Aptamer‐Assisted Assembly of Gold Nanoframe Dimers

The assembly of nanoframe dimers assisted by aptamer‐functionalized smaller spherical gold nanoparticles as prospective surface‐enhanced Raman scattering (SERS) biotraps for riboflavin, an important molecule for biological electron transfer reactions, is reported. In this approach, the aptamer‐coated gold nanoparticles designed for selective binding of riboflavin also serve as the electrostatic driver for nanoframe dimerization in dilute solutions. The gold nanoframe dimers provide unique conditions for plasmonic coupling in a hot spot with sufficient space for the binding of bulky biomolecules. The use of an aptamer allows for highly selective binding of the targeted analyte as compared with conventional organic ligands with excellent low detection limit of one micromole of riboflavin.     

Gold(III) reduction in a tris-HCl buffer: Effect of riboflavin,rutin, 1,1-dipyridyl,and 1-naphthol

Reduction of chloroauric acid on platinum and gold electrodes in a 0.1 M tris-HCl buffer of pH 8 containing riboflavin, rutin, 1,1-dipyridyl, or 1-naphthol is studied by cyclic voltammetry and in situ ESR methods. On the basis of the obtained data it is assumed that in the buffer there occurs the reduction of Au(III) to Au(I). In the presence of 1,1-dipyridyl, there occurs the reduction of complex [Au(III)-1,1-dipyridyl]. The reduction of Au(III) in the presence of 1-naphthol is realized in the composition of complex [Au(III)-tris-1-naphthol]. The hampering of the electrode process of the Au(III) reduction in the presence of 1-naphthol is caused by the adsorption of the [tris-1-naphthol] associates at the electrode surface. The presence of Au(III) does not exert any influence on the process of electroreduction of riboflavin. The obtained results make it possible to presume that the resistance of gold-accumulating cells Micrococcus luteus toward toxic compounds that are inhibitors of the respiratory chain, such as 1,1-dipyridyl and 1-naphthol, is caused by their binding in gold-containing complexes in the composition of Au-protein.     

新型荧光增强法检测水样品中碘离子

Hg2+可以猝灭核黄素的荧光,碘离子(I-)可以与Hg2+形成HgI2,基于此,发展了一种新型的荧光增强法检测水中I-的方法。Hg2+加入后,核黄素在525 nm处的荧光被猝灭;继续在体系中加入不同浓度的I-,体系中Hg2+被不断消耗,导致核黄素在525 nm处的荧光逐渐增强。该方法检测I-的线性范围在1-100μmol·L-1,检测限是0.4μmol·L-1;同时,该方法具有较快的响应时间(2 min);对其他卤素离子具有较好的选择性;用于水中I-检测时得到了较好的回收率。     

基于纳米TiO2的化学发光法检测核黄素

纳米TiO2与NaOH溶液作用能产生化学发光辐射,在表面活性剂十六烷基三甲基溴化铵(CTAB)的存在下,核黄素的加入能增强纳米TiO2-NaOH溶液的化学发光强度。基于此,构建了纳米TiO2-NaOH溶液化学发光新体系,建立了纳米TiO2-NaOH-核黄素体系检测核黄素的化学发光新方法。在优化实验条件下,核黄素质量浓度在5.0×10-6～3.5×10-4g/mL范围内与化学发光强度呈良好的线性关系,检出限为3.0×10-6g/mL,对2.5×10-5g/mL的核黄素进行11次平行测定,相对标准偏差为2.9%。该方法用于维生素B2片剂的测定,其结果与药典方法测得一致。该文同时对化学发光反应的机理进行了初步探讨。     

高效液相色谱法测定大鼠血浆和全血中核黄素的含量

为了直接反映核黄素营养状况对血中核黄素水平的影响,建立了高效液相色谱测定大鼠血浆及全血中核黄素含量的方法。采用Diamonsil C 18 色谱柱(250 mm×4.6 mm i.d.,5 μm)分离,以甲醇-5 mmol/L 乙酸铵(体积比为35∶65)为流动相,流速1.2 mL/min ,荧光检测器检测(激发波长:450 nm,发射波长:520 nm)。样品经乙腈、三氯甲烷处理后进样分析。核黄素测定的线性范围为5～200 nmol/L ,最低检测限为2.5 nmol/L (S/N＝2),日     

