärteten Harze wurde mittels TG in einer statischen Luftatmosphäre un deiner Aufheizgeschwindigkeit von 10 Grad/min die Kinetik des termischen Abbaues untersucht. Man fand, daß die thermiscehn Abbaureaktionen in einem Schritt ablaufen und ihre Aktivierungsenergie im Intervall 27.6–51.4 kJ·mol−1 liegt.
    Notizen: Abstract The curing reactions of the epoxy resins tetraglycidyl diaminodiphenyl methane (TGDDM) and tetraglycidyl methylenebis (o-toluidine) (TGMBT) using diaminodiphenyl sulfone (DDS), diaminodiphenyl methane (DDM) and diethylenetriamine (DETA) as curing agents were studied kinetically by differential scanning calorimetry. The dynamic scans in the temperature range 20°–300°C were analyzed to estimate the activation energy and the order of reaction for the curing process using some empirical relations. The activation energy for the various epoxy systems is observed in the range 71.9–110.2 kJ·mol−1. The cured epoxy resins were studied for kinetics of thermal degradation by thermogravimetry in a static air atmosphere at a heating rate of 10 deg·min−1. The thermal degradation reactions were found to proceed in a single step having an activation energy in the range 27.6–51.4 kJ·mol−1.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 39 (1993), S. 87-95 
    ISSN: 1572-8943
    Schlagwort(e): gamma radiation effects ; graphite-hematite system ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Mittels isothermer und dynamischer TG wurde im Graphit-Eisen(III)oxidsystem in Luft der Einfluß von60Co-Gammastrahlung und von verschiedenen Probenzusammensetzungen auf die Reduktion von Hämatit zu Eisen untersucht. Entsprechend verschiedener theoretischer Modelle heterogener Reaktionen wurde eine kinetische Analyse der isothermen Daten durchgeführt und die Ergebnisse zeigten, daß das dreidimensionale Phasengrenzenmodell die beste Übereinstimmung liefert. Die Analyse der dynamischen TG-Daten wurde mittels der Integralmethode von Ozawa, der Coats-Redfem-Methode und einer zusammengesetzten Methode auf der Grundlage der modifizierten Coats und Redfern Gleichung durchgeführt. Die Aktivierungsparameter wurden berechnet und die Ergebnisse der verschiedenen Methoden miteinander verglichen und diskutiert. Strahlung scheint keine Änderung des Reaktionsmodelles oder des Mechanismus hervorzurufen. Durch Bestrahlung gibt es aber ein Absinken der Aktivierungsenergie und des Frequenzfaktors sowie ein Absinken der Halbwertszeit der Reaktion, was bei höheren Temperaturen und höherer Dosis bemerkenswert groß ist.
    Notizen: Abstract The effects of60Co-gamma radiation and of various sample composition on the reduction of hematite to iron in the graphite-iron(III) oxide system in air were studied using isothermal and dynamic TG techniques. Kinetic analysis of isothermal data were performed according to various theoretical models of heterogeneous reactions and the results showed that the three-dimensional phase boundary model gives the best fit of data. Analysis of dynamic TG data were made using Ozawa integral method, Coats-Redfern method and a composite method based on the modified Coats and redfern equation. The activation parameters were calculated and the results of the different methods were compared and discussed. Radiation apparently did not introduce a change in the reaction model or mechanism. However, there is a decrease in activation energy and frequency factor upon irradiation and a decrease in the half-life time of the reaction which is remarkable at the higher temperatures and higher doses.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 39 (1993), S. 217-220 
    ISSN: 1572-8943
    Schlagwort(e): DSC ; edible oils ; isothermal method ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Unter Einsatz der isothermen Methode wurden kinetische Untersuchungen der thermooxidativen Zersetzung einiger Speiseöle durchgeführt. Zur Bestimmung des Umwandlungsgrades wurde ein DS-Kalorimeter von DuPont eingesetzt. Grundlage der Untersuchung bildeten Leinöl, Rizinusöl und Olivenöl.
    Notizen: Abstract The thermooxidative decompositions of some edible oils were investigated. Isothermal measurements of convention were made with a Du Pont differential scanning calorimeter. Linseed oil, castor oil, olive oil and cod-liver oil were investigated.
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 39 (1993), S. 351-358 
    ISSN: 1572-8943
    Schlagwort(e): epoxy resin ; kinetics ; polyamide hardener
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Mittels DSC wurde die Optimierung des Einsatzverhältnisses von Epoxidnovolackharz Dobeckot E4 und Polyamidhärtungsmittel EH411 durchgeführt. Die Daten ergaben, daß ein Harz-Polyamid-Verhältnis von 100∶40 bzw. 100∶50 das Optimum zu sein scheint, bei dem die Aushärtung am größten ist. Mittels isothermer und dynamischer DSC-Methoden wurden die kinetischen Parameter für diese Ansätze ermittelt. Unter Anwendung der isothermen DSC-Methode im Temperaturbereich 70°–90°C wurde die Geschwindigkeitskonstante für den Aushärtungsprozeß dieser Ansätze ermittelt. Diese wurden mittels Extrapolation der erhaltenen Angaben für höhere Temperaturen auch für die Temperatur 201°C (Raumtemperatur) vorhergesagt. Vorhergesagte und experimentell ermittelte Werte stehen in guter Übereinstimmung zueinander.
    Notizen: Abstract The optimization of proportions of novolac epoxy resin, Dobeckot E4 and polyamide hardener, EH411 has been established by DSC and the data indicates that resin-polyamide, 100∶40 and 100∶50, appear to be optimum where ‘extent of cure’ is maximum. The kinetic parameters for these formulations have been evaluated using isothermal and dynamic modes by employing DSC. The rate constants have been evaluated for curing process of these formulations using isothermal DSC mode in the temperature range of 70°–90°C. These have also been predicted at 20°±1°C (room temperature) by extrapolating the data obtained at elevated temperatures. A comparison of the predicted values with the experimental values shows that there is a good agreement between them.
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  • 15
    ISSN: 1573-4943
    Schlagwort(e): Sulphydryl groups ; multiple ; hemoglobin ; kinetics ; ionizable groups
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Pigeon hemoglobin has eight reactive sulphydryl groups per (tetramer) molecule, as determined by Boyer titration with p-chloromercuribenzoate. However, only four of these are titra-table with 5,5′-dithiobis(2-nitrobenzoate) under the same experimental conditions. The time course of the reaction of pigeon hemoglobin with 5,5′-dithiobis(2-nitrobenzoate) is biphasic. In thepH range 6–9, the fast phase is between one and two orders of magnitude faster than the slow phase. For the fast phase,k app, the apparent second-order rate constant, increases monotonously withpH. Quantitative analysis reveals that the reactionof the sulphydryl group responsible for this phase is coupled to the ionization of two groups with pK a values of 6.15±0.1 and 8.5±0.1. These pK a values are assigned to HisHC3(146)β and to the CysF9(93)β sulphydryl group, respectively. For the slow phase thek app vs.pH profiles are bowl-shaped. Analysis reveals that the reaction of the sulphydryl group to which this phase may be attributed is coupled to the ionization of two groups with mean pK a values of 6.53±0.1 and 8.25±0.1. Examination of the structure of hemoglobin allows us to assign these values to HisG19(117)β and CysB5(23)β, respectively. The CysB5(23)β sulphydryl is in the region of the molecule where amino acid substitutions have been found to give rise to significant changes in the oxygen affinity of hemoglobin [Huanget al. (1990),Biochemistry 29, 7020–7023.
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  • 16
    ISSN: 1573-5028
    Schlagwort(e): bark storage protein ; gene clustering ; RFLP ; systemic response
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two wound-inducible cDNAs from poplar leaves show sequence identity to vegetative storage proteins (VSP) that accumulate seasonally in poplar bark tissues. We have compared the genomic organization, cDNA sequences and expression of the genes encoding the wound-inducible cDNAs (win4) with that of a bark VSP (called bark storage protein, or BSP). There appear to be several win4 genes in the poplar genome which segregate as a single locus and are therefore likely to be clustered. The same is true of the BSP genes. The win4 locus is linked (map distance of 5 cM) to the BSP locus, consistent with a common evolutionary origin of the genes. A near full-length win4 cDNA shows 75% sequence identity to BSP cDNAs. Both win4 and BSP are systemically wound-inducible; win4 transcripts accumulate in leaves and stems, whereas BSP transcripts accumulate almost exclusively in stems. A phloem transport-dependent signaling mechanism appears to be involved in systemic win4 expression after wounding. In contrast to BSP gene expression, win4 genes are not expressed in response to short day conditions. The data indicate win4 and BSP genes are differentially regulated, and their products may play important roles in the storage and reallocation of nitrogen in perennial plants.
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 21 (1993), S. 99-108 
    ISSN: 1573-5028
    Schlagwort(e): fusion protein ; Oenothera ; plastome ; RFLP ; unidentified open reading frame
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The chloroplast DNA encodes genes for components of photosynthesis and the transcription-translation machinery; a number of unidentified open reading frames (ORFs) are also present. To determine whether a large ORF in the inverted repeat of chloroplast DNA of tobacco (ORF2280) encodes a chloroplast protein, a conserved region of the ORF was expressed in Escherichia coli. An antibody against the ORF protein was prepared using the purified fusion protein as an antigen. When incubated with proteins from the soluble fraction of tobacco, spinach and Oenothera chloroplasts, the antiserum detects relatively labile polypeptides, which have apparent molecular weights of 170 to 180 kDa. The ORF in tobacco and spinach is large enough to encode a protein of 240–250 kDa, thus it is possible that post-transcriptional or post-translational processing reduces the size of the expression product. Analysis of Oenothera chloroplasts representing four different plastome types revealed endonuclease restriction fragment length polymorphisms in chloroplast DNA indicative of insertion/deletion events in a region of the chloroplast DNA that shared significant sequence similarity with ORF2280. The ORF2280 antiserum was used to demonstrate that there are qualitative differences in the ORF proteins from different Oenothera plastome types.
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  • 18
    ISSN: 1573-4943
    Schlagwort(e): Hemoglobin ; sulphydryl group ; ionizable groups ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Dog hemoglobin has four sulphydryl groups per (tetramer) molecule located at the G18(111)a and F9(93)β positions. The two sulphydryls at the G18(111)a positions are unreactive toward nonmercurial sulphydryl reagents, but those at the F9(93)β positions are reactive toward these reagents. We have studied the kinetics of the reaction of dog hemoglobin with 5,5′-dithiobis (2-nitrobenzoic acid) as a function ofpH. At allpH values studied, the reaction is kinetically monophasic. Quantitative analysis of thepH dependence of the apparent second-order rate constant shows that two ionizable groups are linked to the reaction of the sulphydryl group. TheirpK a values are 5.57 and 9.0. These values are assigned to HisHC3(146)β and to the CysF9(93)β sulphydryl. We find that dog carbonmonoxyhemoglobin is significantly—almost an order of magnitude—less reactive than the aquomet, azidomet, and oxy derivatives. This result may be due to a greater tendency (at acidpH) for the salt bridge between HisHC3(146)β and AspFG1(94)β to form in the carbonmonoxy than in the other derivatives. Formation of this salt bridge is known to hinder access to the CysF9(93)β sulphydryl [Perutz, M. F. (1970),Nature 228, 734–739].
