基于太赫兹光谱的氨基酸检测

太赫兹是指频率从0.1到2.0 THz之间的远红外波。与傅里叶红外相比,太赫兹时域光谱能量低,信躁比高,并且无辐射损伤。氨基酸分子的低频振动模式(扭转,集体振动模式和氢键)处在 THz波段。氨基酸是一类重要的生物分子,是组成蛋白质最基本的物质。氨基酸分子以分子间氢键相互连接构成晶体。氨基酸在THz波段比在红外波段体现更多独特吸收特征。到目前为止,已经获得了20种氨基酸分子的太赫兹吸收谱,包括利用太赫兹技术对部分氨基酸的定量分析。氨基酸的太赫兹光谱研究,有利于深层次理解蛋白质/ DNA的低频振动模式及相关生物反应和活性。文章综述了20种氨基酸分子的太赫兹吸收光谱并建立了吸收光谱数据库。总结了太赫兹技术在氨基酸应用方面存在的问题,并对未来发展方向进行展望。     

X‐ray K absorption spectral studies of copper (II) hydroxamic acid mixed ligand complexes

X‐ray absorption spectra at the K‐edge of copper have been studied in copper mixed ligand complexes having hydroxamic acid as one of the ligands. The X‐ray absorption spectra have been recorded at BL‐8 Dispersive Extended X‐ray Absorption Fine Structure (EXAFS) beamline at the 2.5‐GeV INDUS‐2 Synchrotron Source, RRCAT, Indore, India. The data obtained has been processed using EXAFS data analysis program Athena. The energies of the K absorption edge, chemical shifts, edge‐widths and shifts of the principal absorption maximum in the complexes have been determined and discussed. The chemical shift data have been utilized to estimate effective nuclear charge on the absorbing atom. The normalized EXAFS spectra have been Fourier transformed. The position of the first peak in the Fourier transform gives the value of first shell bond length, which is shorter than the actual bond length as a result of energy dependence of the phase factors in the sine function of the EXAFS equation. This distance is thus the phase‐uncorrected bond length and has also been determined by Lytle, Sayers and Stern's (LSS) graphical method. The results obtained from LSS and the Fourier transformation methods are comparable with each other. The first shell bond length has also been estimated by Lytle's and Levy's methods from the EXAFS data. Copyright © 2014 John Wiley & Sons, Ltd.     

Terahertz spectroscopy of biological molecules

We study experimentally the absorption and refraction spectra for a number of amino acids, proteins and nucleic acids in the frequency range 0.1–3.5 THz. The characteristic absorption lines are revealed. The spectroscopy of water solutions of proteins and nucleic acids is carried out under conditions of total internal refraction. This method can be used for studies of the functional properties of biomolecules and the dynamics of their interaction.     

An infrared spectroscopic study of tert-butyl peroxoesters

The infrared spectra of peroxoesters based on tert-butyl hydroperoxide and aliphatic acids, tert-butyl peroxobenzoate, and their nonperoxo analogs have been studied. The observed absorption bands have been assigned to the vibrations of individual bonds, the characteristic features of the structure of the peroxoester molecules have been investigated, and the force constants have been calculated. A set of absorption bands suitable for the identification and analysis of tert-butyl peroxoesters based on aliphatic acids has been proposed.     

Computational study of new azo dyes with different anchoring groups for dye-sensitised solar cells

Some of new azo dyes with different anchoring groups, such as biscarbodithiolic acid, hydroxamic acid, phosphonic acid, carboxcylic acid and sulfonic acid have been investigated theoretically to evaluate the effects of various anchoring groups on the optical and electronic properties of the dyes in dye-sensitised solar cells. Optical and electronic properties, UV–Vis absorption spectra, light-harvesting efficiency, lifetime of the excited state, chemical hardness and lowest unoccupied molecular orbital (LUMO) orbital weight of the dyes on the anchoring groups, have been studied to shed light on how the various anchoring groups influence the properties of the dyes. The biscarbodithiolic acid-based dye shows the longest maximum absorption wavelength and the widest absorption spectra together with the highest light-harvesting efficiency, the longest lifetime of the excited state and the highest the LUMO orbital weight of the dye on the atoms of the anchoring group, suggesting the good ability in electron injection. Theoretical calculations have been also performed on the adsorption of these dyes on the TiO₂ anatase (101) surface. These results show that the biscarbodithiolic acid-based dye has the highest adsorption energy and the largest negative shift of the conduction band of TiO₂ due to the adsorption of the dye onto the TiO₂.     

