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  • RFLP  (50)
  • kinetics
  • Springer  (86)
  • Institute of Physics
  • 1995-1999
  • 1990-1994  (86)
  • 1940-1944
  • 1993  (86)
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  • 1995-1999
  • 1990-1994  (86)
  • 1940-1944
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  • 1
    ISSN: 1572-879X
    Keywords: Fischer-Tropsch synthesis ; reaction activation barrier ; carbon chain growth and termination ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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  • 2
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    Cellular and molecular life sciences 49 (1993), S. 110-117 
    ISSN: 1420-9071
    Keywords: Polymerization ; sickle hemoglobin ; sickle cell disease ; kinetics ; thermodynamics ; polymer domains ; nucleation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: 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.
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  • 3
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    Biodegradation 4 (1993), S. 163-170 
    ISSN: 1572-9729
    Keywords: factorial analysis ; kinetics ; methane ; methanotrophs ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
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  • 4
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    Aquatic sciences 55 (1993), S. 103-111 
    ISSN: 1420-9055
    Keywords: iron(III) (hydr)oxide ; fulvic acid ; iron redox cycling ; dissolution ; surface reactivity ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
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  • 5
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    Plant cell reports 12 (1993), S. 293-297 
    ISSN: 1432-203X
    Keywords: Lycopersicon esculentum ; Genetic marker ; Intraspecific genetic map ; DNA polymorphism ; Isozyme ; RFLP ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
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  • 6
    ISSN: 1432-203X
    Keywords: Rice (Oryza sativa) ; Genetic Marker ; Genetic Map ; Integrated Linkage Map ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
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  • 7
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    European journal of clinical pharmacology 44 (1993), S. 231-235 
    ISSN: 1432-1041
    Keywords: Carbamazepine ; kinetics ; population pharmacokinetics ; bioavailability ; controlled release ; non-linear model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: 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.
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  • 8
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    Journal of thermal analysis and calorimetry 39 (1993), S. 15-20 
    ISSN: 1572-8943
    Keywords: alloys ; high-temperature sulphidation ; kinetics ; new thermobalane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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.
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  • 9
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    Journal of thermal analysis and calorimetry 39 (1993), S. 65-74 
    ISSN: 1572-8943
    Keywords: electrical conductivity ; hydrazone complexes ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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.
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  • 10
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    Journal of thermal analysis and calorimetry 39 (1993), S. 75-86 
    ISSN: 1572-8943
    Keywords: chlorination ; kinetics ; WO3+CCl4 reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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.
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  • 11
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    Journal of thermal analysis and calorimetry 39 (1993), S. 229-238 
    ISSN: 1572-8943
    Keywords: epoxy resins ; kinetics ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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.
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  • 12
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    Journal of thermal analysis and calorimetry 39 (1993), S. 87-95 
    ISSN: 1572-8943
    Keywords: gamma radiation effects ; graphite-hematite system ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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.
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  • 13
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    Journal of thermal analysis and calorimetry 39 (1993), S. 217-220 
    ISSN: 1572-8943
    Keywords: DSC ; edible oils ; isothermal method ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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
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    Journal of thermal analysis and calorimetry 39 (1993), S. 351-358 
    ISSN: 1572-8943
    Keywords: epoxy resin ; kinetics ; polyamide hardener
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 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.
    Notes: 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
    Keywords: Sulphydryl groups ; multiple ; hemoglobin ; kinetics ; ionizable groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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
    Keywords: bark storage protein ; gene clustering ; RFLP ; systemic response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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
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    Plant molecular biology 21 (1993), S. 99-108 
    ISSN: 1573-5028
    Keywords: fusion protein ; Oenothera ; plastome ; RFLP ; unidentified open reading frame
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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
    Keywords: Hemoglobin ; sulphydryl group ; ionizable groups ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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
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    Plant molecular biology 22 (1993), S. 437-446 
    ISSN: 1573-5028
    Keywords: RFLP ; genome ; PFGE ; multicopy markers ; symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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
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    The journal of membrane biology 132 (1993), S. 167-178 
    ISSN: 1432-1424
    Keywords: red cell ; glucose transport protein ; GLUT1 ; kinetics ; rapid reactions ; tryptophan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: 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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    The journal of membrane biology 133 (1993), S. 145-160 
