Parvalbumin characteristics

In lower vertebrates, TN-C is absent, and the calcium-binding function is performed by structurally similar proteins, 12,000, known as Parvalbumins (see). The parvalbumins characteristically contain no cystine, cysteine, tyrosine or tryptophan, and therefore have no absorption maximum at 280 nm. Higher vertebrates also contain these proteins. Parvalbumins have been isolated from the muscle of chicken, turkey, rabbit and human. 

It should be pointed out that the addition of substances, which could improve the biocompatibility of sol-gel processing and the functional characteristics of the silica matrix, is practiced rather widely. Polyethylene glycol) is one of such additives [110— 113]. Enzyme stabilization was favored by formation of polyelectrolyte complexes with polymers. For example, an increase in the lactate oxidase and glycolate oxidase activity and lifetime took place when they were combined with poly(N-vinylimida-zole) and poly(ethyleneimine), respectively, prior to their immobilization [87,114]. To improve the functional efficiency of entrapped horseradish peroxidase, a graft copolymer of polyvinylimidazole and polyvinylpyridine was added [115,116]. As shown in Refs. [117,118], the denaturation of calcium-binding proteins, cod III parvalbumin and oncomodulin, in the course of sol-gel processing could be decreased by complexation with calcium cations. 

The lanthanides form a series of ions of closely related size and bonding characteristics and in many respects resemble Ca +, for which they often substitute isomorphously in biological systems. Since different Ln ions can be probed with particular spectroscopic techniques (e.g. Eu + and Tb +, fluorescence Gd +, ESR Nd +, electronic spectra), in favourable circumstances it should be possible to obtain information about the binding site of spectroscopically inactive Ca + in several ways. Systems smdied include the calciumbinding sites in calmodulin, trypsin, parvalbumin, and the Satellite tobacco necrosis virus. 

Because of our interest in utilizing Cd NMR spectroscopy as a probe for calcium sites in biological systems (42,43,49,51), we have been interested in the isotropic Cd chemical shifts in these compounds. In the systems studied (Concanavalin A (42), Parvalbumin (43), Troponin C (50),. Calmodulin (49), and Insulin (51)), replacing calcium with cadmium places cadmium in an environment in which all of the atoms in the first coordination sphere are oxygens. The cadmium is assumed to be six coordinate. The isotropic chemical shifts for these compounds (82) fall into a characteristic range of chemical shifts from -85 to -130 ppm with respect to 0.1 M Cd(C104)2 To date, there are no model compounds that can be studied in aqueous solutions which have isotropic shifts within this range. 

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