E. E. Lawson

Biomedical Applications of Raman Spectroscopy

Raman spectroscopy has been used in a variety of biomedical applications including normal and diseased human tissues, single cells, implants and the presence of foreign inclusions following implantation and the interaction of certain chemical agents with tissues. This paper surveys recent advances in biomedical Raman spectroscopy.

Fourier-transform Raman spectroscopy of ivory: II. Spectroscopic analysis and assignments

Abstract The FT-Raman spectra of African and Asian elephant and woolly mammoth ivory are reported and comprehensive molecular vibrational assignments are proposed. Since ivory is composed of proteinaceous collagen embedded in an inorganic matrix of carbonated hydroxyapatite, the Raman spectrum of pure natural collagen recorded under similar conditions aids the identification of the vibrational modes. Several bands are identified which could be used for the Raman spectroscopic characterisation of the mammalian ivories studied.

Structural determination of substituted mercaptothiadiazoles using FT-Raman and FT-IR spectroscopy

Abstract The FT-Raman and FT-IR spectra of 2,5-dimercapto-1,3,4-thiadiazole (DMTD), 5-methyl-1,3,4-thiadiazole-2-thiol (MMTD) and 5-amino-1,3,4-thiadiazole-2-thiol (AMTD) are reported and vibrational assignments are made. The spectroscopic study reveals that the thiol groups of these molecules participate in a thiol-thone tautomeric equilibrium. DMTD exists mainly as a dithiol whereas MMTD and AMTD exist as thiones at ambient temperature.

FT-RAMAN SPECTROSCOPIC INVESTIGATION OF A PSEUDOPOLYMORPHIC TRANSITION IN CAFFEINE HYDRATE

Abstract The FT-Raman spectra of caffeine hydrate and anhydrous β-caffeine have been recorded. The accelerated dehydration of the hydrate has been monitored at 30, 35 and 40°C using an environmental chamber. The spectra representing the individual pseudopolymorphic phases differed subtly throughout the entire spectral range. Gradual broadening of the CH stretching vibration observed at 3121 cm−1 and the progressive appearance of a CO stretch at 1656 cm−1 were ascribed to intermolecular bonding between CH and CO in the anhydrous phase. Accompanying loss of resolution of CH deformations in the lower wavenumber region observed at 1475 and 1255 cm−1 supports the suggestion of intermolecular association involving CH. Concurrent loss of resolution of the weak CN stretch at 1454 cm−1 and recession of the medium intensity HCN deformation at 1255 cm−1 were also detected, acknowledging the loss of interaction between N9 of the imidazole ring and the water molecule. The concomitant disappearance of the weak H2O libration at 890 cm−1 is observed, which suggests the occurrence of molecular realignment associated with corresponding loss of water of crystallisation. On removal of the hydrate backbone of the caffeine hydrate crystal structure, the lattice collapses, resulting in reduction of the intermolecular distance between individual caffeine molecules. The subsequent formation of a less rigid structure is evident, whereby molecules are weakly associated by unconventional CH…O interactions.

Fourier-transform Raman spectra of ivory. III: Identification of mammalian specimens.

The FT-Raman spectra of six mammalian ivories, other than elephant and mammoth, are presented and spectral differences formulated into a protocol for the identification of animal species from the ivory samples. In this study, sperm whale, walrus, wart hog, narwhal, hippopotamus and domestic pig are considered. The results, which are obtained non-destructively from a variety of specimens, suggest that FT-Raman spectroscopy provides a potentially useful method for the identification of mammalian ivory.

FT Raman spectroscopic study of the wavenumber region 2800-2630 cm−1 of selected organic compounds

Abstract A Raman spectroscopic study investigating the origin of a number of weak features observed in the Raman spectra of a comprehensive range of organic compounds in the wavenumber range 28002630 cm −1 has been undertaken. These bands have been found to be characteristic of (CH 3 C) groups in the wavenumber region 28002710 cm −1 , and of (CH 2 C) and (CHC) groups below 2710 cm −1 . In the wavenumber region 28002765 cm −1 , it is possible to distinguish between three different types of (CH 3 C) structural moieties, (CH 3 CMe 3 ), (CH 3 CMe 2 ) and (CH 3 CMe). Application of these observations to the Raman spectra of organic compounds provides new information on the extent of methyl branching in organic compounds.