超临界流体色谱同时测定维生素B2,B3和烟酰胺

采用超临界流体色谱同时定量测定维生素制剂中维生素B2(核黄素)、维生素B3(烟酸)和烟酰胺的含量。在CO2流动相中添加15%(体积分数)的甲醇(含0.1%二乙胺),于填充柱上分离,检测波长为268 nm。上述3种维生素在测定范围内,其浓度与相应的峰面积呈良好的线性关系(r＞0.999),平均回收率为97.3%-102.3%;5 min即可完成分析。其日内和日间峰面积测定的相对标准偏差(RSD)小于1.5%。该方法简便,样品前处理简单,可用于上述3种维生素的快速分析。     

Inclusion complex of riboflavin with cucurbit[7]uril: study in solution and solid state

The aqueous solution of riboflavin and cucurbit[7]uril complex has been studied based on fluorescence and ¹H NMR spectroscopic results. Upon addition of cucurbit[7]uril, the fluorescence intensity of riboflavin was quenched and a slight red shift was observed for the maximum emission peak. These results indicated that the cucurbit[7]uril–riboflavin complex was formed at a 1:1 mole ratio. The temperature-dependent inclusion constants were calculated, from which ΔH and ΔS values were calculated. Meanwhile, rationale of the interaction mechanism was also discussed based on ¹H NMR results. The solid inclusion complex was prepared from co-evaporation method and characterised by differential thermal analysis and fluorescence lifetime analysis methods. The experimental results indicated that riboflavin and cucurbit[7]uril formed stable host–guest inclusion complex in both solution and solid states.     

Design of a spray-cycle bioreactor and its application for riboflavin production

A highly efficient spray-cycle reactor for oxygen supply was developed. A typical arrangement of the reactor consists of a spray column fitted with a nozzle and a coaxal tube, and a reservoir vessel. The culture broth was circulated between the column and vessel by a peristaltic pump. The volumetric oxygen-transfer coefficient, k₁a was evaluated as a parameter for oxygen supply. The liquid circulation rate in the spraycycle reactor was represented in terms of the number of circulations. The k₁a value increased as the number of circulations increased, reaching 208 h^-1 at 4.4 min^-1 of circulation numbers. This value was 1.8 times higher than that in a 1500-mL stirred-tank reactor under the agitation of 20.7g and the aeration of 1.0 volume per min. The spray-cycle reactor was applied to riboflavin production by an aerobic microorganism. The riboflavin production increased as k₁a values increased and the maximal riboflavin production was 161 mg/L at 208 h^-1 of k₁a. These results suggest that the spray-cycle reactor is useful to oxygen-demanding fermentation because of the high k₁a value in comparison with the stirred-tank reactor.     

A Strategy to Employ Polymerised Riboflavin in the Development of Electrochemical Biosensors

Electrochemically polymerised riboflavin (PRf) film was applied in development of glutamate and hypoxanthine biosensors using appropriate oxidases as recognition elements. PRf served as an enzyme immobilisation matrix composed of natural monomer and as a redox mediator. The PRf film was deposited on glassy carbon electrode (GCE) or on the laser‐designed microstructures of the chitosan‐graphene oxide (Chit‐GO) film deposited on glass slide, which served as a chip sensor. The redox polymer was stable and efficient mediator, however, Chit‐GO was placed on the top of PRf/GCE in order to increase the response signal. Such an approach allowed to extend the stability of glutamate and hypoxanthine biosensors to at least 1 month and 15 days, respectively. The chip microelectrode was a single use disposable biosensor due to insufficiently good Chit‐GO adhesion on the top of the cover‐glass. The glutamate microbiosensor had extremely high sensitivity of 16 μA cm⁻² μmol L⁻¹.     

LED光诱导化学发光检测饮料中的核黄素

以化学发光法为基础,建立了以发光二极管(LED)诱导化学发光体系(LED-CL)测饮料中核黄素含量的分析方法。样品溶液与鲁米诺溶液混合后由蠕动泵带出,经LED灯照射后产生化学发光,产生的化学发光信号由光电检测器检测。核黄素浓度检测线性范围为0.39 μg.L-1 ~79.56 μg.L-1(R≥0.9997),加标回收率在99.3% ~103%之间,可用于饮料中核黄素的检测。