小型光泵NH3分子远外激光器的模式竞争

通过求解四能级系统的半经典 密度矩阵方程迭代法计算了ＣＯ２－１０Ｒ泵浦小型超辐射光泵ＮＨ３分子远红外激光器的Ｐ埃Ｑ支跃迁输出光强的增量比。计算表明在超辐射小型ＮＨ３光泵远红外激光器中，Ｖ２：α→ｓＰ（５，４）和α→ｓＱ（５，４）模式竞争结果，Ｑ支跃迁占优势，使Ｐ支被抑制。理论计算与实验结果一致。     

Co(Ⅱ)、Ni(Ⅱ)非有机溶剂液液萃取行为的研究

本文研究了ＰＥＧ２０００铬菁Ｒ（ＮＨ４）２ＳＯ４体系对Ｃｏ（Ⅱ）、Ｎｉ（Ⅱ）的非有机溶剂萃取行为。指出在ｐＨ＝５的（ＮａＡｃＨＡｃ）水溶液中，有（ＮＨ４）２ＳＯ４存在下，Ｎｉ（Ⅱ）可被ＰＥＧ相几乎完全萃取，而Ｃｏ（Ⅱ）则基本上不被萃取。从而获得了Ｃｏ（Ⅱ）与Ｎｉ（Ⅱ）混合离子的定量分离。     

小型光泵NH_3分子远红外激光器的模式竞争

通过求解四能级系统的半经典密度矩阵方程，用迭代法计算了ＣＯ２－１０Ｒ（６）泵浦小型超辐射光泵ＮＨ３分子远红外激光器（ｍｉｎｉ－ＮＨ３－ＯＰＦＩＲＬ）的Ｐ支和Ｑ支跃迁输出光强的增量比。计算表明在超辐射小型ＮＨ３光泵远红外激光器中，Ｖ２ａ→ｓＰ（５，４）和ａ→ｓＱ（５，４）模式竞争结果，Ｑ支跃迁占优势，使Ｐ支被抑制。理论计算与实验结果一致     

HCl＋Xe掺杂CO矩阵晶体中Xe＋2Cl－电子态跃迁

报道ＨＣｌ＋Ｘｅ掺杂ＣＯ矩阵晶体中，在３０８ｎｍ激光的激发下，首次观测到准分子Ｘｅ＋２Ｃｌ－的特征辐射荧光谱。双光子诱导电荷转移合作吸收反应：Ｘｅ＋ＨＣｌ＋２ｈν→αＸｅ＋（ＨＣｌ）－中，双光子吸收截面大于５×１０－４２ｃｍ４ｓ［６］。     

低能氮离子对胞嘧啶水溶液损伤作用的光谱分析

利用N2常压弧光放电产生低能N^ ,经电场加速后注入胞嘧啶（C）水溶液,研究了低能N^ 作用后胞嘧啶水溶液的紫外及红外吸收光谱的变化。结果表明,低能N^ 对溶液样品造成成了多种形式的损伤,形成丰富多彩的损伤产物,其中不仅包括水溶液中多种损伤碎片之间的重新化合,还包括N^ 与溶液中元素形成新的化学基团,继而与其他碎片结合形成产物,使外来的N^ “沉积”在溶液样品中。     

过渡金属氢化物和聚集双键化合物反应的研究Ⅲ．用ESR方法考察二茂锆氢化物与RNCS的反应机理

本文用ＥＳＲ方法考察了Ｃｐ＿２Ｚｒ（Ｈ）Ｃｌ与ＲＮＣＳ（Ｒ＝Ｃ＿６Ｈ＿５，ｃ－Ｃ＿６Ｈ＿（１１），ｎ－Ｃ＿４Ｈ＿９）的反应的过程，结果表明，在这类反应过程中，Ｚｒ－Ｈ键发生均裂，中心金属锆经过＋４─→＋３─→＋４的价态变化，反应通过自由基机理进行．     

