维生素B12缺乏致神经损害临床分析

维生素B12缺乏多继发于胃肠道外科手术后、贫血及其它内科疾病；其引起的神经系统损害临床表现多样；主要为周围神经损害及亚急性联合变性。测维生素B12值、查肌电图等可明确诊断。补充维生素B12治疗有效。     

利用智能手机测定药剂中维生素B12含量的研究

提出了一种利用智能手机测定维生素B12含量的分光光度法，利用智能手机光线感应器及相关软件"RGB调色板"和"phyphox"等对不同浓度维生素B12的透光强度进行测量，数据处理后得到相应的吸光度值，发现其与维生素B12的浓度在4.0~96.0 μg/mL范围内呈现良好的线性关系。此方法具有简单、快捷等优点，可应用于药剂中维生素B12含量的测定。     

多壁碳纳米管修饰金电极测定维生素B12

抗贫血药物维生素B12(VB12)俗称(氰)钴胺素,维生素B12是DNA合成的必需物质,若体内缺乏它,就会引起巨幼细胞贫血,高同型半胱氨酸血症和神经系统损害。因此,检测维生素B12可为血液系统和神经系统一些疾病的诊治提供依据[1],建立快捷简便的检测方法,在药物分析和医学检验中有应用价值。测定VB12的方法有高效液相色谱法[2]、荧光法[3]、毛细管电泳法[4]、伏安法[5]等。作者研究了VB12在碳纳米管修饰金电极上的电化学行为,并用以测定了VB12样品的含量,结果令人满意。1实验部分1.1仪器与试剂CHI618B电化学工作站(上海辰华仪器公司);KQ?400…     

维生素研究大师——福克斯

维生素B12是结构复杂的维生素,在治疗恶性贫血等方面具有重要应用。介绍了维生素研究领域的大师--福克斯的科研历程,重点阐述1948年维生素B12的纯化及结晶过程,以纪念这位科学家。     

辅酶B12及其模型化合物

辅酶B12，即5’-脱氧腺苷钴胺素，是一个天然存在的有机金属化合物。它与维生素B12，即氰钴胺素组成和结构相似，但生理功能不同，维生素B12是一种抗恶性贫血的药物，而辅酶B12在生物体内多种代谢过程中起着重要作用，其中研究得最多的是与分子内重排有关的酶反     

与缺铁性贫血有关的维生素及微量元素

主要介绍了维生素及微量元素与缺铁性贫血之间的关系。缺铁性贫血(IDA)是世界范围内普遍存在的营养性疾病，是因人体储存铁缺乏导致血红蛋白合成量减少而形成的一种贫血。许多营养素都与IDA有关，与IDA有关的维生素有核黄素、维生素C、维生素A、维生素E、叶酸及维生素B12，与IDA有关的微量元素有铁、铜、锌、镉、钒、铅等。     

钴的生理作用及其与健康的关系

(1)钴以维生素B12和辅酶B12形式发挥生理作用,维生素B12和辅酶B12都是含钴的配合物。维生素B12的主要作用是刺激造血功能。维生素B12供给不足会导致巨幼红细胞性贫血。维生素B12只有与特殊运转蛋白———内因子结合才能在回肠部被吸收。维生素B12被吸收进入血流后与转钴蛋白结合而运至肝脏、骨髓和全身。因此,内因子或转钴蛋白的先天缺乏或合成不足皆会引起巨幼红细胞贫血。辅酶B12可作为自由基的载体和贮存库,有利于氧的结合或释放。在已知的酶的反应中,至少有10种需辅酶B12参与。辅酶B12对神经功能也具有特殊的重要性。维生素B12又称氰钴氨素。辅酶B12包括甲基钴氨素和5′-脱氧腺苷钴氨素。甲基钴氨素生成缺乏会引起高胱氨酸尿。受其影响的婴儿可有巨幼红细胞性贫血、发育迟滞、神经发育缺陷。后者生成缺乏会引起婴儿的甲基丙二酸尿,因而发生精神压抑,代谢性酸中毒、低糖血症和高氨基乙酸血症。这类儿童不产生巨幼红细胞性贫血。但甲基丙二酸作用于骨髓干细胞会引起各类血细胞的减少。(2)钴作为某些酶的辅助因素发挥作用,已证实,钴是碳酸酐酶、DNA聚合酶、RNA聚合酶、逆转录酶等14种酶的辅助因素,可催化水解、氧化、聚合、水化、转...     

