Proteins, protonation equilibria modeling

To model the moiety of glycoproteins which coimects the protein and carbohydrate parts of the molecule, amino acid - carbohydrate adducts (e.g. V-D-gluconylamino acids, thiazolidine-4-carboxylic acid derivatives of carbohydrates, " D-fructose amino acid derivates, etc.) have been synthetized. The protonation and metal ion (Cu2+, Ni2+, Co ", Zn2+ and Et2Sn2+) coordination equilibria of these model compounds have been studied by means of potentiometric equilibrium measurements. CD, EPR, NMR, EXAFS and MSssbauer investigations (the latter in frozen solutions) have been used to determine the structure and symmetry of the coordination sphere of the complexes. >6... 

The most fundamental experimental determinations in model studies of proton transfer at weakly basic carbon are of the rate and equilibrium constants for carbon deprotonation to form an unstable carbanion (Eq. (1.1)). These parameters define the kinetic and thermodynamic barriers to proton transfer (Eq. (1.2) for Fig. 1.1). They are of interest to enzymologists because they specify the difficulty of the problem that must be solved in the evolution of proteins which catalyze proton transfer with second-order rate constants kcat/ m of 10 "-10 s that are typically ob-... 

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