光泽精－H_2O_2－KCl中性非缓冲体系电生化学发光行为及机理研究

本文用自制的电生化学发光仪，选择光泽精－Ｈ２Ｏ２－ＫＣｌ中性（非缓冲）水溶液作为电生化学发光（ＥＣＬ）体系。该体系具有比前人所研究的ＬＵＣ－Ｏ２的碱性水溶液的ＥＣＬ体系灵敏度高，ＥＣＬ强度大，还原产物不易沉积在阴极上影响发光及所发的ＥＣＬ不与传统的ＣＬ相混淆的优点。光泽精浓度在８×１０－５～４×１０－８ｍｏｌ．Ｌ－１范围内与ＥＣＬ强度成正比，光泽精检测限为１０－９ｍｏｌ．Ｌ－１。此外还对该体系的测定条件及机理进行了研究，并提出了可能的机理。     

N（4Su）＋CH）（a^4Σ^—）体系的分子反应动力学研究

用轨线法对Ｎ（＾４Ｓｕ）＋ＣＨ（０,０）→ＣＮ（ｖ＇,Ｊ＾＇）＋Ｈ（Ｓｇ）和Ｎ（＾４Ｓｕ）＋ＣＨ（０,０）→ＮＨ（ｖ＇,Ｊ＇）＋Ｃ（＾３Ｐｇ）反应进行计算,研究了上反应的阈能、反应截面、产物散射分析和微观反应机理。     

DNA构象研究中脱氧核糖拉曼信号的作用

小牛胸腺ＤＮＡ水溶液激光拉曼谱中，表征鸟嘌呤核苷糖环折叠分别为Ｃ３’内式与Ｃ２’内式的特征模６７１与６８２ｃｍ＾－１同时存在，我们认为这表明在ＤＮＡ水溶液中具有Ａ－ＤＮＡ与Ｂ－ＤＮＡ两种构象。计算出６７１ｃｍ＾－１相对含量为３９．４％，与用我们提出的Ｂｒｏｗｎ改进法Ｉ８０７／Ｉ１１００计算得出的３５％Ａ型ＤＮＡ构象含量相接近。其它的脱氧核糖构象拉曼模与磷酸脱氧核糖骨架振动特征模也定性地表明了同样的     

A3M2Ge3O12石榴石体系中Cr3+离子的宽带发射光谱

首次报告在Ａ３Ｍ２Ｇｅ３Ｏ１２∶Ｃｒ（Ａ＝Ｃｄ２＋,Ｃａ２＋;Ｍ＝Ａｌ３＋,Ｇａ３＋,Ｓｃ３＋）锗酸盐石榴石体系中,Ｃｒ３＋离子室温下的红—近红外（Ｒ—ＮＩＲ）宽发射带光谱性质。随位于八面体格位上的Ａｌ３＋→Ｇａ３＋→Ｓｃ３＋和十二面体格位上的Ｃｄ２＋→Ｃａ２＋组成顺序变化,室温下,Ｃｒ３＋离子的４Ｔ２→４Ａ２能级跃迁的Ｒ－ＮＩＲ宽发射带,发射峰及光谱的长波和短波边逐渐向低能长波边移动。这是由于晶场强度减弱,阳离子的离子半径增大的结果。在镉（钙）铝和镉（钙）镓锗酸盐体系中,少量Ｓｃ３＋取代八面体上的Ａｌ３＋和Ｇａ３＋时,可使Ｃｒ３＋的Ｒ－ＮＩＲ荧光发射强度增强。     

Inner‐shell chemical shift of DNA/RNA bases and inheritance from their parent purine and pyrimidine

Inner‐shell electronic structures, properties and ionization spectra of DNA/RNA bases are studied with respect to their parent pyrimidine and purine species. Density functional theory B3LYP/aug‐cc‐pVTZ has been employed to produce the geometries of the bases, whereas LB94/et‐pVQZ//B3LYP/aug‐cc‐pVTZ is used to calculate site‐related Hirshfeld charges and core (vertical) ionization energies, as well as inner‐shell spectra of C1s, N1s and O1s for DNA/RNA bases and their parent pyrimidine and purine species. The site‐dependent variations of properties indicate the changes and inheritance of chemical environment when pyrimidine and purine become substituted. In general, although the changes are site‐dependent, they are also ring‐dependent. Pyrimidine bases change less significantly with respect to their parent pyrimidine than the purine bases with respect to their parent purine. Pyrimidine bases such as uracil, thymine and cytosine inherit certain properties from their parent pyrimidine, such as the Hirshfeld charge distributions and the order of core ionization energy level etc. No particular sites in the pyrimidine derivatives are engaged with a dramatic chemical shift nor with energy crossings to other sites. For the core shell spectra, the purine bases inherit very little from their parent purine, and guanine exhibits the least similarities to the parent among all the DNA/RNA bases.     

