Polynucleotides -adenosine complex

Emission quenching is also observed with mononucleotides. In that case the quenching efficiency decreases from GMP (guanosine 5 monophosphate) to AMP (adenosine 5 monophosphate) i.e. it also follows the redox potentials of the bases, as G is more easily oxidisable than A, although the oxidation potential valura reported in the literature are rather different from one author to the other [101-104], Moreover the quenching rate constant by GMP in a Kries of different TAP and HAT complexes plotted versus the reduction potential of the excited state (Fig. 12) [95] is consistent with an electron transfer process. Indeed, as will be demonstrated in Sect. 4.3.1, these quenchings (by the mono-and polynucleotides) originate from such processes. 

The interactions between each of the stereoisomers of [(phen)2Ru(//-hat)Ru(phen)2]" " and GMP and adenosine-5 -monophosphate (AMP) have been investigated, and the effects on the photophysical properties of this complex of the presence of mono- and polynucleotides have been examined. Strong ion pairs are formed between [(phen)2Ru(//-hat)Ru(phen)2]" " and GMP or... 

To demonstrate polymerase activity in a model cell, Chakrabarti et al. [79] encapsulated polynucleotide phosphorylase in vesicles composed of dimyris-toylphosphatidylcholine (DMPC). This enzyme can produce RNA from nucleoside diphosphates such as adenosine diphosphate (ADP) and does not require a template, so it has proven useful for initial studies of encapsulated polymerase activity (Fig. 10a). Furthermore, DMPC liposomes are sufficiently permeable so that 5-10 ADP molecules per second enter each vesicle. Under these conditions, measurable amounts of RNA in the form of polyadenylic acid were synthesized and accumulated in the vesicles after several days incubation. The enzyme-catalyzed reaction could be carried out in the presence of a protease external to the membrane, demonstrating that the vesicle membrane protected the encapsulated enzyme from hydrolytic degradation. Similar behavior has been observed with monocarboxylic acid vesicles [80], and it follows that complex phospholipids are not required for an encapsulated polymerase system to function. 

The purine base adenine (6-aminopurine, previoulsy also known as vitamin B4,5-131) is generally widespread as a building unit of the ribofuranoside adenosine and its phosphates, such as adenosine 5 -monophosphate (AMP, adenylic acid), adenosine 5 -diphosphate (ADP) and adenosine 5 -triphosphate (ATP), polynucleotides, such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA), vitamins (riboflavin, adenosylvitaminBjj) and cofactors NAD(P)+ and FAD. Adenylic acid was once considered a member of the vitamin B complex (as vitamin Bg). The agent in shiitake (Lenttnula edodes) mushrooms that can reduce the level of cholesterol in the blood is a purine derivative, (2fi,3fi)-dihydroxy-4-(9-adenyl)butyric acid (5-132) called eritadenine (lentinacin, lentysine). 

---