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11.
DNA repair has received heightened attention in recent years as ozone depletion threatens to significantly increase DNA damage by UVB radiation[1—6]. The major lesions formed in DNA by this radiation are cis-syn cyclobutane pyrimidine dimers, which are created by the linkage of two neighboring pyrimidine bases in DNA via C5-C5 and C6-C6 atoms by [2+2] cycloaddition[2,5—8]. This potentially lethal or mutagenic damage can be repaired either by the removal of the damaged bases by excisio… 相似文献
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《Analytical letters》2012,45(17):3138-3146
Abstract A new, simple, and sensitive method for the determination of riboflavin based on the single-sweep polarographic reduction wave of the photolysis products of riboflavin has been developed. Under the irradiation of an iodine-tungsten lamp, the photolysis reaction of riboflavin in pH 9.3 NH3-NH4Cl buffer solution can be complete in about 20 min. The reaction products yield a single adsorptive reduction wave at ?0.63 V (vs. SCE) negative to the reduction wave of riboflavin by 0.18 V. The derivative wave height is linearly proportional to the concentration of riboflavin in the range of 0.01–17.5 µg/mL (correlation coefficient 0.996). The detection limit is 0.00 5µg/mL. The proposed method has been applied to the determination of multivitamin tablets with satisfactory results. In comparison with the methods directly using the reduction wave of riboflavin for the determination, this method eliminates the effect of the degradation of riboflavin on the determination accuracy and is much more sensitive. The new method could be useful in many fields. 相似文献
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Ilia A. Dereven'kov Sergei V. Makarov Pavel A. Molodtsov Anna S. Makarova 《国际化学动力学杂志》2021,53(1):146-153
Selenocysteine (Sec) is a crucial component of mammalian thioredoxin reductase (TrxR) where it serves as a nucleophile for disulfide bond rupture in thioredoxin (Trx). Generation of the reduced state of Sec in TrxR requires consecutive two electron transfer steps, namely: (i) from NADPH to flavin adenine dinucleotide, (ii) from reduced flavin to the disulfide bond Cys59‐S‐S‐Cys64, and finally (iii) from Cys59 and Cys64 to the selenosulfide bond Cys497‐S‐Se‐Sec498. In this work, we studied the reaction between reduced riboflavin (RibH2) and selenocystine (Sec‐Sec), an oxidized form of Sec. The interaction between RibH2 and Sec‐Sec proceeded relatively slowly in comparison with its reverse reaction, that is, reduction of riboflavin (Rib) by Sec. The rate constant for the reaction between RibH2 and Sec‐Sec was (7.9 ± 0.1) × 10?2 M?1 s?1 (pH 7.0, 25.0°C). The reaction between Rib and Sec proceeded via two steps, namely, a rapid reversible binding of Rib to Sec having a protonated selenol group to form a Sec‐Rib complex, followed by nucleophilic attack of Sec‐Rib by a second Sec molecule harboring a deprotonated selenol group. The equilibrium constant for the overall reduction process of Rib by Sec is (1.2 ± 0.1) × 106 M?1 (25.0°C). The finding that the interaction of RibH2 with oxidized selenol is reversible with its equilibrium favored toward the reverse reaction provides an additional explanation for the exceptional mechanism of the mammalian Trx/TrxR system involving transient reduction of a disulfide bond. 相似文献
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Riboflavin‐Based Fluorogenic Sensor for Chemo‐ and Enantioselective Detection of Amine Vapors 下载免费PDF全文
Dr. Hiroki Iida Marie Miki Soichiro Iwahana Prof. Dr. Eiji Yashima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4257-4262
A novel turn‐on fluorogenic chiral sensory system has been developed using a protonated riboflavin and riboflavin‐derived cationic polymer as a fluorophore precursor and a specific amine receptor, respectively, which enables the solid‐state chemo‐ and enantioselective fluorogenic visual detection of primary and secondary amine vapors. 相似文献
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Flavin Derivatives with Tailored Redox Properties: Synthesis,Characterization, and Electrochemical Behavior 下载免费PDF全文
Attila Kormányos Mohammad S. Hossain Ghazaleh Ghadimkhani Joe J. Johnson Prof. Csaba Janáky Prof. Norma R. de Tacconi Prof. Frank W. Foss Jr. Prof. Yaron Paz Prof. Krishnan Rajeshwar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(27):9209-9217
This study establishes structure–property relationships for four synthetic flavin molecules as bioinspired redox mediators in electro‐ and photocatalysis applications. The studied flavin compounds were disubstituted with polar substituents at the N1 and N3 positions (alloxazine) or at the N3 and N10 positions (isoalloxazines). The electrochemical behavior of one such synthetic flavin analogue was examined in detail in aqueous solutions of varying pH in the range from 1 to 10. Cyclic voltammetry, used in conjunction with hydrodynamic (rotating disk electrode) voltammetry, showed quasi‐reversible behavior consistent with freely diffusing molecules and an overall global 2e?, 2H+ proton‐coupled electron transfer scheme. UV/Vis spectroelectrochemical data was also employed to study the pH‐dependent electrochemical behavior of this derivative. Substituent effects on the redox behavior were compared and contrasted for all the four compounds, and visualized within a scatter plot framework to afford comparison with prior knowledge on mostly natural flavins in aqueous media. Finally, a preliminary assessment of one of the synthetic flavins was performed of its electrocatalytic activity toward dioxygen reduction as a prelude to further (quantitative) studies of both freely diffusing and tethered molecules on various electrode surfaces. 相似文献
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Rapid electron transfer from electron adduct and reducing OH adduct of 2'-deoxyadenosine-5'-monophosphate acid (dAMP) to riboflavin (RF) and flavin adenine dinudeotide (FAD) was studied using the time-resolved pulse radiolysLs techniques. Both spectroscopic and kinetic analyses showed that transient absorption spectrum of electron adduct or OH adduct of dAMP formed at first, and then changed to that of radical anion of RF or FAD after several microseconds of pulse. The evidence indicated that electron transfer from electron adduct and reducing OH adduct of dAMP to RF or FAD did occur. From buildup or bleaching kinetics of radical anions of RF and FAD, the rate constants for electron transfer were determined, respectively. 相似文献
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M. F. Abdel-Wahab Y. M. Megahed A. E. EI-Arab 《Isotopes in environmental and health studies》2013,49(10):355-357
The results of this work have revealed that riboflavin content is diminished by irradiation with γ-rays. The more the dose and the longer the time of irradiation the more the effect on riboflavin solution. Addition of other materials as ascorbic acid, starch, and thiourea as radioprotectors to riboflavin solution, caused a decrease in the percentage loss, ranging from 12.5 — 86%. Thiourea used as protector in a ratio, 1:1 – riboflavin: thiourea, gave the best result especially with lower doses of radiation. 相似文献
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采用原位还原法制备金纳米粒子/聚多巴胺/碳纳米管(Au-PDA-MWNTs)复合材料,并将其用于建立高灵敏检测核黄素的电化学方法.采用紫外–可见光谱、扫描电镜、x-射线能谱对Au-PDA-MWNTs复合材料进行表征,采用循环伏安法和差示脉冲伏安法探讨核黄素(RF)在Au-PDA-MWNTs修饰的玻碳电极上的电化学行为,并对RF含量进行测定.该方法对核黄素的检测在5×10-9 mol·L-1~1×10-5 mol·L-1的范围内呈良好的线性关系(R=0.9906),检测限为1.7×10-9 mol·L-1.本方法操作简便、抗干扰能力强,方法可行,因此该方法成功实现了维生素药片中RF含量的测定. 相似文献