Investigation of Absorption and Emission Spectra of Nitrogen Oxides NO,N2O,NO2, and N2O4

Russian Physics Journal - The absorption and emission spectra of NO, N2O, NO2, and N2O4 nitrogen oxides have been studied with high and intermediate spectral resolution in the range 0.25–25...     

A solid-state N magic-angle spinning NMR study of some amino acids

Experimental strategies for the acquisition of high-quality 14N magic-angle spinning (MAS) NMR spectra of the simple amino acids, which exhibit 14N quadrupole coupling constants (C(Q)) on the order of 1.2 MHz, are devised. These are the first useful 14N MAS spectra reported for nitrogen compounds having a C(Q)(14N) value in excess of 1 MHz. The complete manifolds of spinning sidebands (ssbs), i.e., about 300 ssbs for a spinning frequency of 6.0 kHz, have been observed in the 14N MAS NMR spectra of a series of amino acids. In their crystal structure these amino acids all exhibit the zwitterionic form and thus the 14N MAS NMR spectra represent those of a rotating -NH(3)(+) group and not of an amino (-NH(2)) group. Computer simulations combined with fitting of simulated to the experimental ssb intensities result in the determination of precise values for the 14N quadrupole coupling (C(Q)) and its associated asymmetry parameter (eta(Q)) for the nitrogen sites in these molecules. For some of the amino acids the 14N MAS NMR spectra exhibit overlap between the manifolds of ssbs from two different nitrogen sites in accordance with their crystal structures. Computer analysis of these spectra results in two different sets of (C(Q), eta(Q)) values which mainly differ in the magnitudes for eta(Q).     

A solid-state 14N magic-angle spinning NMR study of some amino acids

Experimental strategies for the acquisition of high-quality 14N magic-angle spinning (MAS) NMR spectra of the simple amino acids, which exhibit 14N quadrupole coupling constants (C(Q)) on the order of 1.2 MHz, are devised. These are the first useful 14N MAS spectra reported for nitrogen compounds having a C(Q)(14N) value in excess of 1 MHz. The complete manifolds of spinning sidebands (ssbs), i.e., about 300 ssbs for a spinning frequency of 6.0 kHz, have been observed in the 14N MAS NMR spectra of a series of amino acids. In their crystal structure these amino acids all exhibit the zwitterionic form and thus the 14N MAS NMR spectra represent those of a rotating -NH(3)(+) group and not of an amino (-NH(2)) group. Computer simulations combined with fitting of simulated to the experimental ssb intensities result in the determination of precise values for the 14N quadrupole coupling (C(Q)) and its associated asymmetry parameter (eta(Q)) for the nitrogen sites in these molecules. For some of the amino acids the 14N MAS NMR spectra exhibit overlap between the manifolds of ssbs from two different nitrogen sites in accordance with their crystal structures. Computer analysis of these spectra results in two different sets of (C(Q), eta(Q)) values which mainly differ in the magnitudes for eta(Q).     

Spectroscopic and proton-acceptor properties of biologically active molecules of benzoic acid and its derivatives

We have measured the absorption, fluorescence, fluorescence excitation spectra, fluorescence quantum yields, and IR Fourier-transform spectra of aromatic acids in solutions. We have considered spectroscopic particular features of benzoic acid, its hydroxylated and methoxylated derivatives. Using quantumchemistry methods, we have calculated and interpreted electronic spectra. Data of calculations have been compared with experimental results. We have ascertained the main channels and mechanisms of photophysical relaxation processes in the molecules under study. Proton-acceptor properties of molecules of aromatic acids have been evaluated. We have analyzed in detail mechanisms by which hydrogen bonds are formed, intramolecular charge redistribution is realized, and the electron density of oxygen atoms changes. Spectroscopic indications of participation of oxygen-containing groups in intramolecular interactions and in intermolecular interactions with the formation of cyclic dimers have been revealed.     

