
Molecular Weight | 28,500 |
---|---|
CAS # | 39450-01-6 |
Unit Dedinition | One unit of enzyme liberates Folin-positive amino acid peptides corresponding to 1umol tyrosine in 1min at 37 ℃ using denatured hemoglobin as substrate. |
Proteinase K is a non-specific serine protease having a very high specific activity. It is used to purify target material from contaminating proteins, for the isolation of mRNA or high molecular weight DNA and to inactivate other enzymatic activities. Proteinase K is active with or without the presence of SDS, EDTA and urea.
Proteinase K is stable in a wide variety of detergents and buffer salts and at various temperatures and pH. The isoelectric point of proteinase K is 8.9.
Proteinase K is typically used at a concentration of 50-100 μg/ml. It is active with or without the presence of SDS, urea, EDTA or various metal ions, but the activity of proteinase K can be increased by adding the denaturing agents and the structure of proteinase K can be stabilized by addition of Ca2+. Proteinase K is inactivated by heating to 95°C for 10 minutes or using an inhibitor such as PMSF, AEBSF or DFP.
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荚膜(capsule)是某些细菌在生长繁殖过程中分泌的一层黏液性物质,包围在细胞壁外,通常这种黏液层厚度小于0.2μm,成分是多糖或多肽,只有在营养丰富时或在动物体内,细菌才产生这种半抗原性质的黏液性物质。它具有保护菌体免受巨噬细胞等的捕捉和吞噬,因而具有抗吞噬抗消化、侵袭力强、与致病性关系密切等特点。像肺炎球菌、炭疽杆菌等都有这类荚膜。有些细菌的荚膜层较薄,小于0.2μm,称为微荚。
像链球菌的M蛋白、伤寒杆菌的Vi抗原、大肠杆菌的K抗原等都属于这类微荚膜。
荚膜是某些细菌在细胞壁外包围的一层粘液性物质,一般由糖和多肽组成,是细菌的一种特殊结构。
作用:
①抗吞噬作用:荚膜因其亲水性及其空间占位、屏障作用,可有效抵抗寄主吞噬细胞的吞噬作用。
②黏附作用:荚膜多糖可使细菌彼此间粘连,也可黏附于组织细胞或无生命物体表面,是引起感染的重要因素,具有荚膜的S-型肺炎链球菌毒力强,有助于肺炎链球菌侵染人体;废水生物处理中的细菌荚膜有生物吸附作用,将废水中的有机物、无机物及胶体吸附在细菌体表面上。
③抗有害物质的损伤作用:处于细菌细胞最外层,荚膜犹如盔甲可有效保护菌体免受或少受多种杀菌、抑菌物质的损伤,如溶菌酶、补体等。
④抗干燥作用:荚膜多糖为高度水合分子,含水量在95%以上,可帮助细菌抵抗干燥对生存的威胁。
⑤当缺乏营养时,荚膜可被利用作碳源和能源,有的荚膜还可作氮源。
所以一个细菌或病毒可以有很多的抗原。
若已进入细胞内。则先由巨噬细胞吞噬降解。并形成抗原-MHC复合体传送到表面。被辅助性T淋巴细胞识别和效应T淋巴细胞识别后。效应T淋巴细胞被激活。分解靶细胞。然后再由效应B细胞分泌的抗体进一步消灭病毒。
还有不清楚的么?

