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The ionic speciation and the optical properties of aqueous H2SO4 have been investigated as a function of temperature and acid concentration by spectroscopic techniques. FT-Raman spectra have been obtained of 1.43−44.04 molal (12−81 wt %) aqueous H2SO4 in the temperature region from 300 to 220 K. The degree of dissociation of the second dissociation step in aqueous H2SO4 (α2: HSO4- ⇄ H+ + SO42-) is derived from the relative intensities of the HSO4- Raman bands around 1050 cm-1 versus the SO42- band around 980 cm-1, and a polynomial parametrization of α2 is presented. FT-IR specular reflectance spectra are obtained of 6.46−44.04 molal (38−81 wt %) aqueous H2SO4 in the temperature region from 300 K to as far down as possible before crystallization by freezing occurred. The complex index of refraction is obtained from the IR reflectance spectra by the use of the Kramers−Kronig transformation, and the importance of including far-infrared data in the transformation is demonstrated. A revised parametrization of...

Microscopic near-infrared Fourier transform Raman investigations were performed of skin samples from the Nekht-Ankh mummy found in the ‘Tomb of the Two Brothers’ in Egypt (ca 2000 BC). Spectra were obtained from various sites on the samples. The lipids and proteins seemed well preserved, although different degrees of protein deterioration were observed. In some spots the protein degradation was rather high. Some sites showed very well preserved protein secondary structures with both helical and sheet contents, indicating that the artificial mummification process had a positive effect although no embalming chemicals were left in those spots. Sodium sulphate was the only artificial chemical that could be detected and the degradation of lipid and protein seemed to be rather high in the region containing sodium sulphate. The Raman spectra of the best preserved skin samples from the Nekht-Ankh mummy are very similar to those obtained from the best preserved child rock-cleft mummy (I/2) from Qilakitsoq in Greenland. The conclusion is that the artificial embalming process used by the ancient Egyptians was an efficient way to preserve the mummies even under hot conditions. Copyright © 2003 John Wiley & Sons, Ltd.

Raman spectroscopy is able to provide novel information non-destructively in the analysis of ancient skin tissue samples. The technique is well-suited to partially desiccated or wet samples of skin, which may have been subjected to varying degrees of degradation, depending on the burial environment. Suitable selection of wavelength of excitation and use of a Raman microscope offer a means of accessing information from small samples, which may be required for study afterwards using destructive analytical methods. From comparisons with the Raman spectra of healthy and diseased contemporary skin specimens, it is possible to discover whether the skin preservation has been natural or assisted by chemicals used in mummification processes. Such information is of importance in archaeological conservation and can shed light on historical practices. In this study will be presented the results from Raman spectroscopic analysis of the skin of the 5200-year-old “ice-man” of the Alps and, skin and nail samples from the mediaeval Qilakitsoq ice-mummies (500-year-old) and skin from the hot-desert Chiribaya Mummies (1000-year-old).

Isotopic substitution is used in cw-Raman studies of fast dynamics in molecules of biological interest. Simple liquid amides are considered as model systems for hydrogen bonding in peptides and proteins. Collectivity of amide I modes is studied by resonance energy transfer (RET) and coalescence of bands in mixtures of isotopomers (CBMI). A 1:1 mixture of HC16OND2 and HC18OND2 shows only one amide I band with a peak maximum between those observed for each of the pure isotopomers. Dilution studies of this mixture in D2O show that the collective effects disappear in diluted solutions, where two bands are observed, one from each isotopomer. This is confirmed by dilution experiments performed on HC16OND2 in D2O. Raman spectroscopy is a fast experimental technique reflecting the fast molecular dynamics on a picosecond and faster time scale. Future aspects of the collectivity of vibrational modes in peptides and proteins are mentioned. In this context a vibrational coupling between the amide I modes and the bending mode of water may be important. A comparison between low-frequency Raman and thermodynamic studies of water/lysozyme mixtures seems promising in terms of the difference between protein bound water and the formation of water clusters.

