منابع مشابه
Value of general Acid-base catalysis to ribonuclease a.
Bovine pancreatic ribonuclease A (RNase A; EC 3.1.27.5) has been one of the most studied of all enzymes.’ RNase A efficiently catalyzes the cleavage of RNA.2 Early X-ray diffraction analyses revealed that the active site of RNase A contains two histidine residues, histidine 12 (H12) and histidine 119 (H1 19).3 The results of chemical modification4 and pHrate’ studies are consistent with an enzy...
متن کاملConcerted General Base and Bifunctional General Acid Catalysis of the Aminolysis of Phenyl Acetate by Pyrazole'
The reaction of phenyl acetate with pyrazole is catalyzed by general bases and by bifunctional general acids. The Br~lnsted plot for general base catalysis shows downward curvature. It is consistent with either a Hammond effect on proton transfer, as described by a positive coefficient p x = a/3/-apKAH, or separate lines with p = 0.65 for cacodylate and substituted acetate monoanions and /3 = 0...
متن کاملAcid-base Interactions 10.1 GENERAL CONCEPT OF ACID-BASE INTERACTIONS
Acid-base interactions have found numerous applications in research dealing with adsorption of molecules of liquids on the surfaces of solids. The main focus of this research is to estimate the thermodynamic work of adhesion, determine mechanism of interactions, analyze the morphology of interfaces and various surface coatings, develop surface modifiers, study the aggregation of macromolecular ...
متن کاملChemical rescue, multiple ionizable groups, and general acid-base catalysis in the HDV genomic ribozyme.
In the ribozyme from the hepatitis delta virus (HDV) genomic strand RNA, a cytosine side chain is proposed to facilitate proton transfer in the transition state of the reaction and, thus, act as a general acid-base catalyst. Mutation of this active-site cytosine (C75) reduced RNA cleavage rates by as much as one million-fold, but addition of exogenous cytosine and certain nucleobase or imidazol...
متن کاملNucleobase-mediated general acid-base catalysis in the Varkud satellite ribozyme.
Existing evidence suggests that the Varkud satellite (VS) ribozyme accelerates the cleavage of a specific phosphodiester bond using general acid-base catalysis. The key functionalities are the nucleobases of adenine 756 in helix VI of the ribozyme, and guanine 638 in the substrate stem loop. This results in a bell-shaped dependence of reaction rate on pH, corresponding to groups with pK(a) = 5....
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ژورنال
عنوان ژورنال: Journal of Chemical Education
سال: 2007
ISSN: 0021-9584,1938-1328
DOI: 10.1021/ed084p38