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1.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1988,44(7):749-761
I.r. and Raman spectra of p-cresol and its seven deuterated analogs were investigated in dilute solutions of hydrophobic solvents. Assignments of the observed i.r. and Raman bands were made on the basis of isotopic frequency shifts, Raman polarization properties, i.r. intensifies and normal coordinate calculations. The calculated normal frequencies are in good agreement with the experimental ones: the average error below 1700 cm−1 is 3.8 cm−1 for 164 in-plane vibrations and 3.3 cm−1 for 59 out-of-plane vibrations. The calculated vibrational modes may be useful in analysing the vibrational spectra of tyrosine. It is suggested that several doublets due to Fermi resonance and a trio of Raman bands in the 1260-1160 cm−1 region are potential probes for the micro-environments of tyrosine side chains in proteins. 相似文献
2.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1993,49(2):209-221
Fourier transform infrared (FTIR) and Raman spectra in the 1600-100 cm−1 range have been employed in a structural analysis of biopolymers of the polygalactane type. In spite of the complexity of the spectra in this region, precise assignments have been made, first on the basis of previously calculated frequencies of the basic unit (d-galactose) and secondly by comparing the spectra of kappa-, iota-, and lambda-carrageenans, as well as agar and appropriate disaccharides. The results of this work provide confirmation of previous assignments of IR absorptions at 930, 820, 805 and 845 cm −1 and the interpretation of several other bands, notably those due to bending vibrations of the glycosidic linkages and those between 1040 and 1010 cm−1. The latter are associated with the OSO symmetrical stretch. Assignments are also presented for the 700-100 cm−1 region, on which there are no previous reports. The present analysis may provide a basis for further studies of the conformational changes accompanying gelation, a process which is different from one polygalactane to another. 相似文献
3.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1976,32(1):175-183
The i.r. spectra of gaseous and solid CH3CCl2F and CH3CHClF have been recorded from 140 to 4000 cm−1. The corresponding Raman spectra of the liquids have also been recorded and depolarization values have been measured for the CH3CCl2F molecule. Also the Raman spectrum of gaseous CH3CHClF has been recorded. All spectra have been interpreted in detail and the 18 normal vibrations of both molecules have been characterized. Hot bands of the internal torsional mode for CH3CCl2F were observed at 248(2 ← 1) and 232 cm−1 (3 ← 2) in the far-i.r. spectrum of the gas. These frequencies are in good agreement with those calculated using the 4·42 kcal/mole barrier obtained in an earlier Raman study. The internal torsional mode for CH3CHClF was observed at 261 cm−1 in the spectra of the solid and the three-fold periodic barrier was calculated to be 4·38 kcal/mole. The barriers are compared in a series of chloro, fluoro and bromo substituted ethane derivatives. 相似文献
4.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1991,47(3-4):509-512
We report the first near IR FT-Raman spectroscopy of normal diseased human artery. In normal human aorta, two bands at 1669 cm−1 and 1452 cm−1 dominate the spectrum and can be assigned to protein amide I and C-H in-plane bending vibrations, respectively. Weaker bands are also observed between 1250 and 1350 cm−1. Non-calcified atherosclerotic lesions with a large amount of necrotic debris below the tissue surface show a relative increase in the intensity of the 1452 cm−1 band. In atherosclerotic aortas which contain calcified deposits several hundred microns below the tissue surface, a strong 961 cm−1 band is observed due to the symmetric stretch of phosphate groups in the calcified salts. The results show that this method provides the capability to probe biological substituents several hundred microns below the tissue surface. 相似文献
5.
This research was done on hureaulite samples from the Cigana claim, a lithium bearing pegmatite with triphylite and spodumene. The mine is located in Conselheiro Pena, east of Minas Gerais. Chemical analysis was carried out by Electron Microprobe analysis and indicated a manganese rich phase with partial substitution of iron. The calculated chemical formula of the studied sample is: (Mn3.23, Fe1.04, Ca0.19, Mg0.13)(PO4)2.7(HPO4)2.6(OH)4.78. The Raman spectrum of hureaulite is dominated by an intense sharp band at 959 cm−1 assigned to PO stretching vibrations of HPO42− units. The Raman band at 989 cm−1 is assigned to the PO43− stretching vibration. Raman bands at 1007, 1024, 1047, and 1083 cm−1 are attributed to both the HOP and PO antisymmetric stretching vibrations of HPO42− and PO43− units. A set of Raman bands at 531, 543, 564 and 582 cm−1 are assigned to the ν4 bending modes of the HPO42− and PO43− units. Raman bands observed at 414, and 455 cm−1 are attributed to the ν2 HPO42− and PO43− units. The intense A series of Raman and infrared bands in the OH stretching region are assigned to water stretching vibrations. Based upon the position of these bands hydrogen bond distances are calculated. Hydrogen bond distances are short indicating very strong hydrogen bonding in the hureaulite structure. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral hureaulite to be understood. 相似文献
6.
