Functional groups, of proteins

Reactions of cy anate with functional groups of proteins. III. Reactions with amino and carboxyl groups. Biochemistry 4, 1030—1036 (1965). 

Acid anhydrides, as their name implies, are formed from the dehydration reaction of two carboxylic acid groups (Fig. 72). Anhydrides are highly reactive toward nucleophiles and are able to acylate a number of the important functional groups of proteins and other macromolecules. Upon nucleophilic attack, the anhydride yields one carboxylic acid for every acylated product. If the anhydride was formed from monocar-boxylic acids, such as acetic anhydride, then the acylation occurs with release of one carboxylate group. However for dicarboxylic acid anhydrides, such as succinic anhydride, upon reaction with a nucleophile the ring structure of the anhydride opens, forming the acylated product modified to contain a newly formed carboxylate group. 

Some reagents bind to several functional groups of proteins, e.g. dansylchloride, acetic anhydride. The list of the most frequently used conjugation reagents is given in Table 7. The most important ones are briefly characterized below. 

Although this review has focused on the reactivity modes that can be used to modify the amino acids directly, it is equally important to be able to predict what will not react with the native functional groups of proteins. Reactions that can proceed in aqueous solution while ignoring the natural amino acids are exceptionally useful for the development of secondary labeling strategies. In these approaches, one reaction described above is used to attach a chemically distinct functional group to a particular amino acid. A second reaction then is used to install... 

IMA is based upon affinity of surface functional groups of protein for the immobilized metal ions. The strength of association between the chelated and bound metal ion and the residues on protein surface may be quite high and even approach the strength of interaction between enzyme and cofactor/inhibitor or even that between antigen and antibody [140]. Considering that affinity of pro-... 

Impact of the Relative Oil-like Character of Functional Groups of Proteins on the T,-divide... 

A brief discussion of the chemical reactivity of the products of these enzymes is central to our proposed use of these enz)nnes as antinutritive bases of resistance. Polyphenol oxidase (PPO) and peroxidase (POD) oxidize phenolics to quinones, which are strong electrophiles that alkylate nucleophilic functional groups of protein, peptides, and amino acids (e.g., -SH, -NHof -HN-, and -OH)(Figure 1)(53,63-65). This alkylation renders the derivatized amino acids nutritionally inert, often reduces the digestibility of protein by tryptic and chymotryptic enzymes, and furthermore can lead to loss of nutritional value of protein via polymerization and subsequent denaturation and precipitation (63,66-69). POD is also capable of decarboxylating and deaminating free and bound amino acids to aldehydes (e.g., lysine, valine, phenylalanine. 

Tannage process. Tannage consists in injection of tanning substances into the dermis structure and their interaction with functional groups of protein molecular chains, which results in formation of additional stable cross bonds. Tannage is one of the most important processes for leather manufacture. This stage in the leather industry radically changes dermis... 

Two other unpublished histochemical methods for functional groups of proteins, which may be useful in studying the morphology of the mitotic spindle in conjunction with sulfhydryl and disulfide groups, are (1) a method which demonstrates terminal primary amino groups (to appear in the J. Hisfochem. and Cytochem. with Dr. L. P. Weiss and Dr. K-C Tsou) and (2) a method for terminal carboxyl groups with Dr. E. W. Dempsey. 

An important type of electrostatic interaction are interactions between ions and dipoles (permanent dipoles) that occur, for example, during interactions of salt ions with water molecules (the process is called hydration of ions) or during interactions of ionised functional groups of proteins and of some polysaccharides with water. The energy of interaction is several tens of kj/mol (e.g. 21 kJ/mol in mutual interactions of ionised functional groups of proteins and 50-100 kJ/mol in interactions of monovalent salt ions with water). 

Ions of salts, Ionised functional groups of proteins and carbohydrates... 

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