Raman spectroscopy is used to study the fast dynamics of simple liquid amides and proteins. Raman spectra in the visible region of liquid amides are obtained with a triple additive scanning monochromator, whereas FT-Raman technique is used in the near-IR region in order to avoid fluorescence from impurities in the proteins. Raman spectra are shown in the amide-I region of HCONHCH 3 ( N -methylformamide with all isotopes in their natural abundance), H 13 CONHCH 3 , HC 18 ONHCH 3 , human growth hormone, frog tropomyosin and chymotrypsin inhibitor 2 including C-13 and N-15 enriched samples of the latter. Resonance energy transfer (RET) between amide molecules gives rise to a non-coincidence effect of the anisotropic and the isotropic components of the amide-I band. This effect influences the band position in mixtures of liquid amide isotopomers. A further spectral feature caused by collective vibrational modes in the hydrogen bonded liquid amides is named coalescence of bands in mixtures of isotopomers (CBMI). The result of this effect is that only one band is found in mixtures of isotopomers where bands at different frequencies are observed for each of the isotopomers. A similar effect may account for the observation of protein amide-I bands with frequencies dependent only on the secondary structure of the protein and not on the amino acid residues. RET and CBMI are due to a collectivity of vibrational modes in different amide molecules. This collectivity may be related to a cooperativity of hydrogen bonds. A low-frequency band around 100 cm −1 is observed in hydrogen bonded liquid amides and proteins. Isotopic substitution shows that the mode corresponding to this band involves displacements of atoms in hydrogen bonds. This mode may drive a breaking of the hydrogen bond.

Raman spectra have been obtained for three different stoichiometric compositions of Pd/Mg(Al)O. Two different laser wavelengths, 1064 and 514.5 nm, were used. All three compounds showed an intense background with laser excitation in the near-infrared region. The broad backgrounds were reduced as the laser excitation wavelength was decreased. The near-infrared spectrum (5000–11 000 cm −1 ) of Pd/Mg(Al)O was recorded. This spectrum showed that the material contains OH-groups may be even water. It is proposed that luminescence from overtones and combination levels of OH-groups are responsible for the very different appearance of the Raman spectra.

Far-infrared and low-frequency Raman spectra in the wavenumber range from 15 to 500 cm −1 were recorded for glycerol, triacetin (glycerol triacetate) and o -terphenyl at temperatures from 253 to 355 K. The far-infrared spectra of glycerol appear complex compared with the spectra of triacetin owing to the presence of hydrogen bonding in glycerol. The experimental results obtained for o -terphenyl are in good agreement with normal mode analyses carried out for crystalline o -terphenyl (A. Criado, F.J. Bermejo, A. de Andres, Mol. Phys. 82 (1994) 787). The far-infrared results are compared with the low-frequency Raman spectra of these three glass-forming liquids. The difference in temperature dependences found from these spectra is explained on the basis of different temperature contributions of the relaxational and vibrational processes to the low-frequency vibrational spectra.

Near-infrared Fourier transform (NIR-FT) Raman spectroscopy was employed to compare archaeological skin samples of a late Neolithic man (5200 BP) preserved in a glacial field in the Alps (the Iceman), skin of fifteenth century mummies preserved at low temperature and dry air in stone graves in Qilakitsoq, Greenland, and skin samples from mummified bodies from the Chiribaya culture from the Southern Peruvian desert (1000 BP). In all the spectra of mummified skin, a progressive loss of protein amide I (1640–1680 cm−1) and amide III (1220–1290 cm−1) band intensities was found, indicating either loss of protein or changes in the secondary protein structure. Thus, the observed changes or degradation in protein structure in the samples of the 500-year-old skin of the Qilakitsoq mummy and the 1000-year-old skin of Chiribaya mummies have been observed to be broadly similar to those found in the 5200-year-old Iceman. This implies that most changes in the molecular structure of the skin take place in a relatively short time interval during the natural mummification process. The spectra of lightly pigmented Peruvian mummies showed a relatively strong peak near 1300 cm−1 and an increased intensity of the ν(CH) peak at 2850 cm−1. The band near 1300 cm−1 is characteristic of twisting and wagging CH2 vibrations in lipids and the 2850 cm−1 band represents lipid CH stretching vibrations. These spectral changes suggest an increased lipid content in lightly pigmented Peruvian mummy skin compared with contemporary skin and the skin of the mummies preserved in ice. We ascribe this increased lipid intensity in the skin of the Peruvian mummies to embalming, by which means a better preservation is achieved. In conclusion, NIR-FT-Raman spectroscopy has potential use for the non-destructive chemical analysis of archaeological biomaterial. By using this technique it is possible to assess the degree of protein degradation and also to provide an analysis of embalming materials employed for the mummification processes. Copyright © 1999 John Wiley & Sons, Ltd.

Far-infrared spectra in the region 25–500 cm −1 were obtained for glycerol and triacetin (glycerol triacetate) at temperatures from 253 to 323 K. Far-infrared spectra of glycerol look more complicated in comparison with spectra of triacetin due to the hydrogen bonding. Band fitting performed for the frequency range 25–250 cm −1 shows that four bands have contributed to spectra of glycerol and triacetin in this region. The experimental results obtained for glycerol are in good agreement with normal mode analyses performed recently for crystalline glycerol [E.J. Bermejo, A. Criado, A. de Andress, E. Enciso, H. Schober, Phys. Rev. B 53 (1996) 5259.] and for glycerol in the liquid state [T. Uchino, T. Yoko, Science 273 (1996) 480.]. The far-infrared result are compared to the low-frequency Raman spectra of the two liquids. The difference in temperature behaviour revealed from these two kind of spectra is explained on the basis of different temperature contribution of relaxational and vibrational processes to the low-frequency vibrational spectra.

