Nucleic acids resonance Raman studies

With this normal mode description, then, it is instructive to review the resonance Raman intensity-derived excited-state structural dynamics. The first UV resonance Raman study of thymine was not done until 1994 by Lagant, et al. [113], Although Raman and IR spectra of thymine had been recorded much earlier. Most earlier studies of nucleic acid components focussed on the nucleosides and nucleotides. Indeed, much of the earlier research on nucleic acid components was done by the groups of Peticolas and Spiro, working independently. Spiro focussed more on nucleosides and larger nucleic acid structures (see below), while Peticolas examined the nucleobases initially. Peticolas s approach was to combine ab initio computations of the ground-state and excited-state structures and vibrational frequencies, with... 

In 1980-1982 comprehensive reviews on Raman and resonance Raman studies of biological and biochemical systems appeared in the literature (Carey and Solares, 1980 Carey, 1982). Particularly work on protein conformation, natural, protein-bound chro-mophores, resonance Raman labels (as already mentioned above), nucleic acids and nucleic acid-protein complexes as well as on lipids, membranes, and carbohydrates were reviewed. 

This initial report was followed closely by the UV resonance Raman spectra of uridine (UMP), cytidine (CMP) and guanidine (GMP) monophosphates by Nishimura, et al. [149] and the application of UV resonance Raman spectroscopy to nucleic acids and their components started in earnest. In the years that followed, Peticolas and Spiro provided much of the research effort in this area. For nucleosides and nucleotides, Peticolas studied guanosine [150], UMP [151-154], GMP [152, 155], AMP [144, 152, 156] and CMP [153], Spiro was the only one to measure the UV resonance Raman spectra of TMP, in addition to those of all the other naturally occurring nucleotides [157, 158], For all of these nucleotides, UV resonance Raman excitation profiles have been determined. 

UV and NMR studies showed that l-methyl-A -hydroxycytosine and its methyl derivatives exist predominantly in the oxo-imino form (up to 90%) (98BPC87). A review of the structure and properties of isolated nucleic acid bases with the special attention given to metal-cation-assisted tautomerization and the solvent effects has been published (99CR3247). Tautomerism of protonated cytosine has been studied experimentally by IR and Raman spectra and theoretically by ab initio and DFT calculations (96JPC5578). Neutral and protonated forms of cytidine monophosphate have been studied by ultraviolet resonance Raman spectroscopy. The amino oxo tautomer was found to be the most stable, followed by the imino oxo form. The imino-hydroxy tautomer was determined to be the least stable one. Upon protonation, the amino-oxo structure is retained (93JA760). 

Colorectal carcinomas have been studied using UV-resonance Raman spectroscopy by Manoharan et al, [16] and Boustany et al. [15]. Spectra were modeled as a linear combination of nucleotide, aromatic amino acid, and lipid line shapes, enabling quantification of nucleotide and amino acid signal contributions. In most dysplastic tissue and carcinoma samples, lower amino acid/nucleotide ratios were found, as well as lower adenyl levels. Feld et al. [45] also used NIR-Raman spectroscopy to identify the differences between normal colon tissue and colon adenocarcinoma. Nucleic acid vibrational modes at 1340, 1458, 1576, and 1662 cm" were more intense in carcinomas, indicating a higher nuclear content the normal samples showed more intense lipid signal contributions. 

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