Single-pulse CARS spectra in solid propellant combustion at atmosphere pressure

The unstable-resonator spatially enhanced detection (USED) coherent anti-stokes Raman spectroscopy (CARS) measurements of temperature and N2 concentration in the combustion of solid propellant at atmosphere pressure are reported. The USED CARS measurement system has a high spatial solution of ~ 0.1 mm in diameter and 3 mm in length, and permits instantaneous measurement at 10-Hz rate. The single-pulse N2 Q-branch CARS spectra have been obtained from the propellant combustion. The temperatures and N2 concentrations of the propellant flame at different height have been achieved by fitting the experimental data to theoretical spectra. The results indicate that the temperature is up to ~ 2500 K with N2 concentration in a range from 10% to 26%.     

Isotope shifts in spectra of molecular liquids

In the IR absorption spectra of low-temperature molecular liquids, we have observed anomalously large isotope shifts of frequencies of vibrational bands that are strong in the dipole absorption. The same effect has also been observed in their Raman spectra. At the same time, in the spectra of cryosolutions, the isotope shifts of the same bands coincide with a high accuracy (±(0.1–0.5) cm^–1) with the shifts that are observed in the spectra of the gas phase. The difference between the spectra of examined low-temperature systems is caused by the occurrence of resonant dipole–dipole interactions between spectrally active identical molecules. The calculation of the band contour in the spectrum of liquid freon that we have performed in this work taking into account the resonant interaction between states of simultaneous transitions in isotopically substituted molecules can explain this effect.     

青蒿素与氢氧化钠反应的动态紫外吸收光谱

采用ICCD动态光谱测量系统,准确地拍摄出了青蒿素自身的紫外吸收光谱,并对不同浓度的青蒿素与氢氧化钠反应的全过程进行了动态光谱实时测量,每幅光谱的曝光时间为0.1 ms。实验结果显示,青蒿素自身有一明显的紫外吸收带,吸收峰值为212.52 nm;青蒿素极易与氢氧化钠反应,不同浓度的青蒿素与氢氧化钠反应的吸收光谱变化情况是相似的,只是变化发生的时刻有所不同。反应初首先出现一以288 nm为峰值的新吸收带,随着反应的进行,在260 nm处的吸收逐渐增强,反应的最终产物在200～350 nm之间形成一稳定连续的强吸收带。此反应过程的动态光谱信息在国内外还未见有报道。其结果为了解青蒿素这一潜在抗癌药物与碱性物质反应的特性提供了实验依据,对正确使用青蒿素具有参考价值。     

Ferromagnetic and Spin-Wave Resonance in the [CoFe/Cu]N Superlattice Thin (30-nm) Film

Physics of the Solid State - Angular dependences of the microwave absorption spectra of a (CoFe/Cu)N multilayer film have been studied by the ferromagnetic and spin-wave resonance techniques. The...     

Effect of pH on the fluorescence and phosphorescence spectra of indolecarboxylic acids. Evidence for the existence of a singlet excited-state indole acid dianion

Room-temperature electronic absorption, fluorescence, and low-temperature (77 K) phosphorescence spectra of a series of indolecarboxylic acids have been measured in predominantly aqueous solutions at pH 1.2, 7.0, 12.5, and in 5 N NaOH. The ¹L_a and ¹L_b π, π ¹ states have been assigned to the electronic transitions for all the compounds under study. The quenching of fluorescence, the appearance of a new fluorescence emission band, red-shifted by 40 nm, in very alkaline media, and the disappearance of the indole carboxylate short-wavelength band have been attributed to the formation of an excited singlet-state indolate carboxylate (dianion) stabilized by hydrogen bonding with the solvent. The existence of two successive excited singlet-state prototropic equilibria is discussed.     

The effect of temperature on the fluorescence of aromatic amino acid solutions

The temperature dependence of the fluorescence and the absorption spectra, as well as the duration of the excited state of indole, aromatic amino acids, and glycyl-trytophane in dipolar glassy solvents were studied. It was established that for indole, tryptophane, and glycyl-tryptophane, the temperature shifts of the spectra can be explained on the basis of a relaxation mechanism of an orientational interaction.In conclusion, the authors express their gratitude to A. N. Sevchenko for his continuous interest in the work.     