Vibrational structure of four molecules known to undergo an extremely rapid excited state proton transfer: [2,2′-bipyridyl]-3,3′-diol, 5,5′-dimethyl[2,2′-bipyridyl]-3,3′-diol, [2,2′-bipyridyl]-3-ol and 2-(2-pyridyl)phenol was studied with FTIR and Raman spectroscopy and ab initio quantum chemical calculations. The assignments for all the observed vibrations lying below 600 cm−1 were proposed, based on the comparison of experimental and computational results of transition energies, shifts upon deuterium and methyl substitution, and the analysis of the evolution of individual bands along the series. The calculations appear to be very reliable in predicting the vibrational frequencies, and in reproducing frequency shifts resulting from deuteration and methylation. The assignment of low-frequency modes may be helpful in understanding of the phototautomerization mechanism, as well as in interpretation of the complicated structure of the band corresponding to the OH stretching vibration.

— Near-infrared Fourier transform Raman spectroscopy is an analytical, nondestructive technique that provides information about the molecular structure of the investigated sample. The molecular structure of proteins and lipids differs between neoplastic and normal tissues and therefore Raman spectroscopy has been considered promising for the diagnosis of cancer. We aimed to compare the molecular structure of normal skin, benign and malignant skin lesions by the near-infrared Fourier transform Raman spectroscopy. Biopsies were obtained from the following skin lesions: skin tag, dermatofibroma, seborrhoeic keratosis, actinic keratosis, keratoacan-thoma, basal cell carcinoma, squamous cell carcinoma, nevus intradermal, nevus compositus, dysplastic nevus and lentigo maligna. Control skin was harvested from the vicinity of these lesions. In the Raman spectra, the secondary structure of the proteins was reflected by the amide vibrations of peptide bonds. The principal lipid vibrations were twisting and wagging (CH2) and CH stretching vibrations. Histologically distinguishable lesions showed specific combinations of band changes indicating alterations in the protein conformation and in the molecular structure of the lipids. Histogenetically related lesions (actinic keratosis and sqamous cell carcinoma) produced similar but not identical patterns of spectral changes. Because the examined skin lesions produced reproducible and unique spectra, we suggest that Raman spectroscopy will be useful for diagnosis of skin lesions.

Low-frequency Raman and far-infrared spectra of liquid acetone/chloroform mixtures show a different behaviour on the concentrations. The frequency of the band maximum of the low-frequency Raman spectra in the R( ν )- representation shows a blue shift linearly with the mole fraction of acetone. This behaviour is in accordance with the behaviour of the isothermal compressibility of acetone/chloroform mixtures. The frequency of the band maximum of the far-infrared spectra shows a more complex behaviour as a function of the relative concentrations. This can be explained in terms of an additional absorption arising from a complex between acetone and chloroform.

Influence of intermolecular hydrogen bonding upon the vibrational pattern in the low-frequency region was studied for 2-(2-hydroxyphenyl)-3-pyridynol—a molecule which reveals both intra and intermolecular hydrogen bonds in the crystal phase. Combined use of IR and Raman spectroscopy and ab initio 6-31G∗∗ calculations for the isolated and water-complexed compound made it possible to find low frequency transitions corresponding to the vibrations of the water solvate.

Skin cancers are the most common form of malignant neoplasms in man. In this work, near-infrared Fourier transform (NIR-FT) Raman spectroscopy was used to study the molecular alterations in the most common skin cancer, basal cell carcinoma (BCC). Biopsies from 16 histopathologically veri‐ed BCC and 16 biopsies from normal skin were harvested and analysed by NIR-FT-Raman spectroscopy using a 1064 nm Nd : YAG laser as a radiation source. Di†erences in Raman spectra between BCC and normal skin indicated alterations in protein and lipid structure in skin cancer samples. Spectral changes were observed in protein bands, amide I (1640‐1680 cm~1), amide III (1220‐1300 cm~1) and m(C‐C) streching (probably in the amino acids proline and valine, 928‐940 cm~1), and in bands characteristic of lipids, scissoring vibration (1420‐1450 cm~1) and in-phase CH 2 E(CH 2 ) n E twist vibration around 1300 cm~1. Moreover, possible changes in polysaccharide structure were found in the region 840‐860 cm~1. Analysis of the band intensities in the regions 1220‐1360, 900‐990 and 830‐900 cm~1 allowed for a complete separation between BCC and normal skin spectra. In addition to a direct assessment of spectral intensities, a neural network analysis was performed, which con‐rmed the di†erences in spectra between BCC and normal skin. In conclusion, Raman spectra from BCC di†er considerably from those of normal skin. Hence, Raman spectroscopy can be viewed as a promising tool for the diagnosis of skin cancer. 1997 by John Wiley &