Applications of Raman spectroscopy to skin research: ReviewArticle.

Raman spectroscopy has been used for a range of biomedical applications: the study of normal and diseased tissues, and the interaction of chemical agents with tissues, implants and even single cells. The object here was to review the extent to which the Raman spectroscopic technique has been applied to skin research, considering the implications of different instrumentation, comparing animal and human skin, healthy and diseased skin and in vivo and in vitro sampling.

Infrared spectroscopic study of ionic association of lithium trifluoromethanesulfonate in several solvents

Abstract The ionic pairing of lithium trifluoromethanesulfonate (triflate) in four solvents (water, acrylonitrile, acetonitrile and acetone) has been studied by dispersive infrared (IR) spectroscopy. Spectra were taken between 950 and 1400 cm −1 , where the anion internal stretching modes appear, and for a range of concentrations of 0.5–2.0 mol dm −3 (0.5–1.25 mol dm −3 for acetonitrile). The following bands have been analyzed: S-O symmetric stretching ( v 1 ), C-F antisymmetric stretching ( v 7 ) and S-O antisymmetric stretching ( v 10 ). In the v 1 envelope, three components are detected in all the solvents studied except water. These components are interpreted in terms of ionic pairs with different solvation degrees. The v 7 band also shows two components in the organic solutions. Its absorption coefficient is higher in organic solvents than in water, where only one component is detected. The complex and broad v 10 band is understood in terms of degeneracy lifting as an effect of the ionic pairing.

Interaction of Salicylic Acid with Verrucae Assessed by FT-Raman Spectroscopy

FT-Raman spectroscopy has been used to investigate treated verrucae (warts from the sole of the foot) with a local application of a salicylic acid paint. Differences in the molecular structure of the stratum corneum across the verruca sample were observed, and by comparison with normal and hyperkeratotic skin it was concluded that the tissue around the edges of the verrucae was typically hyperkeratotic skin. In the centre of the verruca, the molecular structure of the skin was altered showing evidence of the interaction with salicylic acid. Salicylic acid was not observed in its characteristic dimerised acid structure, but spectroscopic evidence suggested that fission of the intermolecular H-bonding essentially cleaved the dimer. Observed changes in the v(CCO) stretching mode of the carboxyl and hydroxyl groups indicate the inter H-bonds have broken. These spectral changes are believed to be more consistent with salicylic acid bonding within the human papillomavirus-containing verruca tissue rather than simple acid dissociation upon dissolution in water within the tissue. No evidence for the presence of the other paint components, lactic acid and flexible collodion, was found in the verrucae spectra. This Raman approach may help to elucidate the molecular basis for therapeutic agents interacting with diseased skin.

FT-Raman spectroscopy of the reaction of polybutadiene with mercapto-thiadiazoles

Abstract Mercapto-thiadiazoles having potential anti-wear behaviour are reacted with polymers with existing viscosity index-improving properties in order to produce materials which may find a use as multifunctional lubricant additives. 2,5-Dimercapto-1,3,4-thiadiazole, 2-amino-5-mercapto-1,3,4-thiadiazole and 2-methyl-5-mercapto-1,3,4-thiadiadiazole were reacted with low MW polybutadiene containing vinyl -1,2, cis -1,4 and trans -1,4 (CC) groups. The reactions were monitored using FT-Raman spectroscopy in order to determine quantitatively the consumption of the individual structural units when reacted with thiadiazoles. 2,5-Dimercapto-1,3,4-thiadiazole reacted readily with the polybutadiene, achieving 80% reaction within a few hours. The thiadiazole reacted selectively with the order of addition being cis > vinyl > trans . 2-Amino-5-mercapto-1,3,4-thiadiazole and 2-methyl-5-mercapto-1,3,4-thiadiazole were found to react more slowly and hence to a lesser extent (40 and 25%, respectively) over a similar time scale.