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 22 (1993), S. 437-446 
    ISSN: 1573-5028
    Schlagwort(e): RFLP ; genome ; PFGE ; multicopy markers ; symbiosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Pulsed-field gel electrophoresis (PFGE) was used to study a cluster of molecular markers in the soybean genome. There were 550 kb per centimorgan (cM) in the cluster, which is close to the calculated average for the whole genome. The analysis was complicated by the presence of duplicated sequences, and some ambiguities arising from this were resolved by using second-dimension conventional electrophoresis to relate physical maps to the RFLP map of soybean. The results show that there is a high degree of conservation of ‘rare cutter’ sites between homoeologous regions. Finally, PFGE can confirm physical linkage of monomorphic copies of markers, which can aid in the study and comparison of homoeologous regions that are invisible to RFLP analysis.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 132 (1993), S. 167-178 
    ISSN: 1432-1424
    Schlagwort(e): red cell ; glucose transport protein ; GLUT1 ; kinetics ; rapid reactions ; tryptophan
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The kinetics of the initial phases of d-glucose binding to the glucose transport protein (GLUT1) of the human red cell can be followed by stopped-flow measurements of the time course of tryptophan (trp) fluorescence enhancement. A number of control experiments have shown that the trp fluorescence kinetics are the result of conformational changes in GLUT1. One shows that nontransportable l-glucose has no kinetic response, in contrast to d-glucose kinetics. Other controls show that d-glucose binding is inhibited by cytochalasin B and by extracellular d-maltose. A typical time course for a transportable sugar, such as d-glucose, consists of a zero-time displacement, too fast for us to measure, followed by three rapid reactions whose exponential time courses have rate constants of0.5–100 sec+−1 at 20°C. It is suggested that the zero-time displacement represents the initial bimolecular ligand/GLUT1 association. Exponential 1 appears to be located at, or near, the external membrane face where it is involved in discriminating among the sugars. Exponential 3 is apparently controlled by events at the cytosolic face. Trp kinetics distinguish the K d of the epimer, d-galactose, from the K dfor d-glucose, with results in agreement with determinations by other methods. Trp kinetics distinguish between the binding of the α- and β-d-glucose anomers. The exponential 1 activation energy of the β-anomer, 13.6 ± 1.4 kcal mol+−1, is less than that of α-d-glucose, 18.4 ± 0.8 kcal mol+−1, and the two Arrhenius lines cross at ≈23.5°C. The temperature dependence of the kinetic response following α-d-glucose binding illustrates the interplay among the exponentials and the increasing dominance of exponential 2 as the temperature increases from 22.3 to 36.6°C. The existence of these interrelations means that previously acceptable approximations in simplified reaction schemes for sugar transport will now have to be justified on a point-to-point basis.
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 133 (1993), S. 145-160 
    ISSN: 1432-1424
    Schlagwort(e): Acetabularia ; K+ channels ; kinetics ; planar lipid bilayers ; voltage dependence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Plasma membrane from Acetabularia acetabulum was prepared by aqueous-polymer two-phase partitioning and incorporated into planar 1-palmitoyl-2-oleoyl phosphatidylethanolamine bilayers by stirring in the presence of a (cis∶trans) 325∶100 mm KCl gradient. Under these conditions five distinct K+-selective channels were observed which had unitary chord-conductances (determined between 30 mV either side of the reversal potential) and frequencies of incorporation (in parentheses) of 1,600 pS (26%), 485 pS (21%), 259 pS (53%), 140 pS (37%) and 27 pS (37%). Two Cl−-selective channels were also observed, which had unitary chord-conductances of 8 and 48 pS and were present in 21 and 16% of bilayers, respectively. The voltage dependencies of channel open probability (P o ), open-state time constant (τ o) and closed-state time constant (τ c) were determined for the 259, 140 and 27 pS K+ channels. The P o of all three channels increased with increasingly positive membrane potentials. Thus, since these channels were oriented with their extracellular face adjacent to the cis chamber, which was grounded, all would exhibit outward rectification in vivo. Changes in P o were effected by modulation of τ c in all channels, which shortened as membrane potentials became more positive, and also of τ o in the 140 and 27pS channels, which increased as membrane potentials became more positive. Extracellular (cis) KCl concentration (and/or the KCl gradient across the bilayer) affected the P o of all three K+ channels, shifting the P o /membrane potential relationship in the direction of the change in the potassium reversal potential. In all channels this was achieved largely by changes in τ c .
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  • 22
    ISSN: 1432-2242
    Schlagwort(e): Pea ; Pea seed-borne mosaic virus ; Disease resistance ; Genome mapping ; RFLP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The location of sbm-1 on the Pisum sativum genetic map was determined by linkage analysis with eight syntenic molecular markers. Analysis of the progeny of two crosses confirmed that sbm-1 is on chromosome 6 and permitted a more detailed map of this chromosome to be constructed. The inclusion of Fed-1 and Prx-3 among the markers facilitated the comparison of our map with the classical genetic map of pea. The sbm-1 gene is most closely linked to RFLP marker GS185, being separated by a distance of about 8 cM. To determine the practical value of GS185 as a marker for sbm-1 in plant breeding programs, the GS185 hybridization pattern and virus-resistance phenotype were compared in of a collection of breeding lines and cultivars. Three GS185 hybridization patterns were discerned among the lines. A strong association was found between one of these patterns and resistance to PSbMV.
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 181-188 
    ISSN: 1432-2242
    Schlagwort(e): Sugarcane ; Gramineae ; Tissue culture ; RFLP ; Molecular analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The genomic stability of tissue culture regenerants of sugarcane (Saccharum spp. hybrids, cvs ‘CP721210’, ‘CP68-1067’ and ‘B43-62’) was analyzed by DNA restriction fragment length polymorphism (RFLP). Plants regenerated from calli, cell suspensions, cryopreserved cell suspensions and protoplasts were used. Total DNA isolated from 19 different sources was digested with EcoRI, HindIII, BamHI, BamHI, EcoRI and PstI and probed with six known maize mitochondrial genes (coxI, coxII, atpA, atp6, atp9 and rrn18-rrn5), three random maize mitochondrial cosmid clones, two random maize chloroplast cosmid clones and a wheat Nor locus clone. Hybridization patterns indicated that the variation observed was minor and appeared only in the secondcycle regenerants. No differences were observed among the three cultivars and the regenerants from calli, suspension culture, cryopreserved suspension culture and protoplasts. Mitochondrial DNA (mtDNA) isolated from ‘CP72-1210’ plants and its embryogenic cell suspensions, and bulk samples from all ‘CP72-1210’ regenerants pooled together were digested with EcoRI, HindIII, PstI, BamHI and SalI and probed with three recombinationally active wheat mtDNA clones, K′, K3 and X2. No variation in the mtDNA restriction patterns was observed between the ‘CP72-1210’ plants and its regenerants. However, restriction pattern variation was observed only from EcoRI digestion, and hybridization patterns of K3, K′ and X2 revealed minor variations in the mtDNA of cell suspensions when compared with the DNA of the ‘CP72-1210’ plant. Except for a qualitative variation detected by the X2 probe and minor stoichiometric variations detected by the K3 probe, sugarcane DNAs were found to be stable after plant regeneration.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 301-307 
    ISSN: 1432-2242
    Schlagwort(e): RFLP ; Polyploid ; Nondisjunction ; Interspecific hybrid ; Cottonwood
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary While constructing a genetic linkage map of a hybrid poplar genome (Populus trichocarpa x P. deltoides), we identified several restriction fragment length polymorphismus (RFLPs) for which the parental trees are heterozygous. Although 8 of the 11 F1 hybrid offspring inherited, as expected, single RFLP alleles from each parent, 3 F1 trees in the mapping pedigree inherited both maternal alleles along with a single paternal allele at some loci. Aneuploidy or polyploidy in these 3 F1 trees due to partial or complete nondisj unction during female gametogenesis is the simplest explanation for this finding. Of the 3 f1 offspring with supernumerary RFLP alleles 2 have triploid nuclear DNA contents as measured by fluorescence flow cytometry; the 3rd F1 with supernumerary alleles has a sub-triploid nuclear DNA content and is probably aneuploid. Among the tri/aneuploid hybrids, leaf quantitative traits either are skewed toward those values characteristic of the P. trichocarpa female parent (adaxial stomate density, petiole length: blade length ratio; abaxial color) or show transgressive variation (epidermal cell size). Abaxial leaf color was used to screen a large population of P. trichocarpa x P. deltoides hybrids for further evidence of tri/aneuploidy. In each case where a “white” abaxial leaf surface was observed and the nuclear DNA content measured, the hybrid proved to be tri/aneuploid. All sexually mature female triploids examined were sterile, although the inflorescences completed their development in the absence of embryo formation. The (probably) aneuploid F1 hybrid is a fertile female. Of 15 female P. trichocarpa parents used in crosses to P. deltoides, 10 produced one or more tri/aneuploid hybrid offspring. In an intraspecific cross using a P. trichocarpa female that had produced triploid hybrids with five different P. deltoides males, no tri/aneuploid offpsring were found.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 329-332 
    ISSN: 1432-2242
    Schlagwort(e): RFLP ; Alfalfa ; Genetic map ; Segregation distortion ; Plant breeding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have developed a restriction fragment length polymorphism (RFLP) linkage map in diploid alfalfa (Medicago sativa L.) to be used as a tool in alfalfa improvement programs. An F2 mapping population of 86 individuals was produced from a cross between a plant of the W2xiso population (M. sativa ssp. sativa) and a plant from USDA PI440501 (M. sativa ssp. coerulea). The current map contains 108 cDNA markers covering 467.5 centimorgans. The short length of the map is probably due to low recombination in this cross. Marker order may be maintained in other populations even though the distance between clones may change. About 50% of the mapped loci showed segregation distortion, mostly toward excess heterozygotes. This is circumstantial evidence supporting the maximum heterozygote theory which states that relative vigor is dependent on maximizing the number of loci with multiple alleles. The application of the map to tetraploid populations is discussed.
