Weak Exchange Interaction Supported by a Biologically Relevant Long Chemical Bridge in a Cu-Peptide Model Compound
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- 作者：Ernanni D. Vieira ; Nieves M. C. Casado ; Gianella Facchin ; Maria H. Torre ; Antonio J. Costa-Filho ; and Rafael Calvo
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：April 3, 2006
- 年：2006
- 卷：45
- 期：7
- 页码：2942 - 2947
- 全文大小：152K
- 年卷期：v.45,no.7(April 3, 2006)
- ISSN：1520-510X
文摘
The copper complex of the dipeptide L-alanyl-L-phenylalanine, catena-(L-alaninate-L-phenylalaninate-copper(II)monohydrate), identified as Cu(II)Ala-Phe, provides a convenient system to study a weak exchange interactionbetween unpaired spins transmitted through a biologically relevant long chemical bridge (18.34 Å). In this complex,the copper ions are arranged in two symmetry-related anisotropic layers parallel to the ab plane at 13.17 Å, separatedby a double layer of water molecules. The equatorial-equatorial bridge considered as the most relevant path forexchange interactions between copper ions in neighbor layers contains 11 diamagnetic atoms (including threehydrogens), with two covalent amidate bridges plus three weak and moderate H bonds that go across the waterlayer. This interaction was studied using electron paramagnetic resonance in single-crystal samples, at 9.5 and34.5 GHz. The measured magnitude of the interlayer interaction, 
J3/kB = 1.7(2) × 10-3 K, is discussed in termsof values obtained for similar paths in other model compounds and in proteins. These results in model systemsprovide information that may be important in understanding biological functions at the molecular level.
J3/kB = 1.7(2) × 10-3 K, is discussed in termsof values obtained for similar paths in other model compounds and in proteins. These results in model systemsprovide information that may be important in understanding biological functions at the molecular level.