维生素B12与DNA相互作用的电化学研究

维生素B12与DNA相互作用的电化学研究;维生素B12; DNA; 循环伏安法; 紫外可见吸收光谱法     

石墨烯修饰电极对维生素B12的电化学响应及其分析应用

应用石墨烯修饰的玻碳电极结合循环伏安法研究了维生素B12在该电极上的电化学行为;用差示脉冲溶出伏安法考察了石墨烯修饰量、缓冲溶液种类、pH、富集电位及富集时间对响应电流的影响。在最佳实验条件下,响应电流与维生素B12的浓度在1.6×10-7~9.5×10-6mol/L范围内有良好的线性相关,检出限为5.9×10-8mol/L。方法可用于药物和人尿样品中维生素B12的检测。     

差分脉冲伏安法同时测定维生素B2和维生素B12

用循环伏安法制备了银掺杂聚L-精氨酸修饰玻碳电极(Ag-PLA/GCE),研究了修饰电极的电化学交流阻抗及维生素B2和维生素B12(Vb2)在Ag-PLA/GCE电极上电化学行为,分析了维生素B2(Vb12)的吸附特性,建立了同时测定Vb2和Vb12的新方法。阻抗图谱说明,由于Ag-PLA修饰,提高了电子传输速率。当Vb2和Vb12同时存在时,在pH 5.0的磷酸盐缓冲溶液中,采用差分脉冲伏安法(DPV法)进行扫描测定,Vb2和Vb12的氧化峰电位分别为-0.470 V和-0.880 V,两种维生素的峰电位差值为:ΔE=0.410 V,不需分离,可同时进行测定。同时测定Vb2和Vb12的线性范围分别为0.10~15.0μmol/L和0.75~12.5μmol/L,检出限分别为0.03μmol/L和0.5μmol/L。方法已用于复合维生素药片中维生素B2和维生素B12的测定。     

Alpha-ribazole, a fluorescent marker for the liquid chromatographic determination of vitamin B12 in foodstuffs

A method to determine the contents of free vitamin B12 in various foods by reversed phase liquid chromatography-fluorimetry is reported. It includes a purification of the samples by passage through an immunoaffinity column and a pre-column conversion of vitamin B12 into the fluorescent alpha-ribazole (successive treatments of the extract with 2.5 M sodium hydroxide (at 100 degrees C for 15 min) and alkaline phosphatase (7.5 U) at 37 degrees C and pH 8 for 16 h). An enzymatic hydrolysis prior to the purification step (pepsin at 37 degrees C and pH 4 for 3 h) made it possible to release the vitamin B12 bound to proteins and thus to obtain the total vitamin B12 contents of these foodstuffs. The method proposed for the determination of free and bound vitamin B12 gives a good recovery rate (95-100%) and a satisfactory repeatability (R.S.D.r between 1.0 and 5.4%). Owing to its low quantification limit (3 ng g(-1)) and the good resolution of the alpha-ribazole peak, it could most probably be applied to the determination of this vitamin in any foodstuff.     

Discovering nature's diverse pathways to vitamin B12: a 35-year odyssey

The chronology of the discoveries along the pathway of vitamin B(12) biosynthesis is reviewed from a personal perspective, including discussion of the most recent finding that two pathways to B(12) exist-one aerobic and one anaerobic-which differ mainly in the ring contraction mechanisms that convert porphyrin to corrin.     