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 811-821 
    ISSN: 1432-2242
    Schlagwort(e): Brassica ; Interspecific hybridization ; Amphidiploid ; RFLP ; Evolution ; Nuclear ; cytoplasmic interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In a previous study we proposed that cytoplasmic genomes have played an important role in the evolution of Brassica amphidiploid species. Based on this and other studies, we hypothesized that interactions between the maternal cytoplasmic genomes and the paternal nuclear genome may cause alterations in genome structure and/or gene expression of a newly synthesized amphidiploid, which may play an important role in the evolution of natural amphidiploid species. To test this hypothesis, a series of synthetic amphidiploids, including all three analogs of the natural amphidiploids B. napus, B. juncea, and B. Carinata and their reciprocal forms, were developed. These synthetic amphidiploids were characterized for morphological traits, chromosome number, and RFLPs revealed by chloroplast, mitochondrial, and nuclear DNA clones. The maternal transmission of chloroplast and mitochondrial genomes was observed in all of the F1 hybrids examined except one hybrid plant derived from the B. rapa x B. oleracea combination, which showed a biparental transmission of organelles. However, the paternal chloroplast and mitochondrial genomes were not observed in the F2 progeny. Nuclear genomes of synthetic amphidiploids had combined RFLP patterns of their parental species for all of the nuclear DNA clones examined. A variation in fertility was observed among self-pollinated progenies of single amphidiploids that had completely homozygous genome constitutions. Comparisons between natural and synthetic amphidiploids based on restriction fragment length polymorphism (RFLP) patterns indicated that natural amphidiploids are considerably more distant from the progenitor diploid species than the synthetic amphidiploids. The utility of these synthetic amphidiploids for investigating the evolution of amphidiploidy is discussed.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 833-836 
    ISSN: 1432-2242
    Schlagwort(e): T. aestivum ; RFLP ; Fingerprint
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two probes, specific for HMW-glutenins and γ-gliadins have been used to identify 50 common wheat Italian cultivars, most of which are closely related, and four common wheat cultivars originating outside Italy. The probes revealed complex polymorphic patterns; three probe/enzyme combinations had the necessary sensitivity for the identification of all 54 cultivars. As already shown for potato and barley, the use of four-cutter restriction enzymes and polyacrylamide gels proved particularly useful for detecting polymorphism.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 383-388 
    ISSN: 1432-2242
    Schlagwort(e): Mitochondria ; Inheritance ; RFLP ; Larix ; Conifers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Restriction fragment length polymorphisms between Larix leptolepis and Larix decidua were identified in heterologous hybridization experiments, using wheat mitochondrial DNA probes specific for atp9, coxI, nad3/rps12, and orf25. Analysis of eight individuals of each reciprocal hybrid of these two species revealed that mitochondrial DNA was maternally inherited. Furthermore, sequences homologous to wheat orf25 were also identified in Larix gmelini, Larix siberica, Larix olgensis, and Larix laricina, as well as Ginkgo biloba, Picea mariana, Picea glauca and Pinus contorta.
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  • 29
    ISSN: 1432-2242
    Schlagwort(e): DNA ; RFLP ; Soybean ; Genetic map
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Genetic markers were mapped in segregating progeny from a cross between two soybean (Glycine max (L.) Merr.) cultivars: ‘Minsoy’ (PI 27.890) and ‘Noir 1’ (PI 290.136). A genetic linkage map was constructed (LOD ⩾ 3), consisting of 132 RFLP, isozyme, morphological, and biochemical markers. The map defined 1550cM of the soybean genome comprising 31 linkage groups. An additional 24 polymorphic markers remained unlinked. A family of RFLP markers, identified by a single probe (hybridizing to an interspersed repeated DNA sequence), extended the map, linking other markers and defining regions for which other markers were not available.
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 573-578 
    ISSN: 1432-2242
    Schlagwort(e): COXI ; COXII ; Maternal inerhitance ; mtDNA ; RFLP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have studied two mitochondrial DNA polymorphisms in 741 individuals from 16 allopatric populations ofPinus banksiana Lamb. andPinus contorta Dougl. Restriction fragments of both polymorphisms distinguished the two species qualitatively, except in aP. Banksiana population whose ancestors were involved in hybridization withP. contorta.COXI-associated restriction fragments were monomorphic within species, whileCOXII-associated restriction fragments were highly variable inP. contorta (Hes=0.68). Population differentiation was substantial inP. contorta (Fst=0.31 among subspecies; mean Fst=0.66 within subspecies) and consistent with predictions for maternally inherited markers. Plant mitochondrial markers appear to be useful for the investigation of seed migration routes, hybridization and introgression, breeding zone designation, and the development of germ plasm conservation sampling strategies.
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  • 31
    ISSN: 1432-2242
    Schlagwort(e): Hordeum vulgare ; Microdissection ; Microcloning ; Chromosome specific library ; RFLP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have applied a refined microdissection procedure to create a plasmid library of the barley (Hordeum vulgare L.) chromosome arm 1HS. The technical improvements involved include synchronization of meristematic root tissue, a metaphase drop-spread technique, paraffin protection of the collection drop to avoid evaporation, and a motorized and programmable microscope stage. Thirteen readily-discernible telocentric chromosomes have been excised from metaphases of synchronized root-tip mitoses. After lysis in a collection drop (2 nl), the DNA was purified, restricted withRsaI, ligated into a vector containing universal sequencing primers, and amplified by the polymerase chain reaction. Finally, the amplified DNA was cloned into a standard plasmid vector. The size of the library was estimated to be approximately 44,000 recombinant plasmids, of which approximately 13% can be utilized for RFLP analysis. Tandem repetitive probes could be rapidly excluded from further analysis after colony hybridization with labelled total barley DNA. Analysis of 552 recombinant plasmids established that: (1) the insert sizes ranged between 70 and 1150 bp with a mean of 250 bp, (2) approximately 60% of the clones contained highly repetitive sequences, and (3) all single- or low-copy probes tested originate from chromosome 1HS. Four probes were genetically mapped, using an interspecificH. vulgare xH. spontaneum F2 population. One of these probes was found to be closely linked to theMla locus conferring mildew resistance.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 837-842 
    ISSN: 1432-2242
    Schlagwort(e): Androgenesis ; RFLP ; Maize ; Agronomic evaluation ; Gametoclonal variation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The homogeneity of anther culture-derived lines of maize has been evaluated by means of field observations and molecular markers. The homogeneity of the doubled haploid (DH) lines was shown by the absence of segregation for morphological oligogenic traits. The intravariance for polygenic traits for 42 DH and two conventionally derived lines was similar, which confirmed the homozygosity of the DH lines. More than 100 RFLP markers were tested on 189 DH lines derived from two crosses, DH5 x DH7 and A188 x DH7, and 60 single-seed descent (SSD, F6) lines derived from A188 x DH7. The overall rate of heterozygosity for all of the DH lines was approximatively 1% and pertained to 6 lines out of 189, while it was 8.5% for the SSD lines after four selfings. A precise description of the material used suggested that the events which led to this unexpected heterozygozity in DH lines were more likely to have occurred after rather than during the androgenetic process. Nine duplicated pairs of genotypes were found within the DH lines, indicating that a single microspore-derived structure can fragment to give two identical plantlets. Despite the extensive screening with more than 100 markers, only 2 lines showed unexpected banding profiles, and these were probably gametoclonal variants. The use of a direct regeneration system that avoids any callus phase might explain this low frequency of gametoclonal variation.
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  • 33
    ISSN: 1432-2242
    Schlagwort(e): DNA ; RFLP ; QTL ; Soybean ; Recombinant inbreds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An experimental test is described for linkages between RFLP markers and quantitative trait loci (QTL). Two hundred and eighty-four F7-derived recombinant inbred lines (RIL) obtained from crossing the soybean cultivars (Glycine max L. Merr.) ‘Minsoy’ and ‘Noir 1’ were evaluated for maturity, plant height, lodging, and seed yield. RIL exhibiting an extreme phenotype for each trait (earliest and latest plants for maturity, etc.) were selected, and two bulked DNA samples were prepared for each trait. A Southern transfer of the digested bulked DNA was hybridized with restriction fragement length polymorphism (RFLP) probes, and linkages with QTL were established by quantitating the amount of radioactive probe that bound to fragments defining alternative parental RFLP alleles. When an RFLP marker was linked to a QTL, one parental allele predominated in the bulked DNA from a particular phenotype; the other allele was associated with the opposite phenotype. When linkage was absent, radioactivity was associated equally with both alleles for a given phenotype (or with both phenotypes for a given allele). These results confirmed RFLP-QTL associations previously discovered by interval mapping on a smaller segregating population from the same cross. New linkages to QTL were also verified.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 87 (1993), S. 278-287 
    ISSN: 1432-2242
    Schlagwort(e): Maize ; RFLP ; Recombination ; Disturbed segregation ; DH/SSD lines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Doubled-haploid (DH) and single-seed-descent (SSD) lines in maize have been compared for quantitatively inherited traits and for RFLP markers. The comparisons of the distributions for agromorphological traits do not allow definite conclusions to be drawn on the similarity of the two reproductive systems. We have used more than 100 RFLP markers to provide a precise description of the parental allele frequency and the recombination fractions. A comparison of two DH populations shows that non-random meiotic reassortment is influenced by differences in the anther culture capacities of the two parental lines. For the DH lines derived from the cross DH5 x DH7, involving two responsive lines in anther culture, the distortion in segregation (P 〈 0.05) affected less than 20% of the genome with half of the deviations towards each parent. DH lines derived from the cross A188 x DH7, where A188 is a non-responsive line, showed more than twice this level of distortion and an excess of DH7 alleles was found for almost all of the skewed loci. The recombination fractions were homogeneous between the two DH populations for most of the genome. The genome sizes calculated with the DH and the SSD lines derived from the same cross, A188 x DH7, were also similar, which suggests that no selection against recombinant gametes occurs during anther culture. The observed recombination fraction after five meioses (SSD) is on average twice as large as after one meiosis (DH). No difference is observed for recombination fractions greater than 20%. Despite a precise description of the material at the molecular level, it has not been possible to make a definite conclusion as to whether or not the differences in some morphological characters are the consequences of differences in the segregation ratio and/or the recombination frequency. However, the agromorphological evaluation shows a narrow range in differences between the two types of lines and suggests that the use of DH lines is possible in breeding programmes.
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 85 (1993), S. 784-792 
    ISSN: 1432-2242
    Schlagwort(e): Wheat ; Rye ; Barley ; RFLP ; Biochemical markers ; Genetic maps
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Genetic maps of the homoeologous group-2 chromosomes were constructed, comprising 114 loci in wheat and 34 loci in rye. These include the genes coding for sucrose synthase, sedoheptulose-1,7-bisphosphatase, a bZIP protein (EmBP-1), a peroxidase and an abscisic acid-induced protein (#7). Overall, gene orders are highly conserved in the genomes of wheat, barley and rye, except for the distal ends of chromosome arms 2BS and 2RS, which are involved in interchromosomal, probably evolutionary, translocations. Clustering of loci in the centromeric regions of the maps, resulting from the concentration of recombination events in the distal chromosomal regions, is observed in wheat and rye, but not in barley. Furthermore, loci for which homoeoloci can be detected in rye and barley tend to lie in the centromeric regions of the maps, while non-homoeologous and wheat-specific loci tend to be more evenly distributed over the genetic maps. Mapping of the group-2 chromosomes in the intervarietal ‘Timgalen’ x ‘RL4137’ cross revealed that the T. timopheevi chromosome segment introgressed into chromosome 2B in ‘Timgalen’ is preferentially transmitted. Recombination is also greatly reduced in that segment.