3种核酸碱基(胞嘧啶、胸腺嘧啶、尿嘧啶)在银电极表面的吸附形态

通过表面增强拉曼散射研究了胞嘧啶、胸腺嘧啶和尿嘧啶在粗糙银电极表面上的吸附形态随电极电位的变化关系.大量的结构信息可从丰富的表面拉曼信号及其随电极电位相应的变化而获得.分析表明在电极电位负移过程中,胞嘧啶一直通过N3位垂直吸附于纳米银颗粒表面;而胸腺嘧啶分子和尿嘧啶分子在表面的吸附状态都随电位改变发生了变化,较正电位下...     

核酸碱基和核苷的高效液相色谱——表面增强拉曼光谱在线联机分析研究

本文将反相高效液相色谱(RP——HPLC)与表面增强拉曼光谱(SERS)联机,对三个核嘧啶、四个核嘌呤和两个核嘧啶及其核苷混合物进行在线联机分析研究。在流动条件下,对影响 SERS 测定的因素,如激光照射、温度、pH 值、流速、记忆效应,以及联机系统的接口装置等进行了讨论。文中给出了联机测得的三维和二维 SERS 色谱图。     

DNA纤维质子化及脱嘧啶的拉曼光谱研究

对鲱精DNA纤维用pH 1 85酸溶液处理不同时间后 ,将样品进行拉曼光谱分析。结果表明DNA分子发生明显的质子化作用 ,有部分GC碱基对之间形成Hoogsteen型氢键的证明。酸不仅导致了DNA中部分嘌呤的脱落 ,同时还有部分嘧啶的脱落 ,其原因与嘧啶的质子化可能强于嘌呤有关。质子化、脱嘌呤、脱嘧啶的共同作用进一步引起原有正常配对的氢键断裂 ,DNA分子内双链状态不稳定 ,可见酸处理DNA时发生了酸变性这一现象 ,但其产物性质显著不同于热变性或碱变性产物。     

紫外辐射对小牛胸腺DNA水溶液影响的拉曼光谱研究

报道了小牛胸腺DNA水溶液经9,20,40min紫外辐射的拉曼光谱图,紫外线的辐射照度为1868W·m-2。实验结果表明波长为2537nm的紫外光在起主要作用的紫外辐射对DNA的损伤是严重的,短短10min的紫外辐射就使1094cm-1这个强峰分裂成几个小峰,说明DNA的构象受到破坏,DNA的构型发生变化,部分单双键发生了断裂,出现了各种各样由于DNA键断裂产生的多核苷酸;4种碱基均受到不同程度的影响,碱基间的氢键造成断裂,其中嘧啶、嘌呤碱基受到的损伤较为严重;紫外辐射对脱氧核糖也产生了破坏。另外,该实验也表明,在水溶液中,DNA以B型结构为主,局部的A型结构仍然存在。     

Vibrational Spectroscopic and Theoretical Studies of Urea Derivatives with Biochemical Interest: N,N′-Dimethylurea,N,N,N′,N′-Tetramethylurea,and N,N′-Dimethylpropyleneurea

