Mass spectrometric investigations on lactate adduction to equine myoglobin

Research focused on determining the fundamental mechanisms by which lactate influences color stability has not considered a direct effect of lactate on myoglobin. Thus, the objective of this study was to use Matrix Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry to examine lactate adduction to myoglobin. Equine oxymyoglobin and equine carboxymyoglobin (0.15 mM) were incubated with sodium lactate (200 mM) at 4 °C, pH 5.6 in 50 mM sodium citrate buffer or at 37 °C, pH 7.4 in 50 mM sodium phosphate buffer, simulating typical meat storage and physiological conditions, respectively. Controls consisted of myoglobin plus a volume of deionized water equivalent to that used to deliver the lactate treatments. No peaks corresponding to lactate-Mb adducts could be detected in the mass spectra of samples incubated up to 360 min at pH 7.4, 37 °C or 8 days at pH 5.6 and 4 °C. Our results suggest that lactate did not form covalent adducts with equine oxy- and carboxy-myoglobin.     

Effects of modification of silica gel and ADH on enzyme activity for enzymatic conversion of CO2 to methanol

CO₂ can be converted to MeOH through an enzymatic approach in three steps: (1) converting CO₂ to HCOOH by formate dehydrogenase (FateDH), (2) converting HCOOH to HCHO by formaldehyde dehydrogenase (FaldDH) and (3) converting HCHO to MeOH by alcohol dehydrogenase (ADH). Polyethylene glycol (PEG) was used to adjust the pore size of immobilization carrier silica gel and SC-PEG was used to improve the catalytic property of ADH. The catalytic properties of pegylated ADH were investigated using the conversion of HCHO to MeOH as model reaction. The results show that PEG modification of the silica matrix and/or the ADH significantly increases the enzymatic activities.     

植物乳杆菌乳酸脱氢酶的抽提与初步纯化

研究了从植物乳杆菌RS2 2中提取胞内乳酸脱氢酶的工艺过程,探讨了超声破碎时菌体质量浓度、处理量及处理时间对破碎效果的影响;对酶的提取工艺研究表明,0.05mol/L磷酸缓冲液(pH7.0)添加0.10～0.30mol/LNaCl可达到较好的抽提效果;对硫酸铵盐析去杂蛋白质及DEAE离子交换层析工艺进行了初步优化.在优化的工艺条件下,酶的总回收率为40.2%,比酶活提高到原来的18.9倍.     

基于高分子化辅酶的脱氢酶修饰碳糊电极

制备了基于高分子化辅酶（PEI-Fc-NAD＋）的脱氢酶修饰碳糊电极。用直接混合法将高分子化辅酶、脱氢酶、碳粉与粘合剂适量混合,利用超声振荡得到均匀的碳糊,从而制得电极并利用循环伏安法进行表征。电化学实验表明高分子化的电子媒介体在电极表面的电极传递过程属于准可逆的电化学过程,而且电化学活性高分子化辅酶修饰电极后可以实现脱氢酶和电极之间的电子传递。     

Chemical, sensory and shelf life evaluation of sliced salmon treated with salts of organic acids

This study was carried out to evaluate the shelf life, chemical quality and sensory attributes of salmon slices treated by dipping in 2.5% aqueous solution of sodium acetate (NaA), sodium lactate (NaL), or sodium citrate (NaC) during refrigerated storage at 1 degrees C. The chemical analyses demonstrated significant reduction in K value, hypoxanthine (Hx) concentration, total volatile base nitrogen (TVB-N), and trimethylamine (TMA) in treated salmon slices when compared with the control. Sensory scores of treated salmon were in a typical category for appearance, juiciness and tenderness compared with the control. Only minor changes in the sensory attributes were recognized by few panellists in NaA- and NaL-treated samples. A shelf life of 12, 12 and 15 days has been estimated for salmon treated with NaL, NaC, and NaA, respectively, versus 8 days for control. The salts of organic acids can therefore be used as safe preservatives for fish under refrigerated storage.     

