CONFORMATION AND ORIENTATION OF THE HAPTENS, 2,4-DINITROPHENYL AMINO-ACIDS, ON COLLOIDAL SILVER FROM SURFACE-ENHANCED RAMAN-SCATTERING
CONFORMATION AND ORIENTATION OF THE HAPTENS, 2,4-DINITROPHENYL AMINO-ACIDS, ON COLLOIDAL SILVER FROM SURFACE-ENHANCED RAMAN-SCATTERING
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DOI：
10.1021/la00082a037
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发表时间：
1988-07-01
期刊：
影响因子：
3.9
通讯作者：
SIIMAN, O
中科院分区：
文献类型：
--
作者：
CURLEY, D;SIIMAN, O
本文报道了N-取代2，4-二硝基苯基（DNP）氨基酸在胶体银上的表面增强拉曼散射（Sers）。在远离DNP基团在360 nm处的电子吸收带的488.0 nm激发下，N-（2，4-二硝基苯基）-取代的蛋氨酸、胱氨酸、天冬氨酸和赖氨酸的Sers光谱主要由DNP基团的强带所支配，其在正常的拉曼光谱中显示出比单独的氨基酸大得多的散射强度。使用亲本氨基酸的Sers光谱来建立至少一个羧酸酯基团与银表面的结合。使用具有386.4-nm激发的DNP-Met在水溶液中的严格共振拉曼光谱来分别在1271和1330 cm-1处对邻硝基和帕拉基团伸缩模式yB（o-NO2）和y8（p-NO2）进行谱带归属。在银颗粒悬浮液中0.1-100 µ范围内，Sers谱带的绝对和相对强度均随总半抗原浓度而变化。Sers增强的下限在103-104范围内。与p8（o-NO2）、p8（p-NO2）和833 cm-1处DNP环对称呼吸模式相关的谱带的相对强度变化主要用于监测半抗原在银表面上的构象和取向。在高浓度（10-100 µ）下，DNP氨基酸采用折叠构象以占据每个分子更少的表面积。在这种情况下，γ 8（p-NO2）带是强的，并且DNP环显示为相对于表面位于端部。在低浓度下，假定更开放或延伸的构象。在这种结构中，DNP环具有两种可能的取向，相对于表面是平坦的或边缘上的。在低（< 1 μ）和中间（1-10 μ）浓度范围内的相对Sers带强度变化，其显示出yB（p-NO2）、vs（o-NO2）和发射呼吸）中的强度的完全损失或仅v8（o-NO2）带中的强度，支持低浓度下的平坦取向和中间浓度下的边缘取向。从该半胱氨酸的Sers光谱可以得出关于DANS-Asp中的5-（二甲氨基）萘-1-磺酰基（DANS）基团在胶体银上的取向的类似结论，该半胱氨酸的荧光发射完全掩盖了其在溶液中的正常拉曼光谱。
Surface-enhanced Raman scattering (SERS) from N-substituted 2, 4-dinitrophenyl (DNP) amino acids adsorbed on colloidal silver has been observed. SERS spectra of lV-(2, 4-dinitrophenyl)-substituted me-thionine, cystine, aspartic acid, and-lysine, taken with 488.0-nm excitation far from the electronic absorption band of the DNP group at 360 nm, were dominated by intense bands of the DNP group, which in normal Raman spectra showed a much greater scattering intensity than the amino acid alone. SERS spectra of the parent amino acids were used to establish binding of at least one carboxylate group to the silver surface. A rigorous resonance Raman spectrum of DNP-Met in aqueous solution with 386.4-nm excitation was used to make band assignments for the ortho and para nitro group stretching modes, yB (o-N02) and y8 (p-N02), at 1271 and 1330 cm'1, respectively. Both absolute and relative intensities of SERS bands changed with the total hapten concentration in the range 0.1-100 µ in the silver particle suspension. Lower limits on SERS enhancements were placed in the 103-104 range. Relative intensity changes in bands associated with p8 (o-N02), p8 (p-N02), and the DNP ring symmetrical breathing mode at 833 cm'1 were used mainly to monitor the conformationand orientationof the haptens on the silver surface. At high concentrations (10-100 µ) it is proposed that the DNP amino acids adopt a folded-over conformation to occupy less surface area per molecule. In this case the y8 (p-N02) band was intense, and the DNP ring is shown to lie end-on with respect to the surface. At low concentrations a more open or extended conformation is assumed. In this structure the DNP ring has two possible orientations, either flat or edge-on with respect to the surface. Relative SERS band intensity changes in the low (< 1 µ) and intermediate (1-10 µ) concentration ranges, which show either a complete loss of intensity in yB (p-N02), vs (o-N02), and firing breathing) or only intensity in the v8 (o-N02) band, support a flat orientation at low concentrations and an edge-on orientation at intermediate concentrations. Similar conclusions regarding orientation of the 5-(dimethylamino) naphthalene-l-sulfonyl (DANS) group in DANS-Asp on colloidal silver could be reached from the SERS spectrum of thishapten, whose fluorescence emission totally obscures its normal Raman spectrum in solution.