Polarographic behavior of nucleosides and nucleotides of purines, pyrimidines, pyridines, and flavines

Janik, Borivoj; Elving, Philip J.

doi:10.1021/cr60253a003

Cited by 270 publications

(109 citation statements)

References 13 publications

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“…[3]. Using an so of 1 V/s, the surface standard rate constant is found to be 40 s-', which is indicative of a relatively fast surface reaction, similar to the rate of H+ reduction at Pt electrodes in alkaline solutions (40).…”

Section: Iv) Kinetics Of Oxidation and Reduction Of Adsorbed Fadmentioning

confidence: 75%

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The electrochemical behavior of flavin adenine dinucleotide in neutral solutions

Birss¹,

Elżanowska²,

Turner³

1988

Can. J. Chem.

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Can. J. Chem. 66, 86 (1988) A detailed investigation of the electrochemical behavior of flavin adenine dinucleotide (FAD) in neutral solutions has been carried out at Hg and glassy carbon electrodes. At FAD concentrations of about M, cyclic voltammetiy (CV) shows apair of anodic and cathodic peaks having a peak separation at low sweep rates indicative of a two-electron transfer process and yielding a formal redox potential for FAD of -0.206 k 0.003 V vs. NHE at pH 7. Evidence for FAD adsorption was obtained in experiments at high sweep rates, from the effect of time of exposure of the electrode surface to FAD in solution and from the effect of the potential limits on the cyclic voltammetric response. The process of FAD adsorption was studied in detail in dilute FAD solutions (ca M ) using a hanging mercury drop electrode and the techniques of CV and ac voltammetry. Three distinct stages of FAD adsorption were observed and a model of the orientation of FAD on the electrode surface as a function of time and potential is presented. In addition, the kinetics of oxidation and reduction of adsorbed FAD was studied for each of the stages of FAD deposition, and a surface standard rate constant of ca.

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Section: Iv) Kinetics Of Oxidation and Reduction Of Adsorbed Fadmentioning

confidence: 75%

“…For example, steric hindrance, solution pH, and ionic strength all give rise to unique microenvironments (2, 3), and therefore may affect the redox potential of the flavin.…”

Section: Introductionmentioning

confidence: 99%

The electrochemical behavior of flavin adenine dinucleotide in neutral solutions

Birss¹,

Elżanowska²,

Turner³

1988

Can. J. Chem.

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“…[27][28][29][30][31][32] However, a cathode peak of the reduction of guanine, which was believed to be at about -1.85 V, was not observed. 33,34 The maximum cathode peak current of ds-DNA in the presence of Al(III) was 6.6% higher than that of the thermal denatured sd-DNA ( Fig.…”

Section: Electroanalytical Studies On the Denaturation Of Ds-dna By Amentioning

confidence: 95%

Electrochemical and Spectrometric Studies of Double-Strand Calf Thymus Gland DNA Denatured by Al(III) at Neutral pH

et al. 2009

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The interaction between double-strand calf thymus gland DNA (ds-DNA) and Al(III) was studied by using differential pulse voltammetry (DPV) at a hanging mercury drop electrode (HMDE), Raman spectrometry and circular dichroism (CD) spectra. It was shown that at neutral pH ds-DNA did not produce any cathodic peak at the HMDE in the potential window from -550 to -2000 mV vs. SCE. However, in the presence of Al(III), a cathodic peak was generated at about -1660 mV, which is ascribed to a reduction of adenine and cytosine residues of single denatured DNA (sd-DNA). It was concluded that ds-DNA was completely denatured to sd-DNA by Al(III) at a neutral pH. The apparent denaturing kinetic velocity constants of ds-DNA by Al(III) were derived from linear increases of the cathodic peak currents with time.3 ≥ 2 × 10 -26 , the precipitation of Al(OH)3 was observed and identified by the Raman spectrum, and inductively coupled plasma atomic emission spectrometry (ICP-AES). CD spectra showed that the B-type of structure conformations of ds-DNA and related sd-DNA did not change with the increment of Al(III) from 5.0 × 10 -7 to 1.0 10 -5 M, but the corresponding absorption strengths increased. The related physiological significances and possible applications of the observations were considered.