To investigate molecular changes in mummified skin, near-infrared Raman spectroscopy was applied to the skin obtained from four mummies found in Qilakitsoq in Greenland. The mummies date from AD 1475 (±50 years) and are the oldest preserved bodies in the Arctic region. The spectra of the skin obtained from the different mummies were very similar, but they were distinctly different from those of fresh and freeze-dried contemporary skin. Especially in the spectra of the ancient skin the amide I (1640–1680 cm-1) and amide III (1220–1300 cm-1) bands had very low intensity, indicating loss of protein and/or changes in the secondary protein structure. Similar spectral changes have previously been found in the 5200-year-old skin of the Iceman. This may suggest that most changes in molecular structure take place in a relatively short time after mummification. © 1997 by John Wiley & Sons, Ltd.

Solid phase peptide synthesis (SPPS) of H-(Ala)nLys-OH with n up to 10 is performed on a TentaGel® resin. The linker is (p-(hydroxymethyl)phenoxy) acetic acid (HMPA) and 9-fluorenylmethyloxycarbonyl (Fmoc) is used as the N-α-protecting group. For each step in the synthesis near-infrared-(NIR)-Fourier transform-(FT)-Raman spectra with an excitation wavelength at 1064 nm are obtained of both the protected and deprotected resin bound peptide. No fluorescence background was observed. Amide-I and amide-III bands are used to obtain information about the secondary structure of the growing peptide chain. Bands are observed, which can be attributed to the occurence of β-sheet structures. The efficiency of the standard deprotection procedure, which consists of a treatment with 20% piperidine in dimethylformamide (DMF), v/v, for 10 min depends upon the secondary structure. With six to ten residues attached, standard treatment with piperidine only results in a partial removal of the Fmoc-group, in accordance with the occurrence of β-sheet structures. An important conclusion of the present investigation is that resins even like TentaGel® containing monosubstituted phenyl rings can be used in NIR-FT-Raman studies of SPPS. The Raman spectroscopic studies were corroborated by HPLC and mass spectrometry analysis.

Fourier transform (FT) Raman spectra were obtained for water and aqueous solutions in a stainless-steel, windowless, liquid captive cell of simple design. It was demonstrated that high-quality Raman spectra in the low-wavenumber region (down to 100 cm−1) can be obtained from highly colored samples without the presence of interfering bands from the usual sample containers made of glass or plastic. Raman bands at 520 and 232 cm−1 due to the symmetric stretching modes of the Cr-O vibration of the Cr(H2O) and the Cr-Cl vibration of the CrCl complexes were observed for very dark samples that are not amenable to conventional Raman techniques. FT-Raman studies of aqueous Cr(III) solutions can provide valuable information on the slow ligand exchange rates.

Solid state NIR-FT-Raman and far IR spectra of K 2 MX 4 and [M(NH 3 ) 4 ]Y 2 (where M = Pd(II) or Pt(II), X = Cl − or Br − , and Y = Cl − or NO 3 − ) from 100 to 700 cm −1 are measured. The crystal structures of the samples are investigated by X-ray powder diffraction. Anhydrous compounds with the general formula K 2 MX 4 have isomorphous structures with the complex ions in a site symmetry of D 4 h . Extra peaks found in the Raman spectrum of a reddish brown form of K 2 PtBr 4 are due to the presence of some dihydrate K 2 PtBr 4 · 2H 2 O, and not to crystalline K 2 PtBr 6 . Based on the revised assignments of the bromo-compounds and reliable frequency data for all compounds, the valence force constants (GVFF) of the MX 4 2− (X = Cl − , Br − ) ions, the M(NH 3 ) 4 2+ ions are calculated and compared.

The impregnation of ammine aqua cobalt(III) complexes on η-Al 2 O 3 was investigated by NIR FT-Raman spectroscopy and in a few cases by UV—vis spectroscopy and X-ray powder diffraction. The cobalt(III) impregnated alumina samples were prepared from different precursors using different impregnation methods. The observed Raman bands for the impregnated alumina around 522–537 cm −1 were tentatively assigned to the vibrational modes for the CoOAl or CoO(H)Al bonds (Al = aluminium atom on Al 2 O 3 surface).

