Mialostatin,a Novel Midgut Cystatin from Ixodes ricinus Ticks: Crystal Structure and Regulation of Host Blood Digestion

The hard tick Ixodes ricinus is a vector of Lyme disease and tick-borne encephalitis. Host blood protein digestion, essential for tick development and reproduction, occurs in tick midgut digestive cells driven by cathepsin proteases. Little is known about the regulation of the digestive proteolytic machinery of I. ricinus. Here we characterize a novel cystatin-type protease inhibitor, mialostatin, from the I. ricinus midgut. Blood feeding rapidly induced mialostatin expression in the gut, which continued after tick detachment. Recombinant mialostatin inhibited a number of I. ricinus digestive cysteine cathepsins, with the greatest potency observed against cathepsin L isoforms, with which it co-localized in midgut digestive cells. The crystal structure of mialostatin was determined at 1.55 Å to explain its unique inhibitory specificity. Finally, mialostatin effectively blocked in vitro proteolysis of blood proteins by midgut cysteine cathepsins. Mialostatin is likely to be involved in the regulation of gut-associated proteolytic pathways, making midgut cystatins promising targets for tick control strategies.     

复合絮凝剂聚硅硫酸铁的形貌结构及性能研究

向聚硅酸中引入铁盐制得聚硅硫酸铁(PFSS)复合絮凝剂,通过电子显微镜观察分析了不同铁硅摩尔比的PFSS的形貌,用红外光谱研究了其中铁离子与聚硅酸的相互作用情况,并对其稳定性和絮凝性进行了考察.结果发现:聚硅硫酸铁的形貌均为长链枝杈状聚集态,铁硅摩尔比对形貌结构及絮凝性能有较大影响;红外光谱证实PFSS中硅与铁形成了Si-O-Fe键;聚硅硫酸铁的稳定性高于聚硅酸,并且随着n(Fe)∶n(Si)的增大而提高.     

二维层状超分子化合物[Mn（C8H5NO6）（H2O）2]n的合成及晶体结构研究

分子间的弱相互作用在配位化合物中往往表现为配合物分子内和(或)分子间的配体间相互作用。因此,研究配合物中的配体间弱相互作用就成为由配位化学向超分子化学过渡的桥梁。本文以锰离子为中心离子,以2,4,6-吡啶三羧酸为配体进行晶体合成实验。通过检测手段了解了合成的配合物配体间的弱相互作用。