Lu Z R, Kopecková P, Wu Z, Kopecek J
Departments of Pharmaceutics and Pharmaceutical Chemistry/CCCD and of Bioengineering, Mass Spectrometry Facility, University of Utah, Salt Lake City, Utah 84112, USA.
Bioconjug Chem. 1998 Nov-Dec;9(6):793-804. doi: 10.1021/bc980058r.
Semitelechelic poly[N-(2-hydroxypropyl)methacrylamide]s (ST-PHPMA) with different functional end groups, namely carboxyl, methyl ester, hydrazide, and amino groups, were prepared by chain transfer free-radical polymerization. 2,2'-Azobisisobutyronitrile (AIBN) was used as an initiator and 3-mercaptopropionic acid, methyl 3-mercaptopropionate, 3-mercaptopropionic hydrazide, and 2-mercaptoethylamine were used as chain-transfer agents. The semitelechelic polymers have been characterized by end-group analysis, size-exclusion chromatography (SEC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The effects of the concentrations of the mercaptans and the initiator on the molecular weight of the polymers have been investigated. The higher the concentration of mercaptan, the lower the molecular weight of ST-PHPMA. The concentration of initiator did not have a significant effect on the molecular weight of the semitelechelic polymers. The end groups of the ST polymers can be readily transformed by polymeranalogous reactions. A model protein, alpha-chymotrypsin, has been modified with ST-PHPMA-CONHNH2 and ST-PHPMA-COOSu and the conjugates characterized by MALDI-TOF MS. The activity of modified chymotrypsins toward a high molecular weight substrate, P-Gly-Leu-Phe-NAp (where P is the HPMA copolymer backbone, and NAp is p-nitroanilide), was slightly lower than the activity of the native enzyme. The cleavage of a low molecular weight substrate, Z-Gly-Leu-Phe-NAp, by modified chymotrypsins was dependent on their structure. Whereas the activity of the amino group modified chymotrypsins was higher than that of the native enzyme, the activity of carboxyl-modified chymotrypsins was lower than that of the native enzyme. In summary, the data seem to indicate that ST-PHPMA is an effective protein-modifying agent.
通过链转移自由基聚合制备了具有不同官能端基（即羧基、甲酯基、酰肼基和氨基）的半遥爪聚[N-(2-羟丙基)甲基丙烯酰胺]（ST-PHPMA）。使用2,2'-偶氮二异丁腈（AIBN）作为引发剂，3-巯基丙酸、3-巯基丙酸甲酯、3-巯基丙酸酰肼和2-巯基乙胺作为链转移剂。通过端基分析、尺寸排阻色谱（SEC）和基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）对这些半遥爪聚合物进行了表征。研究了硫醇和引发剂浓度对聚合物分子量的影响。硫醇浓度越高，ST-PHPMA的分子量越低。引发剂浓度对半遥爪聚合物的分子量没有显著影响。ST聚合物的端基可以通过聚合物类似反应轻松转化。一种模型蛋白α-胰凝乳蛋白酶已用ST-PHPMA-CONHNH2和ST-PHPMA-COOSu进行了修饰，并通过MALDI-TOF MS对缀合物进行了表征。修饰后的胰凝乳蛋白酶对高分子量底物P-Gly-Leu-Phe-NAp（其中P是HPMA共聚物主链，NAp是对硝基苯胺）的活性略低于天然酶的活性。修饰后的胰凝乳蛋白酶对低分子量底物Z-Gly-Leu-Phe-NAp的切割取决于它们的结构。氨基修饰的胰凝乳蛋白酶的活性高于天然酶，而羧基修饰的胰凝乳蛋白酶的活性低于天然酶。总之，数据似乎表明ST-PHPMA是一种有效的蛋白质修饰剂。