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  • 36
    ISSN: 1432-2242
    Schlagwort(e): Translocations ; Rye ; RFLP ; Genetic maps ; Comparative mapping ; Co-linearity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary An RFLP-based genetic map of Secale Cereale has provided evidence for multiple evolutionary translocations in the rye genome relative to that of hexaploid wheat. DNA clones which have previously been mapped in wheat indicated that chromosome arms 2RS, 3RL, 4RL, 5RL, 6RS, 6RL, 7RS and 7RL have all been involved in at least one translocation. A possible evolutionary pathway, which accounts for the present day R genome relative to the A, B and D genomes of wheat, is presented. The relevance of these results for strategies designed to transfer useful genes from rye, and probably other related species, to wheat is discussed.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 97-104 
    ISSN: 1432-2242
    Schlagwort(e): Vigna ; Numerical taxonomy ; RFLP ; Asiatic grams ; Cowpea ; Bambara groundnut
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The taxonomy of the genus Vigna has been primarily based on morphological attributes. We have used 27 genomic clones from soybean, common bean, mungbean and cowpea to examine restriction fragment length polymorphism (RFLP) among 44 accessions of different species belonging to four subgenera of the genus Vigna. One accession each of common bean (Phaseolus vulgaris) and soybean (Glycine max) was included in the study. Total DNA from the various genotypes was digested with one restriction enzyme (Eco RV). Results of a numerical taxonomic analysis showed a high level of genetic variation within the genus with a remarkably higher amount of variation associated with Vigna sp. from Africa relative to those from Asia. The distinctness of the Asiatic grams in subgenus Ceratotropis, cowpea in section Catiang, bambara groundnut (V. subterranean) and members of the subgenus Plectotropis was elucidated by this study. Members of the subgenus Plectotropis were closer in genome homology to those of subgenus Vigna section Catiang than to those of subgenus Ceratotropis. The relative positions of some genotypes to one another on the dendrogram and minimum spanning tree were discussed in regard to hybridisations aimed generating well-saturated genomic maps and interspecies transfer of desirable genes.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 975-984 
    ISSN: 1432-2242
    Schlagwort(e): Chemiluminescence ; Genotyping costs ; RAPD ; RFLP ; Zea mays
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Three molecular marker protocols, chemiluminescent restriction fragment length polymorphisms (c-RFLPs), radioactivity-based restriction fragment length polymorphisms (r-RFLPs), and randomly amplified DNA polymorphisms (RAPDs) were compared in terms of cost and time efficiency. Estimates of cost of supplies and time requirements were obtained from simulations of maize (Zea mays L.) genotyping experiments utilizing protocols currently in use. The increase in total cost with increasing numbers of individuals genotyped and markers analyzed is higher for RAPDs than for RFLPs. RAPDs were generally found to be more cost and time efficient for studies involving small sample sizes, while RFLPs have the advantage for larger sample sizes. Because of the shorter exposure times involved, c-RFLPs require less time than r-RFLPs to obtain a given amount of information. Variations in the protocols, such as number of re-uses of Southern blots or cost of Taq DNA polymerase per reaction of amplification, also affect the relative merits of RAPDs and RFLPs. Two examples were analyzed where molecular markers are used: a germ plasm survey and quantitative trait loci (QTL) mapping in a segregating population. No protocol was found to be the most cost and time efficient over the entire range of sample sizes and number of marker loci studied.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 87 (1993), S. 81-88 
    ISSN: 1432-2242
    Schlagwort(e): Theobroma cacao ; RFLP ; Mitochondrial genome ; Chloroplast genome ; Diversity study
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The variability of cocoa (Theobroma cacao) cytoplasmic genomes has been investigated. A total of 177 cocoa clones was surveyed for restriction fragment length polymorphism (RFLP) in chloroplast DNA and in mitochondrial DNA using two restriction endonucleases and various heterologous cytoplasmic probes. A high level of polymorphism was found for the mitochondrial genome. This study points up a structuring of the species that fits with the distinction between the Criollo and Forastero populations. In contrast to all previous analyses, a higher level of polymorphism is found among the Criollo clones while the Forastero clones form quite a homogeneous group.
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  • 40
    ISSN: 1432-2242
    Schlagwort(e): Barley ; RFLP ; 5S rDNA ; Genetic mapping ; Physical mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The 5S rDNA locus on the long arm of barley chromosome 2(2H) was genetically mapped in two crosses in relation to 30 other RFLP loci. Comparison of the genetic maps with the previously published physical position of the 5S rDNA, determined by in-situ hybridization, showed that there was a marked discrepancy between physical and genetic distance in both crosses, with recombination being less frequent in the proximal part of the arm. Pooled information from the present study and other published genetic maps showed that at least 26 of the 44 (59%) RFLPs that have been mapped on 2(2H)L lie distal to the 5S rDNA locus even though this region is only 27% of the physical length of the arm. The distribution of RFLP markers is significantly different from expected (P 〈 0.01), implying that the low-copy sequences used for RFLP analysis occur more frequently in distal regions of the arm and, or, that sequences in distal regions are more polymorphic.
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  • 41
    ISSN: 1432-2242
    Schlagwort(e): Solanum spegazzinii ; Globodera rostochi ensis ; Nematode resistance ; QTL ; RFLP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We report the identification and mapping of two quantitative trait loci (QTLs) of Solanum spegazzinii BGRC, accession 8218-15, involved in resistance to the potato cyst-nematode Globodera rostochiensis pathotype Ro1, by means of restriction fragment length polymorphisms (RFLPs). For this purpose we crossed a susceptible diploid S. tuberosum with the resistant S. spegazzinii, and tested the F1 population for resistance to the Ro1 pathotype. Since the F1 segregated for the resistance, the S. spegazzinii parent was concluded to be heterozygous at the nematode resistance loci. For the mapping of the resistance loci we made use of RFLP markers segregating for S. spegazzinii alleles in the F1. One hundred and seven RFLP markers were tested in combination with four different restriction enzymes; 29 of these displayed a heterozygous RFLP pattern within S. spegazzinii and were used for mapping. Analysis of variance (ANOVA) was applied to test the association of the RFLP patterns of these markers with nematode resistance. Two QTLs involved in disease resistance to Globodera rostochiensis pathotype Ro1 were identified and mapped to chromosomes 10 and 11 respectively.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 87 (1993), S. 561-567 
    ISSN: 1432-2242
    Schlagwort(e): Senecio ; Somatic hybrid ; Cybrid ; RFLP ; Isozyme
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Twenty fusants of S. Jacobaea L. (chlorophyll deficient) (x) fuchsii Gmel. (wild-type) were investigated by studying chromosome number, isozymes, and restriction fragment length polymorphism (RFLP). Sublines were established from primary shoots, and clones were grown from isolated protoplasts. Out of the 12 hybrid lines 9 had the amphidiploid chromosome number of 80 (2x = 40) as concluded from each one subline. Three hybrid lines showed reduced chromosome numbers between 60 and 76, indicating karyotypic instability. Additive isozyme complements with peroxidase, esterase, malate dehydrogenase, and glutamate-oxalacetate transaminase activities were found. In the RFLP analyses, three ptDNA probes were able to demonstrate the origin of plastomes from either one or both parents, but singular chondriomes from either parent were traced with a mtDNA probe. The results of detailed studies with sublines and clones of two hybrid lines revealed that the chlorophylldeficiency mutation of one parental S. jacobaea clone is located in the genome and that of the other one is located in the plastome. Eight fusant lines were putative cybrids. Mutant plastids were not transmitted into the regenerated putative cybrid shoots. The mtDNA of S. jacobaea alone was detected with a mtDNA probe in seven putative cybrid lines; in one line mtDNA fragments of both the parents were traced. In three lines, the nucleus and the plastids only showed S. fuchsii characters, but the mtDNA was of S. jacobaea.
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  • 43
    ISSN: 1432-2242
    Schlagwort(e): Potato ; G. Rostochiensis ; RFLP ; Marker
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Resistance to the root cyst nematode Globodera rostochiensis is an agronomic trait that is at present incorporated into most new potato varieties. Major dominant genes are available that originate from wild and cultivated Solanum species closely related to the cultivated European potato (Solanum tuberosum ssp. tuberosum). One of those genes, H1, from S. Tuberosum ssp. andigena, was mapped to a distal position on potato chromosome V using restriction fragment length polymorphism (RFLP) markers. The H1 locus segregates independently from Gro1, a second dominant gene presumably from S. Spegazzinii that confers resistance to G. Rostochiensis and which has been mapped to chromosome VII. One marker, CP113, was linked without recombination to the H1 locus.
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 85 (1993), S. 513-520 
    ISSN: 1432-2242
    Schlagwort(e): RFLP ; RAPD ; Linkage map ; Bean Common Mosaic Virus resistance ; Segregation distortion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A restriction fragment length polymorphism (RFLP)-based linkage map for common bean (Phaseolus vulgaris L.) covering 827 centiMorgans (cM) was developed based on a F2 mapping population derived from a cross between BAT93 and Jalo EEP558. The parental genotypes were chosen because they exhibited differences in evolutionary origin, allozymes, phaseolin type, and for several agronomic traits. The segregation of 152 markers was analyzed, including 115 RFLP loci, 7 isozyme loci, 8 random amplified polymorphic DNA (RAPD) marker loci, and 19 loci corresponding to 15 clones of known genes, 1 virus resistance gene, 1 flower color gene, and 1 seed color pattern gene. Using MAPMAKER and LINKAGE-1, we were able to assign 143 markers to 15 linkage groups, whereas 9 markers remained unassigned. The average interval between markers was 6.5 cM; only one interval was larger than 30 cM. A small fraction (9%) of the markers deviated significantly from the expected Mendelian ratios (1∶2∶1 or 3∶1) and mapped into four clusters. Probes of known genes belonged to three categories: seed proteins, pathogen response genes, and Rhizobium response genes. Within each category, sequences homologous to the various probes were unlinked. The I gene for bean common mosaic virus resistance is the first disease resistance gene to be located on the common bean genetic linkage map.
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  • 45
    ISSN: 1432-2242
    Schlagwort(e): CMS ; Wild beet ; Cultivated sugar beet ; RFLP ; MtDNA variability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Mitochondrial DNA (mtDNA) variation in natural Beta maritima populations has been characterized by way of Southern blot hybridizations of total DNA using non-radioactive probes and chemiluminescent detection. It was found that the previously described N (“normal”) mitochondrial type could be subdivided into three subtypes. A new mitochondrial genotype (type R) was distinguished in addition to the previously described type S. Both are male-sterile cytoplasms and can produce a. segregation of sexual phenotypes in their progenies depending on the nuclear background. The populations contained at least two to four different mitochondrial genotypes.
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  • 46
    ISSN: 1432-2242
    Schlagwort(e): Repeated DNA ; Restriction satellite ; RFLP ; Solanaceae ; Species-specificity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Highly repeated DNA of potato (Solanum sp.) was characterized by cloning various major repeated elements of the nuclear genome. The percentage of the nuclear genome of the specific fractions and the restriction enzyme patterns were determined in order to show the distribution and organization of the respective repeats in the genome of Solanum tuberosum cultivars, dihaploid breeding lines and in wild species of Solanum. Several of the clones obtained were represented in a high copy number but showed no informative RFLP patterns. More information was gained from ‘restriction satellite’ repeats. The clone pR1T320 was found to contain satellite repeats (360 bp in length) that are proportionally present in the genome of all Solanum species at frequencies, between 0.5% and 2.6% and which are differently organized. This repeat was also found in the genera Lycopersicon, Datura and Nicotiana. With various restriction enzymes characteristic RFLP patterns were detected. A more or less genus-specific element for Solanum was the 183-bp repeat (clone pSA287; between 0.2–0.4% of the nuclear genome) that was present in the majority of the Solanum species analyzed except S. kurtzianum, S. bulbocastanum and S. pinnatisectum. In a few wild species (prominently in S. kurtzianum, S. demissum and S. acaule) a specific repeat type was detected (clone pSDT382; repeat length approximately 370 bp) that could be used to trace the wild species introduced into S. tuberosum cultivars. The repeats analyzed together with the 18S, 5.8S and 25S ribosomal DNA (1.9–5.2%, corresponding to 1800-5500 rDNA copies) comprised approximately 4–7% of the Solanum genome.
