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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.

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.

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.

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.

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 &

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.

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.

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.

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.

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.

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 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.

The infrared spectra of maleic anhydride and its mono- and dideuterated species were recorded in the region 5000-50 cm −1 in the vapour phase and in solution. Raman spectra of the solids and supercooled melts were obtained. Assignments of the fundamental vibrational frequencies are given, based upon semiquantitative polarization data and the infrared vapour contours as well as on the product rule and complete isotopic rule for the three compounds.

The i.r. spectra of monomethyl and dimethyl maleic anhydride were studied in all three physical states in the region 5000-50 cm −1 . Raman spectra of monomethyl maleic anhydride as a liquid and dimethyl maleic anhydride in solution and as a solid were also investigated. The fundamental frequencies have been assigned and force constant calculations have been performed.

The i.r. and Raman spectra of dichloro- and dibromodiacetylene were recorded over the region 4000-50 cm−1, and of diiododiacetylene over the region 4000-200 cm−1. For most measurements the compounds were studied in solution (CCl4, CS2, C6H6 and CH2Cl2), while dichloro-diacetylene was also studied as a vapour in the infrared and as a liquid for the Raman spectrum. The spectra of the dichloro- and dibromodiacetylene were further studied at liquid nitrogen temperature in i.r. and Raman cryostats. The spectra were interpreted in terms of D∞h symmetry, and except for diiododiacetylene, complete assignments are presented for the nine fundamental frequencies of each compound. A set of precalculated frequencies, derived from force fields employed for the monohalodiacetylenes served as an aid to the assignments. Based upon the fundamental frequencies assigned for the present dihalodiacetylenes, the monohalodiacetylenes and diacetylene itself, force fields were derived for these seven molecules using the overlay technique.

The IR and Raman spectra in the range 4000-10 cm − of 3-azetidinol and the O,N-dideuterated derivative have been recorded in the solid state and in aqueous solution. The interpretation of the vibrational spectra has been based upon ab initio calculations in the STO-3G approximation. A model structure for the calculations has been adopted in which 3-azetidinol binds two molecules of water and two molecules of ammonia. The results obtained for the aqueous solution are in accordance with the occurrence of 3-azetidinol as a hydrated, stacked, intermolecularly hydrogen-bonded chain.

Conformation de poly(N-carbazolylcarbonyl-L-lysine) a l'etat solide et en solution. En solution, la liaison hydrogene des chaines laterales est rompue

The infrared absorption spectrum of 1, 2, 5-oxadiazole has been recorded in the region 5000-400 cm−1 in the vapor and in the liquid phases, in CS2 and C2Cl4 solutions. Also, the Raman spectrum of liquid 1, 2, 5-oxadiazole has been obtained. A complete assignment is given. The thermodynamic functions −(F 0 -H 0 0 ) T , S0, (H 0 -H 0 0 ) T , C p 0 have been calculated.

Infrared absorption spectra of vinyl fluoride and its seven deuterated derivatives have been taken. The assignment of fundamental vibrational frequencies for vinyl fluoride originally given by T orkington and T hompson must be slightly modified. A final assignment for all eight isotopic species is suggested.

The i.r. absorption spectra (5000–400 cm −1 ) of 1,2,5-[D]oxadiazole and 1,2,5-[D 2 ] oxadiazole have been studied. Raman spectra of the same compounds have been recorded and the Raman spectrum of 1,2,5-oxadiazole has been reinvestigated. A complete assignment of the fundamental vibrations of the deuterated 1,2,5-oxadiazoles, which fulfils the Teller-Redlich product rule and the complete isotopic rule, has been achieved. This necessitates changes in the previous assignment of v 7 and v 13 of 1,2,5-oxadiazole.

Mean amplitudes of vibration for methyl ketene and several of its isotopic molecules which include deuterium, 13 C and 18 O substitutions are calculated. Some remarkable secondary isotope effects are reported for nonbonded CC, CH and OH distances.

The previously published rotational constants of eight isotopic species of vinyl fluoride have been used to calculate an rs (substitution) structure for the molecule. The results are: r(CC) = 1.329 ± 0.006 A, r(CF) = 1.347 ± 0.009 A, ⦠ (FCC = 120.8° ± 0.3°, ∡FCH = 110° ± 1°, r(CH) = 1.082 ± 0.004 A; in the CH2 group : r(CH) = 1.077 ± 0.003 A and ∡HCC = 119.0° ± 0.3° for the CH bond trans to F; r(CH) = 1.087 ± 0.003 A and ∡HCC = 120.9° ± 0.3° for the CH bond cis to F.

