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 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 (alpha(2): HSO4- reversible arrow 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 alpha(2) 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 the density of aqueous sulfuric acid is given and an interpolation algorithm for obtaining the complex index of refraction of aqueous sulfuric acid solutions as a function of acid weight fraction and temperature is presented.

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 (C) 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.

The R(<()over bar>)-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. Spectra of lysozyme/water mixtures ranging from very dry lysozyme to diluted aqueous solutions were recorded. Low-frequency spectra in the R(<()over bar>)-representation showed that a tetrahedrically hydrogen bonded water structure exists in mixtures with water contents above 13-30%(w/w). Spectra were also obtained in the OH-stretching region above 3000 cm(-1), but no significant information was obtained in this region. The spectroscopic results were compared to thermodynamic measurements including the partial enthalpy of water in the water/lysozyme mixtures. The conclusions regarding the water structure were consistent with the results obtained either at the long thermodynamical or the short spectroscopic time scale. Furthermore.. the influence of water content on the lysozyme secondary structure was investigated by curve fitting of the amide-I bands: The secondary structure seemed to be insensitive to the water content apart from the first 10%(w/w) of water. Finally, the low-frequency wafer band at 180 cm(-1) is used to monitor the presence of bulk water-lice structures in complex human skin samples.

Amber samples from different regions of the world were analyzed by NIR-FT-Raman spectroscopy. The results indicate that all the samples from the Baltic Sea and the one from Mexico correspond to mature amber, whereas the samples from the Dominican Republic and Madagascar correspond to younger amber(copal). All sample from the Baltic showed the characteristic bands centered at 1646 and 1450 cm(-1), but in the samples from Madagascar, Mexico and the Dominican Republic the last band was observed at 1440 cm(-1). The presence of an exocyclic =CH2 band at 3080 cm(-1) along with those at 1646 and 886 cm(-1) was evident in the spectra of almost all the samples from the Baltic Sea, Madagascar and the Dominican Republic. The band at 3080 cm(-1) was not seen in the spectrum of the Mexican sample. The sample from the Baltic Sea of maritime source and the Mexican sample showed the lowest intensity ratio I(C=C)(1646) / I(CH2)(1450/1440) with 0.35 and 0.42, respectively. This fact indicates that these samples correspond to the most fossilized amber of all the samples. For the other samples this ratio was around 0.6.

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 HCONHCH3 (N-methylformamide with all isotopes in their natural abundance), H13CONHCH3, HC18ONHCH3, 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 100cm−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.

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 up), 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 hare 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 nu(CH) peak at 2850 cm(-1). The band near 1300 cm(-1) is characteristic of twisting and wagging CH, 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 (C) 1999 John Wiley & Sons, Ltd.

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, (C) 1999 Elsevier Science B.V. All rights reserved.

Far-infrared and low-frequency Raman spectra in the wavenumber range from 15 to 500cm−1 were recorded for glycerol, triacetin (glycerol triacetate) and o-terphenyl at temperatures from 253 to 355K. 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.

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.

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.

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(v) 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.

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.