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1.
Of concern are systems of linear evolution equations
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Cooperative conformational transitions of proteins and nucleic acids are of decisive importance to many processes of molecular biology, and particularly to their regulation. They proceed via numerous interdependent elementary processes, and their kinetics are therefore often complicated. They are frequently also very fast. However, kinetic analyses can be carried out by chemical relaxation methods. The theoretical interpretation is comparatively simple in the case of linear biopolymers. When the linear Ising model extended for kinetics was applied to model peptides and polynucleotides, it provided an insight into the fundamental principles of cooperative transformations. 相似文献
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V. Kolarik M. Juez-Lorenzo W. Engel N. Eisenreich 《Fresenius' Journal of Analytical Chemistry》1993,346(1-3):252-254
Summary The formation of -Fe2O3 on Fe3O4 during the oxidation of iron below 570°C occurs very slowly and the scales are so thin that they cannot be detected by microscopy. X-ray diffraction with grazing incidence, equipped with a high temperature device, allows an in situ study of the -Fe2O3 formation even the initial reactions. The formation of -Fe2O3 was studied in isothermal experiments at 400, 450, 500 and 550°C. -Fe2O3 could already be detected at the beginning of the experiments. The difference method, a numerical treatment for kinetic evaluation, yields curves showing the growth of the -Fe2O3 layer. Fitting the parabolic time law to these curves yields the rate constants. 相似文献
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LetP be a finite partially ordered set. The lengthl(x) of an elementx ofP is defined by the maximal number of elements, which lie in a chain withx at the top, reduced by one. Letw(P) (d(P)) be the maximal number of elements ofP which have the same length (which form an antichain). Further let
. The numbers
and
as well as all partially ordered sets for which these maxima are attained are determined. 相似文献
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Rate coefficients for the collisional quenching of O2*(1Δg) by NO and CO2 at 2–8 torr and 300 K have been determined. kNO = (2.48 ± 0.23) × 10?17 cm3 molecule?1 s?1 and = (2.56 ± 0.12) × 10?18 cm3 molecule?1 s?1. 相似文献
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Multiresidue screening of pesticides in foods using retention time locking, GC-AED, database search, and GC/MS identification 总被引:1,自引:0,他引:1
Fruit and vegetable extracts were screened for over 400 pesticides by gas chromatography with atomic emission detection (GC-AED) and an experimental database. A technique called retention time locking was used to match GC-AED and GC with mass spectrometry (MS) retention times to those of the database. Samples were analyzed for sulfur, nitrogen, phosphorus, and chlorine by GC-AED. Possible pesticides were suggested by database search and identified by GC/MS. Forty-four pesticide standards were analyzed to determine the precision of retention time matching and the accuracy of the database search. Analytical retention times matched database retention times within 0.32 min. Using elemental criteria, the database search identified the correct compound for 41 of 44 pesticide standards. For blind spikes of fruit and vegetable extracts, the database suggested 22 of 26 spiked pesticides as matches. Nineteen were identified by GC/MS. The combination of retention time locking, GC-AED, database search, and GC/MS can be a powerful tool for identifying pesticides in a complex matrix. 相似文献
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Abstract The ability of phosphonic acid analogues isosteric with natural phosphate esters to Serve as inhibitors of enzymatic phosphate hydrolysis has been documented in a wide variety of systems.1 The use of such an analogue in place of the natural phosphate ester provides a functionality which the enzyme may not be able to distinguish from the natural ester, but which is incapable of being hydrolyzed. In some instances the use of hydroxymethylene analogues has resulted in a greater degree of recognition, and resultant inhibition of hydrolytic activity, than the simple methylene analogues.2 On this basis, the methylene and hydroxymethylene analogues of tyrosine O-phosphate appear to be reasonable candidates to Serve as inhibitors for phosphoprotein phosphatases and alkaline phosphatase, and as probes for biological mechanisms. 相似文献
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