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 173-180 
    ISSN: 1432-2242
    Schlagwort(e): DNA fingerprinting ; Grapevine ; RFLP ; rDNA ; Satellite DNA ; Vitis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Repetitive DNA sequences present in the grapevine genome were investigated as probes for distinguishing species and cultivars. Microsatellite sequences, minisatellite sequences, tandemly arrayed genes and highly repetitive grapevine sequences were studied. The relative abundance of microsatellite and minisatellite DNA in the genome varied with the repeat sequence and determined their usefulness in detecting RFLPs. Cloned Vitis ribosomal repeat units were characterised and showed length heterogeneity (9.14–12.15 kb) between and within species. A highly repetitive DNA sequence isolated from V. vinifera was found to be specific only to those species classified as Euvitis. DNA polymorphisms were found between Vitis species and between cultivars of V. vinifera with all classes of repeat DNA sequences studied. DNA sequences suitable for DNA fingerprinting gave genotype-specific patterns for all of the cultivars and species examined. The DNA polymorphisms detected indicates a moderate to high level of heterozygosity in grapevine cultivars.
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 85 (1993), S. 1049-1054 
    ISSN: 1432-2242
    Schlagwort(e): RFLP ; Rye ; Dwarfism ; Vernalisation ; Genetic mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary RFLP mapping of chromosome 5R in the F3 generation of a rye (Secale cereale L.) cross segregating for gibberellic acid (GA3)-insensitive dwarfness (Ct2/ct2) and spring growth habit (Sp1/sp1) identified RFLP loci close to each of these agronomically important genes. The level of RFLP in the segregating population was high, and thus allowed more than half of the RFLP loci to be mapped, despite partial homozygosity in the parental F2 plant. Eight further loci were mapped in an unrelated F2 rye population, and a further two were placed by inference from equivalent genetic maps of related wheat chromosomes, allowing a consensus map of rye chromosome 5R, consisting of 29 points and spanning 129 cM, to be constructed. The location of the ct2 dwarfing gene was shown to be separated from the segment of the primitive 4RL translocated to 5RL, and thus the gene is probably genetically unrelated to the major GA-insensitive Rht genes of wheat located on chromosome arms 4BS and 4DS. The map position of Sp1 is consistent both with those of wheat Vrn1 and Vrn3, present on chromosome arms 5AL and 5DL, respectively, and with barley Sh2 which is distally located on chromosome arm 7L (= 5HL).
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  • 49
    ISSN: 1432-2242
    Schlagwort(e): RFLP ; Mapping ; Barley ; Genome ; Centromeres
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A map of the barley genome consisting of 295 loci was constructed. These loci include 152 cDNA restriction fragment length polymorphism (RFLP), 114 genomic DNA RFLP, 14 random amplified polymorphic DNA (RAPD), five isozyme, two morphological, one disease resistance and seven specific amplicon polymorphism (SAP) markers. The RFLP-identified loci include 63 that were detected using cloned known function genes as probes. The map covers 1,250 centiMorgans (cM) with a 4.2 cM average distance between markers. The genetic lengths of the chromosomes range from 124 to 223 cM and are in approximate agreement with their physical lengths. The centromeres were localized to within a few markers on all of the barley chromosomes except chromosome 5. Telomeric regions were mapped for the short (plus) arms of chromosomes 1, 2 and 3 and the long (minus) arm of chromosomes 7.
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 481-491 
    ISSN: 1432-2242
    Schlagwort(e): Potato ; Heterozygosity ; Heterosis ; RFLP ; Polyploids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract It has been theorized that in cross-pollinated polyploid species hybrid vigor is maximized by the frequent occurrence of more than two alleles per chromosomal locus. In polyploid crops this condition of maximum heterozygosity has been reported to be associated with increased yield and optimum field performance. We report herein the first direct test of the maximum heterozygosity hypothesis. Molecular markers were used to examine the association between maximum heterozygosity and several components of yield in three different populations of tetraploid potatoes. The results indicate that the value of maximum heterozygosity is not universal but dependent on the genetic background of the material under evaluation. In a cross between adapted breeding lines, homozygosity was negatively correlated with tuber yield, and maximum heterozygosity was positively correlated with the proportion of tuber yield in the large-size fraction. In contrast, in crosses between adapted and unadapted parents, maximum heterozygosity had no detectable effect on any character. Quantitative trait locus (QTL) analysis of the three populations reveals that, regardless of the genetic background, additive genetic effects are more strongly correlated with the components of yield than are any measures of heterozygosity and that some common QTLs may be influencing yield in all three populations.
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 880-888 
    ISSN: 1432-2242
    Schlagwort(e): cDNA clones ; RFLP ; Genetic mapping ; Beta-tubulin ; Gene duplication
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The proportion of non-tandem duplicated loci detected by DNA hybridization and the segregation of RFLPs using 90 independent randomly isolated cDNA probes was estimated by segregation analysis to be 17%. The 14 cDNA probes showing duplicate loci in progeny derived from a cross between Arabidopsis-thaliana ecotypes ‘Columbia x Landsberg erecta’ detected an average of 3.6 loci per probe (ranging from 2 to 6). The 50 loci detected with these 14 probes were arranged on a genetic map of 587 cM and assigned to the five A. Thaliana chromosomes. An additional duplicated locus was detected in progeny from a cross between ‘Landsberg erecta x Niederzenz’. The majority of duplicated loci were on different chromosomes, and when linkage between duplicate locus pairs was detected, these loci were always separated by at least 15 cM. When partial nucleotide sequence data were compared with GENBANK databases, the identities of 2 cDNA clones which recognized duplicate unlinked sequences in the A. Thaliana genome were determined to encode a chlorophyll a/b-binding protein and a beta-tubulin. Of the 8 loci carrying beta-tubulin genes 6 were placed on the genetic map. These results imply that gene duplication has been an important factor in the evolution of the Arabidopsis genome.
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 86 (1993), S. 907-913 
    ISSN: 1432-2242
    Schlagwort(e): DNA ; RFLP ; QTL ; Genetic map ; Soybean
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Quantitative trait loci (QTL) were mapped in segregating progeny from a cross between two soybean (Glycine max (L.) Merr.) cultivars: ‘Minsoy’ (PI 27.890) and ‘Noir 1’ (PI 290.136). The 15 traits analyzed included reproductive, morphological, and seed traits, seed yield and carbon isotope discrimination ratios (13C/12C). Genetic variation was detected for all of the traits, and transgressive segregation was a common phenomenon. One hundred and thirty-two linked genetic markers and 24 additional unlinked markers were used to locate QTL by interval mapping and one-way analysis of variance, respectively. Quantitative trait loci controlling 11 of the 15 traits studied were localized to intervals in 6 linkage groups. Quantitative trait loci for developmental and morphological traits (R1, R5, R8, plant height, canopy height, leaf area, etc.) tended to be clustered in three intervals, two of which were also associated with seed yield. Quantitative trait loci for seed oil were separated from all the other QTL. Major QTL for maturity and plant height were linked to RFLP markers R79 (31% variation) and G173 (53% variation). Quantitative trait loci associated with unlinked markers included possible loci for seed protein and weight. Linkage between QTL is discussed in relation to the heritability and genetic correlation of the traits.
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  • 53
    ISSN: 1432-2242
    Schlagwort(e): Rice blast ; RFLP ; Retrotransposon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A genetic map of Magnaporthe grisea (anamorph=Pyricularia oryzae and P. grisea), the causal agent of rice blast disease, was generated from segregation data utilizing 97 RFLP markers, two isoenzyme loci and the mating type locus among progeny of a cross between parental strains Guy 11 and 2539. Of the seven chromosomes of M. Grisea, three were resolved by contour-clamped homogeneous electric field (CHEF) electrophoresis, while the remaining four migrated as two doublet bands. By utilizing differences between CHEF mobilities of unresolved chromosomes from the parental strains, Southern analysis with selected markers allowed the chromosomal assignment of all linkage groups. A small translocation involving 1 marker was found in the parental strains used to produce the segregating population from which the map was constructed. Nine classes of repetitive DNA elements were found in the genome of a fungal isolate pathogenic to rice. These occurred only a few times or not at all in the genomes of isolates showing reduced virulence on rice. One repetitive DNA was shown to have structural similarity to the Alu sequences found in primates, a sequence similarity to the copia-like elements of Drosophila, and peptide similarity to transposable elements found in Drosophila, other fungi, and higher plants.
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  • 54
    ISSN: 1573-9171
    Schlagwort(e): benzyl bromide, trimethylvinylsilane, addition ; radicals ; metal-complex initiation ; kinetics ; mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The general kinetics of the addition of benzyl bromide to trimethylvinylsilane in the presence of the Fe(CO)5—DMF system has been studied. The reaction orders with respect to each reagent found in the study correspond to a radical chain mechanism of the process. The metal-complex system takes part only in the initiation stage and only at a strictly defined ratio of the components.
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  • 55
    ISSN: 1573-9171
    Schlagwort(e): kinetics ; organomercury nitroxyls ; organothallium nitroxyls ; coordination bond ; hydrazobenzene ; reduction ; rate constant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An increase is found in the reactivity of organomercury and organothallium nitroxyl mono- and biradicals of the imidazoline type in comparison with the analogous compounds without organometallic fragments. This is explained by the formation of coordination bonds N→Hg, N→Tl, and N→O→Hg.
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  • 56
    ISSN: 1573-9171
    Schlagwort(e): cationic polymerization ; polyisobutylene ; Lewis acids ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Polymerization of isobutylene in hexane at −78 °C under the action of the complex AcBr · 2AlBr3 (Ac-2) affords polyisobutylene having C=O groups at the head and C-Br or C=C groups at the tail of all the molecules. The presence of the latter indicates that there occurs proton elimination from the growing carbocation with the formation of a superacid HBr · 2AlBr3 which is unable to initiate the polymerization repeatedly under given contitions. This makes it possible to consider proton elimination as the reaction of the decay of active centers with the rate constantk d. This value has been calculated from the rate of accumulation of the polymeric molecules having terminal C=C bonds:k d=3.5 · 10−4 s−1. The rate constant of chain growthk g has been determined from polymerization kinetics and from the content of active centers:k g=6.2 L mol−1 s−1.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 42 (1993), S. 1027-1031 
    ISSN: 1573-9171
    Schlagwort(e): nitroxyls ; hydrazobenzene ; reduction ; tetranitromethane ; oxidation ; kinetics ; constants ; mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The values of isotropic HFS constantsa N were obtained for nitroxyl radicals (NR) of the piperidine series in hexane and water. The interrelation between rate constants for NR reduction and oxidation reactions, isotropic HFS constantsa N, inductive constants σ″ of the piperidine substituents, and electrochemical characteristics of NR were found. The dependence of the rate constants for the reduction of NR by hydrazobenzene (HB) and its oxidation by tetranitromethane (TNM) upon the Hammett type inductive constantsσ EPR, obtained using HFS constantsa N as the basis, was analyzed. The solvent effect on the reduction and oxidation reaction rate constants, the kinetic isotopic effect of the reduction reaction for a number of NR-HB systems, and alternative reaction mechanisms are considered.
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 42 (1993), S. 1811-1815 
    ISSN: 1573-9171
    Schlagwort(e): hydroxylammonium nitrate ; preparation ; thermal decomposition ; kinetics ; mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of thermal decomposition of melted hydroxylammonium nitrate have been investigated by the rate of heat production in the temperature range 84.8–120.9°C. The decomposition proceeds with autocatalysis and up to 60 % of conversion the rate of the process increases proportionally to the square of the degree of decomposition. The initial rate is proportional to the square of the concentration of HNO3 formed due to dissociation of the salt. The activation energy of this process is 15.3±1.8 kcal/mol. It is suggested that the initial stage the process proceeds via interaction between N2O3 and NH3OH+, whereas the subsequent acceleration is due to oxidation of NH3OH+ by nitrogen oxides formed as well as by nitrous acid.