    ISSN: 1432-1424
    Keywords: Acetabularia ; K+ channels ; kinetics ; planar lipid bilayers ; voltage dependence
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    Topics: Biology , Chemistry and Pharmacology
    Notes: 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
    Keywords: Pea ; Pea seed-borne mosaic virus ; Disease resistance ; Genome mapping ; RFLP
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    Topics: Biology
    Notes: 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
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    Theoretical and applied genetics 86 (1993), S. 181-188 
    ISSN: 1432-2242
    Keywords: Sugarcane ; Gramineae ; Tissue culture ; RFLP ; Molecular analysis
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    Topics: Biology
    Notes: 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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    Theoretical and applied genetics 86 (1993), S. 301-307 
    ISSN: 1432-2242
    Keywords: RFLP ; Polyploid ; Nondisjunction ; Interspecific hybrid ; Cottonwood
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    Topics: Biology
    Notes: 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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    Theoretical and applied genetics 86 (1993), S. 329-332 
    ISSN: 1432-2242
    Keywords: RFLP ; Alfalfa ; Genetic map ; Segregation distortion ; Plant breeding
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    Topics: Biology
    Notes: 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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    Theoretical and applied genetics 86 (1993), S. 811-821 
    ISSN: 1432-2242
    Keywords: Brassica ; Interspecific hybridization ; Amphidiploid ; RFLP ; Evolution ; Nuclear ; cytoplasmic interaction
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    Topics: Biology
    Notes: 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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    Theoretical and applied genetics 86 (1993), S. 833-836 
    ISSN: 1432-2242
    Keywords: T. aestivum ; RFLP ; Fingerprint
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    Topics: Biology
    Notes: 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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    Theoretical and applied genetics 86 (1993), S. 383-388 
    ISSN: 1432-2242
    Keywords: Mitochondria ; Inheritance ; RFLP ; Larix ; Conifers
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    Topics: Biology
    Notes: 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
    Keywords: DNA ; RFLP ; Soybean ; Genetic map
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    Topics: Biology
    Notes: 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
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    Theoretical and applied genetics 86 (1993), S. 573-578 
    ISSN: 1432-2242
    Keywords: COXI ; COXII ; Maternal inerhitance ; mtDNA ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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
    Keywords: Hordeum vulgare ; Microdissection ; Microcloning ; Chromosome specific library ; RFLP
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    Notes: 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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    Theoretical and applied genetics 86 (1993), S. 837-842 
    ISSN: 1432-2242
    Keywords: Androgenesis ; RFLP ; Maize ; Agronomic evaluation ; Gametoclonal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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
    Keywords: DNA ; RFLP ; QTL ; Soybean ; Recombinant inbreds
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    Notes: 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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    Theoretical and applied genetics 87 (1993), S. 278-287 
    ISSN: 1432-2242
    Keywords: Maize ; RFLP ; Recombination ; Disturbed segregation ; DH/SSD lines
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    Topics: Biology
    Notes: 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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    Theoretical and applied genetics 85 (1993), S. 784-792 
    ISSN: 1432-2242
    Keywords: Wheat ; Rye ; Barley ; RFLP ; Biochemical markers ; Genetic maps
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    Topics: Biology
    Notes: 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
    Keywords: Translocations ; Rye ; RFLP ; Genetic maps ; Comparative mapping ; Co-linearity
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    Notes: 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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    Theoretical and applied genetics 86 (1993), S. 97-104 
    ISSN: 1432-2242
    Keywords: Vigna ; Numerical taxonomy ; RFLP ; Asiatic grams ; Cowpea ; Bambara groundnut
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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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    Theoretical and applied genetics 86 (1993), S. 975-984 
    ISSN: 1432-2242
    Keywords: Chemiluminescence ; Genotyping costs ; RAPD ; RFLP ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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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    Theoretical and applied genetics 87 (1993), S. 81-88 
    ISSN: 1432-2242
    Keywords: Theobroma cacao ; RFLP ; Mitochondrial genome ; Chloroplast genome ; Diversity study
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    Notes: 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
    Keywords: Barley ; RFLP ; 5S rDNA ; Genetic mapping ; Physical mapping
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    Notes: 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
    Keywords: Solanum spegazzinii ; Globodera rostochi ensis ; Nematode resistance ; QTL ; RFLP
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    Notes: 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
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    Theoretical and applied genetics 87 (1993), S. 561-567 
    ISSN: 1432-2242
    Keywords: Senecio ; Somatic hybrid ; Cybrid ; RFLP ; Isozyme
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    Topics: Biology
    Notes: 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
    Keywords: Potato ; G. Rostochiensis ; RFLP ; Marker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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
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    Theoretical and applied genetics 85 (1993), S. 513-520 
    ISSN: 1432-2242