Abstract

Mid-infrared, far-infrared, and Raman vibrational spectroscopic studies were combined with density functional theory (DFT) calculations and normal coordinate force field analyses for N,N′-dimethylurea (DMU), N,N,N′,N′-tetramethylurea (TMU), and N,N′-dimethylpropyleneurea (DMPU: IUPAC name 1,3-dimethyltetrahydropyrimidin-2(1H)-one). The equilibrium molecular geometry of DMU (all three conformers), TMU, and DMPU and the frequencies, intensities, and depolarization ratios of their fundamental infrared (IR) and Raman vibrational transitions were obtained by DFT calculations. The vibrational spectra were fully analyzed by normal coordinate methods as well. A starting force field for DMPU was obtained by adapting corresponding force constants for DMU and TMU, resulting after refinements in the stretching force constants C=O (7.69, 7.30, 7.68 N·cm^?1), C–N (5.16, 5.55, 5.05 N·cm^?1), and C-Me (5.93, 4.00, 4.22 N·cm^?1) for DMU, TMU, and DMPU, respectively. The dominating conformer of liquid DMU was identified as trans-trans, strong intermolecular hydrogen bonding was verified in solid DMU, and weak dipole–dipole association was found in liquid TMU and in DMPU. Special attention was paid to analyzing the methyl group frequencies, which revealed deviations from local C_3v symmetry. A linear correlation was found between the CH stretching force constants and the inverse of the CH bond lengths (1/r ²). The averaged NH stretching frequencies of gaseous, dissolved, and solid urea and of DMU, with variations for hydrogen bonding of different strength, are linearly correlated to the NH stretching force constants. Characteristic skeletal vibrations were assigned for a broad variety of urea derivatives and also for pyrimidine derivatives, which all contain the N₂C=O entity. The very strong IR bands of C=O stretching (1,676 ± 40 cm^?1) and asymmetric CN₂ stretching (1,478 ± 60 cm^?1), and the very intense Raman feature of symmetric CN₂ stretching or ring breathing (757 ± 80 cm^?1), can be recognized as fingerprint bands also for the pyrimidine derivatives cytosine, thymine, and uracil, which all are nucleobases in DNA and RNA nucleotides.     

UVA和UVB区段紫外线照射对DNA影响的拉曼光谱分析

本文检测了鲱鱼精DNA水溶液和经UVA和UVB紫外线辐射后的拉曼光谱。研究结果表明,尽管该区段紫外辐射远比UVC照射对DNA影响小,但经过较长时间辐射仍会对鲱鱼精DNA造成损伤,首先受影响的是碱基嘧啶和脱氧核糖。     

M-RNA碱基复合物(M=Ca~+和Mg~+)特征振动的密度泛函理论分析

采用密度函数理论的B3LYP交换关联能泛函在6-311+G(2df,2p)基组水平上,优化计算了Ca+,Mg+与RNA碱基嘧啶各同分异构体形成稳定复合物的结构,发现其中C1M,T1M和U1M(M=Ca+和Mg+)为最稳定复合物,并对这些复合物红外振动进行了计算.计算结果显示碱基嘧啶单体主要存在的两个红外特征振动,是由环振动和环外氧原子及与其成键的环上碳原子之间产生伸缩振动引起的.当形成复合物时,由于离子的参与,使单体碱基分子的振动情况发生了改变,主要表现在离子倾向于与环外负电子原子N和O原子成键,使与离子直接作用环外原子参与的特征振动频率减小,谱线红移;不与离子直接作用环外原子引起的特征振动频率增大,谱线蓝移.     

Quantum-mechanical calculation of the intensity distribution in resonance Raman spectra of cytosine

A quantum-mechanical calculation of the relative intensities of lines in resonance Raman (RR) spectra of cytosine excited by laser radiation at 266, 218, and 200 nm was performed in different approximations of the vibronic theory. Both the Herzberg-Teller effect and the contribution from electronic states located close to the resonance state are shown to play a significant role in determining the relative intensities of lines. A satisfactory agreement between the calculated results and experimental data is obtained. The specific features of the intensity distribution in the RR spectra of cytosine are compared with those in the spectra of the previously studied thymine and uracil, which have a similar structure and also belong to the simplest nucleic acid bases.     

天然脱氧核糖核酸分子中碱基价键的振动变化

天然脱氧核糖核酸分子中碱基价键的振动变化余多慰，柯惟中（南京师范大学南京２１００９７）ＲａｍａｎＣｈａｒａｃｔｅｒｉｓｔｉｃＡｎａｌｙｓｅｓｏｆＴｈｅＴｗｏＣｏｖａｌｎｅｃｅＢｏｎｄｓｂｙＴｈｅＢａｓｅＳｌｄｅｏｆＧｌｙｃｏｓｉｄｌｃＢｏｎｄｉｎＤＮ...