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“…These values are lower in the pH range 3-5 probably due to lower interaction and reach the maximum value at pH 6 vis-à-vis the lowest kЈ value at that pH due to the lowest redox potentials of RF in this region. The redox potentials of RF increase with pH 53) and appear to influence the rate of reaction and the interaction with caffeine. In the pH range 7-10 the K values are decreasing while the kЈ values are increasing with pH.…”

Section: Stability Constants Of Rf-caffeine Complexmentioning

confidence: 99%

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Ahmad

Ahmed

Sheraz

et al. 2009

CHEMICAL & PHARMACEUTICAL BULLETIN

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1363Riboflavin is a highly photosensitive compound and is degraded in aqueous solution by several mechanisms [1][2][3] including intramolecular photoreduction 4,5) and intramolecular photoaddition. [6][7][8][9] These reactions are affected by pH, 4,5,[10][11][12] solvent polarity and viscosity, 13,14) ionic strength, 15) buffer kind and concentration [6][7][8][9]16) and light intensity and wavelengths. [6][7][8][9]17) Various methods including the use of photostabilizers, incorporation into liposomes and cyclodextrin complexation have been used to stabilize riboflavin solutions in the presence of light. [18][19][20][21] Another approach to achieve stabilization of drugs is through complexation with caffeine and other agents. [22][23][24][25][26] Riboflavin is known to form molecular complexes with caffeine [27][28][29][30][31][32] which has been found to influence the rate of its chemical 33) and photochemical degradation.17) Riboflavin-caffeine complexation may improve the bioavailability 34) and therapeutic activity 35) of the vitamin. NMR studies have been conducted to understand the nature of association between caffeine and flavin mononucleotide 36) that may help in the understanding of the mode of riboflavin stabilization. The present work is based on a detailed study of the kinetics of riboflavin photolysis in the presence of caffeine over a wide range of pH using a specific multicomponent spectrophotometric method 12) for the determination of riboflavin and photoproducts. The kinetic data have been used to determine the stability constants for riboflavin-caffeine complex. The quantitative and kinetic evaluation of such interactions may suggest the possibility of achieving the stabilization of photolabile compounds and thus enhance their biological action. The chemical structures of riboflavin, its photoproducts and caffeine are shown in Fig. 1. ExperimentalThe materials and methods used are the same as previously described for a similar study.5) The photolysis of 5ϫ10 Ϫ5 M riboflavin (RF) solutions was carried out in the presence of 0.5-2.5ϫ10Ϫ4 M caffeine using a Philips HPLN 125 W high pressure mercury vapor fluorescent lamp (emission at 405 and 435 nm) 9) as the irradiation source. The spectral measurements on RF and degraded solutions were performed on a Shimadzu UV-1601 recording spectrophotometer using silica cells of 10 mm path length. The intensity of the fluorescent lamp was determined by potassium ferrioxalate actinome- The effect of caffeine complexation with riboflavin on the kinetics of riboflavin photolysis in the pH range 2.0-10.5 has been studied. The photolysis of riboflavin solutions (5؋10 ؊ ؊5 M) was carried out in the presence of caffeine (0.5-2.5؋10 ؊ ؊4 M) using a visible radiation source. A specific multicomponent spectrophotometric method was used for the determination of riboflavin and photoproducts in photolysed solutions. The apparent first-order rate constants (k) for the photolysis reactions range from 2.71؋10 ؊4 to 4.26؋10 ؊2 min Effect of Caffeine Complexation on the Photol...

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Polarographic behavior of nucleosides and nucleotides of purines, pyrimidines, pyridines, and flavines

Cited by 270 publications

References 13 publications

The electrochemical behavior of flavin adenine dinucleotide in neutral solutions

The electrochemical behavior of flavin adenine dinucleotide in neutral solutions

Electrochemical and Spectrometric Studies of Double-Strand Calf Thymus Gland DNA Denatured by Al(III) at Neutral pH

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

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