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 42 (1993), S. 457-460 
    ISSN: 1573-9171
    Schlagwort(e): kinetics ; mechanism ; 6-tert-butyl-2-methylphenol ; alkylation with methyl acrylate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A kinetic scheme of the reaction between 6-tert-butyl-2-methylphenol and methyl acrylate in the presence of an alkali metal phenoxide has been proposed. The rate constants of the elementary steps describing the catalytic mechanism have been calculated. The reaction gives methyl 3-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionate as the only product (Calkylation). The nature of the metal cation does not affect the reaction mechanism.
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  • 60
    ISSN: 1573-9171
    Schlagwort(e): H-complexes ; polyimide ; 3,3′,4,4′-benzophenonetetracarboxylic acid, diethyl ester ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of thermal imidization of the H-complexes derived from the diethyl ester of 3,3′,4,4′-benzophenonetetracarboxylic acid (EBZP) and various diamines have been studied. A comparison of kinetic parameters obtained for the imidization of H-complexes based on ethyl or methyl esters of this acid has disclosed the differences in the behavior of each of the two H-bonds and the contribution of each bond to the mechanism of polyimide formation from the respective H-complexes.
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 239 (1993), S. 115-121 
    ISSN: 1617-4623
    Schlagwort(e): RFLP ; Disease resistance ; Duplicated sequence ; Recombination ; Linked repeats ; Hypervariable loci
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Rp1 is a disease resistance complex and is the terminal morphological marker on the short arm of maize chromosome 10. Several restriction fragment length polymorphisms (RFLPs), which map within 5 map units of Rp1, were examined to determine if they are also complex in structure. Two RFLP loci, which mapped distally to Rp1, BNL3.04 and PIO200075, existed in a single copy in all maize lines examined. These two loci cosegregated perfectly in 130 test cross progeny. Two RFLP loci that map proximally to Rp1 had unusual structures, which have not yet been reported for maize RFLPs; the loci were complex, with variable numbers of copies in different maize lines. One of the loci, NPI285, occasionally recombined in meiosis to yield changes in the number of copies of sequences homologous to the probe. The other proximal locus, detected by the probes NPI422, KSU3, and KSU4, was relatively stable in meiosis and no changes in the number of restriction fragments were observed. The similarity in map position between Rp1 and the complex RFLP loci indicate there may be genomic areas where variable numbers of repeated sequences are common. The structure of these complex loci may provide insight into the structure and evolution of Rp1.
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Plant systematics and evolution 187 (1993), S. 115-125 
    ISSN: 1615-6110
    Schlagwort(e): Poaceae ; Secale ; cpDNA variation ; RFLP ; phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The chloroplast genomes of 44 accessions ofSecale were surveyed for restriction site polymorphisms. The accessions were chosen to represent the geographic as well as taxonomic range of the genus. Using 12 restriction enzymes a total of 348 sites were detected. Twenty-nine mutation sites were phylogenetically informative and used in a cladistic analysis. Further, a 0.1 kb insertion separatedSecale from the outgroup species. Only the annual speciesS. sylvestre was distinct from the rest of the taxa. Cultivated rye together with both wild annual and wild perennial accessions were mixed among each other. Sequence divergence (p) among taxa ofSecale was low, varying from 0.000 to 0.005, suggesting a rather recent origin of the genus.
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  • 63
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Bovine milk ; Multivariate optimization ; Glycerophospholipids ; Molecular species separation ; Chemometrics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The molecular species profile, representing the fatty acid combinations on the glycerol backbone, is the most fundamental description of an intact glycerophospholipid class and provides a key to understanding its functional characteristics. We have developed a powerful RP-HPLC method for the separation of molecular species, including so-called “critical pairs”, of natural mixtures of 1,2-diacyl-sn-glycero-3-phosphocholine 1,2-diacyl-sn-glycero-3-phosphoethanolamine from bovine milk and other natural sources. We have used a novel multivariate development and optimization strategy to locate the region of optimum separation conditions within a prechosen domain of the chromatographic parameter space.
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  • 64
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Open tubular columns ; Cross-linked polyacrylate stationary phase ; Photopolymerization ; Antracene derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Polyacrylate films containing a lauryl moiety were fabricated on about 12 μm I.D. fused silica capillaries by in-situ photopolymerization of acrylates. Relatively thick films up to 1 μm were obtained by the technique. The films were tested as retentive layers for reversed phase open tubular liquid chromatography (OTLC). Due to the presence of the incorporated lauryl moiety in the layer considerable retention could be achieved for polar compounds with aqueous mobile phases. The efficiency of the prepared columns approximates to the theoretical value. The polyacrylate films appear to be extremely stable even under strong basic conditions. The films swell considerably in the presence of nonpolar solvents resulting in more favourable retention and a significant improvement of the chromatographic performance.
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 627-630 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fatty acid analysis ; Fish oils
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A chromatographic method has been developed for the determination of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in fish oil dietary supplements containing triglycerides rich in (n−3) polyunsaturated fatty acids (PUFAs). Following the ester saponification, free fatty acids were resolved by TLC into two fractions: i) a more mobile group of saturated and monounsaturated fatty acids and ii) a less mobile group containing PUFAs. The PUFA fraction was further analyzed by HPLC to determine the levels of EPA and DHA in the fish oil sample.
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  • 66
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carbidopa and levodopa in plasma ; Electrochemical detection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A validated reversed-phase high-performance liquid chromatographic procedure employing electrochemical detection (LCEC) for the analysis of carbidopa and levodopa in human plasma is reported. The method is sensitive and specific with amperometric detection at a glassy carbon working electrode with Eapp=0.75 V vs. Ag/AgCl. The retention times of levodopa, internal standard, and carbidopa are 3.3, 4.5, and 9.7 minutes, respectively, with an overall chromatographic run time of 12.0 minutes. The peak height ratio versus plasma concentration is linear over the range of 5.0 to 500 ng/mL for each analyte and exhibits correlation coefficients of 0.9957 or better (n=9). The mean absolute recovery of carbidopa and levodopa using the described assay is 36.6 and 66.0%, respectively. The inter- and intra-day accuracy and precision are within 11.8% of the actual values for all concentrations. Also, due to the demonstrated instability of carbidopa and levodopa in plasma a procedure is provided to circumvent this. Blood collected in pre-treated Vacutainer tubes can be stored in an ice bath for up to 4 hours without any significant degradation, thereby providing a practical means for processing several clinical samples simultaneously.
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  • 67
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fullerenes ; FullereneSep® ; Separation factor ; HPLC-particle beam mass spectrometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary High-performance liquid chromatographic separation of fullerene mixtures in the range C60 to C100 can be achieved using a novel stationary phase which rivals the performance of the more expensive ‘Pirkle-type’ columns currently employed.
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 675-678 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Ion chromatography ; Trace metal determination ; Sample contamination ; Human hair
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The dynamic ion-exchange chromatographic analysis of bivalent ions, such as Cu, Pb, Zn, Ni, Co and Mn in resistant organic matrices needs preliminary wet ashing with oxidizing acids (HNO3 and HClO4). Such treatment may lead to an increase in the amounts of metals present in the sample due to their release from containers or equipment used in an acidic environment and to metal impurities contained in the acids. The effect of these interferences in the determination of trace metals in human hair was studied.
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  • 69
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; GC/ECD detection ; PCBs, ortho and non-ortho ; Chromatographic separation ; Congener determination ; FTIR identification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An analytical procedure for the individual determination of ortho and non-ortho PCB congeners in sediments, using high performance liquid chromatography (HPLC) preseparation and gas chromatography/ECD detection, is described. Gas chromatography/FTIR spectrometry (GC/FTIR) and gas chromatography/mass spectrometry (GC/MS) were employed for individual congener identification and determination. Sample extraction, clean-up of extract and selective elution procedures were optimized by using reference certified marine sediment samples. Recovery and precision were typically 83% and 16% respectively at 2 ng/g of total PCB content. The proposed procedure, tested by analyzing real sediment samples, showed a reproducibility better than 20% at 13 ng/g PCB level.
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  • 70
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Glutamine ; Pyroglutamic acid ; Amino acids formulations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The aminoacid glutamine in aqueous solution and in conditions of high temperature and long term storage is partly transformed into pyroglutamic acid which exhibits potential neurotoxic effects. Commercially available aminoacid mixtures supplemented with glutamine are heat-sterilized and some losses of glutamine and formation of pyroglutamic acid may occur. The aim of the work was to set up an easy and reliable HPLC method which allows the determination of pyroglutamic acid as a degradation product of glutamine. The column was a 5 μm Hypersil ODS (100×4.6 mm) and the mobile phase 100% 0.007 M phosphate buffer pH 3.5. Stability studies in different conditions of temperature and time of storage were performed on aminoacid mixture available in the commerce.
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  • 71
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carbonyl compounds ; Luminarin hydrazides ; Fluorescence detection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Fluorogenic reagents (luminarin 3, luminarin 11 and luminarin 12), having a quinolizinocoumarin moiety as fluorophore and a carboxylic acid hydrazide function as reacting group, have been developed. These reagents were found to be highly sensitive fluorescence derivatization reagents for aldehydes and ketones in high-performance liquid chromatography. The reagents readily react with carbonyl compounds in aqueous sulphuric acid solution (0.1 M) at room temperature to produce the corresponding hydrazone derivatives, which can be separated on both reversed or normal-phase column. The structures of the derivatives were studied, together with their properties in reversed and normalphase chromatographic systems. UV absorbance, corrected fluorescence spectral data and quantum yields of luminarin 3, luminarin 11 and luminarin 12 are presented. The detection limits (signal to noise ratio=3) for aldehydes and ketones were in the sub-pmol range. Luminarin 3 was also applied to the determination of hydroxymethylfurfural (HMF) in orange juices and concentrates. The method for HMF involves the solid-liquid extraction of the juice by using a C-18 cartridge prior to derivatization and normal-phase separation of the derivative with fluorimetric detection at 387 nmex., 444 nm em. The calibration curve was linear for amounts of HMF ranging from 0.1 to 10 nmol. Intrarun relative standard deviation was 12.8% for 0.1 nmol and 2.6% for 1 nmol. Recovery studies indicated an average of 98.7±1.9% for juice concentrate and 99.8±3.2% for pasteurized juice.
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  • 72
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Method development ; Chemometrics ; Response criteria ; Analysis of drug purity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Optimization procedures require adequate response criteria to assess the quality of each chromatogram obtained during the process. The objective of this paper is to evaluate the possibility of using different resolution functions, in the chromatographic separation of a drug and its impurities (particularly the impurity just eluted after the drug). This study shows the limits of some resolution expressions. The interest of the simple Δt criterion, the difference between retention times, is presented in this paper.
