Determination of the potential of cyanobacterial strains for hydrogen production

Hydrogen (H₂) is a renewable, abundant, and nonpolluting source of energy. Photosynthetic organisms capture sunlight very efficiently and convert it into organic molecules. Cyanobacteria produce H₂ by breaking down organic compounds and water. In this study, biological H₂ was produced from various strains of cyanobacteria. Moreover, H₂ accumulation by Synechocystis sp. PCC 6803 was as high as 0.037 μmol/mg Chl/h within 120 h in the dark. The wild-type, filamentous, non-heterocystous cyanobacterium Desertifilum sp. IPPAS B-1220 was found to produce a maximum of 0.229 μmol/mg Chl/h in the gas phase within 166 h in the light, which was on par with the maximum yield reported in the literature. DCMU at 10 μM increased H₂ production by Desertifilum sp. IPPAS B-1220 by 1.5-fold to 0.348 μmol H₂/mg Chl/h. This is the first report on the capability of Desertifilum cyanobacterium to produce H₂.     

米根霉乳酸脱氢酶的特性研究

乳酸脱氢酶(LDH)是米根霉发酵生产L-乳酸中催化丙酮酸转化成L-乳酸过程的关键酶。本研究从米根霉As3.819中初步分离出乳酸脱氢酶,并结合发酵条件对其酶学特性进行了研究。结果表明,该乳酸脱氢酶的最适反应pH为7.4,最适催化温度为30～50℃。Mg2+、Ca2+对该酶有激活作用,K+、Zn2+对该酶有抑制作用。以NADH和丙酮酸为底物的米氏常数分别为7.22×10-4mol/L和1.24×10-3mol/L。     

CeO2 nanoparticles decorated multi-walled carbon nanotubes for electrochemical determination of guanine and adenine

Sub-10 nm CeO₂ nanoparticles decorated multi-walled carbon nanotubes has been constructed for electrochemial determination of guanine and adenine. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the nanoparticles CeO₂/MWCNTs. Electrochemical impedance spectroscopy (EIS) was used to characterize the electrode modifying process. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to study the electrocatalytic activity toward the electrochemical oxidation of guanine and adenine. The detection limit (S/N = 3) for adenine and guanine was found to be 20 and 10 nM, respectively. The obtained sensitivity toward guanine and adenine was 1.26 and 1.13 μA/μM in the linear concentration range 5–50 μM and 5–35 μM, respectively. These results demonstrate that the carbon nanotubes could provide huge locations and facilitate the adsorptive accumulation of the guanine and adenine, and the CeO₂ nanoparticles are promising substrates for the development of high-performance electrocatalysts for biosensing.     

烟酸和烟酰胺的现状与前景

叙述了烟酸和烟酰胺的性状、用途、制法和发展前景。     

鸟嘌呤、腺嘌呤、胸腺嘧啶和胞嘧啶的紫外吸收谱研究

利用紫外光度法对构成核酸的鸟嘌呤(G)、腺嘌呤(A)、胸腺嘧啶(T)和胞嘧啶(C)的紫外吸收谱进行了研究.通过对含四种碱基的磷酸盐缓冲溶液(pH=7)分别进行分析,发现G在240～280nm范围内有两个紫外吸收峰,分别位于244nm和274nm处;而A、C和T的吸收峰值则较为接近.分别位于258nm、264nm和266nm处.对A、C和T分组混合或共混后进行测试,发现当峰值出现在260nm时,溶液中至少存在A和C.当峰值位于258nm处时.溶液中存在A或T.在300～1100nm范围内未发现该四种碱基的吸收峰.     

