Nuclear magnetic resonance solution hydrolysis

Wen the and Cordes [187] carried out a nuclear magnetic resonance study of the acid catalyzed hydrolysis of dimethyl acetonal in D20—CD3OD solution, viz. 

Dissolved amino acids are commonly divided into two pools that must be analyzed separately DFAA exist as individual monomers in solution, while DCAA are defined operationally as additional amino acids liberated by acid hydrolysis. DCAA are thus presumably present mostly as polypeptides, a supposition supported in at least the high molecular weight (HMW) fraction by N-nuclear magnetic resonance (NMR) spectroscopy data (discussed below). The operational nature of the DFAA versus DCAA definitions means that amino acids liberated from difficult matrixes (e.g., humic substances) also could make up a part of DCAA. Total hydrolysable amino acid (THAA) is another term commonly used to denote both pools together, when the sample is hydrolyzed but DFAA are not independently determined. Because the DFAA pool is typically much smaller than DCAA, THAA values are often assumed to be similar to DCAA. 

The second objective Is to examine the Influence of reversed micellar solution parameters, Including the Interaction of substrates with the surfactant Interface, on observed Initial rate kinetics. This Is of Interest because a number of reports have Indicated that enzymes In reversed micellar solutions exhibit an enhanced reactivity, or "super-activity" (7-9I. As a model system, the hydrolysis reactions of synthetic substrates of a-chymotrypsln were studied In a reversed micellar solution. Nuclear magnetic resonance was used to examine the Interactions between these substrates and the micellar environment. 

Sinisterra et al. [85] reported the stereoselective hydrolysis of racemic A-benzoyl-phenylalanine methyl ester catalyzed by PEG-chymotrypsin in aqueous methanolic solution. The hydrolyzed products, A -benzoylphenylalanine, obtained by PEG-chymotrypsin as well as unmodified enzyme were extracted from the reaction mixture and analyzed by both polarimetry and proton nuclear magnetic resonance spectrophotometry. The enantiomeric ratios of the products were 98 2 and 50 50 (S R) for PEG-enzyme and unmodified enzyme, respectively. In this case, chymotrypsin acquired enantioselectivity by the chemical modification witii PEG. 

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