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When a peptide was synthesized by use of an unsymmetrical carbodiimide in which the electron density on one nitrogen atom is lower than that on the other, it has been found that the formation of N-acylurea is markedly suppressed and the racemization of the product is limited to a less extent in comparison with the case using DCC(dicyclohexylcarbodiimide).

An immobilized derivative of γ-gluamylcysteine synthetase was prepared by chemically combining γ-glutamylcysteine synthetase with Sepharose 4B. The immobilized enzyme had a similar pH-activity profile to that of the native one and was much more stable to heat than the native enzyme. The immobilized enzyme retained its full activity after storage at least for 5 months at 4°C, while the native enzyme lost its activity within 2 weeks under the same conditions.

Ribonuclease T1 [EC 3.1.4.8] was coupled to a water-insoluble cross-linked polyacrylamide (Enzacryl AH) by the acid azide method. The immobilized enzyme exhibited about 45% and 77% of the original activity toward yeast RNA and 2', 3-cyclic GMP, respectively, as substrates. Although the specific activity was lowered by the coupling, the immobilized enzyme was found to be far more stable to heat and extremes of PH than the native enzyme. The immobilized enzyme was active toward RNA even above pH 9 (at 37 degree C) or above 60 degree C (at pH 7.5), where the native enzyme was inactive. The immobilized enzyme retained much of its activity as assayed at 37 degree C after incubation in the range of pH 1 to 10 at 37 degree C, or after heating at 100 degree C (at pH 7.5) under conditions where the native enzyme was inactivated to a considerable extent. The enzyme derivative could be repeatedly recovered and reused without much loss of activity. The active site glutamic acid-58 in the immobilized enzyme appeared to be nearly as reactive with iodoacetate as that in the native enzyme.

When a peptide was synthesized by use of an unsymmetrical carbodiimide in which the electron density on one nitrogen atom is lower than that on the other, it has been found that the formation of N-acylurea is markedly suppressed and the racemization of the product is limited to a less extent in comparison with the case using DCC(dicyclohexylcarbodiimide).

A modified polystyrene-divinylbenzene copolymer, in which ethylcarbodiimidomethyl groups were linked so as to be available as a condensing agent for peptide synthesis, were prepared. This polymer proved of great use in synthesizing some protected peptides without accompanying any troublesome by-product which would otherwise be formed.

Several substituted phenylsulfenyl chlorides were synthesized for the investigation of the properties of sulfenyl N-protecting groups and new sulfenyl (o-nitrophenylsulfenyl and 2, 4-dinitrophenylsulfenyl) derivatives of some amino acids were obtained. The disubstituted phenylsulfenyl derivatives were far more stable than the monosubstituted ones in 80% acetic acid. Thus the sulfenyl derivatives of S-benzyl-L-cysteine was synthesized in pure state and used successfully to form cysteinyl peptides.

Di-, tri-, and tetra-arginine were prepared from carbobenzoxy-nitro-L-arginine via carbobenzoxy-nitro-L-arginyl-nitro-L-arginine methyl ester, carbobenzoxy-nitro-L-arginyl-nitro-L-arginyl-nitro-L-arginine methyl ester, and carbobenzoxy-nitro-L-argi-nyl-nitro-L-arginyl-nitro-L-arginyl-nitro-L-arginine methyl ester, respectively, by mixed anhydride and dicyclohexyl-carbodiimide (DCC) methods. Measurement of the optical rotation of the peptide hydrolysates at 224 mμ showed that no racemization has occurred during the syntheses. Mean residue rotations at 224 mμ of these peptides have some relationship with the chain length. Color values of the Sakaguchi reaction per residue of these peptides decreased as the peptide chain became longer.

A water-insoluble derivative of ribonuclease T1 (RNase T1) was prepared by chemically combining RNase T1 with a copolymer of acrylamide and divinylbenzene (Enzacryl AH), and its enzymatic properties were examined. The enzyme derivative retained much of its original activity and was considerably more stable to heat and extremes of pH than the native enzyme.

A modified polystyrene-divinylbenzene copolymer, in which ethylcarbodiimidomethyl groups were linked so as to be available as a condensing agent for peptide synthesis, were prepared. This polymer proved of great use in synthesizing some protected peptides without accompanying any troublesome by-product which would otherwise be formed.