A number of deuterated pyrroles have been prepared and their microwave spectra recorded. For each isotopic species the two 1→2 transitions observable around 20 000 MHz were localized together with a number of Q‐lines in the 17 400—26 000 MHz region scanned. For all isotopic molecules rotational constants were calculated. In this way seven mutually independent numerical data were obtained which is insufficient for a direct calculation of the nine geometrical parameters of pyrrole. Additional assumptions as to the length of the two C, H bonds lead to definite models for pyrrole.

The Raman spectrum of liquid 1,3,4-oxadiazole has been recorded. Also, the infrared absorption spectrum of crystalline 1,3,4-oxadiazole at −196°C has been recorded in the region 4000-400 cm −1 . The tentative assignment previously published is slightly revised and the thermodynamic functions −( F 0 − H 0 0 )/ T , S 0 , ( H 0 − H 0 0 )/ T and C p 0 are calculated.

Microwave spectra of benzonitrile, C6H5CN, and 9 isotopic species are reported. Moments of inertia of these 10 molecules are combined to give the rs structure of benzonitrile. The final structure is: C(1)C(2) = 1.391 A, C(2)C(3) = 1.393 A, C(3)C(4) = 1.400 A, C(1)C(7) = 1.455 A, C≡N = 1.159 A, C(2)H(2) = 1.069 A, C(3)H(3) = 1.082 A, C(4)H(4) = 1.081 A, C(6)C(1)C(2) = 122.5°, C(1)C(2)C(3) = 118.45°, C(2)C(3)C(4) = 120.3°, C(3)C(4)C(5) = 120.0°, C(1)C(2)H(2) = 121.8°, C(4)C(3)H(3) = 119.9°.

Microwave spectra of [2- 13 C] furan, [3- 13 C] furan, and [ 18 O] furan are reported. Moments of inertia of these species are combined with earlier data on furan and deuterated furans to give the r s -structure of furan. The final structure is: OC(2) = 1.362 A, C(2)C(3) = 1.361 A, C(3)C(4) = 1.431 A, C(2)H(2) = 1.075 A, C(3)H(3) = 1.077 A, C(5)OC(2) = 106°33′, OC(2)C(3) = 110°41′, C(2)C(3)C(4) = 106°3′, OC(2)H(2) = 115°55′, C(4)C(3)H(3) = 127°57′.

The i.r. spectra of chloro and bromo maleic anhydride were recorded in the liquid and solid states in the region 5000–50 cm −1 and in the vapour phase between 4000 and 400 cm −1 . Roman spectra of chloro maleic anhydride as a solid and in acetonitrile solution and of bromo maleic anhydride as a liquid were obtained and semiquantitative polarization data calculated. The fundamental frequencies have been assigned and a force constant calculation carried out.

The microwave spectra of 2- C 13 -thiophene and of 3- C 13 -thiophene have been recorded and analyzed. In addition, three lines from the S 34 -thiophene were found and identified. Taken together with earlier published data for thiophene, thiophene-2 d , and thiophene-3 d , an unambiguous calculation of the (‘ r 8 ’-) structure of thiophene is now possible, the structural parameters being: (distances) CS = 1.714 A; CC = 1.370A; CC = 1.423 A; C(2)H(2) = 1.078 A; C(3)H(3) = 1.081 A; (angles) C(5)SC(2) = 92°10′; SC(2)C(3) = 111°28′; C(2)C(3)C(4) = 112°27′; SC(2)H(2) = 119°51′; C(4)C(3)H(3) = 124°16′.

2‐ and 3‐monodeutero, 3,3′‐dideutero, and tetradeuterothiophene have been prepared and their microwave spectra recorded together with the microwave spectrum of ordinary thiophene (C4H4S). Lines originating from the 4% content of C4H4S34 and the 2% content of C3C13H4S in ordinary thiophene (both the 2‐ and the 3‐C13 species) were also identified. For all isotopic species rotational constants of high accuracy were obtained. The total material is sufficient for a complete determination of all the 8 geometrical parameters of thiophene.

The infrared spectra of three dihaloacetylenes with equivalent halogens (dichloro-, dibromo- and diiodoacetylene) and two with different halogens (bromochloro- and chloroiodo- acetylene) were recorded in the region 4000-50 cm−1. They were studied in the vapour phase and in solution, but the less volatile diiodoacetylene was recorded in solution and as a solid. Using helium-neon laser excitation, Raman spectra of all the compounds were recorded and the depolarization ratio of the bands determined. For each of the molecules the five fundamental frequencies were assigned, and they agreed reasonably well with the frequencies derived from a preliminary force constant calculation. A progression of “hot bands” were observed at the low frequency side of the CC stretching fundamental for all the molecules.