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 36 (1993), S. 147-151 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Polarity ; Retinoids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention of retinoids in reversed-phase liquid chromatography was studied using aqueous mobile phases of different composition (methanol 94–86% and acetonityrile 92–82%) at five temperatures (40–60 °C). With both organic modifiers the effect of the molecular structure increased as the water content and the polarity of the mobile phase increased. The temperature-dependence increased in the same manner with aqueous acetonitrile mobile phases. The π-π interactions between the retinoids and acetonitrile diminish when the water content of the mobile phase is increased, as happens also to the hydrophobic interactions with both organic modifiers. The net effect of these changes depends on the composition of the mobile phase. There was excellent correlation of retention with all polarity parameters studied(ϕ, P′, xe, xd, xn, E T N , δT, δ, δo and δd), when the calculations were made separately with methanol and acetonitrile. The volume fraction of the organic modifier, ϕ, was the only parameter describing the retention well in both organic modifiers simultaneously.
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  • 74
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Aromatic amines ; Arylbenzylamide methylthioether derivative ; SL 85.1016 ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An HPLC method has been developed for the determination of SL 85.1016, a new calcium antagonist arylbenzylamide methylthioether derivative. SL 85.1016 and the internal standard, SL 87.0210, are extracted from alkaline human plasma withn-hexane and back extracted into 0.05 M phosphate buffer (pH 2.5; 0.2 ml). Acetonitrile (50 μl) is added to the final aqueous extract in order to prevent absorption of the compounds of interest onto the walls of the glass tube; this solution then is partially processed by HPLC on a C18 column with UV detection (254 nm). The determination limit of the method is 2 ng.ml−1 of SL 85.1016 in human plasma; the response to the drug is linear in the range 2–200 ng.mg−1.
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  • 75
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 36 (1993), S. 347-350 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Allium ; Derivatization ; S-alk(en)yl-L-cysteine sulfoxides ; Sulfur amino acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Two pre-column derivatization procedures coupled with reversed phase HPLC have been compared for the analysis ofS-Alk(en)yl0L-cysteine sulfoxides in variousAllium species. In order to establish external standards some (+/-) sulfoxides were synthesized, using a new method to enhance asymmetric synthesis of the diastereoisomers. The first derivatization method is the formation ofo-phthaldialdehyde/tert.-butylthiol derivatives which can be analyzed using UV detection. The second, presently used for amino acid analysis, is the Waters Pico-Tag method, which employs phenylisothiocyanate as derivatization reagent. As the Pico-Tag method was found to be the most efficient for determination ofS-alk(en)yl-L-cysteine sulfoxides it was used to determine the alliin content of various samples of garlic.
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  • 76
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chlortetracycline ; Reversed-phase silical gel ; C8 bonded phase ; Collaborative study
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An established method for the analysis of chlortetracycline by liquid chromatography using octylsilylated silica gel as the stationary phase was examined in a multicentre study involving five laboratories and a total of six columns. Three chlortetracycline hydrochloride samples were analysed. The main component and the impurities were determined. An analysis of variance, treating each column as a different laboratory, showed an absence of consistent between-laboratory bias and the presence of a significant laboratory-sample interaction. The repeatability and the reproducibility of the method, expressed as relative standard deviations of the result of the determination of chlortetracycline hydrochloride, were calculated to be 0.9% and 1.1% respectively.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 37 (1993), S. 627-634 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; ODS phases ; NMR and FTIR characterization ; Stationary phase functionality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Two spectroscopic methods, solid state NMR and diffuse reflectance FTIR, have been used in conjunction with liquid chromatographicretention data to identify and distinguish the functionality of octadecylsilica (ODS) stationary phases. NMR and FTIR spectra are indicative of various features of the different functionalities of the phases and this information can be used to elucidate the configuration of the organosilyl moiety in the ODS on the silica surface and explain why DSS phases have different molecular shape (mainly planarity) recognition capability.
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 37 (1993), S. 423-428 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Polymer-modified silica ; Polypyrrole cloride ; Polypyrrole dodecylsulfate ; Small molecules ; Polyaromatic hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Polypyrrole chloride and polypyrrole dodecylsulfate coated-silica packing materials have been synthesized. Reverse-phase chromtographuy was employed to characterise both packings. A series of test compounds with known properties was used as molecular probes. They included benzene and derivatives, basic drugs, and polyaromatic hydrocarbons. A commericial C18 column was also used for the purpose of comparison in some cases.
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  • 79
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chiralcel OD ; N-Alkyl-N-methylanilineN-oxide enantiomers ; Chiral nitrogen centre ; Flavin-containing monooxygenase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A high-performance liquid chromatographic method for the resolution of the enantiomers of a series ofN-alkyl-N-methylanilineN-oxides is reported. The resolutions were achieved using a Chiralcel, OD chiral stationary-phase with a mobile-phase of hexane and ethanol in varying proportions. The chromatographic order of elution of the enantiomers ofN-ethyl-N-methylanilineN-oxide was determined to be (+)-(R) before (−)-(S).
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 37 (1993), S. 539-542 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Sotolon ; Vin jaune ; Flor-sherry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Sotolon (4,5-dimethyl-3-hydroxy-2(5H)-furanone) is a key flavour compound in the french flor-sherry “Vin jaune”. This compound was determined quantitatively by extraction of 25 ml of wine on a XAD-4 resin, elution with diethyl ether, separation by HPLC on a Lichrospher 100 Diol column, elution with dichloromethane/hexane (60/40) and UV detection at 232 nm. The amount of sotolon in “Vin jaune” (120 to 268 μg/l) was related to the development of the yeast film over a period of 6 years. Only 6 to 51 μg/l were found in the “Vin de paille” which is made with overmaturated grapes of the same Savagnin vine-plant but without development of yeasts, and 80 to 140 μg/l in “Tokai” which are partly grown under a yeast film.
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  • 81
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Immunoaffinity chromatography ; Proteins ; Surface plasmon resonance detection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The BIAcoreTM Biosensor System utilizes a detection principle known as Surface Plasmon Resonance (SPR) which, in simple terms, detects changes in the refractive index of a solution in contact with a gold film. The gold film is surface modified with carboxymethylated dextran to produce a hydrophillic matrix onto which macromolecules may be covalently immobilized. In this respect, the BIAcoreTM is similar to any other insoluble matrix, such as a chromatographic support. The SPR detection principle, however, allows one to directly ‘visualize’ the interaction under study, in real time and without the need for reporter molecules such as enzyme-labels. In addition, the very small sample requirements, automated robotics unit and ease of data analysis suggest the potential use of the BIAcoreTM instrumentation for assay development and possibly process development, especially where bio-specific interactions such as immunoaffinity chromatography are used as a step in the process. In this report, we demonstrate the use of the BIAcoreTM SPR detector for the micro-scale determination of conditions for immunoaffinity chromatography of soluble complementreceptor 1, sCR1.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 5-12 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Post-column reaction detector ; Explosives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Improvements in selectivity and sensitivity in the analysis of common explosives, like nitrate esters, nitramines and nitroaromatic compounds can be achieved by post-column derivatisation in a two step reaction detector. The first step in derivatisation is the photolysis of the analytes with UV at 254 nm. The photo reactor consists of a crocheted 20 m Tefzel capillary, which is coiled around a low pressure mercury lamp. In second step the nitrite ion generated is subsequently detected by a colourimetric reaction. The azo dye formed can be selectively detected at 540 nm. Addition of alkali after chromatographic separation to prevent oxidation of initially formed nitrite to nitrate during photolysis leads to a complex multistage arrangement. However, the contribution to peak broadening by the reactor is negligible and it is possible to detect 25–50 ppb of nitramines and 30–100 ppb of nitrate esters. Another advantage of the method is the selective detection of nitro compounds, even in complex matrices. The trace analysis of explosives is of growing interest in forensic science as well as in environmental analysis. It has been shown [1] that explosives can easily be extracted from soil and debris by the use of supercritical carbon dioxide. The separation and determination of explosives by gas chromatography is hindered by their thermal instability. In HPLC only the nitro aromatic explosives can be detected with sufficient sensitivity. Other types of explosives like the esters of nitric acid or nitramines do not absorb sufficiently in the UV region for sensitive detection. It has been shown [2] that explosives are liable to photochemical decomposition in the UV region, resulting in nitrate and nitrite, which have been detected after separation by ion-pair chromatography with electrochemical detection. A more sensitive and selective detection of nitrite has been possible in flow injection analysis [3]. Here a modified Griess reaction has been used. In a first step nitrite ions are used to form the diazonium salt with sulfanilamide which is coupled in a second step with N-[naphthyl-(1)]-ethylene diamine (NED) to form a redviolet azo dye with an absorption maximum at 540 nm. The advantage of this method is selective detection in the visible region, where hardly any other organic components are detected, which might be present in a crude environmental sample. In this paper the transfer of the Griess reaction to post-column derivatisation in RP chromatography of explosives will be described, and the optimisation of trace analysis of these solutes will be discussed.
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  • 83
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Reverse phase ; Optimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An interpretive optimization procedure in which pH can be one of the variables is presented with the emphasis on optimizing separations. When varying the pH in reversed-phase liquid chromatography the retention of ionogenic solutes will change. Thus, the selectivity between ionogenic and neutral solutes or between ionogenic solutes mutually can be optimized. However, pH also greatly affects the efficiency (plate count) and peak shape (asymmetry). Optimum selectivity (i.e. large differences in retention times) may be observed under conditions where peaks are broad and asymmetrical. Thus, it is essential to simultaneously consider retention, peak width and peak shape and their effects on separation (effective resolution) in pH-optimization studies. A procedure in which this is done is presented and applied to optimizing the separation of a synthetic mixture of selected pharmaceuticals. After initial experiments to establish the parameter space (boundaries for pH and binary methanol — water composition), twelve experiments are performed according to a 3×4 experimental design. At each loaction the retention, peak height, peak area and peak symmetry are recorded for each solute. These data are then used to build models for each of the four characteristics and for each solute. From this set of models the response surface, describing the quality of separation as a function of pH and composition, can be calculated. A variety of optimization criteria (quantifying quality of separation) can be used. The optimum corresponds to the highest point on the response surface.
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 38-44 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fullerenes ; On-line and off-line identification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The separation of fullerenes with a monomeric octadecylsilica bonded phase using n-hexane or toluene/methanol mobile phase systems is described. Analytical and preparative separations, incorporating on-line UV/VIS spectral measurements, confirmed the existence of large fullerenes such as C76, C78 and C84. However, isomers of C78 and C84 were not conclusively found.
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 50-54 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Wine ; Volatile phenols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An alternative to the traditional solvent extraction method used to extract and rapidly quantify ethyl-and vinylphenol and ethyl-and vinylgaiacol from wine is presented. The method is based on retention of volatile phenols on adsorbants. Among the tested resins, the most efficient, AG 2-X8 (anion exchange resin), worked as well with a synthetic solution as with wines. The percolation of clarified wine adjusted to pH 9 on this resin permits, in particular, the elimination of organic acids. Phenols are not eluted after rinsing the column with 1N HCl, but are eluted with methanol after this treatment. Good recovery (91 %) and good repeatability are observed. The eluate is directly analysed by HPLC on an RP18 column after two-fold dilution in water. The four volatile phenols were completely separated and detected by UV at 280 nm with high sensitivity (20–40 ppb). No interference with other compounds were noted in the different wines analysed.