The NIR-FT-Raman spectra are presented for the hexammine [Cr(NH3)6]X3 (where X = Br−, NO−3), pentamminechloro [Cr(NH3)5Cl]X2 (where X = Cl−, ClO−4), and pentammineaqua [Cr(NH3)5(H2O)]X3 (where X = ClO−4, CF3SO−3) chromium(III) complexes. The NIR-FT-Raman spectra, with an excitation wavelength of 1064 nm, were obtained at room temperature without problems from the strongly colored samples, which often cause problems with excitation by lasers in the visible region. All the Raman frequencies observed from the complexes have been assigned to the skeleton vibrational region from 100 to 600 cm−1. The symmetry and the general valence force constants for the bonds chromium(III)nitrogen, chromium(III)oxygen and chromium(III)chloro have been obtained. The nature of the metalligand bond between chromium(III) ammine complexes has been compared with recent results obtained for similar cobalt(III) ammine complexes.

Near-infrared Fourier transform (NIR-FT) Raman and surface-enhanced Raman spectroscopic (SERS) techniques were used in studies of the vibrational spectrum of 9-methoxy-2-N-methylellipticinium chloride. NIR-FT-Raman spectra were obtained on the powder and SER spectra were measured in silver colloids using dilute aqueous solutions of the drug (2 × 10−6 M, pH 7.5). Some Raman bands in the SER spectrum show increased relative intensities compared with the corresponding bands in the NIR-FT-Raman spectrum, whereas other bands show decreased relative intensities. A general valence force field was used in the calculation of the potential energy distribution of the vibrational modes. This calculation reveals that bands from the indole moiety of the molecule show intensity enhancements, whereas bands arising from modes localized in the isoquinolinium part of the molecule show decreasing intensities in the SER spectra. These results strongly indicate that the indole part of the molecule is close to or attached to the silver surface.

Raman spectra were obtained for two different samples of alumina. One is usually used as a support for hydro-treating catalysts in heterogeneous catalysis and the other was synthesized in the laboratory. Different excitation wavelengths were used: 457.9, 488.0, 514.5, 647.1 and 1064 nm. The commercially available alumina showed an intense broad background with excitation in the near-infrared region, whereas no significant background was observed with visible excitation. The synthetic alumina showed a broad background band with laser excitation in the visible region. It is shown that the appearance of these backgrounds is not due to fluorescent impurities (e.g. iron, chromium or organic compounds). Tentative explanations of the spectral features are provided in terms of density of states (alumina A) or bulk hydroxyl groups (alumina B).

Vibrational spectra of cobalt(III) hexammine, aquopentammine, chloropentammine, hydroxopentammine and cis -diaquotetrammine and their deuterated complexes have been investigated by near-infrared-Fourier transform-Raman and IR spectroscopy in the solid state. Raman spectra of some aqueous solutions have also been recorded. Observed frequencies of the complexes have been assigned in the skeletal vibrational region from 200 to 600 cm −1 . The spectra indicate that the cobalt(III) monoaquo- and diaquo-coordinated ammine complexes both have structural symmetries very similar to the hexammine octahedral complex. This is supported by a space group determination for the monoaquo complex by X-ray powder diffraction. The skeletal symmetry force constants of the cobalt(III) ammine complexes have been calculated from the observed Raman and IR data. The calculated frequencies of the complexes agree well with the observed results. The general valence force field (GVFF) stretching force constants of cobalt(III)—oxygen, cobalt(III)—nitrogen and cobalt(III)—chlorine bonds have been determined from the calculation.

Low frequency Raman spectra of some nylon samples are presented. In order to ensure the reliability of near-IR (NIR) FT-Raman spectra at low frequencies, spectra obtained by excitation with a Nd—YAG laser are compared with spectra recorded with excitation in the visible region. Spurious laser emission lines appear due to the insufficiency of the spike filter at low frequencies. Samples of nylon 6, nylon 6.6 and nylon 12 are investigated. The NIR FT-Raman spectra are reliable down to approximately 50 cm−1, when corrections for spurious laser lines and spectrometer response are performed in a proper way. In order to avoid the influence of the intense Rayleigh line the spectra are also presented in the R( ν ) representation. A band around 100 cm−1 is assigned to a hydrogen bond mode. This band might depend upon the nylon structure.

NIR-Raman spectra of [Co(NH 3 ) 5 H 2 O)]Cl 3 , [Co(NH 3 ) 5 OH]Cl 2 , [Co(NH 3 ) 5 Cl]Cl 2 and [Co(NH 3 ) 4 (H 2 O) 2 ] 2 -(SO 4 ) 3 are reported. Thermal decomposition was observed for the aquo complexes even using very low laser power. This decomposition is connected with the loss of H 2 O. Preliminary assignment of some metal ligand vibrations are proposed.

