Hydrolytic binding

N -Heterocyclic Sulfanilamides. The parent sulfanilamide is manufactured by the reaction of A/-acetylsulfanilyl chloride with excess concentrated aqueous ammonia, and hydrolysis of the product. Most heterocycHc amines are less reactive, and the condensation with the sulfonyl chloride is usually done in anhydrous media in the presence of an acid-binding agent. Use of anhydrous conditions avoids hydrolytic destmction of the sulfonyl chloride. The solvent and acid-binding functions are commonly filled by pyridine, or by mixtures of pyridine and acetone. Tertiary amines, such as triethylamine, may be substituted for pyridine. The majority of A/ -heterocycHc sulfanilamides are made by simple condensation with A/-acetylsulfanilyl chloride and hydrolysis. 

As we have already seen zinc-finger peptides are well-studied polypeptide motifs that have found many applications in synthetic systems, mostly because of their abihty to bind metal ions and interact with oligonucleotides. In this context the report by lima and Crooke [44] of the hydrolytic cleavage by a zinc-finger peptide devoid of any metal ion is a surprising. The system they studied, a 30-amino acid sequence, is based on a catalytic mechanism very similar to that discussed above... 

Cutinase is a hydrolytic enzyme that degrades cutin, the cuticular polymer of higher plants [4], Unlike the oflier lipolytic enzymes, such lipases and esterases, cutinase does not require interfacial activation for substrate binding and activity. Cutinases have been largely exploited for esterification and transesterification in chemical synthesis [5] and have also been applied in laundry or dishwashing detergent [6]. 

Conditional stability constants have been determined for cadmium binding to humic acid in freshwater, log Kk 6.5 [27], which may be comparable to binding to humic acid coated particles. The experiments demonstrated the importance of cadmium uptake from particles rather than from the dissolved phase. The authors recognised that the overall conclusion was similar to previous studies [28], but there remain inconsistencies in the uptake levels which may be related to the heterogeneity of the systems. Uptake from the intestine into the mucosal cells was not investigated. It was presumed that the material was digested extracellularly by hydrolytic enzymes and the released metal was taken up by facilitated diffusion. 

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