鸟嘌呤,鸟苷及其甲基化衍生物的近红外傅里叶变换表面增强拉慢光谱

本文给出了采用表面增强傅里叶变换拉慢光谱法测定的鸟嘌呤、鸟苷及其甲基化衍生物的拉曼散射，实验结果表明，采用了近红外波长的平拉曼散射及傅里叶变换技术成功地获得鸟嘌呤、鸟苷及其甲基化衍生物的水溶液在较低浓度下（０．１－０．０１ｍｇ／Ｌ）不受荧光干扰的拉曼光谱图，其频率与相对强度分布表明，水溶液状态下吸附在Ａｇ膜上的鸟嘌呤（苷）及其衍生物结构中的有关振动谱带ｒ（Ｃ＝Ｏ）、ＮＨ２和杂环上的Ｎ获得显著增强。     

维生素B类药物在薄层原位的近红外付立叶变换表面增强拉曼光谱

维生素Ｂ类药物在薄层原位的近红外付立叶变换表面增强拉曼光谱汪瑗，于秉正张煦（首都师范大学分析测试中心北京１０００３７）（北京大学分析测试中心北京）关键词维生素Ｂ_１，维生素Ｂ_２，薄层色谱，表面增强拉曼散射，近红外付立叶变换拉曼光谱将薄层色谱（ＴＬＣ）...     

拉曼光谱在分析化学中的应用进展

评述了各种拉曼技术在分析化学方面的应用进展,涉及到的拉曼光谱技术有常规拉曼光谱、常规共振拉曼光谱、表面增强拉曼光谱、表面增强共振拉曼光谱、傅里叶变换拉曼光谱、傅里叶变换表面增强拉曼光谱及其联用技术。共引用９１篇文献。     

傅里叶变换红外光谱和傅里叶变换拉曼光谱法无损鉴别药材的真伪

利用傅里叶变换红外（FT-IR）和近红外傅里叶变换拉曼（NIR FT-aman）光谱法对大黄（西宁大黄）与伪品大黄（华北大黄、山大黄、水根大黄）进行了无损快速的鉴别。结果表明：尽管正品大黄与伪品大黄差别较小，有大部分的化学成分有很大的相同之处，但在红外、拉曼谱图中各自的特征峰较突出，根据谱峰的强度和位置可容易地将它们区别开来。红外和拉曼光谱法相互印证，相互补充，具有快速、准确、操作简单、重复性好、不需对样品进行分离提取，可直接鉴别等特点。     

氨基酸在薄层原位的傅里叶变换表面增强拉曼光谱

应用表面增强技术将薄层色谱与红外傅里叶变换拉曼光谱联用，在薄层色谱原位获得两种氨基酸光谱。研究表明，在薄层原位微量样品的ＮＩＲ－ＦＴ－ＳＥＲＳ光谱与纯固体样品ＦＴ－Ｒａｍａｎ光谱的主要特征谱带频率基本一致，在银微粒作用下，色氨酸分子中吲哚环环伸缩振动获最大增强，组氨酸分子中Ｃ＝Ｎ双键的伸缩振动是明显增强，对８μｇ样品就能在薄层色谱原位较可靠地反映了分子的结构信息。     

傅里叶变换拉曼光谱法无损鉴别植物生药材

首次利用傅里叶变换拉曼光谱法（ＦＴ－Ｒａｍａｎ）直接测定了２３种常用植物生药材。各种药材因所含化学成分的不同而反映出拉曼谱振动峰的差异,并遵循一定的变化规律。该方法快速,准确,不破坏样品。     

维生素B1-银胶体系SERS受卤离子竞争吸附的影响

利用傅里叶变换.表面增强拉曼光谱(FT-SERS)研究了卤素离子(Cl-、Br-、I-)对维生素B1(VB1)分子表面增强拉曼散射光谱(SERS)的影响.实验结果表明,在此体系中加入卤素离子则SERS效应减弱,且三种卤素离子在银胶上的吸附能力顺序为I->Br->Cl-.     

卷积伏安法实验数据的平方根卡尔曼滤波Ⅱ卷积伏安法中重叠峰的分辨

本文探讨采用平方根卡尔曼滤波进行卷积伏安重叠峰的分辨．模拟数据试验表明，１∶Ｎ平方根卡尔曼滤波器、结合标准加入法和快速傅里叶变换，用于重叠峰的分辨，具有较高的准确度和较强的分辨能力，滤波结果有良好的线性关系．用于Ｉｎ（Ⅲ）～Ｃｄ（Ⅱ）重叠响应信号的分辨，获得满意结果     

血卟啉衍生物(HpD)的表面增强共振拉曼光谱

近年来,采用光敏剂(H_pD)与光的协同效应,诊治癌肿疾病有了较大的进展,所以,研究其光谱特性是有其现实意义的。 用共振拉曼光谱和表面增强拉曼光谱所获得的散射强度,都比通常的拉曼光谱有几个数量级的增强,并可得到稀溶液(10~(-6)～10~(-3)mol/L)的高质量光谱,本文报道了8×10~(-3)mol/L HpD水溶液的共振拉曼光谱和5×10~(-5)mol/L HpD水溶液的表面增强共振拉曼光谱,结果表明,表面增强共振拉曼光谱比共振拉曼光谱的散射强度滴出三个量级。     