Des spectres Raman de polyamides (nylons) ont ete realises par excitation a 1064 nm. Des spectres basses frequences ont ete obtenus aux alentours de 50 cm -1 . Une bande proche de 100 cm -1 a ete assignee a un mode correspondant. a des liaisons hydrogene. Des etudes quantitatives des bandes basses frequences ont ete realisees en utilisant les vibrations de «bending» du groupe methylene proche de 1450 cm -1 comme etalons internes. La bande proche de 100 cm -1 pourrait donner des informations sur la liaison hydrogene (c-a-d:structure secondaire) des polyamides

Low-frequency infrared and Raman spectra at 10–400 cm −1 are presented for some simple amides. Both the Stokes and the anti-Stokes sides are given for N -methylformamide to ensure that no fluorescence bands are present in the spectrum. Spectra are presented for compounds in the liquid state and that for N -methylacetamide is compared with spectra of the crystalline compound at −15°C−20°C. The liquid state spectra are all given in the R( v )-representation. A complex is formed between lithium ions and formamide molecules and the vibrational spectra are discussed in terms of this complex. Hydrogen bonding in these simple amides is used as a model for more complicated hydrogen-bonded biological systems. Some synthetic polymers such as nylon, are also very useful in this context. The spectrum of nylon-6 is presented and a low-frequency band with a maximum at 103 cm −1 is assigned to a vibration involving H-bonded atoms.

Nucleotides and nucleosides have been studied in the low-frequency region through a comparison of the performance between near-infrared Fourier transform Raman techniques and Ar + -excitation Raman spectroscopy. This allowed us to evaluate the influence of the filter cut-off on the low-frequency bands of the Fourier transform Raman spectra. This assessment was then applied to a study of the low-frequency bands of two samples of deoxyribose nucleic acid and five ellipticines, whose interaction with deoxyribose nucleic acid could be of importance in their use as anti-cancer drugs. In order to assign the low-frequency bands of ellipticines and understand the dynamical ring deformations, a force constant calculation was performed.

Investigations of the hydrogen bonding of 3-azetidinol in the solid state by X-ray spectroscopy have been extended to solutions in CCl 4 and water. Ab initio calculations ranging from the STO-3G to the 6–31G** level indicate that in addition to the non-associated form (A) a conformer with intramolecular hydrogen-bonding OH ··N (B) might occur in the approximate ratio 2:1. IR and 1 H NMR spectroscopic studies on CCl 4 solutions give evidence in support of this prediction. The IR spectra at low temperatures (−5°C) disclose the presence of an intermolecular hydrogen- bonded chain-stacking form (C) which has a strong affinity to water. Raman spectra in the R ( ν ) representation of an aqueous solution of 3-azetidinol in the range −400 to 400 cm −1 support the presence of C. A structure for is proposed based upon the X-ray results, involving stacking of the azetidinol rings and strong intermolecular hydrogen bonding necessitating the incorporation of water molecules. The proposal is supported by the ab initio results.

Low frequency infrared and Raman spectra are investigated from 10 to 400 cm−1. The spectra are obtained in the liquid state of benzene, benzonitrile, fluorobenzene and toluene. Raman spectra are presented in the R( ν )-format. In order to avoid interference with fluorescense from trace amounts of impurities, the R( ν spectra are presented from −400 to 400 cm−1. Different scattering configurations are used in the Raman spectra in order to obtain polarization characteristics. Different sample temperatures are used for benzonitrile, fluorobenzene and toluene ranging from the melting to the boiling point. Low-frequency bands with maxima below 100 cm−1 are assigned to damped librational motions.

Melanoma is the most aggressive skin cancer. The specificity and sensitivity of clinical diagnosis varies from around 40% to 80%. Here, we investigated whether the chemical changes in the melanoma tissue detected by Raman spectroscopy and neural networks can be used for diagnostic purposes. Near-infrared Fourier transform Raman spectra were obtained from samples of melanoma (n=22) and other skin tumors that can be clinically confused with melanoma: pigmented nevi (n=41), basal cell carcinoma (n=48), seborrheic keratoses (n=23), and normal skin (n=89). A sensitivity analysis of spectral frequencies used by a neural network was performed to determine the importance of the individual components in the Raman spectra. Visual inspection of the Raman spectra suggested that melanoma could be differentiated from pigmented nevi, basal cell carcinoma, seborrheic keratoses, and normal skin due to the decrease in the intensity of the amide I protein band around 1660 cm-1. Moreover, melanoma and basal cell carcinoma showed an increase in the intensity of the lipid-specific band peaks around 1310 cm-1 and 1330 cm-1, respectively. Band alterations used in the visual inspection were also independently identified by a neural network for melanoma diagnosis. The sensitivity and specificity for diagnosis of melanoma achieved by neural network analysis of Raman spectra were 85% and 99%, respectively. We propose that neural network analysis of near-infrared Fourier transform Raman spectra could provide a novel method for rapid, automated skin cancer diagnosis on unstained skin samples.

