Sam has three ionizable groups besides the sulfonium pole : the carboxyl and the aminic groups of the amino acidic chain with pk 1 . 8 and 7 . 8 respectively and the aminic group of the purine with pk 3 . 4 . in an acid environment sam is positive charged , so it could be adsorbed by weak - acid cation exchange resin Sam除具有一个带正电荷的锍外，还有三个可离子化的基团： pk _ a分别为1 . 8 、 7 . 8的氨基酸链上的羧基和氨基， pk _ a为3 . 4的嘌呤环上的氨基。
Both the frequency and intensity of 1146 . 0cm - 1 change largely , etc . discussed and compared the mechanism of these interaction in detail we got some conclusions as following : both zn2 + and cd2 + ions can chelate with po2 - and come into being - po2 - me2 + n7 ( purine ) chelate . as to zn2 + ions , when r2 . 0 , the quantity of po2 - zn2 + n7 is directly linear with r . when r2 . 0 , zn2 + ions even can chelate with c at n3 - o2 sites and this chelation will disrupt the h - bond between gc base pairs and make the dna structure unstable . as to cd2 + ions , only when r is within 1 . 0 - 1 . 5 can this chelation take place and the relation of the quantity of this chelate with r is not easy to conclude 通过对这些变化进行详细讨论和分析，我们得到了如下的结论： zn ~ ( 2 + )和cd ~ ( 2 + )都可以跟dna的磷酸基团螯合，形成- po _ 2 ~ - … me ~ ( 2 + ) … n7 ( g )螯合物，但是前者的螯合跟离子浓度有很大的关系，在摩尔浓度比小于2 . 0时，螯合物的生成量跟r成正比关系，而后者的螯合跟离子的关系不是很明显，只有当r处于1 . 0至1 . 5之间时，螯合作用才能进行，并且螯合物的生成量跟r之间没有很明显的关系存在。
Unlilie other cells that also use the salvage pathway for purine biosynhesis , prolfferating b and t cells are solely dependent on the de novo pathway for the generation of wsine . by blocking impdh , b and t cells cannot synthesise the necessary levels of ana and dna to molm a proliferathe response to ags and ndogens 根据对balb c和c57bl 6小鼠互为供、受者进行移植的结果表明，在排斥发生时间上不同的鼠株移植组合存在差异b 0刀匀， balb儿小鼠的同种应答强度较c57bl 6小鼠为弱。
