نتایج جستجو برای: 2h isotope shift
تعداد نتایج: 178729 فیلتر نتایج به سال:
ethanol. Kinetic measurements on treated enzyme that had been separated from the modifying agent by gel filtration showed that K, values were unaffected and that inactivation was purely a V,,,. phenomenon. Thus chemical modification leads in both of the cases studied to totally inactive enzyme. The action of phenylglyoxal is presumably on an essential arginine residue@), which may be at, or clo...
Heavy-enzyme isotope effects (15N-, 13C-, and 2H-labeled protein) explore mass-dependent vibrational modes linked to catalysis. Transition path-sampling (TPS) calculations have predicted femtosecond dynamic coupling at the catalytic site of human purine nucleoside phosphorylase (PNP). Coupling is observed in heavy PNPs, where slowed barrier crossing caused a normal heavy-enzyme isotope effect (...
High-resolution spectroscopy of xenon is performed on four transitions from the 5p S0 ground state to the 5d8@3/2#1 , 8d@1/2#1 , 8d@3/2#1, and 7s8@1/2#1 excited states ( j l-coupling notation! by means of 1VUV 11UV photoionization spectroscopy. Spectra of all nine stable isotopes are resolved enabling the determination of the hyperfine splittings and isotope shifts. Magnetic dipole ~for both Xe...
Angle-resolved photoemission spectroscopy with low-energy tunable photons along the nodal direction of oxygen isotope substituted Bi(2)Sr(2)CaCu(2)O(8+delta) reveals a distinct oxygen isotope shift near the electron-boson coupling "kink" in the electronic dispersion. The magnitude (a few meV) and direction of the kink shift are as expected due to the measured isotopic shift of phonon frequency,...
The isotope shift between singly-charged Eu and Eu in the 4f(S)6s S 4 /−− 4f (S)6p1/2 J = 4 transition at 4129 ] has been measured using fast ion beam-laser technique. This Eu line has attracted interest in connection with efforts of obtaining a cosmochronometer based on observed Th/Eu abundance ratios. Knowledge of the isotope shift is of importance in order to check that contaminations from l...
This paper reports experimental results on the low-temperature (<100 oC) 18O and 2H fractionation of goethite (hematite)-water in a closed system. Both goethite (-FeOOH) and hematite (-Fe2O3) exhibited closer fractionation factor values but the Hematite-Water value is slightly higher (~0.9932) than the Goethite-Water (~0.9924) for the 18O isotope. The average fractionation factor (1000ln...
A combined experimental and theoretical investigation of the deuterium isotope effects on the bacterial luciferase reaction is described. The experimental studies focus on determining if the unusual aldehydic deuterium isotope effect of approximately 1.5 observed in these reactions is an intrinsic isotope effect resulting from a single rate-limiting step or is a composite of multiple rate-limit...
Activation of the zymogen of collagenase by Ehrlich-ascites-tumour-cell-surface trypsin-like enzyme.
dehydrogenase (Rose et al., 1969). The ,H labelling of ['HI lactate in 2H,0 and the 'H labelling of [2H]lactate in 'H,O has been studied. A comparison of the exchange in whole cells and lysates has also been undertaken. The detailed measurement of exchange kinetics permitted by the n.m.r. technique has revealed the dependence of the exchange on the different enzyme activities and on the triose ...
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