RESUMO
The susceptibility of highly fluorescent luminarine nucleosides to acid promoted anomerization reactions has been studied in order to select a derivative with suitable properties for chemical synthesis of luminarine-labeled oligo(deoxy)ribonucleotides. Both O-acetylated derivatives Ia-c and parent luminarosine IIa, as well as 2'-O-methylluminarosine IIb, and 2'-deoxyluminarosine IIc undergo anomerization at pH = 4 however, at considerably different velocities. In the case of O-protected nucleosides (Ia-c), the anomerization leads to an equilibrium mixture of respective beta and alpha furanosides, the rate and extent of anomerization decreasing in the following order: Ic >> Ia > Ib. Parent nucleosides (IIa-c) bearing free hydroxyls are generally more susceptible to anomerization than the O-acetylated derivatives but a similar order of reactivity (IIc >> IIa > IIb) is observed. In each case, a complex mixture containing both beta and alpha ribopyranosyl and -furanosyl forms is formed. Their structure and anomeric configuration have been proved by 1H and 13C NMR spectroscopy. The results point to 2'-O-methylluminarosine as the fluorophore of choice for further derivatization and chemical introduction into oligo(deoxy)ribonucleotides.
Assuntos
Proteínas Luminescentes/química , Pteridinas/química , Ribose/análogos & derivados , Cromatografia Líquida de Alta Pressão , Cinética , Espectroscopia de Ressonância Magnética , Oligonucleotídeos/síntese química , Ribose/química , Fatores de TempoRESUMO
Photophysical properties of fluorescentN-[2-amino-9-(2',3',5'-tri-O-acetyl-ß-D-ribofuranosyl)-purin-6-yl]-4-dimethylaminopyridinium chloride (GDMAP) are determined in view of its possible use as a probe in DNA. The fluorescence intensity of GDMAP increases and exhibits doubleexponential decay in the presence of common nucleosides. The formation of ground-state complexes with nucleosides is inferred from absorption and emission measurements.
RESUMO
Photoreactivity of Yt base [I] has been studied in aqueous solution [pH approximately 6] saturated with oxygen. Two photoproducts (II,III], resulting from irradiation at lambda = 253.7 nm and lambda greater than or equal to 290 nm, were isolated and their structures determined. The quantum yield for Yt base disappearance [zeta dis] is 0.002 [lambda = 313 nm]. It was shown that dye-sensitized photooxidation of Yt base in aqueous solution occurs according to a Type I mechanism, as well as with participation of singlet state oxygen. Quantum yields, fluorescence decay times and phosphorescence of Yt base have been also determined.
