SERS Investigation of NAD+ Adsorbed on a Silver Electrode

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• 作者：Shi-Ping Chen ; Charles M. Hosten ; Alberto Vivoni ; Ronald L. Birke ; and John R. Lombardi
• 刊名：Langmuir
• 出版年：2002
• 出版时间：December 10, 2002
• 年：2002
• 卷：18
• 期：25
• 页码：9888 - 9900
• 全文大小：238K
• 年卷期：v.18,no.25(December 10, 2002)
• ISSN：1520-5827

文摘

The surface-enhanced Raman scattering (SERS) spectra of nicotinamide adenine dinucleotide (NAD⁺)at different pH values and electrode potentials were investigated at a silver electrode. For comparisonpurposes, the spectra of adenine, N-methylnicotinamide, and nicotinamide mononucleotide were alsorecorded. Good quality spectra are reported, and NAD⁺ adsorbs spontaneously onto the electrode at allof the pH values (9.3-3.6) studied. Normal mode calculations of the in-plane vibrations of adenine wereperformed to assist in band assignments and determination of adsorbate orientation. These calculationsutilized Urey-Bradley force field calculations and the PM3 semiempirical molecular orbital method. Fromthese calculations, it is concluded that at physiological pH values NAD⁺ adsorbs on the silver electrodein a conformer in which the adenine ring binds to the surface through the external amino group on carbon6 and through nitrogen 7. The ribose and phosphate parts of the molecule are also involved in adsorption.In the surface conformer NAD⁺ is in an extended configuration with the adenine ring oriented normal (sideon) with respect to the surface and the nicotinamide ring oriented flat with respect to the surface muchlike in an enzyme bound case.