近红外光谱用于过氧化氢含量的定量分析研究

用长波近红外光谱仪（傅里叶变换,InGaAs检测器）和短波近红外光谱仪（光栅分光,CCD检测器）对比研究了25％～30％过氧化氢水溶液中过氧化氢含量的定量分析方法。结果表明,应用短波近红外光谱结合长光程样品池对25％-30％过氧化氢水溶液样品中过氧化氢含量进行定量分析,可以显著减少过氧化氢分解对定量分析的干扰,使定量分析的准确度和重复性显著提高。短波近红外光谱定量分析模型RMSECV和RMSEP分别为0．06和0．05;长波近红外光谱定量分析模型RMSECV和RMSEP分别为0．10和0．09。     

Stacked and continuous helical self-assemblies of guanosine monophosphates detected by vibrational circular dichroism

The aim of this study was to characterize self-assembled structures of guanosine derivatives in aqueous solutions by vibrational circular dichroism (VCD) and electronic circular dichroism (ECD). Three guanosine derivatives were studied [5'-guanosine monophosphate (GMP), diphosphate (GDP), and triphosphate (GTP)] using a broad range of concentrations and various metal/guanosine ratios. VCD was used for the first time in this field and showed itself to be a powerful method for obtaining specific structural information in solution. It can also help to determine the impact that the cations have, when added to the solution, on the versatile structures of guanine derivatives in terms of their association and disassociation. Based on the markedly different intensities and signs of the VCD signals observed for different concentrations of guanosine derivatives, we propose various structures based on guanine quartets for high guanosine concentrations and high K(+)/guanosine ratios (i.e., columnar helical organization of the quartets, which are rearranged into a continuous helix). We performed a degenerate coupled oscillator (DCO) calculation to interpret the VCD spectra obtained and how they vary during the assembly of guanosine derivatives. The calculations correctly predicted the VCD spectra and enabled us to identify the structures of the metal cation/guanosine monophosphate aggregates. ECD in the ultraviolet region was used as a diagnostic tool to characterize the studied systems and as a contact point between the previously defined structures of the guanine derivative assemblies and the molecular systems studied here. These studies revealed that the VCD technique is a powerful new method for determining the structures of optically active guanosine motifs.     

SERS studies of the adsorption of guanine derivatives on gold colloidal nanoparticles

Surface enhanced Raman scattering spectra of guanine, guanosine and 2'-deoxyguanosine adsorbed on gold colloidal nanoparticles were obtained. From the striking similarity of the SERS spectra of these compounds, it can be evidenced that guanosine and 2'-deoxyguanosine adsorb on gold nanoparticles through the guanine moiety. The molecular sites involved in the interaction with the gold surface are the same for the 3 compounds: the oxygen of the carbonilic group and the N(7) atom. Guanine, guanosine and 2'-deoxyguanosine adsorb on the gold substrates with a tilted orientation with respect to the metal surface. SERS data were interpreted taking into account density functional theoretical (DFT) calculations of guanine.     

Time-resolved resonance Raman investigation of the 2-fluorenylnitrenium ion reactions with C8 guanosine derivatives

A nanosecond time-resolved resonance Raman (ns-TR3) spectroscopic study of the reactions of the 2-fluorenylnitrenium ion with several C8-substituted guanosine derivatives is reported. The TR3 spectra show that the 2-fluorenylnitrenium ion reacts with the C8-substituted guanosine derivatives (C8-methylguanosine and C8-bromoguanosine) to produce C8 intermediates with the methyl and bromine moieties still attached to the intermediate species at the C8 position. The C8-bromoguanosine species was observed to be less reactive toward the 2-fluorenylnitrenium ion compared to the guanosine and C8-methylguanosine species. Comparison of the TR3 spectra to the results obtained from density functional theory calculations was used to characterize the C8 intermediates observed to learn more about their structure and properties. The implications of these results for the chemical reactivity of arylnitrenium ions toward substituted guanosine derivatives are briefly discussed.     

Formamidopyrimidines as major products in the low- and high-intensity UV irradiation of guanine derivatives

Two major UV-induced transformation products of guanosine (Guo) in oxygen-free aqueous solution were isolated and characterized using reverse-phase HPLC-ESI-MS and UV absorption spectrophotometric techniques. These products were identified as two different sugar isomers of 2,6-diamino-4-hydroxy-5-formamidopyrimidine ribonucleosides, FapyGuo. A formation quantum yield of the order of 10(-3) for these products was obtained at a 75 microM concentration of Guo, while an increase in the ground state concentration of Guo from 10(-5) to 10(-4) M decreased their formation yield by a factor of ten. The formation of FapydGuo was also observed in the 254 nm photolysis of 2'-deoxyguanosine. In addition, the formation FapyGua was identified in the UV photolysis of all the guanine derivatives investigated. A formation quantum yield of the order of 10(-4) was obtained for the latter product, except in the photolysis of Gua in which a higher formation yield (10(-3)) was determined. These results suggest that hydration of the radical cation of guanine, followed by opening of the imidazole ring to form Fapy products, is one of the main low-intensity UV radiation-induced photo-transformation pathway of the guanine derivatives in oxygen-free aqueous solutions. Furthermore, the formation of the Fapy products and base release occurs through a similar photo-transformation pathways using a high-intensity UV radiation source.     