Two‐Stage Oxidation of Glucose by an Enzymatic Bioanode

The present study reports the design of a novel bioanode to deeply oxidize glucose in an enzymatic biofuel cell (EFC). This enzymatic glucose cell utilizes three co‐immobilized enzymes: NAD‐dependent glucose dehydrogenase (GDH), NAD(P)⁺‐dependent gluconate‐5‐dehydrogenase (Ga5DH), and diaphorase (DI). Glucose is oxidized to gluconate by NAD‐dependent GDH, gaining two electrons per glucose; the gluconate obtained as a by‐product is oxidized at the C5 carbon to 5‐keto‐gluconate by Ga5DH. Operation of our bioanode enabled the oxidation of glucose in two stages, resulting in the gain of four electrons. The three‐enzyme EFC provides a maximum power density of 10.51 ± 1.72 μW cm^–2, which is about 1.6 times higher than the maximum power density of an EFC using a bioanode based on the co‐immobilization of two enzymes (GDH and DI). Our results hold promise for increasing the current density of EFCs, and for application in glucose biosensor.     

β-烟酰胺单核苷酸对生理机能影响的研究进展

我国处于亚健康状态的超重或肥胖人群与老龄化人口数量都在逐年上升。在衰老和肥胖过程中,细胞内烟酰胺腺嘌呤二核苷酸（nicotinamide adenine dinucleotide,NAD＋）水平会发生系统性下降。NAD＋是细胞能量代谢、调节细胞机能、影响衰老的关键靶点,因此,通过补充NAD＋前体以改善生理机能、延缓衰老已经成为目前研究热点。β-烟酰胺单核苷酸（nicotinamide mononucleotide,NMN）是动物体内NAD＋代谢的中间产物,也是目前最直接高效的NAD＋补充前体。但是NMN对生理机能存在多方面多器官的复杂影响,而且人体临床试验与动物实验结果并不一致,服用量也尚未确定。本文综述到目前为止NMN的动物实验和人体临床试验结果,旨在探究补充NMN对动物、人体生理机能的影响、机制及其适宜剂量和不良反应,以期为未来NMN研究与应用提供思路。     

Thermodynamics and Intermolecular Interactions of Nicotinamide in Neat and Binary Solutions: Experimental Measurements and COSMO-RS Concentration Dependent Reactions Investigations

In this study, the temperature-dependent solubility of nicotinamide (niacin) was measured in six neat solvents and five aqueous-organic binary mixtures (methanol, 1,4-dioxane, acetonitrile, DMSO and DMF). It was discovered that the selected set of organic solvents offer all sorts of solvent effects, including co-solvent, synergistic, and anti-solvent features, enabling flexible tuning of niacin solubility. In addition, differential scanning calorimetry was used to characterize the fusion thermodynamics of nicotinamide. In particular, the heat capacity change upon melting was measured. The experimental data were interpreted by means of COSMO-RS-DARE (conductor-like screening model for realistic solvation–dimerization, aggregation, and reaction extension) for concentration dependent reactions. The solute–solute and solute–solvent intermolecular interactions were found to be significant in all of the studied systems, which was proven by the computed mutual affinity of the components at the saturated conditions. The values of the Gibbs free energies of pair formation were derived at an advanced level of theory (MP2), including corrections for electron correlation and zero point vibrational energy (ZPE). In all of the studied systems the self-association of nicotinamide was found to be a predominant intermolecular complex, irrespective of the temperature and composition of the binary system. The application of the COSMO-RS-DARE approach led to a perfect match between the computed and measured solubility data, by optimizing the parameter of intermolecular interactions.     

高效液相色谱法同时测定保健食品中泛酸、烟酰胺、维生素B1、维生素B2、维生素B6的含量

目的建立高效液相色谱法同时测定保健食品中泛酸、烟酰胺、维生素B_1、维生素B_2、维生素B_6的含量。方法样品经0.2%磷酸溶液超声提取,经Alltima-C18柱分离,以乙腈-5 mmol/L庚烷磺酸钠溶液为流动相进行梯度洗脱,采用二极管阵列检测器(diode array detector,DAD)同时在200 nm、280 nm波长处进行检测。结果泛酸、烟酰胺、维生素B_1、维生素B_2、维生素B_6能实现较好的分离,在各自线性范围内线性关系良好,平均回收率为93.9%~103.2%,相对标准偏差(relative standard deviation,RSD)为0.4%~1.8%。结论该方法操作快速简便、精密度和重复性好,可适用于保健食品中泛酸、烟酰胺、维生素B_1、维生素B_2、维生素B_6含量的同时测定。