    Keywords: RFLP ; RAPD ; Linkage map ; Bean Common Mosaic Virus resistance ; Segregation distortion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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
    Keywords: CMS ; Wild beet ; Cultivated sugar beet ; RFLP ; MtDNA variability
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    Topics: Biology
    Notes: 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
    Keywords: Repeated DNA ; Restriction satellite ; RFLP ; Solanaceae ; Species-specificity
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    Topics: Biology
    Notes: 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
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    Theoretical and applied genetics 86 (1993), S. 173-180 
    ISSN: 1432-2242
    Keywords: DNA fingerprinting ; Grapevine ; RFLP ; rDNA ; Satellite DNA ; Vitis
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    Topics: Biology
    Notes: 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
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    Theoretical and applied genetics 85 (1993), S. 1049-1054 
    ISSN: 1432-2242
    Keywords: RFLP ; Rye ; Dwarfism ; Vernalisation ; Genetic mapping
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    Topics: Biology
    Notes: 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
    Keywords: RFLP ; Mapping ; Barley ; Genome ; Centromeres
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    Notes: 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
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    Theoretical and applied genetics 86 (1993), S. 481-491 
    ISSN: 1432-2242
    Keywords: Potato ; Heterozygosity ; Heterosis ; RFLP ; Polyploids
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    Topics: Biology
    Notes: 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
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    Theoretical and applied genetics 86 (1993), S. 880-888 
    ISSN: 1432-2242
    Keywords: cDNA clones ; RFLP ; Genetic mapping ; Beta-tubulin ; Gene duplication
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    Topics: Biology
    Notes: 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
    ISSN: 1432-2242
    Keywords: DNA ; RFLP ; QTL ; Genetic map ; Soybean
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    Notes: 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
    Keywords: Rice blast ; RFLP ; Retrotransposon
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    Topics: Biology
    Notes: 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
    Keywords: benzyl bromide, trimethylvinylsilane, addition ; radicals ; metal-complex initiation ; kinetics ; mechanism
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    Topics: Chemistry and Pharmacology
    Notes: 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
    Keywords: kinetics ; organomercury nitroxyls ; organothallium nitroxyls ; coordination bond ; hydrazobenzene ; reduction ; rate constant
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    Topics: Chemistry and Pharmacology
    Notes: 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
    Keywords: cationic polymerization ; polyisobutylene ; Lewis acids ; kinetics
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    Topics: Chemistry and Pharmacology
    Notes: 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
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    Russian chemical bulletin 42 (1993), S. 1027-1031 
    ISSN: 1573-9171
    Keywords: nitroxyls ; hydrazobenzene ; reduction ; tetranitromethane ; oxidation ; kinetics ; constants ; mechanism
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    Topics: Chemistry and Pharmacology
    Notes: 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
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    Russian chemical bulletin 42 (1993), S. 1811-1815 
    ISSN: 1573-9171
    Keywords: hydroxylammonium nitrate ; preparation ; thermal decomposition ; kinetics ; mechanism
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    Topics: Chemistry and Pharmacology
    Notes: 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
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    Russian chemical bulletin 42 (1993), S. 457-460 
    ISSN: 1573-9171
    Keywords: kinetics ; mechanism ; 6-tert-butyl-2-methylphenol ; alkylation with methyl acrylate
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    Topics: Chemistry and Pharmacology
    Notes: 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
    Keywords: H-complexes ; polyimide ; 3,3′,4,4′-benzophenonetetracarboxylic acid, diethyl ester ; kinetics
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    Topics: Chemistry and Pharmacology
    Notes: 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
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    Molecular genetics and genomics 239 (1993), S. 115-121 
    ISSN: 1617-4623
    Keywords: RFLP ; Disease resistance ; Duplicated sequence ; Recombination ; Linked repeats ; Hypervariable loci
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    Topics: Biology
    Notes: 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
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    Plant systematics and evolution 187 (1993), S. 115-125 
    ISSN: 1615-6110
    Keywords: Poaceae ; Secale ; cpDNA variation ; RFLP ; phylogeny
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    Topics: Biology
    Notes: 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: 1573-904X
    Keywords: fosinopril sodium ; magnesium ions ; C–P bond cleavage ; kinetics ; mechanism ; tablet formulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Fosinopril sodium (I), a new angiotensin converting enzyme inhibitor, is a diester prodrug of the active moiety II. We report here a novel transformation of fosinopril into β-ketoamide, III, and a phosphonic acid, IV, mediated through metal ion participation. The interaction of fosinopril with magnesium ions was studied in a solution model system in which methanol was used as the solvent and magnesium acetate as the source of metal ions. Kinetic analysis indicated the degradation to be a bimolecular process, with the rate being first order in both metal ion and fosinopril concentration. The degradation products II, III, and IV effectively retarded the magnesium ion mediated reaction of fosinopril. Based on the results of 31P-NMR, 1H-NMR, Mn(II)-EPR spectroscopy experiments and mass spectrometry, a mechanism is postulated for this transformation. A key reactive intermediate has been characterized that supports the proposed mechanism. The results can account for the observed degradation profile of the fosinopril sodium in a prototype tablet formulation.
