Carboxyl groups modification

BS Jacobson, KF Fairman. A colorimetric assay for carbodiimides commonly usd in peptide synthesis and carboxyl group modification. Anal Biochem 106, 114, 1980. 

Siddiqui, K. S., Saqib, A. A. N., Rashid, M. H., et al. (2000). Carboxyl group modification significantly altered the kinetic properties of purified carboxymethyl-cellulase from Aspergillus niger. Enzyme Microbial Technol, 27, 467-474. 

Yoshida M, Allison WS, Esch FS and Futai M (1982) The specificity of carboxyl group modification during the inactivation of the Esaheriohia ooli... 

All of the 20 amino acids have in common a central carbon atom (Co) to which are attached a hydrogen atom, an amino group (NH2), and a carboxyl group (COOH) (Figure 1.2a). What distinguishes one amino acid from another is the side chain attached to the Ca through its fourth valence. There are 20 different side chains specified by the genetic code others occur, in rare cases, as" the products of enzymatic modifications after translation. 

PS has apolar characteristics and, thus, it is difficult to form a bond with metzils or polar materials. The adhesion capability of saturated polyhydrocarbons are dependent on the basis of polar properties of polymers [25]. Mitsu-aki and Masyasu [26] investigated the chemical modification of PS for anchoring of the carboxyl group to PS macromolecules with maleic anhydride (MA) in the presence of radiczil catalysis at 90-150°C. These authors... 

There are many ligands and group-specific reagents that have been demonstrated to alter the properties of H,K-ATPase, and which are not clinically useful. For example, there is a variety of chemicals that have been used in studies on structure-function relations of H,K-ATPase and that inhibit the enzyme in vitro by modification of its amino [49,67,158], sulfhydryl [95,165,166] or carboxyl groups [140]. 

The pH dependence of the rate of modification shows that the pKa of Asp-32 is less than 3.165 It is seen in the high-resolution crystal structures that the carboxyl groups of the two aspartate residues are hydrogen-bonded to each other. This is similar to the ionization of maleic acid, which has pKa values of 1.9 and 6.2 (equation 16.30). 

Modifications at the carboxyl group include reduction (with dibor-ane260 or borohydride, after activation with soluble carbodiimide261,262), esterification (with diazomethane,101,223,283,264 or acyl or aryl chlorides224,264), and formation of amide esters.263,265... 

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