Adenosine, complexes

On the dichotomy of metal-ion binding in adenosine complexes. Comments Inorg. Cltem. 13, 35 (1992). 

Flavin mononucleotide (FMN)-adenosine and flavin adenine dinucleotide (FAD)-adenosine complexes show quenched triplet lifetimes compared to FMN alone, which is cited as evidence of intramolecular com-plexation between the flavins and adenosine by Shiga and Piette [142]. Adenosine phosphates also form complexes with FAD [143]. The com-plexation between a flavin and adenosine is identical to the intermolecular complexing of adenosine and flavin moieties, in the latter case enforced by hydrophobic bonding [144-146]. Rath and McCormick [147] have examined the riboflavin complexes of a series of purine ribose derivatives... 

Miles (1968) has presented data for the interaction between 5 -GMP and poly-cytidylic acid, and has discussed the use of 5 -GMP-6- 0 to assign a band at 1685 cm to a guanine carbonyl in 5 -GMP-6- 0, since the 1685 cm band was the only one to decrease in frequency upon 6- 0 substitution of GMP. He also discussed the melting curves of a poly U-6-methylamino-9-methylpurine complex, and a poly UC (30/70)-adenosine complex. In this paper he has described cells, temperature controls, spectroscopic instrumentation and conditions, and experimental procedures used throughout most of the work discussed in this section on Aqueous Solutions. 

Cao s group in 2011 designed an ECL biosensor based on the construction of triplex DNA for the detection of adenosine which employs an aptamer as a molecular recognition element and quenches ECL of Ru(bpy)3 by ferrocene monocarboxylic acid (FcA) G ig. 6.5). In the presence of adenosine, the aptamer sequence (Ru-DNA-1) more likely forms the aptamer—adenosine complex with hairpin configuration and the switch of the DNA-1 occurs in conjunction with the... 

The question of metal ion-adenine interaction in ATP complexes has been studies by UV measurements in aqueous solution (3). Difference spectra of the ATP complexes versus ee ligand, and comparison with adenosin complexes, indicate that equilibrium 1 is far to the left for Ca-ATP, Mg-ATP, Mn-ATP, Co-ATP, Ni-ATP and Zn-ATP, while in solution of Cu-ATP species II predominate, in which Cu is bound to the adenine ring too. 

Cytidine 2, 3 -cyclicphosphate, polymeric complexes of Cd" and Cu" and cytidine 5 -phosphate, l-(j8-D-arabinofuranosyl)cytosine Pt complex. Adenosine complexed with 5-bromouracil, iS-methyl-5 -thioadenosine, 2, 3 -0-isopropyIideneadenosine, 2, 3 -0-(2-carboxyethyl)ethylideneadeno-sine, the amino-acid adenosine derivatives (5) and (6) which are constitutents of tRNA, 8-[(2-aminoethyl)amino]adenosine 3, 5 -cyclic phosphate. 8-Iodoguanosine, 2-JV-methylguanosine, a guanosine Hg" complex, 2, 35 -tri-(9-acetyl-6-0-(mesitylenesulphonyl)-guanosine, guanosine 5 -phosphate, Cu" complex. ... 

DDTC can inhibit platinum nephrotoxicity without affecting activity (Chapter 2.2). In this case, studies with model compounds showed that the bis(guanosine) complexes were not affected by DDTC (10 mM, 37 C) whereas a mono(guanosine) complex and a bis(adenosine) complex reacted readily with the DDTC ligand [137]. These results confirm observations from studies on DNA, where very little platinum is removed by DDTC at low binding ratios, and allow the prediction that DDTC should not reverse the toxic lesion on DNA, as observed [137]. It would be interesting to correlate the various effects of the nephroprotective sulfur nucleophiles (Chapter 2.2) and their effects on antitumour activity of cisplatin with the behavior toward model compounds (see also Chapter 3.7). 

NMR spectroscopy indicates a dynamic equilibrium of rotamers of the thiourea in complex ions such as [PtCl(diamine)(monofunctional thiourea)] Dynamic processes in platinum(II)-adenosine complexes have been investigated and the Pt NMR spectra recorded.Variable temperature NMR spectroscopy shows restricted rotation of the NO group in [PtCl3(4-X-C6H4NO)] . The intramolecular conformational exchange thermodynamics of a5 -[PtCl2 l,T-(CiiH23SeC5H4-ri )2Fe ] have been determined. 

ELECTROCHEMISTRY AND SPECTROELECTROCHEMISTRY OF ADENINE AND ADENOSINE COMPLEXES WITH 3d TRANSITION METALS... 

Figures 2 and 3 show simplified structural formulas of adenine and adenosine complexes, respectively. The structures of the complexes reflect the pronounced tendency of purines to act as bridging ligands. Binding sites of adenine differ with metal ion variation. Evidence from IR, electronic spectra, and magnetic susceptibilities reported previously suggest structures for the complexes vary both with the central metal and the nature of the ligand.

The adenosine complexes are most probably linear polymeric species, involving single bridges of N(l), N(7)-bonded adenosine between adjacent metal ions with additional coordination sites occupied by perchlorate, ethanol, water, or adenosine and additional ionic perchlorate as needed for electric neutrality. 

The most likely structural type for the Fe(III) adenosine complex is shown in Figure 3c. This is the only complex studied with 3 2 adenosine to metal stoichiometry. The terminal adenosine ligand would be expected to bind through N(7). This complex contains coordinated water and perchlorate. 

The similar linear polymeric structural type for the Ni(II) complex which contains coordinated perchlorate as well as water and an analogous structure without coordinated perchlorate for the Cu(II) complex are shown in 3b and 3a, respectively. The remaining adenosine complex, Fe(II), (3d) is anhydrous with coordination number 4 achieved through tridentate bridging of adenqgine. Structure 3d shows coordination of adenosine through ribose hydroxyl oxygens as indicated by IR data and consistent with other experimental evidence. 

Table 1 summarizes the half wave potentials for the reduction processes occurring on platinum in the potential range +0.4 to -1.8 V obtained by differential pulse and cyclic voltammetry for the 3d metal perchlorates, the adenine complexes, and the adenosine complexes. 

Table 1. Potentials for reduction of adenine, adenosine, 3d metal perchlorates, adenine complexes and adenosine complexes, in DMSO, 0.1 M TBAP solution. 

All the adenosine complexes studied in this work have linear polymeric structures and N(l)-N(7) bonded adenosine and all but the Fe(II) complex contain coordinated water. Spectra obtained during reduction of the Cu-adenosine complex show some copper demetallation with some Cu(I) remaining complexed. A complication is that the mechanism of reduction may be dependent upon the way potential is applied, i.e., products of a single step controlled potential electrolysis at -1.75 V may be different than those obtained following step-by-step reductions prior to peak III. 

Electrochemistry and Spectroelectrochemistry of Adenine and Adenosine Complexes with 3d Transition Metals... 

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