Effect of Vitamin B Complex Treatment on Macrophages to Schwann Cells Association during Neuroinflammation after Peripheral Nerve Injury

Peripheral nerve injury (PNI) triggers a complex multi-cellular response involving the injured neurons, Schwann cells (SCs), and immune cells, often resulting in poor functional recovery. The aim of this study was to investigate the effects of the treatment with vitamin B (B1, B2, B3, B5, B6, and B12) complex on the interaction between macrophages and SCs during the recovery period after PNI. Transection of the motor branch of the femoral nerve followed by reconstruction by termino-terminal anastomosis was used as an experimental model. Isolated nerves from the sham (S), operated (O), and operated groups treated with the B vitamins (OT group) were used for immunofluorescence analysis. The obtained data indicated that PNI modulates interactions between macrophages and SCs in a time-dependent manner. The treatment with B vitamins complex promoted the M1-to M2-macrophage polarization and accelerated the transition from the non-myelin to myelin-forming SCs, an indicative of SCs maturation. The effect of B vitamins complex on both cell types was accompanied with an increase in macrophage/SC interactions, all of which correlated with the regeneration of the injured nerve. Clearly, the capacity of B vitamins to modulate macrophages-SCs interaction may be promising for the treatment of PNI.     

Determination of vitamin B12 in multivitamin tablets and fermentation medium by high-performance liquid chromatography with fluorescence detection

A novel method for the determination of vitamin B12 by high-performance liquid chromatography with fluorescence detection is reported. The method was simple and highly sensitive with good precision. Vitamin B12 was analyzed by HPLC on a muBondapak C18 column (300x3.9 mm, 10 microm) with methanol-water (30:70) as mobile phase and fluorescence detection at 305 nm (with excitation at 275 nm). The calibration graph was linear from 1.000 to 100.0 ng ml(-1) for vitamin B12 with a correlation coefficient of 0.998 (n=6). The detection limit was 0.1 ng ml(-1). The method was successfully applied to the determination of vitamin B12 in vitamin B12 tablets, multivitamin tablets and fermentation medium. The recovery was from 94 to 102% and the relative standard deviation was in the range of 1.8 to 4.1%.     

Reflections on the discovery of nature's pathways to vitamin B12

The chronology of the discoveries along the pathway of vitamin B12 biosynthesis is reviewed from a personal perspective, including discussion of the most recent finding that two pathways to B12 exist--one aerobic and one anaerobic--which differ mainly in the ring contraction mechanisms which convert porphyrin to corrin.     

Cyanide-bridged vitamin B12-cisplatin conjugates

cis-[PtCl(OH2)(NH3)2]+, the monoactivated form of cisplatin, reacts with the cyano ligand of cobalt in vitamin B12 (cyanocobalamin) to form a Co-C[triple chemical bond]N-Pt conjugate (1). Compound 1 is prepared in good yield directly in aqueous solution. The remaining chloride ligand of Pt(II) is labile. It hydrolyzes slowly in aqueous solution and can be exchanged by stronger coordinating ligands, such as 9-methylguanine or 2'-deoxyguanosine, to yield vitamin B12-nucleobase conjugates. X-ray structures of the vitamin B12-cisplatin conjugate 1 as well as of the product with coordinated 9-methylguanine (2) are presented. The coordination geometry at Pt(II) is almost perfectly square-planar. The structure of the cobalamin compound remains essentially unchanged when compared with the original B(12) structure. The guanine moiety of compound 2 binds in a 45 degrees angle to the cisplatin molecule and interacts with neighboring molecules by means of pi stacking and hydrogen bonds.     

