Wang Lijun, Qiu S Roger, Zachowicz William, Guan Xiangying, Deyoreo James J, Nancollas George H, Hoyer John R
Department of Chemistry, Natural Sciences Complex, State University of New York at Buffalo, Buffalo, New York 14260, USA.
Langmuir. 2006 Aug 15;22(17):7279-85. doi: 10.1021/la060897z.
Calcium oxalate monohydrate (COM) kidney stone formation is prevented in most humans by urinary crystallization inhibitors. Urinary osteopontin (OPN) is a prototype of the aspartic acid-rich proteins (AARP) that modulate biomineralization. Synthetic poly(aspartic acids) that resemble functional domains of AARPs provide surrogate molecules for exploring the role of AARPs in biomineralization. Effects of linear aspartic acid-rich peptides on COM growth kinetics and morphology were evaluated by the combination of constant composition (CC) analysis and atomic force microscopy (AFM). A spacer amino acid (either glycine or serine) was incorporated during synthesis after each group of 3 aspartic acids (DDD) in the 27-mer peptide sequences. Kinetic CC studies revealed that the DDD peptide with serine spacers (DDDS) was more than 30 times more effective in inhibiting COM crystal growth than the DDD peptide with glycine spacers (DDDG). AFM revealed changes in morphology on (010) and (-101) COM faces that were generally similar to those previously described for OPN and citrate, respectively. At comparable peptide levels, the effects of step pinning and reduced growth rate caused by DDDS were remarkably greater. In CC nucleation studies, DDDS caused a greater prolongation of induction periods than DDDG. Thus, nucleation studies link changes in interfacial energy caused by peptide adsorption to COM to the CC growth and AFM results. These studies indicate that, in addition to the number of acidic residues, the contributions of other amino acids to the conformation of DDD peptides are also important determinants of the inhibition of COM nucleation and growth.
大多数人可通过尿液中的结晶抑制剂来预防一水合草酸钙（COM）肾结石的形成。尿液骨桥蛋白（OPN）是调节生物矿化的富含天冬氨酸蛋白（AARP）的一个原型。类似于AARP功能域的合成聚天冬氨酸提供了替代分子，用于探索AARP在生物矿化中的作用。通过恒定组成（CC）分析和原子力显微镜（AFM）相结合的方法，评估了线性富含天冬氨酸肽对COM生长动力学和形态的影响。在27聚体肽序列中，每3个天冬氨酸（DDD）基团后合成时引入一个间隔氨基酸（甘氨酸或丝氨酸）。动力学CC研究表明，带有丝氨酸间隔基团的DDD肽（DDDS）抑制COM晶体生长的效果比带有甘氨酸间隔基团的DDD肽（DDDG）高30倍以上。AFM显示，（010）和（-101）COM晶面上的形态变化通常分别与先前描述的OPN和柠檬酸盐的形态变化相似。在可比的肽水平下，DDDS引起的台阶钉扎效应和生长速率降低更为显著。在CC成核研究中，DDDS比DDDG导致诱导期延长更多。因此，成核研究将肽吸附到COM上引起的界面能变化与CC生长和AFM结果联系起来。这些研究表明，除了酸性残基的数量外，其他氨基酸对DDD肽构象的贡献也是抑制COM成核和生长的重要决定因素。
