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  • Chemistry  (802)
  • ASTROPHYSICS  (208)
  • Life Sciences (General)  (198)
  • 1
    Digitale Medien
    Digitale Medien
    Multivariate analysis of a data matrix containing A-DNA and B-DNA dinucleoside monophosphate steps: Multidimensional Ramachandran plots for nucleic acids (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 695-715 
    Details
    ISSN: 0192-8651
    Schlagwort(e): nucleic acid ; multivariate analysis ; Ramachandran plots ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A method to construct the equivalent of multidimensional Ramachandran plots for nucleic acids on the basis of singular value decomposition (SVD) is presented. For this purpose, a data matrix containing 244 DNA dinucleoside monophosphate steps, represented by nine torsion angles, was decomposed into a score and loading matrix. It is shown that biplots, containing both score points and loading vectors, provide a simple tool to interpret the principles of DNA class separation. Scores separate the data matrix into one A-DNA class, two different B-DNA classes, and one so-called crankshaft class. Loading vectors correlate torsion angles. The projections of scores on loading vectors indicate which torsion angles play a dominant role in DNA class separation. The results of the biplots are supported by (simple) physical interpretations. From a three-dimensional score space the nine original torsion angles can be reconstructed. Hence, the potential to create the multidimensional equivalent of a Ramachandran plot is available; that is, forbidden and accessible regions in the reduced space reflect these same regions in the nine-dimensional original space.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 695-715, 1998
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Synthesis of AcPheLeuNH2 by α-chymotrypsin in TTAB reversed micelles: Application of response surface methodology to the optimization of the system (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1031-1042 
    Details
    ISSN: 0006-3592
    Schlagwort(e): peptide synthesis ; alcohol ; chemical modification ; α-chymotrypsin ; reverse micelles ; response ; surface methodology ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The influence of the long chain alcohols, hexanol, octanol, and decanol, as cosurfactants of the reverse micellar system of tetradecyltrimethylammonium bromide on the α-chymotrypsin-mediated AcPheLeuNH2 synthesis was studied. The effect of temperature, buffer molarity, pH, and substrate concentration was also evaluated. The enzyme was chemically modified and the effect of this modification upon the enzyme activity was also analyzed. Octanol allowed a higher activity for both enzyme forms. The peptide synthesis/substrate hydrolysis ratio is independent of the long chain alcohol used. The chemical modification decreases the α-chymotrypsin activity under the system conditions studied, but increases the initial velocity of peptide synthesis relative to the ester substrate hydrolysis. The response surface methodology was applied to optimize the dipeptide synthesis in the system containing octanol as cosurfactant. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260431106
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  • 3
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    Patterns of auxin and abscisic acid movement in the tips of gravistimulated primary roots of maize (1996)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Because both abscisic acid (ABA) and auxin (IAA) have been suggested as possible chemical mediators of differential growth during root gravitropism, we compared with redistribution of label from applied 3H-IAA and 3H-ABA during maize root gravitropism and examined the relative basipetal movement of 3H-IAA and 3H-ABA applied to the caps of vertical roots. Lateral movement of 3H-ABA across the tips of vertical roots was non-polar and about 2-fold greater than lateral movement of 3H-IAA (also non-polar). The greater movement of ABA was not due to enhanced uptake since the uptake of 3H-IAA was greater than that of 3H-ABA. Basipetal movement of label from 3H-IAA or 3H-ABA applied to the root cap was determined by measuring radioactivity in successive 1 mm sections behind the tip 90 minutes after application. ABA remained largely in the first mm (point of application) whereas IAA was concentrated in the region 2-4 mm from the tip with substantial levels found 7-8 mm from the tip. Pretreatment with inhibitors of polar auxin transport decreased both gravicurvature and the basipetal movement of IAA. When roots were placed horizontally, the movement of 3H-IAA from top to bottom across the cap was enhanced relative to movement from bottom to top whereas the pattern of movement of label from 3H-ABA was unaffected. These results are consistent with the hypothesis that IAA plays a role in root gravitropism but contrary to the idea that gravi-induced asymmetric distribution of ABA contributes to the response.
    Schlagwort(e): Life Sciences (General)
    Materialart: Plant growth regulation (ISSN 0167-6903); 20; 253-8
    Format: text
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  • 4
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    Correlations between gravitropic curvature and auxin movement across gravistimulated roots of Zea mays (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We compared the kinetics of auxin redistribution across the caps of primary roots of 2-day-old maize (Zea mays, cv Merit) seedlings with the time course of gravitropic curvature. [3H] indoleacetic acid was applied to one side of the cap in an agar donor and radioactivity moving across the cap was collected in an agar receiver applied to the opposite side. Upon gravistimulation the roots first curved upward slightly, then returned to the horizontal and began curving downward, reaching a final angle of about 67 degrees. Movement of label across the caps of gravistimulated roots was asymmetric with preferential downward movement (ratio downward/upward = ca. 1.6, radioactivity collected during the 90 min following beginning of gravistimulation). There was a close correlation between the development of asymmetric auxin movement across the root cap and the rate of curvature, with both values increasing to a maximum and then declining as the roots approached the final angle of curvature. In roots preadapted to gravity (alternate brief stimulation on opposite flanks over a period of 1 hour) the initial phase of upward curvature was eliminated and downward bending began earlier than for controls. The correlation between asymmetric auxin movement and the kinetics of curvature also held in comparisons between control and preadapted roots. Both downward auxin transport asymmetry and downward curvature occurred earlier in preadapted roots than in controls. These findings are consistent with suggestions that the root cap is not only the site of perception but also the location of the initial redistribution of effectors that ultimately leads to curvature.