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 61-66 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Sugars ; Ion-pair separation ; Pulsed electrochemical detection ; Hypercarb and PLRP-S
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Sugars, sugar acids, amino sugars and oligomers are separated as ion-pairs with hydrophobic counter ions at alkaline pH using PLRP-S and Hypercarb as solid phases. Important parameters for regulation of retention and selectivity are nature and concentration of the counter ion, pH (hydroxide concentration) and temperature. Reversals in the elution order wer obtained in some cases. Oligosaccharides are highly retained in these systems. The addition of organic modifiers to the mobile phase for elution of the solutes were found to interfere with the pulsed electrochemical detection (PED). Anions added to the mobile phase compete with the solutes for ion-pair retention, hence, decreasing the capacity factors, and phosphate could be used for this purpose in the separation of maltooligomers (M2-M10) from corn syrup.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 87
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 55-60 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carbohydrates ; Ion-pair separation ; Glycoconjugates ; PRP-1 and PLRP-S
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new technique for the separation of carbohydrates as ion-pairs in strongly alkaline solution is presented. Carbohydrates are weakly acidic and partly present as anions at pH≥12 [1]. They are retained as ion-pairs on polymeric solid phases (PRP-1 and PLRP-S) with a hydrophobic quaternary ammonium counter ion present in the mobile phase. The effects of nature and concentration of mobile phase components on the retention of carbohydrates have been investigated and an ion-pair distribution model is proposed. The influence of temperature indicated no changes in retention mechanism with high counter ion concentration, but the resolution decreased with increasing temperature. Saccharides added to the mobile phase were shown to increase the retention and the selectivity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 90-92 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; α1-acid glycoprotein ; Complex glycans ; Allergic reaction ; Terfenadine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Little is known about the alterations that have occurred at the individual glycosylation sites in allergy patients or how these glycosylation patterns may change after anti-allergy treatments. Using reverse-phase HPLC, we have quantitated the glycoforms present at the individual glycosylation sites on orosomucoid isolated from the sera of allergic reaction patients and an allergic reaction patient treated with the antihistamine Terfenadine. The glycan structures isolated from the five glycosylation sites for the individual taking Terfenadine were all within normal ranges. It is suggested that if the changes in glycosylation in OMD in the allergic state are functionally driven, then it should be possible to correlate biological activities with quantitative changes at the individual glycosylation sites, and hence further define the role of OMD in allergy and inflammation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 89
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Bonded liquid crystals ; Polymeric stationary phases ; Variable temperature studies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Using two polycyclyic aromatic hydrocarbons as solutes, a comparison is made between a bonded liquid crystal stationary phase and a conventional polymeric C-18 phase. The bonded nematic liquid crystal phase was the silanized form of 4-[4-(allyloxy)benzoyl-oxy]biphenyl and the polymeric phase was Vydac 201TP. Both phases display shape and planarity selectivity as indicated by the results of the variable temperature and mobile phase composition studies. The slot theory of retention can be used to explain these results. However, the liquid crystal phase is more sensitive to molecular geometry, probably due to its more ordered structure on the surface. Variable temperature experiments which compare retention during both heating and cooling provides additional support for this conclusion. With the polymeric bonded C-18 phase, each solute had identical retention at the same temperature during both the heating and cooling cycles. On the bonded liquid crystal phase, measurable differences in retention were observed at identical temperatures depending on whether the column was heated or cooled. This effect is attributed to a degree of partially reversible disordering which occurs as the column temperature was increased. However, conditioning with the appropriate mobile phase can restore the original retention characteristics of the bonded liquid crystal phase.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 133-138 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Ligand exchange chromatography ; Zirconium oxide ; Aluminum oxide ; Lewis acids and bases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The chromatographic properties of alumina and zirconia are compared with respect to their relative Lewis acidities when parabenzoic acid derivatives are chromatographed in aqueous media. Weak Bronsted acids show similar capacity factors on alumina and zirconia. As solute Bronsted acidity increases, the capacity factor increases more significantly on the zirconia phase than on the alumina phase. Efficiencies, as determined by the dominant desorption rate constants, are generally comparable between the two phases with alumina showing slightly higher efficiencies, Secondary interactions between the solutes and the stationary phases are nearly absent on zirconia but are very apparent on the alumina phase.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 91
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Formaldehyde in air ; Fluorimetric detection ; Comparison of fluorescent derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Three different fluorimetric methods for the measurement of atmospheric formaldehyde are described. The relatively unknown 2-diphenylacetylindan-1,3-dionhydrazine (DAIH) method was developed and optimized with an improved limit of detection of 2 ppbv corresponding to a sample volume of 7.5 L. Separation of lutidines necessary for the Nash method was successfully carried out and the separation time was reduced by a factor of 5. The detection limit of the Nash method was improved to 1 ppbv. In comparison, the N,N-diphenyl-1-naphthylamine-5-sulfonhydrazine (DNSH) method performed in a similar manner, reached an LOD of 0.5 ppbv. Finally, measurements made in candle smoke using the three different fluorimetric methods and three standard methods yielded very similar results.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 167-172 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; 18 β-glycyrrhetinic acid ; Glycyrrhizinic acid ; Toothpastes ; Solid phase extraction (SPE)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary HPLC methods suitable for the selective and sensitive determination of 18 β-Glycyrrhetinic acid (GT) and Glycyrrhizinic acid (GZ) in toothpastes have been developed. The methods involve a preliminary quantitative solid phase extraction (C-18 sorbent) for sample clean-up and analyte concentration. Chromatographic separations were performed on reversed phase (C-8; C-18) columns using mixtures of methanol and phosphate buffers (pH 3.0) as the mobile phase under isocratic or gradient elution conditions. The method were applied successfully to the analysis of commercial toothpastes containing low levels (0.013–0.065%) of GT and GZ.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 153-159 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Amphetamine in plasma ; Enantiomeric separation ; Solid phase derivatization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An analytical approach has been developed for the one step determination of enantiomeric amphetamine composition in plasma, using on-line, pre-column solid phase derivatization with reversed phase HPLC separation. The high molecular weight protein components were excluded by the small pore structure of the polymer and washed out of the reaction column before derivatization. Spiked amphetamine in human plasma was extracted and derivatized by the polystyrene based FMOC-L-prolyl solid phase reagent. The derivatized diastereomers were separated on a conventional ODS column with an ACN/H2O mobile phase. No kinetic resolution or racemization was observed in this solid phase derivatization. Calibration plots and reproducibility experiments were performed to demonstrate the validity of the new approach. Automation of the procedure provided a simple and reproducible method for direct chiral recognition in plasma samples.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Pre-column derivatisation ; Morpholine and degradation products ; Boiler feed water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Morpholine and its amine-type thermal degradation products present in boiler feed water and steam condensate were derivatised with N-succinimidyl-p-nitrophenylacetate. These pre-column derivatives were determined by high-performance liquid chromatography with UV detection at 280 nm. The analytical column was Supelco-sil-ODS with an isocratic mobile phase. Morpholine and its breakdown products were monitored in the range 0.01–10 μg ml−1 with a relative standard deviation of 0.4–3.0%. Chromatographic analysis of boiler feed water and steam condensate samples collected from a boiler servicing a petroleum refinery is described.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 189-192 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carotenoid pigments ; Chlorophylls ; Photosynthestic tissue
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A high performance liquid chromatography system for the analysis of photosynthetic pigments is presented. The method employs an octadecylsilica stationary phase, a programmed quaternary mobile phase consisting of mixtures of methanol, acetonitrile, water and hexane, and a photodiode array detector. Carotenoids and chlorophylls are rapidly analysed in a single chromatographic separation. Thecis-trans isomers of most carotenoids are separated by this method.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 206-208 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Monensins A and B ; Fermentation broth ; Streptomyces cinnamonensis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary High performance liquid chromatography on an octadecyl silica column has been used to determine both the monensin A: monensin B ratio and by the method of standard addition, the concentration of both in the fermentation broth ofStreptomyces cinnamonensis. Refractive index detection was preferred to ultraviolet owing to the presence of UV-absorbing components which could not be completely separated from the substances of interest. A linear relationship was obtained from the calibration data. The coefficients of variation for the estimation both of the ratio and the concentrations of the compounds were better then 5%. The estimated limit of detection for both substances was about 1 μg/ml. The results obtained from the determination of the ratios of monensins were compared with those obtained by chemical ionization mass spectrometry. Chromatographic separation of monensins on the silica gel column is also described.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 232-236 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Ascorbic acid ; Antioxidant synergists ; Food, pharmaceuticals and cosmetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A specific and sensitive reverse-phase HPLC method for the quantitative determination of ascorbic acid and antioxidant synergists (1-tartaric acid, citric acid, lactic acid as lithium lactate and EDTA) in fatty pharmaceuticals, cosmetics and food has been developed. Two extraction procedures were used; treatment with hot water, and extraction with water from a hexane dilution of the product. No significant differences between the two procedures were found (p〈0.05), except for ascorbic acid. Quantitative determinations were performed using a C-18 column and sulfuric acid (pH 1.95) mobile phase. With detection, at 210 nm, lactic acid overlapped with ascorbic acid, but the former could be readily identified by TLC. Ascorbic acid was detected at 254 nm, when lactic acid (as lithium lactate) did not interfere in the analysis. Mean recoveries for tartaric, citric and lactic acids were in the range 96–101%.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Microdialysis ; Fermentation monitoring
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An automated on-line sampling and analytical set-up for the control of fermentations was studied incorporating a microdialysis probe as the sampling device. Applications to a penicillin broth and an ethanol fermentation were studied. Typical recovery values of carbohydrates were found to be close to 100% even after exposure of the microdialysis probe in the process for about 30 h.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 264-268 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Enantiomer separation ; Stereospecific synthesis ; Crown ether phase ; Immobilized enzyme reactor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A prototype of a coupled-column chromatographic system has been developed to determine the enantiomeric purity of enzymatically produced chiral compounds. In this system, an immobilized enzyme HPLC reactor based upon α-chymotrypsin (ACHT-IMER) was linked through a switching valve to a chromatographic column containing a crown ether-based chiral stationary phase (CR-CSP). Although ACHT is normally stereospecific for the L-enantiomorphs of aromatic amino acids, L-tryptophan (L-TRP), L-tyrosine and L-phenylalanine, we were able to achieve the hydrolysis of D-TRP methyl and ethyl esters on the ACHT-IMER. The percent of hydrolysis of the D-TRP esters could be manipulated by varying the resident time in the ACHT-IMER. In a series of experiments, D,L-TRP methyl or ethyl esters were injected into the ACHT-IMER, the flow stopped and after resuming the flow, the eluent which contained the hydrolyzed aminoacids, D- and L-TRP, was switched onto the CR-CSP where the enantiomeric composition of the TRP peak was determined. This configuration is a model for other IMER/CSP coupled-column systems which can be used for analytical and preparative applications.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 35 (1993), S. 275-280 
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Thin-layer chromatography ; Anti-hypoxia drugs ; Lipophilic character and retention
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The lipophilicity of 14 anti-hypoxia drugs has been determined by reversed phase thin-layer (RPTLC) and reversed phase high performance liquid chromatography (RPHPLC) in eluent systems containing different concentrations of acetonitrile and potassium dihydrogen phosphate. There was significant correlation between lipophilicity and the specific hydrophobic surface area of the drugs in RPTLC, indicating that the drugs behave as an homologous series of compounds. In RPTLC the concentration of buffer has a negligible effect on the retention of the drugs whereas in RPHPLC the buffer concentration influenced the retention. This discrepancy can be explained by the lower sensitivity of RPTLC. There was strong correlation between lipophilicity values determined by both methods, proving that both are suitable for the determination of molecular lipophilicity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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