Isotope trapping

W. Cheng, D. C. Coleman, C. R. Carroll, and C. A. Hoffman, Investigating shortterm carbon flows in the rhizosphere of different plant species using isotopic trapping. Ai>ron. J. 86 782 (1994). 

Yan, Z. et al. 2005. Rapid detection and characterization of minor reactive metabolites using stable-isotope trapping in combination with tandem mass spectrometry. Rapid Commun. Mass Spectrom. 19 3322. 

Computer simulations also point to the regulatory potential of these non-productive complexes. See Deadend Complexes Inhibition Nonproductive Complexes Product Inhibition Substrate Inhibition Isotope Trapping Isotope Exchange at Equilibrium Enzyme Regulation... 

ISOTOPE EXCHANGE AT EQUILIBRIUM ISOTOPE TRAPPING LACTATE DEHYDROGENASE LIGAND EXCLUSION MODEL NONPRODUCTIVE COMPLEXES PRODUCT INHIBITION SUBSTRATE INHIBITION... 

COMMITMENT-TO-CATALYSIS RAPID EQUILIBRIUM ASSUMPTION KINETIC ISOTOPE EFFECT ISOTOPE TRAPPING COMPARTMENTAL ANALYSIS CATENARY MODEL... 

ISOTOPE TRAPPING BOROHYDRIDE REDUCTION y-Glutamyl phosphate reductase,... 

ISOTOPE TRAPPING STICKY SUBSTRATES LIGAND EXCLUSION MODEL LIGAND FIELD SPLITTING CRYSTAL FIELD SPLITTING LIGAND-INDUCED CONFORMATIONAL CHANGE... 

BIOCHEMICAL NOMENCLATURE STEROID SULFOTRANSFERASE STICKY SUBSTRATES ISOTOPE TRAPPING STIFFNESS (or Stiffness Instability)... 

ISOTOPE TRAPPING STICKY SUBSTRATES Substrate-induced conformational change, INDUCED FIT MODEL SUBSTRATE INHIBITION ABORTIVE COMPLEX FORMATION LACTATE DEHYDROGENASE LEE-WILSON EQUATION... 

Yan, Z., and Caldwell, G. W. (2004). Stable-isotope trapping and high-throughput screenings of reactive metabolites using the isotope MS signature. Anal. Chem. 76 6835-6847. 

Data from existing devices on the amounts of H isotopes trapped in the wall are now becoming available. For example, in Fig. 13 are data from PLT exposures for stainless steel and Si samples81). One notes that nearly all the D trapped in stainless... 

Cheng W. X., Coleman D. C., Carroll C. R., and Hoffman C. A. (1994) Investigating short-term carbon flows in the rhizo-spheres of different plant species, using isotopic trapping. Agron. J. 86(5), 782-788. 

It is crucial in performing TS analysis to know exactly which step of the reaction the experimental KIEs reflect. Using isotope-trapping experiments, it is possible to demonstrate whether formation of the Michaelis complex, E-S, is kinetically significant, and if necessary, to find conditions where it is not. However, internal steps can also complicate the interpretation of KIEs. These can include, but are not limited to (1) establishment of equilibria between different enzyme-bound intermediates, (2) isotopically insensitive steps, such as conformational changes in the enzyme or substrate, or (3) substrate channeling. 

KIEs were determined for a stem-loop RNA substrate A-IO" and an analogous DNA substrate, dA-10 (Table 8). In both these cases, hydrolysis reaction proceeded through a stepwise Dn An mechanism. Isotope-trapping experiments showed that substrate binding was not kinetically significant however, the experimental KIEs with A-10 as substrate were inconsistent with any mechanism where only chemical steps were kinetically significant, implying equilibrium formation of an RTA ox-ocarbenium ion adenine complex, followed by an isotopically insensitive step. In contrast, the KIEs for dA-10 were consistent with a Dn An mechanism. 

PMM/PGM is unable to prevent loss of the intermediate during every catalytic cycle. Isotope-trapping studies demonstrated that approximately 1 out of 15 times that the intermediate is produced, it is lost from the active site. It is not known whether the reorientation of the intermediate is a purely stochastic event or if the enzyme directs it in any way. Random rotational motion of the intermediate would be expected to occur rapidly enough that it would not impede the reaction. However, 50% of the time the intermediate would reseat in the orientation in which it began, so there would be a loss of efficiency. On the contrary, it is difficult to... 

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