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  • 64
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    Journal of pharmacokinetics and pharmacodynamics 21 (1993), S. 299-308 
    ISSN: 1573-8744
    Keywords: saturation ; liposomes ; uptake ; Michaelis-Menten ; kinetics ; AUC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The objective of this study was to examine the AUCdependency of saturable hepatic clearance (CL h )of liposomes and to postulate a mathematical model to describe the characteristics. The AUCdependency of saturable CL h was examined under intravenous rapid administration at various doses. The CL h increased with increasing blood concentration but decreased with the increase of AUCat each dose. In addition, the relationship between AUCand CL h was consistent with that observed in previously reported infusion studies. These experimental data confirm the AUCdependency of saturable CL h of liposomes. A mathematical model was developed for this AUCdependency. The decrease of CL h was described by the uptake amount (X)as follows: CL h =CL m (1−X/X m ),where CL m and X m represent the maximum uptake clearance and the maximum uptake amount, respectively. The rate equation for uptake was analytically solved as CL h =X/AUC=X m AUC(1-exp(CL m /X m AUC)).Uptake clearance can be described by CL m , X m ,and AUC,and so uptake clearance is constant if AUCis constant. These experimental analyses and theoretical considerations show the validity of the AUC-dependent saturable CL h of liposomes.
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  • 65
    ISSN: 1618-0860
    Keywords: Araceae ; Chloroplast DNA ; Molecular phylogeny ; RFLP ; Typhonium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The interrelationship of the ten species of the genusTyphonium and related genera in subtribe Arinae of the Araceae was inferred by chloroplast DNA restriction fragment analysis. A total of 42 site mutations were observed and 26 site mutations were shared by two or more species. A majority rule consensus tree was made by performing 100 bootstrap replicates using Wagner Parsimony. Two groups ofTyphonium were recognized significantly as monophyletic groups, i.e. 1)Typhonium larsenii andT. kunmingense, and 2)T. trilobatum, T. blumei andT. flagelliforme.
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  • 66
    ISSN: 1617-4623
    Keywords: QTL ; Gibberella zeae ; Maize ; RFLP ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The basic prerequisite for an efficient breeding program to improve levels of resistance to pathogens in plants is the identification of genes controlling the resistance character. If the response to pathogens is under the control of a multilocus system, the utilization of molecular markers becomes essential. Stalk and ear rot caused by Gibberella zeae is a widespread disease of corn: resistance to G. zeae is quantitatively inherited. Our experimental approach to understanding the genetic basis of resistance to Gibberella is to estimate the genetic linkage between available molecular markers and the character, measured as the amount of diseased tissue 40 days after inoculation of a suspension of Fusarium graminearum, the conidial form of G. zeae, into the first stalk internode. Sensitive and resistant parental inbreds were crossed to obtain F1 and F2 populations: the analysis of the segregation of 95 RFLP (restriction fragment length polymorphism) clones and 10 RAPD (random amplified polymorphic DNA) markers was performed on a population of 150 F2 individuals. Analysis of resistance was performed on the F3 families obtained by selfing the F2 plants. Quantitative trait loci (QTL) detection was based either on analysis of regression coefficients between family mean value and allele values in the F2 population, or by means of interval mapping, using MAPMAKER-QTL. A linkage map of maize was obtained, in which four to five genomic regions are shown to carry factors involved in the resistance to G. zeae.
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  • 67
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    Euphytica 71 (1993), S. 189-199 
    ISSN: 1573-5060
    Keywords: Capsicum annuum ; domesticated variety ; genome diversity ; intraspecific variability ; pepper ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forty one nuclear probes, distributed across the different linkage groups of the previously published map, were used to examine restrition fragment length polymorphism between cultivated peppers. Total DNA from thirteen accessions of Capsicum annuum var. annuum and one accession of C. baccatum var. pendulum was separately cut with ten restriction enzymes. The analyses were restricted to only one enzyme per probe to reduce the polymorphism redundancy. Nei & Li's genetic distances between accessions were calculated from the 141 resultant nuclear DNA restriction fragments. The genetic variation was larger between C. annuum and C. baccatum than between C. annuum cultivars. Large fruited related accessions closely clustered together. Distances between the small fruited cultivars were larger than within the bell pepper group. A correspondence analysis performed on differences between the global RFLP patterns of each accessions of C. annuum revealed the particular genomic structure of four small fruited cultivars: Criollo de Morelos 334, H3, Perennial and Doux Long des Landes. The percentage of probes revealing at least one RFLP with at least one enzyme ranged from zero to fifty percent for all the pairwise comparisons of C. annuum accessions. 82 presumptive loci were detected with a mean number of 1.46 alleles per locus within C. annuum and 1.83 within all the accessions. This result indicates that molecular markers will be more usable in intraspecific study of C. annuum than isozyme markers.
