Hong Lian, Simon John D
Department of Chemistry, Duke University, Durham, NC, USA.
Photochem Photobiol. 2006 Sep-Oct;82(5):1265-9. doi: 10.1562/2006-02-23-RA-809.
IR absorption spectroscopy is used to examine the binding of the divalent cations Mg(II), Ca(II), Zn(II) and Cu(II) to melanin granules isolated from the ink sacs of Sepia officinalis. The functional groups of the melanin granules interacting with the bound metal ions are deduced by examining the effect of metal concentration on transition frequencies associated with the COOH, NH and OH moieties of the pigment. The coordinating groups vary with metal ion and with concentration. For the experimental conditions used (initial solution pH of 4, ionic strength of 100 mM and a melanin concentration of 1 mg mL(-1)) Mg(II), Ca(II) and Zn(II) bind to carboxylate groups and Cu(II) binds predominantly to phenolic (catechol) groups However, at a concentration of 10 mM Cu(II) also shows evidence of binding to carboxylate and amine groups, reflecting a secondary binding site that becomes populated as the catechol sites are depleted.
红外吸收光谱法用于研究二价阳离子镁（II）、钙（II）、锌（II）和铜（II）与从乌贼墨囊中分离出的黑色素颗粒的结合情况。通过研究金属浓度对与色素的COOH、NH和OH部分相关的跃迁频率的影响，推断出与结合金属离子相互作用的黑色素颗粒的官能团。配位基团随金属离子和浓度而变化。在所使用的实验条件下（初始溶液pH为4，离子强度为100 mM，黑色素浓度为1 mg mL(-1)），镁（II）、钙（II）和锌（II）与羧酸盐基团结合，而铜（II）主要与酚类（儿茶酚）基团结合。然而，在10 mM的浓度下，铜（II）也显示出与羧酸盐和胺基团结合的迹象，这反映出随着儿茶酚位点被耗尽，一个二级结合位点开始被占据。
