Spectral Properties of Single-Stranded Viral DNA Fragment

Abstract

This article presented the results of investigations of the optical absorption (at 300 K) and steady-state and time-resolved luminescence (at 78 K) of (–)PBS and (+)PBS oligonucleotides. (–)PBS is the DNA form of the minus primer binding site (5′GTCCCTGTTCGGGCGCCA3′) of the human immunodeficiency virus type 1 (HIV-1)genome, and (+)PBS (3′CAGGGACAAGCCCGCGGT5′) is its complementary sequence [1]. The optical absorption spectra of (–)PBS and (+)PBS do not coincide with the correspondent equimolar sums of the spectra of nucleotides that are in their composition. The difference between them at 295 nm is related to the existence of some stable complex between bases (possibly, G-complexes). The fluorescence spectral bands of (–)PBS and (+)PBS are close to each other and to the band of oligonucleotide investigated by us in [2]. In our opinion, the (–)PBS and (+)PBS bands are connected possibly with the fluorescence of some complexes that are manifested in the absorption. The phosphorescence spectral bands of (–)PBS and (+)PBS are close to each other and to the band of dAMP (in the wavelength interval 370–470 nm). The difference between the (–)PBS/(+)PBS and dAMP phosphorescence spectra (at 530 nm) is associated with an unknown center (possibly, G-complexes). Thus, the main centers of the triplet excitation capturing in (–)PBS and (+)PBS are A-bases and centers of an unknown nature.