Factor X is a vitamin K-dependent protein zymogen which is synthesized in the liver and circulates in plasma as a two chain molecule linked by a disulfide bond (1,2). Prior to secretion into plasma, post-translational modifications produce 11 gamma-carboxyglutamic acid (gla) residues and a single b-hydroxyaspartic acid residue, which are located within the NH2-terminal light chain. The light chain also contains two epidermal growth factor (EGF) homology domains. The COOH-terminal heavy chain of factor X contains most of the carbohydrate moieties, as well as the latent serine protease domain. The activation of factor X is catalyzed by either the intrinsic factor Xase complex (factor IXa, factor VIIIa, cellular surface and calcium ions) or the extrinsic factor Xase complex (factor VIIa, tissue factor, cellular surface and calcium ions). Activation of human factor X by either complex results in cleavage at Arg52-Ile53 of the COOH-terminal heavy chain and subsequent release of a 52 amino acid activation glycopeptide. Factor Xa then serves as the enzyme component of the prothrombinase complex which is responsible for the rapid conversion of prothrombin to thrombin. The gla residues enable factor X/Xa to bind phospholipid (i.e. cell surfaces) in a calcium dependent manner; a requirement for assembly of the prothrombinase complex. The first EGF homology domain contains a Ca2+ binding site which acts as a hinge to fold the EGF and GLA domains towards each other (12). This region of the molecule is involved in the recognition of cellular binding domains.
Human factor X is isolated from fresh frozen human plasma by a combination of conventional techniques (3) and immunoaffinity chromatography (4). In addition to the standard human factor X preparation, Gla-domainless human factor X is also available. Bovine factor X is isolated from fresh bovine plasma using a modification of the procedure reported by Bajaj et al. (5,6). The purified zymogen is supplied in 50% (vol/vol) glycerol/H2O and should be stored at -20oC. Purity is determined by SDS-PAGE analysis and activity is measured in a factor X clotting assay.
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谢谢各位
非常急！
①在用超滤除白蛋白，IgG中硫酸铵盐时，膜包该如何选择？选择几个？
②如用凝胶过滤来分级纯化血清中65%硫酸铵盐析出的白蛋白和纯化33%硫酸铵盐析出的IgG，其填充介质应选择什么？其洗脱缓冲液应用什么好？
下面有些关于这方面的数据，供参考：
①牛血清白蛋白：分子量：66210；分子形状：椭圆形；分子大小：
40Å*140Å；等电点：4.7；血浆中的含量：52.0g/L。
②IgG:分子量：15300；分子形状：球状；等电点：5.8—7.3;血浆中含量：2.0g/L。
③另外，我从书上看到说：凝胶过滤在分级方法中分辨率为中等，但对脱盐效果优良；流速较低，对分级每周期约≥8小时，对脱盐仅30分钟；适用于大规模纯化的最后步骤，在纯化过程的任何阶段均可进行脱盐处理，尤其适用于两种缓冲液交替时。
期待您的帮助，谢谢您。
（一）高密度脂蛋白胆固醇（HDL-C）
【参考值】
0.94～2.0mmol/L
【临床意义】
降低具有临床意义。HDL-C与TG呈负相关系，见于冠心病、动脉粥样硬化、糖尿病、肝脏损害、肾病综合征。
（二）低密度脂蛋白胆固醇（LDL-C）
【参考值】
沉淀法:2.07～3.12mmol/L，3.15～3.61mmol/L为边缘升高，≥3.64mmol/L为升高。
【临床意义】
升高具有临床意义。LDL-C升高与冠心病发病呈正相关系。
（三）脂蛋白（a），LP（a）
【参考值】 <300mg/L
【临床意义】
脂蛋白（a）升高已作为冠心病及脑血管疾病发病的独立危险因素。