The R(v)-representation of the low-frequency Raman spectrum was used to investigate the low-frequency Raman spectrum of water. The advantages of using reduced representations in low-frequency Raman studies to display water structure are discussed. Tetrahedrically hydrogen bonded water molecules showed a characteristic low-frequency band with a peak maximum around 180 cm-1. O-18 and O-17 isotopic substitution revealed that the corresponding vibrational mode mainly involves displacements of the oxygen atoms, but no significant hydrogen motion. This mode can be used to monitor the existence of water with a bulk-like structure in biological macromolecular materials. To test its applicability NIR-FT-Raman spectroscopy was used in studies of biopolymers in order to avoid fluorescence.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Etude dans des echantillons contenant une faible teneur de Fe. Observation d'une bande de fluorescence large et intense due aux impuretes

Low-frequency vibrational spectra yield the information about molecular dynamics in condensed matter [1]. In this paper the low-frequency Raman (LFR) and farinfrared (FIR) spectra of water/glycerol mixtures at different concentrations are presented. The spectra of glycerol and water in this region are rather complicated due to the presence of hydrogen bonding [2]. The experimental data are analysed in terms of different models. In particular the peak position calculated using the formulae introduced in [3], where the relation of frequency maximum with the isothermal compressibility has been established.

Recently Raman spectroscopy in the NIR-region has been used in the diagnosis of skin diseases [1, 2]. In order to apply Raman spectroscopy for this purpose it is important to understand the changes in the spectra caused by the disease compared to the spectra of normal skin. In this article we will focus on the characteristics of the spectra of normal skin. NIR-FT-Raman spectra of human skin biopsies are analysed by a curvefitting procedure.

Changes in the structural proteins and hydration during aging is responsible for altered skin morphologic and mechanical properties manifested as wrinkling, sagging, loss of elasticity, or apparent dryness. To gain insight into the age-related alterations in protein conformation and water structure, we obtained Raman spectra from the sun-protected buttock skin representing chronologic aging and the sun-exposed forearm skin representing combined effects of photoaging and chronologic aging. Ten aged individuals (five men, five women; age range 74–87) and 10 control young individuals (five men, five women; age range 22–29) entered the study. In the photoaged forearm skin the positions of protein-specific amide I, amide III, and CH stretching bands were shifted, suggesting increased protein folding. In contrast, major changes were seen only in the amide I peak in chronologically aged skin. The intensity of the 3250 cm –1 OH stretching band was increased in photoaged skin (but not in chronologically aged skin) indicating an increased water content. R(ν) representation of the low-frequency region of Raman spectra was applied to determine water structure. In the young skin and chronologically aged skin water was mostly present in the bound form. In the photoaged skin, however, an increase in intensity at 180 cm –1 was noted, which reflects an increase in the not-protein bound water (tetrahedron water clusters). In conclusion, it seems that proteins in the photoaged skin are more compact and interact with water to limited degree. Impairment in protein hydration may add to the understanding of ultrastructural, mechanical, and biochemical changes in structural proteins in the aged skin.

Raman spectroscopy is a nondestructive analytical method for determining the structure and conformation of molecular compounds. It does not require sample preparation or pretreatment. Recently, near-infrared Fourier transform Raman spectroscopy has emerged as being specially suited for investigations of biologic material. In this study, we obtained near-infrared Fourier transform Raman spectra of intact human skin, hair, nail, and stratum corneum. We disclosed major spectral differences in conformational behavior of lipids and proteins between normal skin, hair, and nail. The amide I and III band location indicated that the majority of proteins in all samples have the same secondary alpha-helix structure. Positions of (S-S) stretching bands of proteins revealed a higher stability of the disulfide bonds in the hair and the nail. Analysis of vibrations of protein -CH groups showed that in the hair and the nail the proteins are apparently highly folded, interacting with the surroundings only to a small degree. The position of lipid specific peaks in spectra of hair, nail, and stratum corneum suggested a highly ordered, lamellar crystalline lipid structure. A greater lipid fluidity was found in whole skin. Assessment of the structure of water clusters revealed that mainly bound water is present in the human skin, stratum corneum, and nail. In conclusion, structural changes of water, proteins, and lipids in intact skin and skin appendages may be analyzed by Raman spectroscopy. This technique may be used in the future in a noninvasive analysis of structural changes in molecular compounds in the skin, hair, and nail associated with different dermatologic diseases.

