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Methods for the preparation of various peptidyl-aminoacyl-tRNA derivates are described. Aminoacyl-tRNA's are allowed to initiate the polymerization of different N-carboxy amino acid anhydrides in alkaline dimethylsulfoxide-water (97:3, v/v) to yield the corresponding peptidyl-aminoacyl-tRNA's. Near quantitative yields of ( dl -Ala)n-Val-tRNA, (sarcosyl)n-Val-tRNA, ( l -Asp-β-OBzl)n-Val-tRNA, ( l -Glu-γ-OBzl)n-Val-tRNA, and ( l -Phe)n-Val-tRNA were so obtained. In addition to peptidyl-aminoacyl-tRNA products, the polymerization reaction generates free peptides. The latter products are due to water-initiated polymerizations. Depending on the solubility properties of the particular free polyamino acid involved, one of three procedures can be used to separate it from peptidyl-aminoacyl-tRNA and tRNA. Fractionation of peptidyl-aminoacyl-tRNA away from tRNA is not, however, obtained and the two are recovered together as an aqueous mixture. The length of the petidyl moiety was found to be heterogenous in all the peptidyl-aminoacyl-tRNA derivatives tested. It was never very long relative to its tRNA carrier. The stability of the ester linkage between peptidyl-aminoacyl and polynucleotide in several peptidyl-aminoacyl-tRNA's was also studied. Although different derivatives evidenced different stabilities, all were appreciably more stable then their parent aminoacyl-tRNA compound.

Three new peptides with high steroidogenic activity in vivo have been isolated from porcine pituitary extracts. Similar in molecular weight to porcine ACTH, they differ from the usual amino acid composition in molar ratios of aspartic acid, threonine, serine, glycine, valine, methionine and phenylalanine.

Amino acids are quantitatively recovered from aminoacyl-tRNA in filter paper strips by treatment with 0.3 m ammonium carbonate. A simple apparatus is described for deaminoacylation and separation of amino acids and tRNA. The amino acids, thus recovered, can be directly analyzed by paper chromatography since ammonium carbonate is removed by lyophilization. Nonvolatile reagents such as Tris-HCl and sodium carbonate also hydrolyze aminoacyl-tRNA, but unless the products of deaminoacylation are desalted, the presence of these reagents gives rise to chromatographic artifacts such as peak broadening, appearance of multiple peaks, displacement of R f values, etc. tRNA remaining after deaminoacylation retains only a small fraction of its original capacity to bind amino acids. Part of this loss of activity appears to be due to structural damage to tRNA in the course of washing and counting procedures and in part, due to the effect of filter paper in shifting the equilibrium of the reaction toward hydrolysis of aminoacyl ester bond.

Two strains with mutations in the first structural gene of the histidine operon of Salmonella typhimurium were characterized. (The first structural gene specifies the first enzyme of histidine biosynthesis, phosphoribosyltransferase, which is sensitive to feedback inhibition by histidine.) One mutation, hisG3934 , results in a phosphoribosyltransferase which is no longer sensitive to feedback inhibition by histidine but is instead subject to inhibition by aspartic acid. The other mutation, hisG3935 , allows the histidine operon to be partially repressed by several amino acids, including aspartic acid. Analysis of hisG3935 is consistent with the hypothesis that phosphoribosyltransferase is directly involved in the regulation of the histidine operon.

SUMMARY: Some 300 strains of bacteria representing twenty genera were grown on an acid-hydrolysed casein medium. Using the paper chromatographic technique of Woiwod (1949) a preliminary survey was made of the amino-acid and polypeptide composition of the bacterial culture filtrates. It was proved that: (a) changes may occur in the filtrate chromatogram which have group or species significance; (b) bacteria with simple nutrient requirements, i.e. which utilize ammonia, do not affect the chromatogram in the initial growth stage; (c) whenever the chromatogram is affected serine is the first amino-acid to be metabolized; (d) Gram-positive bacteria eliminate the aspartic acid spot but leave the basic amino-acid group unaffected, and the reverse occurs with Gram-negative bacteria; (e) many bacteria synthesize ninhydrin-positive material, presumably polypeptide, the synthesis of a given kind of polypep-tide being sometimes associated with a particular group or species of bacteria. By a disintegrator technique it was demonstrated that bacteria store many free amino-acids inside the cell.