Vibrational spectra and structures of the anions of urazole and 4-methylurazole: DFT calculations of the normal modes and the influence of hydrogen bonding

Solid state IR and Raman as well as aqueous solution state Raman spectra are reported for the anions of urazole and 4-methylurazole, and their N-deuterated derivatives. DFT calculations, at the B3-LYP/cc-pVTZ level, established that the structures and vibrational spectra of both anions can be interpreted using a model that incorporates hydrogen-bonded water molecules, in conjunction with the polarizable continuum solvation method. In the case of the urazole anion it is shown that deprotonation occurs primarily at N1 rather than N4, but there is also evidence for the second tautomer both in the solid state and in aqueous solution. The vibrational spectra were computed at the optimised molecular geometry in each case, enabling normal coordinate analysis, which yielded satisfactory agreement with the experimental IR and Raman data. Computed potential energy distributions of the normal modes provided detailed vibrational assignments.     

NEAR-INFRARED FOURIER-TRANSFORM RAMAN STUDY OF CHLOROPHYLL a IN SOLUTIONS

Abstract— The 1064 nm excited Fourier-transform (FT) Raman spectra have been measured for chlorophyll a (Chl- a ) in various solutions. Features of the obtained spectra are largely different from those of Soret-resonant Raman spectra of Chl- a . For example, a band due to the C=0 stretching mode of the 13-keto group is much stronger in the former than in the latter. Although the excitation wavelength is rather far from that of the Qy absorption of Chl- a , notable enhancements of bands due to the C=O stretching mode of the 13¹-keto group and to the C=C stretching mode of the vinyl group and those in the 1250–600 cm^-1 region suggest that the 1064 nm-excited Raman spectra of Chl- a are preresonance enhanced via the Qy band. Some of the marker bands for the coordination number of the central Mg atom, which have been used in the visible-excited resonance Raman spectra, are not valid in the 1064 nm-excited Raman spectra. Instead, new marker bands are found in the latter. The 1064-nm excited Raman spectra of Chl- a in a hydrated hexane solution reveal that the dehydrated oligomer of Chl- a as well as Chl- a -water micelles coexist in the solution. They also suggest that the size of the oligomer is considerably larger and the hydrogen bonding of the 13¹-keto group in the oligomer is weaker than that in the micelles.     

Raman spectra of glassy aqueous LiX and CaX2 solutions (X = Cl,Br and I) in the low frequency region

Raman spectra of glassy aqueous LiX and CaX₂ solutions are obtained in the low frequency region (10–900 cm^?1). Two low frequency Raman bands are clearly observed. A qualitative discussion is given for the intensity correlation and observed frequency shifts of these bands with halide ions.     

Calculation of Raman spectra and structure elucidation of guanine in the polycrystalline state and in aqueous solution

The frequencies and relative intensities of lines in the Raman spectra of the condensed states of guanine and its deutero substituted analog have been calculated. The effect of hydrogen bonding on the Raman spectrum has been studied. Guanine exists in different tautomeric forms (G-N₉H and G-N₇H) at different pH in aqueous solution (for acidic and alkaline media, respectively).     

Raman-Spektroskopie und Molekülstruktur

The substitution pattern of benzene derivatives can be determined by means of a series of questions on characteristic Raman bands; frequency range, relative intensity, and degree of polarisation must be considered. Mono-, ortho-, meta-, and para-di-, and 1,3,5-tri-substituted derivatives can be recognised particularly well. Assignments made from Raman spectra appear to us to be more reliable than those obtained from characteristic infrared bands.     

In-situ detection of single particles of explosive on clothing with confocal Raman microscopy

Confocal Raman microscopy is shown to detect picogram quantities of explosives in-situ on undyed natural and synthetic fibres, and coloured textile specimens leaving potentially evidential materials unaltered. Raman spectra were obtained from pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), and ammonium nitrate particles trapped between the fibres of the specimens. Despite the presence of spectral bands arising from the natural and synthetic polymers and dyed textiles, the explosive substances could be identified by their characteristic Raman bands. Furthermore, Raman spectra were obtained from explosives particles trapped between highly fluorescent clothing fibres. Raman spectra were collected from explosives particles with maximum dimensions in the range 5-10 μm. Spectra of the explosives on dyed and undyed clothing substrates were readily obtained in-situ within 90 s and without sample preparation.