Chemical modification as a method of studying the functional groups of carboxylic proteinases

A review of the literature on the chemical modification of the functional groups of carboxylic proteinases is given. The following branches of the subject are considered: spatial organization and the modification of carboxy groups and amino groups of arginine, histidine, tyrosine, tryptophan, methionine, cystine, and cysteine residues. Chemical modification is considered as a method of studying the functional groups of enzymes which, in association with the results of x-ray structural analysis, permits an idea to be obtained of the mechanism of the action of carboxylic proteinases. V. M. Lomonosov Moscow State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 591–607, September–October, 1980.     

Proteinases immobilized on poly(vinyl alcohol) cryogel: novel biocatalysts for peptide synthesis in organic media

Covalent immobilization of subtilisin and thermolysin on cryogel of poly(vinyl alcohol) was carried out. The biocatalysts obtained are characterized by high stability in water and in DMF—MeCN mixtures of various compositions. The synthetic efficiency of immobilized subtilisin in the multiple iterative synthesis of the peptide Z—Ala—Ala—Leu—Phe—pNA was examined in organic mixtures of different solvent compositions. Immobilized subtilisin exhibits high synthetic activity in organic media. A series of N-acylated p-nitroanilides of tetrapeptides of the general formula Z—Ala—Ala—Xaa—Yaa—pNA (Z is benzyloxycarbonyl, Xaa = Leu, Lys, or Glu; Yaa = Phe or Asp; pNA = 4-NO₂—C₆H₄NH-) were synthesized in 70—98% yields using immobilized subtilisin as a biocatalyst without activation and protection of the ionogenic groups of polyfunctional amino acids. Immobilized thermolysin in a DMF—MeCN mixture catalyzed the formation of the peptide Z—Ala—Ala—Leu—pNA, which was obtained in 90% yield (during 1 h). It was demonstrated that the biocatalyst can be used repeatedly and that it retained activity after storage in an aqueous buffer during 6 months.     

Affinity chromatography of pepsin using pepstatin fragments as ligands of specific sorbents

Summary 1. Specific sorbents for the affinity chromatography of pepsin on hexamethylenediamine-Sepharose using valine peptides differing by the acyl groups and configurations of the valine residue have been synthesized.2. The sorbents investigated are effective in the purification of pepsin with a low specific activity when 30–40 mg of protein is deposited on 1 ml of resin, a fourfold purification of the enzyme being achieved.M. V. Lomonosov Moscow State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 387–392, May–June, 1977.     

On the Inhomogeneity of Aqueous Alkaline Solutions of Sulfate Lignin and Wood Resin

By the dynamic light scattering technique, it was shown for the first time that sulfate lignin, wood resin, and their mixtures are dissolved as nanoparticles in an aqueous alkaline medium (pH 12.7) at temperatures from 293 to 333 K. The degree of molecular aggregation in the nanoparticles was estimated and their aggregative instability was established. Larger particles were found to be formed during the combined dissolution of the aforementioned compounds than during the separate dispersing of the components.     

Colloid-Chemical Characteristics of Aqueous Alkaline Solutions of Organic Components of Pine and Birch Wood

The surface activity and sedimentation stability of organic substances passing into solution in kraft cooking of pine wood were studied. The data obtained were compared with the corresponding data characteristic of organic components of birch wood.     

A Dynamic Light Scattering Study of the Temperature Dependence of the Size-Distribution Pattern and Aggregation Stability of Sulfate Lignin and Wood Resin in Aqueous Alkali Solution

A dynamic light scattering study in the temperature range 293-333 K was made for solutions of sulfate lignin and resinous wood components, which are limitedly soluble in water, as well as for their mixture in an alkaline medium (pH 12.7) of sulfate cooking lye. This study proved the heterogeneous nature of these systems.