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  • 68
    ISSN: 1573-5060
    Keywords: intergeneric introgression ; Oryza sativa, prolamins ; RFLP ; Triticum aestivum ; X Oryticum oryzoides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The DNA of a putative rice x wheat hybridization derivative (X Oryticum oryzoides) from China, the DNA of its parental rice cultivar and the DNA of a wheat line were digested with ten different restriction endonucleases, resolved by agarose electrophoresis, Southern blotted and hybridized using genomic wheat DNA as a probe. Phenol extracted, ethanol and cetyltrimethylammonium bromide precipitated DNA of the putative hybrid showed a restriction fragment length polymorphism (RFLP) different from that of the parental rice. When the DNA was further purified by Qiagen chromatography, the RFLP differences were not detected. Hence the apparent RFLP differences were probably due partial digestion of the less pure DNA preparations by the restriction endonucleases. No real introgressed fragments from wheat genome could be shown. The HpaII/MspI sites were more frequently digested with MspI than with HpaII in rice and hybridization derivative DNA, but the sites were evidently more frequently methylated in wheat DNA. Thus, in terms of methylation of the DNA, the hybridization derivative was much more like the rice parent than the wheat parent. The hybridization derivative showed a single endospermal protein (mass 19 kg mol-1) not detected in the parental rice cultivar. This minor protein was soluble in buffered 50% isopropanol and precipitable with methanol. The results indicate that there are no or only short introgressed sequences from wheat in the rice/wheat derivative, a result which might be considered in breeding efforts with the hybrid derivative.
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  • 69
    ISSN: 1573-5060
    Keywords: Brassica napus ; microspore derived population ; RAPD ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The segregation of RFLP and RAPD markers was compared in two oilseed rape (Brassica napus L.) breeding populations from the cross ‘Topas’ x R4, the latter being a low linolenic mutation line. A total progeny of 68 F2 and 40 microspore derived plants were studied with 25 markers. The results indicated a significant excess of ‘Topas’ alleles at five RAPD loci in the microspore derived population. This suggests that genomic regions which probably affect microspore culture ability do not have identical distribution in the two population types.
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  • 70
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    Photosynthesis research 37 (1993), S. 1-17 
    ISSN: 1573-5079
    Keywords: bacterial photosynthesis ; kinetics ; proton binding ; reaction center ; stoichiometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A proton electrochemical potential across the membranes of photosynthetic purple bacteria is established by a light-driven proton pump mechanism: the absorbed light in the reaction center initiates electron transfer which is coupled to the vectorial displacement of protons from the cytoplasm to the periplasm. The stoichiometry and kinetics of proton binding and release can be tracked directly by electric (glass electrodes), spectrophotometric (pH indicator dyes) and conductimetric techniques. The primary step in the formation of the transmembrane chemiosmotic potential is the uptake of two protons by the doubly reduced secondary quinone in the reaction center and the subsequent exchange of hydroquinol for quinone from the membrane quinone-pool. However, the proton binding associated with singly reduced promary and/or secondary quinones of the reaction center is substoichiometric, pH-dependent and its rate is electrostatically enhanced but not diffusion limited. Molecular details of protonation are discussed based on the crystallographic structure of the reaction center of purple bacteriaRb. sphaeroides andRps. viridis, structure-based molecular (electrostatic) calculations and mutagenesis directed at protonatable amino acids supposed to be involved in proton conduction pathways.
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  • 71
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    Plant and soil 154 (1993), S. 67-72 
    ISSN: 1573-5036
    Keywords: ammonium uptake ; cereals ; kinetics ; legumes ; 15N ; nitrate uptake ; translocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Influx isotherms were obtained for nitrate and ammonium from three legumes, Cajanus cajan (L.) Millsp., Cicer arietinum L. and Arachis hypogaea L. and three cereals, Sorghum bicolor (L.) Moench., Pennisetum glaucum L. and Zea mays L. The transition in influx isotherms for both nitrogen sources was found to be within the concentration range (0.05–2.5 mM) tested. There were significant differences in Km and Vmax for ammonium between legumes and cereals. The difference in the kinetic properties for nitrate uptake between the two groups of plants only became apparent at the higher concentration tested. Legumes translocated absorbed nitrate and ammonium to shoots more rapidly than cereals. Results show that there are significant differences in uptake and translocation of ammonium and nitrate between legumes and cereals.
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  • 72
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    Hydrobiologia 260-261 (1993), S. 557-561 
    ISSN: 1573-5117
    Keywords: alginate lyase ; specificity ; kinetics ; product inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A purified preparation of the extracellular alginate lyase has been used to study kinetics and specificity towards purified, homopolymeric fragments of alginate. The enzyme preparation from Bacillus circulans 1351 degraded both block types, although with different efficiency, and thus appears to be nonspecific. Addition of calcium ions markedly enhanced the reaction rate for the polymannuronate block but had little or no effect on the reaction with polyguluronate. Michaelis-Menten kinetics are not obeyed in the absence of calcium ions and only for the polymannuronate in the presence of calcium The study of progress curves in response to variation in substrate and enzyme concentrations strongly suggests that the abalone lyase is subject to a reversible product inhibition.
