Structure-activity of sulfones and sulfonamides on dihydropteroate synthetase from Neisseria meingitidis

The molecular interaction of various sulfones and sulfonamides with partially purified dihydropteroate synthetase from Neisseria meningitidis M-166 has been examined. The mode of action of the sulfones was similar to that of the sulfonamides. Both groups of drugs were competitive inhibitors of dihydropteroate synthetase with respect to p-aminobenzoate in a partially purified enzyme preparation. 4,4'-Diaminodiphenylsulfone was three times more effective than sulfadiazine and nine times more effective than sulfanilamide as a competitive inhibitor of dihydropteroate synthetase. The inhibitory activity of 4-amino-4'-acetamidodiphenylsulfone and 4-amino-4'-formamidodiphenylsulfone in this system eliminated their prior conversion to 4,4'-diaminodiphenylsulfone as a requirement for activity.     

连接条件对00Cr25Ni7Mo3N双相不锈钢扩散连接的影响

利用热模拟试验机并结合扫描电镜(SEM)对00Cr25Ni7Mo3N超级双相不锈钢的超塑扩散连接进行实验研究,对不同连接条件下的孔洞形貌、界面组织进行相应的分析。研究结果表明,超塑性扩散连接试样的界面结合强度随扩散连接压力的增大、表面质量的提高及连接时间的延长而增大。扩散连接在连接温度1100℃时,连接压力为10MPa～20MPa;待连接表面经精磨处理后,连接时间10min～20min的条件下,可实现焊合率为96%～98%的扩散连接,且连接试样的初始连接界面消失,界面孔洞基本闭合,界面剪切结合强度达到407MPa～413MPa。