Simultaneous determination of vitamin B12 and its derivatives using some of multivariate calibration 1 (MVC1) techniques

Resolution of binary mixtures of vitamin B12, methylcobalamin and B12 coenzyme with minimum sample pre-treatment and without analyte separation has been successfully achieved by methods of partial least squares algorithm with one dependent variable (PLS1), orthogonal signal correction/partial least squares (OSC/PLS), principal component regression (PCR) and hybrid linear analysis (HLA). Data of analysis were obtained from UV-vis spectra. The UV-vis spectra of the vitamin B12, methylcobalamin and B12 coenzyme were recorded in the same spectral conditions. The method of central composite design was used in the ranges of 10-80mgL(-1) for vitamin B12 and methylcobalamin and 20-130mgL(-1) for B12 coenzyme. The models refinement procedure and validation were performed by cross-validation. The minimum root mean square error of prediction (RMSEP) was 2.26mgL(-1) for vitamin B12 with PLS1, 1.33mgL(-1) for methylcobalamin with OSC/PLS and 3.24mgL(-1) for B12 coenzyme with HLA techniques. Figures of merit such as selectivity, sensitivity, analytical sensitivity and LOD were determined for three compounds. The procedure was successfully applied to simultaneous determination of three compounds in synthetic mixtures and in a pharmaceutical formulation.     

Studies on the biosynthesis of corrinoids and porphyrinoids. I. The labeling of oxygen of vitamin B12

Recently the amide-oxygen has been suggested to participate in the formation of the corrin ring of vitamin B12. To confirm this hypothesis, 17O-labeled aminolevulinic acid (ALA) was prepared and administered to Propionibacterium shermanii. The isolated vitamin B12 showed only broad 17O signals in the oxygen-17 nuclear magnetic resonance (17O-NMR) spectrum. However, distinct isotope-shifted peaks were observed in the 13C-NMR spectrum of vitamin B12 isolated after incorporation of [1-13C:1,4-18O2]ALA. Of these shifted peaks, one peak (C27) showed very low intensity. This indicates that dilution of 18O occurred at the acetyl chain of the A ring of vitamin B12. This result supports the assumption that the lactone formation of the A ring promotes the ring contraction, as proposed by Eschenmoser.     

维生素B12修饰电极及其催化氧还原性质的研究

发现给生素Ｂ１２能吸附在经阳极化处理的玻碳电极上，从而制成稳定的维生系Ｂ１２修饰玻碳电极详细研究了此电极的电化学性质。并发现此修饰电极能有效地催化分子氧的二电极还原。     

7-Decarboxymethyl-cobyrinates: vitamin B12-derivatives that lack the c-side chain

The synthesis of cobyrinic acid derivatives by reduction of dehydrocobyrinates is largely unexplored. It is, however, a rational path to B(12) analogues that lack specific substituents of the corrin moiety of natural B(12) derivatives. The partial syntheses of four epimeric 7-decarboxymethyl-cobyrinates is described, which is achieved by reduction of Δ7-dehydro-7-de[carboxymethyl]-cobyrinate with zinc or with the 'prebiotic' reducing agent formic acid. A direct and remarkably efficient route was found to 7-decarboxymethyl-cobyrinates, which are cobyrinic acid derivatives in which the c-side chain at ring B of vitamin B(12) is missing. The structures of the hexamethyl-7-decarboxymethyl-cobyrinates were characterized and the stereochemical and conformational properties at their newly saturated ring B were analyzed. The stereochemical outcome of the reduction was found to depend strongly on the reaction conditions. In 7-decarboxymethyl-cobyrinates, both peripheral carbon centres of ring B carry a hydrogen atom, and the characteristic quaternary carbon centre at C7 of the cobyrinic acid moiety of vitamin B(12) is lacking. The still highly substituted 7-decarboxymethyl-cobyrinates are readily dehydrogenated in the presence of dioxygen, furnishing 7-de[carboxymethyl]-Δ(7)-dehydro-cobyrinate as the common, unsaturated oxidation product. The noted stability of vitamin B(12) and of other Co(III)-cobyrinates in the presence of air is a consequence of their highly substituted corrin macrocycle, a finding of interest in the context of chemical rationalizations of the B(12) structure.