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  • 73
    ISSN: 1573-5044
    Keywords: alfalfa (Medicago falcata) ; direct somatic embryogenesis ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method for direct somatic embryogenesis in alfalfa (Medicago falcata) is described. The time course in the development phase has been followed for fresh weight, cell density, pH, sugar uptake and embryo number and type. The method of disrupting the explant material has also been shown to influence subsequent embryo formation.
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  • 74
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    Journal of bioenergetics and biomembranes 25 (1993), S. 525-535 
    ISSN: 1573-6881
    Keywords: Mitochondria ; transport ; carrier proteins ; reconstitution ; kinetics ; liposomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Eight mitochondrial carrier proteins were solubilized and purified in the authors' laboratories using variations of a general procedure based on hydroxyapatite and Celite chromatography. The molecular mass of all the carriers ranges between 28 and 34 kDa on SDS-PAGE. The purified carrier proteins were reconstituted into liposomes mainly by using a method of detergent removal by hydrophobic chromatography on polystyrene beads. The various carriers were identified in the reconstituted state by their kinetic properties. A complete set of basic kinetic data including substrate specificity, affinity, interaction with inhibitors, and activation energy was obtained. These data closely resemble those of intact mitochondria, as far as they are available from the intact organelle. Mainly on the basis of kinetic data, the asymmetric orientation of most of the reconstituted carrier proteins were established. Several of their functional properties are significantly affected by the type of phospholipids used for reconstitution. All carriers which have been investigated in proteoliposomes function according to a simultaneous (sequential) mechanism of transport; i.e., a ternary complex, made up of two substrates and the carrier protein, is involved in the catalytic cycle. The only exception was the carnitine carrier, where a ping-pong mechanism of transport was found. By reaction of particular cysteine residues with mercurial reagents, several carriers could be reversibly converted to a functional state different from the various physiological transport modes. This “unphysiological” transport mode is characterized by a combination of channel-type and carrier-type properties.
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  • 75
    ISSN: 1573-6857
    Keywords: development ; P element ; plasmid rescue ; RFLP ; somatic cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transposition of the P element duringDrosophila ontogenesis was monitored. A modified P element was transposed by the PΔ2-3 transposase source. P elements inserted into the genome were cloned by the plasmid rescue at various developmental stages of the G1 hybrid to trace events in somatic cells. The transposed elements were directly counted by analyzing RFLP of genomic DNA fragments flanking the P elements. Transposition began from the late embryonic stage, but occurred rarely. Frequent transposition was observed from the late third instar to early pupal stage. From these results, transposition of the P element would appear to be affected by the developmental state of somatic host cells.
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  • 76
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    Antonie van Leeuwenhoek 63 (1993), S. 225-235 
    ISSN: 1572-9699
    Keywords: kinetics ; transport ; collision frequency ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Traditional concepts of nutrient uptake and growth kinetics as linked by cell yield are presented. Phenomena affecting the kinetics are examined along with a discussion of those which lead to ambiguity. Concepts of flux control are presented to help understand the distribution of material along metabolic pathways. Specific affinity is described to relate nutrient accumulation rates to transporter density. It is shown to be a primary kinetic constant and the best available index of nutrient collection ability. As an aid to understanding, specific affinity is reexpressed in terms of membrane permeability. Formulations of nutrient transport rate as a function of cellular composition, particularly transporter and enzyme content and known as janusian kinetics, are described as an improvement to specific affinity theory. Procedures for quantified unidirectional fluxes are reviewed to identify the difference between gross and net transport rates of substrate. Collision frequency theory is used to show that in addition to total biomass, cell size and transporter density should also be included in rate equations describing microbial growth. Theory diversity suggests that one reason for microbial metabolic is that the likelihood of additional collisions of substrate molecules with a cell surface, after an initial collision, requires only a sparse distribution of transporter sites for maximal rate, leaving room for additional transporters able to collect other substrate types.
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  • 77
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    Antonie van Leeuwenhoek 63 (1993), S. 353-373 
    ISSN: 1572-9699
    Keywords: aeration ; bioreactor ; growth ; inhibition ; kinetics ; metabolism ; microorganism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The optimization of fermentation processes depends to a large extent on the modelling of microbial activity under complex environmental conditions where aeration is an important limiting and control factor. Simple relationships are used to establish the sensitivity of cultures to oxygen stress. Specific limitation coefficients which can be determined in laboratory reactors allow a projection to industrial operation and the definition of appropriate aeration and agitation profiles. Optimum control can be assured on the basis of directly measurable process parameters. This is shown for the case of ethanol production usingS. cerevisiae at high cell dry weight concentrations.