In a recent minireview with the title “Water: now you see it, now you don’t” Levitt and Park [1] ask four general questions about water molecules interacting with proteins. Where are they? How long do they stay there? How strongly do they interact with the protein? How do they affect protein structure and stability? They mention also the three key techniques of modern structural research: crystallography, NMR spectroscopy, and computer methods. These methods are certainly important, but also other methods like IR and Raman spectroscopy, inelastic neutron scattering and time domain experiments by femtosecond laser pulses can contribute to structural studies of the biological solvent water and its interaction with biomolecules. Water absorbs very strongly in the IR spectrum, making the study of aqueous solutions difficult. Raman spectroscopy is more suited because the Raman signals from water are rather weak. The present investigation deals with the low-frequency Raman spectrum below 400 cm−1 of water in lysozyme, and water in human skin samples.

Malignant melanoma is the most aggressive of skin cancers. Removal of melanoma at an early stage is curative and prevents spreading of the disease and metastases and therefore early detection and treatment is essential. However, despite many attempts to implement various instrumental techniques (total body photography, dermatoscopy, flourescence spectroscopy etc.) a non-invasive, reliable and cost-effective method for early melanoma diagnosis and differentiation from clinically similar nevi has not yet been devised.

The polysaccharides known as glycosaminoglycans are important for the binding of water in the dermis. Spectra of three different glycosaminoglycans, chondroitin sulphate A, B and C are presented and compared. To our knowledge the spectrum of chondroitin sulphate B has not previously been published.The glycosaminoglycans have been reported to be able to bind up to 1000 times their own weight of water, which means that each repeating unit in the carbohydrate binds in the order of 2 × 104 water molecules [1]. It is questionable whether the carbohydrate lines actually are observed in the skin spectra. However, an interesting question is whether the carbohydrates also might influence the three dimensional water structure. In order to use Raman spectroscopy to study this structure an assignment of Raman bands to either water modes or modes belonging to other skin constituents is important. A band around 3220 cm-1 in the Raman spectrum of dermis is assigned to water.

The ground state vibrational spectra of E -hexatriene, Z -hexatriene, E,E -heptatriene, E,E,E -octatriene, and E -2,5-dimethyl-hexatriene are reported. For E - and Z -hexatriene complete vibrational assignments, and for heptatriene, octatriene, and dimethyl-hexatriene near-complete assignments are obtained. The effects of terminal and lateral methyl-substitution are compared.

The i.r. and Raman spectra of 1,3,4-[D]oxadiazole and 1,3,4-[D 2 ]oxadiazole in the vapour and the liquid phases and in solutions were recorded. The Raman spectrum of liquid 1,3,4-oxadiazole was reinvestigated. The low-temperature i.r. and Raman spectra of crystalline 1,3,4-oxadiazole and 1,3,4-[D 2 ]oxadiazole were also studied. A complete assignment of the fundamental vibrations of 1,3,4-oxadiazole and its deuterated species fulfilling the different isotopic rules is given. From the low-temperature spectra it may be concluded that crystalline 1,3,4-oxadiazole possesses the factor group C 2 h or S 6 .

The polarized i.r. spectra of oriented thioacetamide single crystals having the ab plane at right angles to the incident ray were measured in the region 400–4000 cm −1 at room temperature and cooled by liquid air. In the latter instance an extensive correlation splitting was found while evidence for site splitting could only be detected in a few bands. The isotopic shifts of all seven possible 13 C and 15 N substituted thioacetamide species were determined in KBr discs at room temperature 300–4000 cm −1 . A complete assignment of the observed bands is proposed which has necessitated a partial revision of earlier fundamental listings. The broadness and splittings of bands due to vibrations of the amino groups clearly demonstrate this strong hydrogen bonding influence.

The i.r. and Ram anspectra of dichloro-, dibromo- and monobromomalononitrile were recorded in the region 4000-40 cm −1 . Assignment of the fundamentals were proposed on the basis of experimental observations and supported at a later stage by force constant calculations, which also removed a few ambiguities. Difluoromalononitrile was included in these calculations and the reported assignments for this molecule are discussed.

The infrared and Raman spectra of triacetylene were examined in the region 4000-40 cm−1. The infrared spectrum was recorded in the gas phase and in solution, while the Raman spectrum was obtained from a pentane solution at −20 to −30°C. The spectra were interpreted in terms of a linear structure of D∞h-symmetry. Force constant calculations were carried out and the force constants adjusted to fit accurately the fundamental frequencies.