Raman spectrum of the meso tetraphenylporphine (TPP) deposited onto smooth copper surface as thin film were recorded in the region 200–1700 cm−1. To investigate the effect of meso-phenyl substitution rings on the vibrational spectrum of free base porphyrin, we calculated Raman and infrared (IR) spectra of the meso-tetraphenylporphine (TPP), meso tetramethylporphine (TMP), copper (II)porphine (CuPr) and free base porphine (FBP) at the B3LYP/6-311+G(d,p) level of the density functional theory (DFT). The observed Raman spectrum of the TPP is assigned based on the calculated its Raman spectrum in connection with the calculated spectra of the TMP, CuPr and FBP by taking into account of their corresponding vibrational motions of the Raman modes of frequencies. Results of the calculations clearly indicated that the meso tetraphenyl substitution rings are totally responsible for the observed Raman bands at ∼1593, 1234 and 1002 cm−1. The calculated and observed Raman spectra also suggested that the observed Raman band with a medium intense at 962 cm−1 might result from the surface plasmon effect. Furthermore, the observed Raman bands with medium intense at ∼334 and ∼201 cm−1 are as results of the dimerization or aggregation of the TPP or would be that related to intramolecular interaction. We also calculated IR spectra of these molecules at same level of the theory. To investigate the solvent effect on the vibrational spectrum of porphine, the Raman and IR spectra of the TPP and FBP are calculated in solution phase where water used as solvent. The results of these calculation indicated that there is no any significant effect on the vibrational spectrum of the TPP. 相似文献
7.
《Vibrational Spectroscopy》2007,43(1):254-259
The low-frequency region of the infrared and Raman spectra of nitric acid hydrates is analyzed. Theoretical calculations of the vibrational normal modes of the crystals of nitric acid monohydrate and the β-phases of the dihydrate and trihydrate are carried out, focusing the results in the regions below 175 cm−1 and near the symmetric stretch of the nitrate ion NO3−, around 1000–1100 cm−1. A prediction of the corresponding infrared spectra is presented. A joint study is performed of the calculated normal modes, the predicted IR spectra, and the recently published Raman spectra of these compounds, based on symmetry considerations and using the atomic displacements associated to each normal mode as a further source of information. Although most of the modes present a strong mixture of atomic motions, assignments can be proposed for some of the vibrations. 相似文献
8.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1993,49(2):183-190
Laser Raman and IR spectra in the region 50–3000 cm−1 for trichloronitromethane and trichloroacetate ions were recorded. All observed vibrational bands have been assigned to normal modes. Normal coordinate analyses of these molecules have been carried out in the valence force-field approximation. A set of force constants was obtained leading to good agreement between observed and calculated frequencies. The relative displacements of the atoms resulting from normal coordinate calculations were used to compute the IR band intensity of each mode by the CNDO/2-MO procedure. The intensity calculations confirmed the assignments and supported the calculated force constants. 相似文献
9.
The Raman spectrum of amorphous biosynthetic human growth hormone, somatotropin, has been measured at high signal-to-noise ratios, using a CW argon ion laser and single channel detection. The rms signal-to-noise ratio varies from 1800:1 in the Amide I region near 1650 cm−1 region, to 500:1 in the disulfide stretch region near 500 cm−1.Component Raman bands have been extracted from the entire spectral envelope from 1800-400 cm−1, by an interactive process involving both partial deconvolution and band-fitting. Interconsistency of all bands has been achieved by multiple overlapping of adjacent regions that had been isolated for the band-fitting programs.The resulting areas of the Raman component bands have been interpreted to show the ratios of peptide conformations in the hormone: 64% α-helix, 24% β-sheet, 8% β-turns and 4% γ-turns. Analysis of the tyrosine region, usually described as a Fermi resonance doublet near ∼830–850 cm−1, shows four bands, at 825, 833, 853, and 859 cm−1 in this macromolecule. Integrated intensities of these bands (2:2:2:2) are interpreted to show that only half of the eight tyrosine residues function as hydrogen-bond bridges via the acceptance of protons.Both disulfide bridges fall within the frequency ranges for normal, unstressed SS bonds: The 511 and 529 cm−1 bands are indicative of the gauche-gauche-gauche and trans-gauche-gauche conformations, respectively. 相似文献
10.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1992,48(4):509-517
Infrared and Raman spectra of oriented and non-oriented single crystal of iodopentamethylbenzene were measured at room temperature over the 4000-400 cm−1 region. The dichroism of the IR bands is discussed. An assignment of the fundamental vibrations of IPMB is presented and based on a comparison with the spectra of some similar molecules. 相似文献
11.