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  • 78
    ISSN: 1572-9729
    Keywords: cometabolism ; cosubstrate ; 4-chlorophenol ; inhibition ; kinetics ; modeling ; monooxygenase ; phenol ; substrate interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Batch experiments on the simultaneous utilization of phenol (primary substrate) and 4-chlorophenol (cometabolic secondary substrate) demonstrated two critical substrate interactions. First, the cometabolic degradation of 4-chlorophenol was proportional to the rate of phenol oxidation, which provided the electrons for the initial monooxygenase reaction. Second, 4-chlorophenol inhibited the oxidation of the primary substrate, phenol. Modeling analyses of the degradation of phenol alone and of phenol and 4-chlorophenol together showed that the proportionality between phenol and 4-chlorophenol degradation rates averaged 0.1 mg 4-CP/mg phenol, which corresponds to 0.5% of the electrons generated by phenol oxidation being used as a cosubstrate for the monooxygenase reaction of 4-chlorophenol. In addition, modeling analyses suggest that 4-chlorophenol was a noncompetitive inhibitor of phenol oxidation for high phenol concentrations, but a competitive inhibitor for low phenol concentrations.
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  • 79
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    Plant growth regulation 12 (1993), S. 229-236 
    ISSN: 1573-5087
    Keywords: gene ; QTL ; RAPD ; RFLP ; random amplified polymorphic DNA ; restriction fragment length polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract DNA genetic markers, such as restriction fragment length polymorphisms (RFLPs) and random amplified polymorphic DNA markers (RAPDs), are powerful tools for studying the genetics of plant growth and development. DNA markers are defined sequences of DNA that can be used in traditional linkage mapping. Using DNA marker technology, scientists can uncover relationships between cloned cDNA sequences and classically characterized genes. DNA markers make it possible to dissect the contributions of multiple genetic loci underlying complex developmental processes. Moreover, changes in genome organization that occur during development or in response to environmental signals can be monitored using RFLP technology. In the future, it may be possible to clone any gene based solely on its map position. This will involve the use of tightly linked DNA markers as entry points for chromosome walking, in which a series of overlapping genomic clones reaching from the tightly linked DNA marker to the gene of interest are identified.
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  • 80
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    Euphytica 73 (1993), S. 191-198 
    ISSN: 1573-5060
    Keywords: gene-tagging ; marker-assisted-selection ; synteny RAPD ; RFLP ; Near-isogenic-lines ; linkage-maps ; genetic dissection ; gene-specific-markers ; recombinant-inbred-lines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An understanding of the genetic basis of characters of commercial importance is critical if a breeder is attempting to move such characters into breeding material. A number of particularly interesting characters or genes have been identified in cool season food legumes, and in pea many of these have been “tagged” by molecular markers such as allozyme or DNA polymorphisms. This process of mapping and tagging genes has been greatly accelerated by recent developments in molecular biology. It appears that markers will soon be available for many genes in lentil, faba bean, and chickpea and that genetic knowledge developed in one crop will have significant applications in the other cool season food legumes.
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  • 81
    ISSN: 1573-5079
    Keywords: hydrogen peroxide ; hydroxylamine ; kinetics ; manganese ; oxygen release ; photosynthesis ; Photosystem II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Flash-induced amperometric signals were measured with a Joliot-type O2 rate electrode in spinach Photosystem II (PS II) membrane fragments exposed to very low concentrations of added hydroxylamine or hydrogen peroxide. In both cases ‘anomalous O2 signals’ were observed on the first two flashes, and oscillating four-flash patterns were observed on subsequent flashes. The anomalous signals were eliminated in the presence of catalase but not EDTA. The rise times of the O2-release kinetics associated with the anomalous signals were slow (ca. 20 ms with NH2OH and ca. 120 ms with H2O2) compared to the kinetics of O2 release on subsequent flashes and in control membranes (3–6 ms). It is proposed that when the intact PS II O2-evolving complex is perturbed with small concentrations of added reductant, H2O2 can gain access and bind to the complex. Bound H2O2 can then reduce lower S states in some centers leading to anomalous O2 signals on the first two flashes. A model is presented to explain both types of anomalous O2 production. Oxygen observed on the third and subsequent flashes is due to the normal photosynthetic O2-evolution process arising from the S3-state. Anomalous O2 production could be a protective mechanism in PS II centers subjected to stress conditions.
