A Simplified Colorimetry without Incineration of Phosphorus in Phosphatides

An NAD linked formate dehydrogenating enzyme which catalyzed the last step of methanol oxidation system was extracted from the methanol-grown Kloeckera sp. No. 2201. The specific activity of the enzyme in the extract of methanol-grown cells was found to be considerably higher than that of the glucose-grown cells. The enzyme was purified about 35-fold from the extract of methanol-grown cells by heat treatment, column chromatographies on DEAE-cellulose and on hydroxylapatite, and Sephadex G-200 gel filtration. The purified enzyme was shown to be homogeneous by analyses with electrophoresis and ultracentrifuga-tion. The purified enzyme was a kind of NAD: formate oxidoreductase (EC, 1.2.1.2) which catalyzed specifically the oxidation of formate to carbon dioxide. The Km values were 22 mm for formate and 0.1 mm for NAD. The enzyme was inactivated by potassium cyanide, sodium azide, and p-chloromercuribenzoate but not by any metal-chelating reagents tested. Other general properties of the enzyme were also investigated.     

Elevated Body Fat in Rats by the Dietary Nitric Oxide Synthase Inhibitor,L-Nω Nitroarginine

The influence of the dietary nitric oxide (NO) synthase inhibitor, L-N^ω nitroarginine (L-NNA) on body fat was examined in rats. In experiment 1, all rats were fed with the same amount of diet with or without 0.02% L-NNA for 8 wk. L-NNA intake caused elevations in serum triglyceride and body fat, and reduction in serum nitrate (a metabolite of nitric oxide). The activity of hepatic carnitine palmitoyltransferase was reduced by L-NNA. In experiment 2, rats were fed for 8 wk with the same amount of diets with or without 0.02% L-NNA supplemented or not with 4% L-arginine. The elevation in body fat, and the reductions in serum nitrate and in the activity of hepatic carnitine palmitoyltransfererase by L-NNA were all suppressed by supplemental L-arginine. The results suggest that lower NO generation elevated not only serum triglyceride, but also body fat by reduced fatty acid oxidation.     

Asymmetric Dimethylarginine,an Endogenous NOS Inhibitor,Is Actively Metabolized in Rat Erythrocytes

N ^G,N ^G-Dimethyl-L-arginine (asymmetric dimethylarginine: ADMA) is an endogenous competitive inhibitor of nitric oxide synthase (NOS). Plasma ADMA concentrations have been reported to increase in connection with diseases associated with an impaired endothelial L-arginine/NO pathway. In this study, we investigated the metabolism of ADMA in circulating blood cell populations to elucidate the regulatory mechanism of elevation of plasma ADMA, a novel risk factor for cardiovascular disease. We found by RT-PCR and Western blot analyses that protein arginine methyltransferase (PRMT)1 and dimethylarginine dimethylaminohydrolase (DDAH)-1, responsible for the biosynthesis and degradation of ADMA respectively, are expressed in erythrocytes (ECs), leukocytes, and platelets. We also identified a major ADMA-containing protein in ECs as catalase, confirmed by GST-pull down assay to bind to PRMT1 in vitro. This is the first report that the ADMA-metabolizing system, including the arginine methylation of proteins and the breakdown of free ADMA, occurs in circulating blood cell-populations, and that catalase in ECs might be a potential protein targeted by PRMT1.     

磁纳米颗粒标记脂肪干细胞向软骨分化及体外MRI示踪的实验研究

目的:探讨磁纳米颗粒(magnetic iron oxide particles,MIOP)体外标记脂肪间充质干细胞(ASCs)向软骨分化及MRI示踪的可行性。方法:从小鼠脂肪组织中分离培养、扩增脂肪间充质干细胞(ASCs),流式鉴定细胞表型后,分别采用不同浓度(25μg/mL,50μg/mL)的MIOP标记ASCs并向软骨细胞诱导分化。普鲁士蓝染色和透射电镜(TEM)鉴定细胞内磁纳米铁颗粒分布情况,应用3.0T MRI体外检测标记软骨细胞MRI信号。结果:从脂肪组织中可以分离获得大量高表达CD90、CD105、Sca-1的ASCs,不同浓度(25μg/mL,50μg/mL)的MIOP与ASCs共同孵育24小时后,普鲁士蓝染色发现ASCs随MIOP浓度的增加,蓝染程度逐渐加深且标记的ASCs可以向软骨细胞分化;TEM证实细胞内分布大量的黑色纳米铁颗粒。体外MRI T2序列证实随着MIOP浓度(25μg/mL,50μg/mL)的增加MRI信号值逐渐减低且具有统计学差异(P0.05)。结论:MIOP可以标记ASCs向软骨分化,体外应用MRI可以对其进行示踪。     

Band Edge Engineering of Oxide Photoanodes for Photoelectrochemical Water Splitting: Integration of Subsurface Dipoles with Atomic‐Scale Control

One of the crucial parameters dictating the efficiency of photoelectrochemical water‐splitting is the semiconductor band edge alignment with respect to hydrogen and oxygen redox potentials. Despite the importance of metal oxides in their use as photoelectrodes, studies to control the band edge alignment in aqueous solution have been limited predominantly to compound semiconductors with modulation ranges limited to a few hundred mV. The ability to modulate the flat band potential of oxide photoanodes by as much as 1.3 V, using the insertion of subsurface electrostatic dipoles near a Nb‐doped SrTiO₃/aqueous electrolyte interface is reported. The tunable range achieved far exceeds previous reports in any semiconductor/aqueous electrolyte system and suggests a general design strategy for highly efficient oxide photoelectrodes.     

An amperometric lactate biosensor based on lactate dehydrogenase immobilized onto graphene oxide nanoparticles‐modified pencil graphite electrode

A novel amperometric lactate biosensor was developed based on immobilization of lactate dehydrogenase onto graphene oxide nanoparticles‐decorated pencil graphite electrode. The enzyme electrode was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and cyclic voltammetry at different stages of its construction. The biosensor showed optimum response within 5 s at pH 7.3 (0.1 M sodium phosphate buffer) and 35°C, when operated at 0.7 V. The biosensor exhibited excellent sensitivity (detection limit as low as 0.1 μM), fast response time (5 s), and wider linear range (5–50 mM). Analytical recovery of added lactic acid in serum was between 95.81–97.87% and within‐batch and between‐batch coefficients of variation were 5.04 and 5.40%, respectively. There was a good correlation between serum lactate values obtained by standard colorimetric method and the present biosensor (r = 0.99). The biosensor measured lactate levels in sera of apparently healthy subjects and persons suffering from lactate acidosis and other biological materials (milk, curd, yogurt, beer, white wine, and red wine). The enzyme electrode lost 25% of its initial activity after 60 days of its regular uses, when stored dry at 4°C.     

Withaphysalin-type withanolides from Physalis minima

Nine new withaphysalin-type withanolides (1–9), named physaminimins (G-O) were isolated from the whole plants of Physalis minima Linn. The structures of these compounds were elucidated based on spectroscopic methods (1D NMR, HSQC, HMBC, ROESY) and HRESIMS. Physaminimins G, H, and K showed inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in a macrophage (RAW264.7) cells with IC₅₀ values of 17.41 ± 1.04, 36.33 ± 1.95 and 21.48 ± 1.67 μM, respectively.