The microwave spectra of seven isotopic species of propylene have been studied in order to obtain an accurate molecular structure. The complete rs (substitution) structure has been calculated. The more important parameters are: r(C=C)=1.336±0.004 A,r(C–C)=1.501±0.004 A, ≰CCC=124.3∘±0.3∘. The structure is compared with those of related molecules. It is concluded that no difference can be detected in the double‐bond lengths in ethylene, propylene, and the vinyl halides. The CC single‐bond length in propylene is indistinguishable from that in acetaldehyde and other acetyl compounds, and is 0.025 A shorter than the CC distance in saturated hydrocarbons. In the =CH2 group in propylene, the CH bond trans to the methyl group appears slightly shorter than the cis CH bond; a similar effect occurs in the vinyl halides.

The microwave spectrum of methyl ketene, CH3CHCO, has been recorded and analysed. The rotational constants, extrapolated to infinite barrier height, are A = 38·35 kMcs, B = 4507·40 ± 0·11 Mcs and C = 4136·97 ± 0·11 Mcs. The height, V3, of the threefold barrier hindering the rotation of the methyl group, is 1200 ± 10 calmole, or close to the barrier height in acetaldehyde (1150 calmole).

The i.r. spectra of dichloro and dibromo maleic anhydride were recorded in the vapour phase at 160° (4000-400 cm −1 ), in solution and as solids (5000–50 cm −1 ). Raman spectra of the solids were obtained and semiquantitative polarization data calculated from spectra recorded of saturated solutions. The fundamental frequencies have been assigned and the spectra interpreted on the basis of C 2v symmetry. A force constant calculation has been carried out and a force field derived for each molecule which exactly reproduces the observed frequencies.

A harmonic potential function was calculated for dichlorosilane using the observed fundamental frequencies of SiH 2 Cl 2 and SiD 2 Cl 2 . The complete quadratic potential function was obtained for the A 2 -, B 1 -, and B 2 -species, whereas certain assumptions were made regarding the potential function of the A 1 -species. The calculated potential function reproduces excellently the observed chlorine isotopic shifts in the vibrational spectra of SiH 2 Cl 2 , SiDHCl 2 and SiD 2 Cl 2 . Because of the angular redundancy it is only possible to evaluate the valence bond stretching force constants and the interaction constants between these.

By means of microwave spectra of vinyl fluoride and five of its deuterated species the most probable structure of vinyl fluoride has been evaluated. This structure has C(1), F = 1·348 A; C(I), H(1) = 1·073 A; C(2), H(2) = 1·080 A; C(2), H(3) = 1·080 A; C(1), C(2) (double bond distance) = 1·333 A.

The infrared spectrum of methylthionitrite has been recorded in the vapour phase (5000-50 cm −1 ), in the liquid phase (4000-400 cm −1 ) and in solutions (4000-300 cm −1 ). Also, the Raman spectrum of liquid methylthionitrite and the electronic spectrum of a cyclo hexane solution in the region 2100–7000 A have been obtained. The proton magnetic resonance spectrum of methylthionitrite was studied in CH 2 Cl 2 -solutions at various temperatures. A tentative assignment of the fundamental vibrations, except the methyl torsional mode, is given and the conformations of the molecule are discussed.

Low frequency Raman spectra (20–400 cm−1) are presented of formamide dissolved in dimethylsulfoxide (DMSO). The concentration of formamide ranges from 2%–75% (v/v). The two formamide bands at 110 and 190 cm−1 in the neat liquid exhibit only smaller frequency shifts upon dilution. The intensities of both bands are proportional to the concentration of formamide. The conclusion is, that the linear chain structure, found in neat liquid formamide, is conserved in the DMSO solution. Raman spectra of the NH‐stretching region (2950–3500 cm−1) confirm this hypothesis.

Low-frequency Raman spectra from 20 to 400 cm−1 of a 0.1 M aqueous solution of adenylyl-3′,5′-cytidine (ApC) ammonium salt were studied. An aqueous solution of ammonium chloride was used as reference. Experimental data were transformed to the R(ν) representation described previously. Spectra were obtained at temperatures between 0 and 70 °C. A broad band with a maximum below 100 cm−1 was assigned to water/base associate. This result corroborates previous assignments for nucleosides and nucleotides.

The microwave spectrum of thiazole has been recorded in the 16,000–30,000 Mc/sec region and analyzed. Twelve transitions were assigned. The rotational constants are: A = 8529.40 ± 0.05, B = 5505.75 ± 0.04, and C = 3344.32 ± 0.02 Mc/sec. The dipole moment of the molecular ground-state was determined, following the procedure indicated by Golden and Wilson. μ a = 1.286, μ b = 0.966, and μ total = 1.61 ± 0.03 debye.