Resonance Raman scattering study of azulene. II. Nonzero temperature multimode model calculations

Abstract

Resonance Raman scattering study of azulene. I. Experiment and theoretical analysis via transform techniques A theoretical study of resonance Raman scattering from molecules. II. Temperature effect In a recent paper (Az I), well-structured T = 300 K resonance Raman (RR) profiles for the 1400, 1260,900, and 2X825 cm-I lines of azulene in CS 2 and for the 825 cm-I line of azulene in methanol were reported. Previously developed transform techniques were used to (1) compute RR profile line shapes directly from measured optical absorption spectra, and (2) extract ratios of Stokes loss parameters from the line shape scale factors. The transform analysis indicated that (1) our model assumptions (adiabatic and Condon approximations, harmonic phonons, atomic equilibrium position shifts, and small vibrational frequency shifts upon excitation to a single electronic state) are basically correct allowing for minor modifications, and (2) any deviations from these assumptions are likely to be larger for the 900 cm-I mode and smaller for the 1400 and 1260 cm-I modes. In this paper (Az II), we report model calculations of the optical absorption spectra, RR profile line shapes, and relative RR intensities. In these calculations, we use a recently proposed nonzero temperature multimode time-correlator modeling procedure. Compared with the conventional sum-over-states method, our time-correlator modeling procedure is superior in that (1) our optical absorption spectra and RR profiles computed via fast Fourier transform techniques have a practically unlimited spectral range and (2) the computing times are short for nonzero temperature multimode calculations. In our basic model, we adopt the assumptions of Az I and use seven azulene modes to obtain simultaneous good fits of the well-structured RR profile line shapes and optical absorption spectra. However, we find that the basic model does not account for the intensity of the 900 cm -I Raman line relative to that of the 1400 cm -I line, even though the individual profile line shape fits for these modes are very good. The basic model is therefore modified to allow mixing of the normal coordinates of these two modes. By introducing a single, relatively small mode-mixing parameter, we obtain a good fit of the relative RR intensities in addition to simultaneous detailed fits of the optical absorption spectra and RR profile line shapes. In an alternate approach, we modify our basic model and find that the inclusion of two relatively small non-Condon parameters, instead of one mode mixing parameter, can also produce simultaneous detailed fits of all of our optical absorption and RR data. A comparison of the two modified models solely on the basis of simplicity favors the mode-mixing model, since only one extra parameter is required to modify our basic model.

Identification of conserved and divergent domains within the envelope gene of the acquired immunodeficiency syndrome retrovirus.

“…When their deduced amino acid sequences were aligned with the-envelopes of the lymphoadenopathy and AIDS-associated retrovirus isolates, conserved and divergent regions were readily identified. (4,10,11). For example, sequence analysis of the env region of the lymphoadenopathy virus (LAV) and AIDSassociated retrovirus (ARV) isolates revealed the presence of numerous nucleotide substitutions and several reciprocal insertions and-deletions resulting in 9% polynucleotide sequence heterology and a 15% difference in the deduced amino acid sequence (10).…”

Immunoregulatory activities of human immunodeficiency virus (HIV) proteins: effect of HIV recombinant and synthetic peptides on immunoglobulin synthesis and proliferative responses by normal lymphocytes.

“…Immunoglobulin levels of culture supernates were measured by micro-ELISA as described (12). Briefly, wells of polystyrene plates were coated with 0.1 ml of heavy chain-specific rabbit anti-human IgG diluted to 2 gg/ml in 0.05 M sodium carbonate (pH 9.6) containing 0.02% sodium azide.…”

Specific cellular immune response and neutralizing antibodies in goats immunized with native or recombinant envelope proteins derived from human T-lymphotropic virus type IIIB and in human immunodeficiency virus-infected men.

“…Because heterogeneity is greatest in the envelope glycoprotein (3), scepticism has been raised as to the future prospects for a HIV vaccine. The external HIV envelope glycoprotein gpl20, which theoretically would be the prime target for a protective immune response toward HIV, contains conserved and variable regions (3,4). Moreover, computer-assisted analysis predicted highly immunogenic epitopes within the variable and conserved regions of gpl20, as well as in the conserved sequences of the transmembrane envelope glycoprotein gp41 (14).…”

“…Three HIV isolates, HTLV-IIIB, HTLV-IIIMN, and HTLV-IIIRF (2) were cultured in H9 cells in RPMI 1640 medium and 10% (vol/vol) fetal calf serum. These viruses represent the broad spectrum of divergence seen between different HIV isolates (3,4,14). For immunoblots and for T-cell assays, virus concentrated by a factor of 5000 was prepared from the culture supernatant by Frederick Cancer Research Facilities (Frederick, MD) or by Electronucleonics (Silver Spring, MD).…”

“…A logical candidate for such a vaccine is the external envelope glycoprotein gpl20 or corresponding recombinant or synthetic peptides. gpl20 contains conserved and variable regions (3,4) and is mainly responsible for up to 30% of the variability observed between different HIV isolates. Neutralization assays with sera from HIV-infected individuals (5-7) or from immunized animals (8,9) suggest that gpl20 contains epitopes that elicit antibodies capable of neutralizing HIV infection in vitro.…”