The antimalarial agent mefloquine was investigated using Fourier transform near-infrared (FT NIR) Raman and FT IR spectroscopy.
The IR and Raman spectra were calculated with the help of density functional theory (DFT) and a very good agreement with the
experimental spectra was achieved. These DFT calculations were applied to unambiguously assign the prominent features in the
experimental vibrational spectra. The calculation of the potential energy distribution (PED) and the atomic displacements
provide further valuable insight into the molecular vibrations. The most prominent NIR Raman bands at 1,363 cm−1 and 1,434 cm−1 are due to C=C stretching (in the quinoline part of mefloquine) and CH2 wagging vibrations, while the most intense IR peaks at 1,314 cm−1; 1,147 cm−1; and 1,109 cm−1 mainly consist of ring breathings and δCH (quinoline); C–F stretchings; and asymmetric ring breathings, C–O stretching as
well as CH2 twisting/rockings located at the piperidine moiety. Since the active agent (mefloquine) is usually present in very low concentrations
within the biological samples, UV resonance Raman spectra of physiological solutions of mefloquine were recorded. By employing
the detailed non-resonant mode assignment it was also possible to unambiguously identify the resonantly enhanced modes at
1,619 cm−1, 1,603 cm−1 and 1,586 cm−1 in the UV Raman spectra as high symmetric C=C stretching vibrations in the quinoline part of mefloquine. These spectroscopic
results are important for the interpretation of upcoming in vitro and in vivo mefloquine target interaction experiments. 相似文献
12.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1984,40(4):351-359
I.r. spectra of the charge transfer complexes between nine organic sulfides (as well as diethylselenide) with iodine were recorded between 1500 and 400 cm−1 in CS2 and CCl4 solutions and in the region 600-50 cm−1 in C6H12 and C6H6 solutions. Raman spectra of the complexes were recorded below 600 cm−1. For each system, i.r. and Raman bands in the 200-160 cm−1 were assigned to the II stretching mode of the complex. Additional i.r. bands below 160 cm−1, absent in Raman, were ascribed to intermolecular SI stretching vibrations. The integral intensities of these bands were determined and correlated with the thermodynamic functions. Some Raman active fundamentals of 1,4-dithiane became i.r. active in the iodine complex in accordance with a break down of the C2h symmetry. A force constant calculation was carried out for the dimethylsulfide-iodine complex and simplified calculations of the three point mass models were made for all the systems. 相似文献
13.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1993,49(7):953-964
The structures and force field of 1,3,5,7-cyclooctatetraene (COT) have been studied using ab initio theory at the SCF level with the 4-21G basis set. The quadratic force field of the D2d structure obtained by systematic scaling of the ab initio force constants successfully reproduces the observed frequencies of COT and COT-d8 with a mean deviation of less than 10 cm−1 for non-CH stretching modes. On the basis of the calculated results, assignments of the fundamental vibrations are examined. The normal mode υ5 is reassigned to a weak band at 758 cm−1 in the Raman spectrum of COT and to a weak band at 591 cm−1 in the Raman spectrum of COT-d8. The calculations favor the assignment of υ26 given by Lippincott et al. [J. Am. Chem. Soc. 73, 3370 (1951)] over the revised assignment of Perec [Spectrochim. Acta 47A, 799 (1991)]. The calculations also furnish reliable prediction for the inactive A2 fundamentals of COT and COT-d8. The fundamental frequencies and IR and Raman intensities of 13CC7H8, which constitutes about 9% of COT in natural abundance, are also calculated. Only ν10 (calculated at 908 cm−1) of the formal inactive A2 modes has appreciable Raman intensity (0.23 Å4/amu). A spectral feature due to this fundametal is identified in the liquid Raman spectrum of Tabacik and Blaise [C. R. Acad. Sci. Ser. II 303, 539 (1986)] as a weak peak at 908 cm−1. 相似文献
14.
Raman spectroscopy complimented by infrared spectroscopy has been used to study the mineral hemimorphite from different origins. The Raman spectra show consistently similar spectra with only one sample showing additional bands due to the presence of smithsonite. Raman bands observed at 3510–3565 and 3436–3455 cm−1 are assigned to OH stretching vibrations. Using a Libowitzky type formula, these OH bands provide hydrogen bond distances of 0.2910, 0.2825, 0.2762 and 0.2716 pm. Water bending modes are observed in the Raman spectrum at 1633 cm−1. An intense Raman band at 930 cm−1 is attributed to SiO symmetric stretching vibration of the Si2O7 units. Raman bands observed at 451 and 400 cm−1are attributed to out-of-plane bending vibrations of the Si2O7 units. Raman bands at 330, 280, 168 and 132 cm−1 are assigned to ZnO and OZnO vibrations. 相似文献
15.
