Nanocrystalline powders in the Ni-Ti and Ni-Cr systems were prepared by mechanical alloying (MA) of elemental crystalline powders in an inert atmosphere. The microstructure of the mechanically alloyed powders were cha...Nanocrystalline powders in the Ni-Ti and Ni-Cr systems were prepared by mechanical alloying (MA) of elemental crystalline powders in an inert atmosphere. The microstructure of the mechanically alloyed powders were characterized by XRD and TEM. The ball-milling process results in a drastic decrease of the crystallite size to the nanometer scale. X-ray diffraction analysis reveals that in the Ni-Cr system, no diffraction peaks from NiCr compound were observed even after 20 h of bail milling; while the lattice parameter of Ni increased with the milling time. In the Ni-Ti system, amorphous alloy was formed. Crystalline intermetallic compounds were obtained by post heat treatment of the amorphous alloy. The crystallization temperature of the amorphous NiTi alloy was obtained by DSC measurement.展开更多
Comparison of the reaction speed and yield with its analogues and some conventional peptide coupling reagents, pentafluorophenyl diphenylphosphate (FDP) was shown to be a more preferable ''active ester'...Comparison of the reaction speed and yield with its analogues and some conventional peptide coupling reagents, pentafluorophenyl diphenylphosphate (FDP) was shown to be a more preferable ''active ester'' type reagent for the peptide synthesis. The synthesis of oligopeptides using FDP was achieved with high yields. The influences of several reaction parameters such as solvent, base, additive and temperature on the coupling reaction were studied using HPLC method. The degree of racemization with FDP determined by HPLC or Young test was shown to be lower than that of DCCI. Octapeptide Gly-Cys(Bzl)-Ser-Gly-Lys-Leu-Ile-Cys(Bzl)-OH, corresponding to the amino acid sequence of gp41 of HIV-1, was successfully synthesized by 5+3 approach using FDP with high yield.展开更多
文摘Nanocrystalline powders in the Ni-Ti and Ni-Cr systems were prepared by mechanical alloying (MA) of elemental crystalline powders in an inert atmosphere. The microstructure of the mechanically alloyed powders were characterized by XRD and TEM. The ball-milling process results in a drastic decrease of the crystallite size to the nanometer scale. X-ray diffraction analysis reveals that in the Ni-Cr system, no diffraction peaks from NiCr compound were observed even after 20 h of bail milling; while the lattice parameter of Ni increased with the milling time. In the Ni-Ti system, amorphous alloy was formed. Crystalline intermetallic compounds were obtained by post heat treatment of the amorphous alloy. The crystallization temperature of the amorphous NiTi alloy was obtained by DSC measurement.
基金supported by the National Natural Science Foundation of China and the State Key labortory of Bio-organic and Natural Products Chemistry.
文摘Comparison of the reaction speed and yield with its analogues and some conventional peptide coupling reagents, pentafluorophenyl diphenylphosphate (FDP) was shown to be a more preferable ''active ester'' type reagent for the peptide synthesis. The synthesis of oligopeptides using FDP was achieved with high yields. The influences of several reaction parameters such as solvent, base, additive and temperature on the coupling reaction were studied using HPLC method. The degree of racemization with FDP determined by HPLC or Young test was shown to be lower than that of DCCI. Octapeptide Gly-Cys(Bzl)-Ser-Gly-Lys-Leu-Ile-Cys(Bzl)-OH, corresponding to the amino acid sequence of gp41 of HIV-1, was successfully synthesized by 5+3 approach using FDP with high yield.