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  • 82
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    Plant cell, tissue and organ culture 34 (1993), S. 191-198 
    ISSN: 1573-5044
    Keywords: yellow-poplar ; Chinese tuliptree ; micropropagation ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Propagation of hybrids between the Chinese tuliptree (Liriodendron chinense) and the North American yellow-poplar (Liriodendron tulipiferea) could be greatly accelerated with a highly productive somatic embryogenesis system. Flowers were collected from a single Chinese tuliptree and the anthers used for controlled pollinations of 4 yellow-poplar mother trees. Aggregates of samaras resulting from the pollinations were harvested 8 weeks post-pollination. Following surface disinfestation, samaras were dissected and embryos and endosperm were cultured together on a semisolid induction medium containing 9.0 μM 2,4-dichlorophenoxyacetic acid and 1.1 μM benzyladenine. Following 2–3 months on induction medium, an average of 15.6 percent of the explants produced either somatic embryos or proembryogenic masses. Compared to pure yellow-poplar embryogenic cultures, putative hybrid cultures tended not to maintain growth as proembryogenic masses while exposed to auxin, instead proliferating via repetitive embryogenesis as globular-stage embryos. Four to six weeks following transfer of globular embryos to basal medium, mature embryos were produced from the putative hybrid lines. Mature embryos germinated following transfer to basal medium lacking casein hydrolysate. Plantlets survived transfer to potting mix and acclimatization to greenhouse conditions. Verification of the hybrid nature of the embryogenic lines and somatic embryo-derived plantlets was accomplished by Southern hybridization analysis with a species-specific DNA marker.
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  • 83
    ISSN: 1435-232X
    Keywords: CYP11B1 ; RFLP ; congenital adrenal hyperplasia ; ethnic group
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Restriction fragment length polymorphisms (RFLPs) of the CYP11B1 gene were studied in Japanese using cDNA clone P450c11 as a probe. Genomic DNAs from 60 unrelated Japanese individuals were digested with 8 different restriction enzymes and analyzed by Southern blot hybridization. Two RFLPs were detected inMspI digests of the DNA. One(A) was characterized by polymorphic bands at 3.4 and 2.5 kilobasepairs (kb) and the other (B) by polymorphic bands at 1.7 and 1.2 kb. The third RFLP was observed inPvuII-digested samples and was polymorphic at 5.8 and 4.0 kb bands. Two of the three RFLPs found, RFLP (A) and (C), have not been described in the only previous report which was based on Caucasian samples. We also examined the RFLPs of a 3 generation family of 11β-hydroxylase deficiency caused by an abnormality of the CYP11B1 gene. All the family members were homozygous in all three RFLPs and was thus not informative.
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  • 84
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    World journal of microbiology and biotechnology 9 (1993), S. 357-360 
    ISSN: 1573-0972
    Keywords: Candida utilis ; inhibition ; kinetics ; regulation ; sugar ; transport ; xylose ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Low-affinity (K m=67.6±3.2 mM) and high-affinity (K m=1.9±1.2 mM) D-xylose transport occur in Candida utilis grown, respectively, on D-glucose or D-xylose. Starvation of glucose-grown cells decreases the K m value (10.5±2.6 mm). The high-affinity system appearing during starvation required protein synthesis and it was inactivated when cells were exposed to glucose, by a process independent of protein synthesis. High-affinity transport was accompanied by transient alkalinization of yeast suspensions, indicating that it is a proton symport, whereas low-affinity transport was not. Both systems, however, were inhibited by metabolic inhibitors and by replacing H2O in the transport assay with D2O, indicating that both may be proton symports. Glucose and acetic acid also inhibited both high-and low-affinity xylose transport.
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    World journal of microbiology and biotechnology 9 (1993), S. 479-482 
    ISSN: 1573-0972
    Keywords: Benzyl viologen ; dichloromethane ; inhibitor ; kinetics ; nitrous oxide ; nitrous oxide reductase ; tetrachloromethane ; trichloromethane ; Wolinella succinogenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Nitrous oxide reductase from Wolinella succinogenes was tested for benzyl viologen cation (BV+)-chlorinated methane oxidoreductase activity, using di-, tri- and tetra-chloromethanes, and for the inhibition of BV+-N2O oxidoreductase activity by these chloromethanes. No BV+-chlorinated methane oxidoreductase activity was detected. Any such activity, if it exists, must be less than 0.1% of the BV+-N2O oxidoreductase activity of the enzyme. Inhibition of the BV+-N2O oxidoreductase activity by dichloromethane was detected and was apparently reversible and non-competitive, as is the case with the small metal-ligand type inhibitors of the enzyme (e.g. acettlene, azide, cyanide and carbon monoxide). Trichloromethane was a weaker inhibitor and inhibition was not detected with tetrachloromethane.
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  • 86
    ISSN: 1435-232X
    Keywords: RFLP ; BamH1 ; prenatal diagnosis ; β-thalassemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of restriction fragment length polymorphism (RFLP) at theBamH1 site of the β-globin gene was investigated in the Chinese, Indian, and Malay race in Singapore. The sample comprised of 183 normal individuals and 35 β-thalassemia carriers in which 13 were couples with at least one β-major child. The results from this study indicate thatBamH1 polymorphism will be informative in 22% of pregnancies at risk for β-thalassemia major in Chinese, 19% in Malays and 7% in Indians. In prenatal diagnosis usingBamH1 polymorphism for one β-major affected family, the fetus was diagnosed to be normal or β-carrier. The validity ofBamH1 polymorphism in the exclusion of β-thalassemia major was subsequently confirmed at birth by globin chain biosynthesis.
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