Asao Murai

Conformational analysis of amino acids and peptides using specific isotope substitution. I. Conformation of L-phenylalanylglycine.

Abstract L-Phenylalanyl-(R)-[2H]glycine, L-valyl-(R)-[2H]glycine, and L-phenylalanyl [15N]glycine were prepared. Assignments for pro-R and pro-S proton NMR signals of the glycine residue were done and coupling constants between proton and 15N were obtained. Based on the data an attempt to explain the origin of the nonequivalence of the glycine methylene protons was made, and a conformational model for L-phenylalanylglycine is proposed.

Solvent effects on the photochemical addition of acetone to 3,4,6-tri-O-acetyl-D-glucal☆

Abstract Irradiation of a solution of 3,4,6-tri- O -acetyl- D -glucal ( 1 ) in various mixtures of acetone ( 2 ) and isopropyl alcohol was investigated to elucidate solvent effects on the photochemical addition of 2 to 1 . At high concentrations of acetone ( 2 ), 5,6,8-tri- O -acetyl-2,4:3,7-dianhydro-1-deoxy-2- C -methyl- D - glycero - D - ido -octitol ( 3 ) was obtained selectively. In mixtures containing less than 50% (v/v) of 2 , irradiation gave mainly 5,6,8-tri- O -acetyl-3,7-anhydro-1,4-dideoxy-2- C -methyl- D - gluco -octitol ( 4 ). The effects of ethanol and other solvents were examined and the mechanism of the reaction is discussed.

On the derivatives for the ultramicrodetermination of amino acids by mass fragmentography.

The fragmentation of eight volatile derivatives of alanine, valine, leucine, proline, and glutamic acid upon electron impact is studied for the concurrent ultramicrodetermination or the selective identification of amino acids by mass fragmentography. The relationship between the sensitivity of mass fragmentography and Σ10% values (percentage of the total ionization over me) of N-trifluoroacetyl-l-prolyl, N-benzoyl, and N-pentafluorobenzoyl derivatives of alanine, valine, leucine, and proline is also investigated. The results obtained in this study suggest that N-trifluoroacetyl-l-prolyl n-butyl ester, N-benzoyl n-butyl ester, N-pentafluorobenzoyl n-butyl ester, and N-trifluoroacetyl l-menthyl ester derivatives can be used for the concurrent ultramicrodetermination or selective identification of amino acids by mass fragmentography because these four derivatives produce common intense fragment ions at me 166, 105, 195, and 83 or diagnostic ions, respectively. Although N-trifluoroacetyl-l-4-thiazolidinecarbonyl n-butyl ester, N-trifluoroacetyl n-butyl ester, N-trimethylsilyl n-butyl ester, N-trimethylsilyl l-menthyl ester, and trimethylsilylated derivatives do not produce the common intense fragment ions, these derivatives are useful for the selective identification of ultra amounts of amino acids using mass fragmentography monitored the diagnostic ions, respectively. The general common rules between sensitivity and Σ10% values were not adhered among the derivatives studied.

Determination of the primary structure of Paim II, an α-amylase inhibitor from Streptomyces coruchorushii, by high-performance tandem mass spectrometry

This study indicates one of the advantages of tandem mass spectrometry; the primary structures of proteins with little structural difference can be determined by using tandem mass spectrometry without prior purification of each component. The primary structure of Paim II, a protein alpha-amylase inhibitor from Streptomyces coruchorushii, was determined by using tandem mass spectrometry. Paim II consists of two component proteins with ragged N-terminus, and was sequenced on the basis of the structure of Paim I, an analogous alpha-amylase inhibitor from the same natural origin.