The paper presents the study of selected montmorillonite standards by Raman spectroscopy and microscopy supported by elemental analysis, X-ray powder diffraction analysis and thermal analysis. Dispersive Raman spectroscopy with excitation lasers of 532 nm and 780 nm, dispersive Raman microscopy with excitation laser of 532 nm and 100× magnifying lens, and Fourier Transform-Raman spectroscopy with excitation laser of 1064 nm were used for the analysis of four montmorillonites (Kunipia-F, SWy-2, STx-1b and SAz-2). These mineral standards differed mainly in the type of interlayer cation and substitution of octahedral aluminium by magnesium or iron. A comparison of measured Raman spectra of montmorillonite with regard to their level of fluorescence and the presence of characteristic spectral bands was carried out. Almost all measured spectra of montmorillonites were significantly affected by fluorescence and only one sample was influenced by fluorescence slightly or not at all. In the spectra of tested montmorillonites, several characteristic Raman bands were found. The most intensive band at 96 cm−1 belongs to deformation vibrations of interlayer cations. The band at 200 cm−1 corresponds to deformation vibrations of the AlO6 octahedron and at 710 cm−1 can be assigned to deformation vibrations of the SiO4 tetrahedron. The band at 3620 cm−1 corresponds to the stretching vibration of structural OH groups in montmorillonites. 相似文献
16.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1982,38(10):1097-1100
The i.r. (4000-50 cm−1) and laser Raman spectra (4000-50 cm−1) of potassium pentafluoroperoxo niobate monohydrate and potassium pentafluoroperoxo tantalate monohydrate have been investigated. The observed spectra have been analysed on the basis of spectral comparison with related compounds and of the normal vibration calculations employing modified Urey-Bradley force functions. While some coupling has been observed for the niobate, the vibrations of the tantalate are nearly localized. 相似文献
17.
Results of inelastic neutron scattering (INS), infra-red (IR), Raman and 1H NMR spectroscopy used for investigations on the l-asparagine dynamics are reported. The crystallographic structure and experimental vibrational spectra are compared with those calculated by the DFT methods applied to the solid state. Very good conformity of the experimental and theoretical structures has been found. The NH3+ torsional vibration mode is observed in the INS spectra at 494 cm−1, while the bands assigned to the vibrations of the strong NH⋯O hydrogen bonds are observed at 2849, 2650, and 2480 cm−1 in the IR spectrum. A 1H NMR investigation has been carried out at 26.75 MHz in the temperature range 150–300 K. For l-asparagine the activation energy needed for the NH3+ group reorientation is equal 5.6 kcal/mol. 相似文献
18.
V. A. Marikhin E. I. Radovanova E. M. Ivan’kova L. P. Myasnikova B. Z. Volchek D. A. Medvedeva E. N. Vlasova 《Polymer Science Series A》2008,50(4):403-410
The IR absorption spectra of α,ω-alkanediols with different chain lengths, HO(CH2)22OH and HO(CH2)44OH, in the spectral range of 400–5000 cm?1 are analyzed. The assignment of numerous absorption bands to vibration modes in short methylene sequences and terminal hydroxyl groups is suggested. The splitting of IR absorption bands into doublets at 720–730 cm?1 (rocking vibrations of CH2 groups) and 1463–1473 cm?1 (bending vibrations of CH2 groups) testifies that the crystal unit subcells in the lamellae of alkanediols are orthorhombic with parameters typical of normal hydrocarbons. The specific features of absorption bands due to O-H stretching and C-O-H bending vibrations have been analyzed. These bands appear during formation of lengthy associates from hydrogen bonds formed by hydroxyl groups on the surface of elementary lamellae. A sharp increase in the intensity of the absorption bands in progression of C-C stretching and CH2 wagging vibrations due to the anharmonic Fermi resonance with the stretching vibrations of C-O groups in the terminal hydroxyl groups has been detected. 相似文献
19.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1980,36(12):1075-1081
The i.r. spectra of phtalic, isophtalic and terephtalic acids as KBr pellets as well as Raman spectra of microcrystalline powder have been investigated. Most vibrations have been assigned by correlation with the spectra of the previously studied phtalate, isophtalate and terephtalate ions. The COOH characteristic vibrations have been assigned as vibrations of the hydrogen-bonded centrosymmetric “dimers” COOH … HOOC, and a general assignment is proposed for combination bands in the range 3000-2500 cm−1. 相似文献
20.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1992,48(7):931-937
Resonance Raman spectra have been obtained in the region 400–1700 cm−1 for several indolinium steryl dyes under various experimental conditions. The changes in vibrational frequencies have been correlated with changes in the UV—vis absorption maxima observed previously and which are due to solvent polarity variations, the complexation of the dye molecules containing a crown ether ring with Mg2+, and the variations in molecular structure. Preliminary assignments of the observed bands to particular vibrations are made. 相似文献