The metabolic consequences of reduced habitual activities in patients with muscle pain and disease

Abstract

Activities of mitochondrial enzymes have been measured in percutaneous muscle biopsies obtained from 23 patients with non-specific muscle pains (e.g. effort syndromes and post-viral fatigue syndromes), in biopsies obtained from eight patients with McArdle's disease (myophosphorylase deficiency), an enzyme defect known to lead to muscle pain during exercise, and, for comparison, in biopsies obtained from 14 untrained controls. Exercise performance was studied during incremental cycle ergometry in six typical patients with non-specific muscle pains and in six patients with McArdle's disease. The patients in general had a lower content of mitochondria in their muscles than the controls. The patients with nonspecific pain studied during cycle ergometry could not exercise at high intensities and showed decreased endurance, tachycardia, a high degree of exercise stress and an increased dependence on glycolysis at low exercise intensities. Many of the biochemical changes during exercise and many of the symptoms of these patients could be a consequence of their reduced habitual activities. The patients with McArdle's disease also could not exercise at high intensities because of their metabolic defect. The most ‘active’ patients had a normal content of mitochondria in their muscles and performed better during cycle ergometry. Furthermore, in contrast to the others they managed to remain successful in their profession. This study appears to suggest that the physical and mental well-being of patients with muscle pain and disease could be improved by the enhancement of their habitual activity.     

Power generation of Shewanella oneidensis MR-1 microbial fuel cells in bamboo fermentation effluent

This study successfully demonstrates the recovery of energy from the effluent of hydrogen fermentation (EHF) by generating electrical power in batch dual-chamber microbial fuel cells (MFCs) inoculated with Shewanella oneidensis MR-1. The effluent obtained from the hydrogen fermentation process of pretreated liquid on Bambusa stenostachya Hack. bamboo which contained organic compounds such as acetate, lactate, and butyrate as carbon sources for Shewanella oneidensis MR-1 and other electro-active microorganisms. Two scenarios of the anolyte of MFC were considered. The first case comprises a supply of 10 mM of lactate in hydrogen fermentation wastewater while the second one is without lactate-supply. The power density and current density of these MFCs were determined to be 0.3–0.6 W/m² and 1.7–2.7 A/m², respectively. The highest voltage generating from MFC without lactate addition was 0.76 V while others were around 0.65 V. The percentage of COD removal on the effluent of hydrogen fermentation ranged from 75% to 83% after 8 operational days followed by the acclimation process. The differences in the impedance characteristics of these MFCs were analyzed by using EIS technique. The average thickness of biofilm formation on the anode electrode was from 7 μm to 23 μm which showed the enhanced electricity production of the MFC system. Moreover, the experimental results demonstrated that the performance of MFC without the lactate supply was better than the other one. Also, its lower substrate consumption efficiency was mentioned.     

The Aerobic and Anaerobic Components of Work during Submaximal Exercise on a Bicycle Ergometer

Abstract

Inter-subject variability of oxygen intake ([Vdot]O₂)n relation to the anaerobic component of work has been investigated intensely on two healthy subjects and extensively on two groups of young and older men during work on an upright, stationary bicycle ergometer.

Significant differences (p<0·001) in [Vdot]O₂ were shown to exist between the two groups of subjects and the healthy men at the higher work-loads which could not be eliminated entirely by correction for body weight. The residual variation of [Vdot]O₂ on work-load was shown to be a consequence of the variation of anaerobic component of exercise. During work on a bicycle ergometer at exercise above about 50% [Vdot] O₂ max this should be taken into account if a valid assessment of energy expenditure is to be made.     

Inhibition of the formation of advanced glycation end products by thymoquinone

The inhibitory activity of thymoquinone, a major quinone from black seeds (Nigella sativa) against the formation of advanced glycation end products was studied using the hemoglobin-δ-gluconolactone, human serum albumin–glucose, and the N-acetyl-glycyl-lysine methyl ester–ribose assays. A comparison was made with the inhibitory activity of aminoguanidine. The cytotoxicity of thymoquinone was studied by the release of lactate dehydrogenase from platelets and the levels of plasma thiols. At 20 μM, thymoquinone inhibited 39% of hemoglobin glycation, 82% of post-Amadori glycation products, reduced methyglyoxal-mediated human serum albumin glycation by 68%, inhibited 78% of late glycation end products. Aminoguanidine at 10 mM was less effective than thymoquinone. The IC₅₀ for thymoquinone and aminoguanidine were 7.2 μM and 1.25 mM, respectively. Thymoquinone at 20–50 μM was not toxic to platelet lactate dehydrogenase and plasma thiols. The potential of thymoquinone in food applications is discussed.     

延长肉制品货架寿命的研究

简要介绍了肉制品货架寿命理论，具有探讨了Nisin、乳酸钠、微波、包装等因素对肉制品货架寿命的影响，并就各因素影响货架寿命的情况进行了对比与分析。结合目前实际，提出了延长肉制品货架寿命的新思路，展望了肉制品货架寿命的发展前景。