    Schlagwort(e): Life Sciences (General)
    Materialart: Plant physiology (ISSN 0032-0889); 92; 792-6
    Format: text
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  • 5
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    Effect of calmodulin antagonists on the growth and graviresponsiveness of primary roots of maize (1992)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-08-15
    Beschreibung: We examined the effect of calmodulin (CaM) antagonists applied at the root tip on root growth, gravity-induced root curvature, and the movement of calcium across the root tip and auxin (IAA) across the elongation zone of gravistimulated roots. All of the CaM antagonists used in these studies delayed gravity-induced curvature at a concentration (1 micromole) that did not affect root growth. Calmodulin antagonists (〉 or = 1 micromole) inhibited downward transport of label from 45Ca2+ across the caps of gravistimulated roots relative to the downward transport of 45Ca2+ in gravistimulated roots which were not treated with CaM antagonists. Application of CaM antagonists at the root tip (〉 or = 1 micromole) also decreased the relative downward movement of label from 3H-IAA applied to the upper side of the elongation zone of gravistimulated roots. In general, tip application of antagonists inhibited neither the upward transport of 45Ca2+ in the root tip nor the upward movement of label from 3H-IAA in the elongation zone of gravistimulated roots. Thus, roots treated with CaM antagonists 〉 or = 1 micromole become less graviresponsive and exhibit reduced or even a reversal of downward polarity of calcium transport across the root tip and IAA transport across the elongation zone. The results indicate that calmodulin-regulated events play a role in root gravitropism.
    Schlagwort(e): Life Sciences (General)
    Materialart: Plant growth regulation (ISSN 0167-6903); 11; 4; 419-27
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
    Digitale Medien
    Digitale Medien
    A model reaction for an epoxy resin cured with an aromatic amine (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 599-602 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1991.080290417
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  • 7
    Digitale Medien
    Digitale Medien
    Separation of metal complexes by on-line coupled LC-GC (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 170-172 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Liquid chromatography ; Gas chromatography ; LC/GC ; On-line coupling ; Metal complexes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The on-line coupled LC-GC technique was applied to the analysis of several metal chelates of N,N-diethyldithiocarbamic acid. A 10-port valve interface was used to couple the LC and GC instruments. Conditions during sample transfer into the GC gave fully concurrent solvent evaporation. The chelates investigated were separated with a short apolar fused silica column. LC preseparation was made with cyano or amino phases using a hexane/dichloromethane mixture as eluent. On-line LC-GC combination seems to be very suitable for the separation of the metal chelates studied.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240130306
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  • 8
    Digitale Medien
    Digitale Medien
    Application of 15N spectroscopy and dynamic NMR to the study of ureas, thioureas and their lewis acid adducts (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 13 (1980), S. 396-402 
    Details
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Rotational barriers and 15N chemical shifts have been measured in a number of ureas and thioureas. As anticipated on the basis of the 15N shifts, several previously unobserved rotational barriers could be detected by using lanthanide reagents or a high field spectrometer. Nearly constant effects on both the rotational activation energy and the 15N shift are produced on going from ureas to the corresponding thioureas, and correlations are found between the ΔG
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1270130603
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  • 9
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    Alpha-amylase from the Hyperthermophilic Archaeon Thermococcus thioreducens (2003)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-18
    Beschreibung: Extremophiles are microorganisms that thrive in, from an anthropocentric view, extreme environments such as hot springs. The ability of survival at extreme conditions has rendered enzymes from extremophiles to be of interest in industrial applications. One approach to producing these extremozymes entails the expression of the enzyme-encoding gene in a mesophilic host such as E.coli. This method has been employed in the effort to produce an alpha-amylase from a hyperthermophile (an organism that displays optimal growth above 80 C) isolated from a hydrothermal vent at the Rainbow vent site in the Atlantic Ocean. alpha-amylases catalyze the hydrolysis of starch to produce smaller sugars and constitute a class of industrial enzymes having approximately 25% of the enzyme market. One application for thermostable alpha-amylases is the starch liquefaction process in which starch is converted into fructose and glucose syrups. The a-amylase encoding gene from the hyperthermophile Thermococcus thioreducens was cloned and sequenced, revealing high similarity with other archaeal hyperthermophilic a-amylases. The gene encoding the mature protein was expressed in E.coli. Initial characterization of this enzyme has revealed an optimal amylolytic activity between 85-90 C and around pH 5.3-6.0.
    Schlagwort(e): Life Sciences (General)
    Materialart: American Society for Gravitational and Space Biology Conference; Nov 12, 2003 - Nov 16, 2003; Huntsville, AL; United States
    Format: text
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  • 10
    Digitale Medien
    Digitale Medien
    Fast atom bombardment and tandem mass spectrometry for structure determination: Remote site fragmentation of steroid conjugates and bile salts (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 89-98 
    Details
    ISSN: 0887-6134
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of 35 steroid conjugates (sulfates and glucuronides) and bile salts were investigated by using fast atom bombardment and tandem mass spectrometry. Collisional activation of the [M - H]- anions of sulfate conjugates and bile salts predominantly yields fragment ions arising by reactions occurring remote from the charge site. These reactions are sometimes sensitive to differences in stereochemistry at positions remote from the charge site and are useful for positional isomer differentiation. On the other hand, collisional activation of the [M - H]- anions of the glucouronide conjugates leads primarily to charge-driven fragementations.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200150206
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