Exciton photoluminescence, photoconductivity and absorption in GaSe0.9Te0.1 alloy crystals

The photoluminescence, photoconductivity and absorption in GaSe_0.9Te_0.1 alloy crystals have been investigated as a function of temperature and external electric field. It has been observed that the exciton peaks shift to lower energy in GaSe_0.9Te_0.1 alloy crystals compared to GaSe crystals. The long wavelength tails of interband photoluminescence, photoconductivity and absorption spectra are determined by the free exciton states and show an Urbach-Martienssen-type dependence to the photon energy. The maxima of the extrinsic photoluminescence and photoconductivity spectra were found to be determined by the acceptor centers with an energy of E_A=E_V+0.19 eV formed by the polytypism and defects complexes that include Se and Te anions.     

Influence of Indium on the Spectral and Structural Characteristics of Lu0.98 – xInxEu0.02BO3

Physics of the Solid State - The structure, IR absorption spectra, and luminescence spectra of orthoborates Lu0.98 ‒ xInxEu0.02BO3 at 0 ≤ x ≤ 0.1 has been...     

20种氨基酸近红外光谱及其分子结构的相关性

旨在研究20种氨基酸的分子结构与其近红外光谱的相关性,为氨基酸近红外光谱在动物科学、食品和医药等方面的推广应用奠定一定的理论基础。应用岛津傅里叶变换红外光谱仪IRPrestige-21及其近红外附件FlexIRTM Near-Infrared Fiber Optics module,采集20种氨基酸标准物质在1 000～2 502 nm波长范围内的近红外光谱,分辨率8 cm-1,每个样品扫描3次,每次扫描50遍,取其平均值为氨基酸标准品的近红外光谱。根据氨基酸侧链基团的不同,分别比较脂肪族氨基酸、芳香族氨基酸和杂环氨基酸中各氨基酸分子结构与其近红外光谱的相关性。研究表明,20种氨基酸在1 000～2 502 nm区域有非常明显的近红外光谱吸收且差异显著。分子量较大的脂肪族氨基酸其近红外光谱受侧链基团的影响较大,而甘氨酸近红外光谱受羧基和氨基的影响较大;两种芳香族氨基酸近红外光谱的差异主要来自于苯环,酪氨酸苯环上的—OH基团降低了苯分子的对称性,导致更多振动吸收峰的出现;杂环氨基酸因其侧链上杂环分子基团构成不同,其近红外光谱在1 600～1 800 nm区域差异较大。综上,20种氨基酸主要存在4个特征光谱区：第1特征光谱区为1 050～1 200 nm主要由C—H基团的二级倍频构成;第2特征光谱区为1 300～1 500 nm主要由C—H基团的组合频构成;因侧链基团分子构成不同,在第3特征光谱区1 600～1 850 nm和第4特征光谱区2 000～2 502 nm表现出差异较大的特征吸收峰。因此,可以利用此4个近红外光谱特征区域对氨基酸进行定量和定性分析,提高氨基酸近红外光谱模型预测的准确性。     

碳氮缺陷修饰g-C3N4/WS2异质结光催化性质的第一性原理研究

本文采用第一性原理方法计算了四种不同g-C₃N₄/WS₂异质结的超晶胞结构、功函数、能带结构、态密度和吸收光谱,研究了不同缺陷对g-C₃N₄/WS₂异质结的电子结构和光催化性能的影响.发现g-C₃N₄/WS₂、g-C₃N₄/WS₂-V_1N、g-C₃N₄/WS₂-V_1N1C、g-C₃N₄/WS₂-V_1N2C均能形成稳定的异质结,g-C₃N₄/WS₂-V_1N1C和g-C₃N₄/WS₂-...     

氨基酸和羟肟酸混配的VO~(3+)配合物的IR、Raman和UV-Vis光谱研究

本文对四个钒酰配合物 [Vv O( L1- 3) ( bz) ]( H2 L1- 3分别为水杨醛缩合甘氨酸、缬氨酸、甲硫氨酸 ,Hbz为苯甲酰羟肟酸 )和 [Vv O( L4 ) ( bbz) ]( H2 L4 为水杨醛缩合丙氨酸 ,Hbbz为 N-苯基苯甲酰羟肟酸 )进行了 IR、Raman和 UV- Vis光谱研究。结果表明 ,在 IR和 Raman光谱中 ,它们有着相似的振动谱带 ,其νV=O特征振动频率出现在 962～ 976cm- 1之间 ;在 UV- Vis光谱中 ,含有 Hbz的配合物有两个配体场跃迁带 ,而含有 Hbbz的配合物只观测到一个配体场吸收带。