Macromolecular solvation energies derived from small molecule crystal morphology.

The morphology of small molecule crystals provides a model for evaluating surface solvation energies in a system with similar packing density to that observed for amino acid residues in proteins. The solvation energies associated with the transfer of methylene and carboxyl groups between vacuum and aqueous phases are estimated to be approx. $40 and -260 cal/A2, respectively, from an analysis of the morphology of succinic acid crystals. These solvation energies predict values for contact angles in reasonable agreement with measurements determined from macroscopic monolayer surfaces. Transfer free energies between vapor and water phases for a series of carboxylic acids are also predicted reasonably well by these solvation energies, provided the surface exposure of different groups is quantitated with the molecular surface area rather than the more traditional accessible surface area. In general, molecular surfaces and molecular surface areas are seen to have important advantages for characterizing the structure and energetics of macromolecular surfaces. Crystal faces of succinic acid with the lowest surface energies in aqueous solution are characteristically smooth. Increasing surface roughness and apolarity are associated with higher surface energies, which suggests an approach for modifying the surface properties of proteins and other macromolecules.     

Effect of chronic vanadium administration in drinking water to rats

Two-month old Wistar rats of both sexes received, as sole drinking liquid, an aqueous solution of ammonium metavanadate (AMV) at a concentration of 0.01 or 0.05 mg V cm^–3 (0.2 or 1.0 mM) for a period of 4 weeks. It was calculated that the animals took up doses of 1.5 and 5–6 mg V kg body weight^–1 24 h^–1, respectively. Food and AMV solution consumption in the experimental groups was similar to food and water consumption in the control group. A statistically significant decrease of consumption of AMV solution at a concentration of 0.05 mg V cm^–3 was noted only in males. Hematological examination demonstrated a decrease in the erythrocyte count, hemoglobin level and hematocrit index. This decrease in the erythrocyte count was associated with an increased percentage of reticulocytes in the peripheral blood of the animals drinking the solution with a higher vanadium content. Biochemical analyses demonstrated a decrease of l-ascorbic acid levels in the plasma and erythrocytes of animals drinking the AMV solutions. A distinct tendency for the malonyldialdehyde level to increase in the blood was also observed. Among the enzymes examined in the erythrocytes (catalase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase and -aminolevulinic acid dehydratase [ALA-D]) only ALA-D activity was depressed.     

解淀粉芽胞杆菌hemX基因缺失对血红素合成的影响

血红素是一种广泛存在于生物体中的卟啉类化合物,具有多种生理功能。解淀粉芽胞杆菌(Bacillus amyloliquefaciens)具有易于培养、分泌表达能力较强等特点,是一种重要的工业菌株。为了筛选血红素合成的最优出发菌株,以不添加和添加5-氨基乙酰丙酸(5-aminolevulinic acid, ALA)的方式,对实验室保藏菌株进行筛选,发现不添加ALA时,菌株BA、BAΔ6、BAΔ6ΔsigF的血红素产量无明显差别;然而添加ALA后,BAΔ6ΔsigF的血红素产量和比生产能力均为最高,分别达到200.77μmol/L和615.70μmol/(L·g DCW)。因此,以BAΔ6ΔsigF为出发菌株,敲除编码细胞色素组装蛋白HemX的hemX基因,探究其在血红素合成途径中的作用,发现敲除菌株发酵液明显变红,且生长未受到明显影响;摇瓶发酵12 h时ALA浓度最高,为82.13 mg/L,略高于对照的75.11 mg/L;不添加ALA时,血红素产量和比生产能力分别为对照的1.99倍和1.45倍;添加ALA后,血红素产量和比生产能力分别为对照的2.08倍和1.72倍;实时定量荧光PCR...     

利用酵母菌生产有机酸的研究进展

有机酸是含有一种或多种低分子量酸性基团(如羧基、磺酸基)的可生物合成的有机化合物,广泛应用于食品、农业、医药、生物基材料工业等领域。酵母菌具有生物安全、抗逆性强、底物谱广泛、方便遗传改造,以及大规模培养技术成熟等独特优点,因此利用酵母菌生产有机酸的研究日益受到国内外学者的关注。目前利用酵母生产有机酸还存在浓度低、副产物多,以及发酵效率低等缺陷。随着酵母菌代谢工程和合成生物学技术的发展,利用酵母菌生产有机酸取得了快速进展。本文总结了利用酵母合成11种有机酸的研究,包括内源和异源合成的大宗羧酸和高价值有机酸,并对该领域的未来研究方向进行了展望。     

A new approach for extracting information from protein dynamics

Increased ability to predict protein structures is moving research focus towards understanding protein dynamics. A promising approach is to represent protein dynamics through networks and take advantage of well-developed methods from network science. Most studies build protein dynamics networks from correlation measures, an approach that only works under very specific conditions, instead of the more robust inverse approach. Thus, we apply the inverse approach to the dynamics of protein dihedral angles, a system of internal coordinates, to avoid structural alignment. Using the well-characterized adhesion protein, FimH, we show that our method identifies networks that are physically interpretable, robust, and relevant to the allosteric pathway sites. We further use our approach to detect dynamical differences, despite structural similarity, for Siglec-8 in the immune system, and the SARS-CoV-2 spike protein. Our study demonstrates that using the inverse approach to extract a network from protein dynamics yields important biophysical insights.     

Production of pectin lyase by Penicillium griseoroseum as a function of the inoculum and culture conditions

Optimum activity of an extracellular pectin lyase produced by Penicillium griseoroseum in submerged culture was after 120 h using 0.1% (w/v) citrus pectin as substrate. Sucrose at 0.1% (w/v) stimulated enzyme production and citrus pectin gave the highest activity of enzyme per unit growth.     

Metabolic engineering of Mannheimia succiniciproducens for malic acid production using dimethylsulfoxide as an electron acceptor

Microbial production of various TCA intermediates and related chemicals through the reductive TCA cycle has been of great interest. However, rumen bacteria that naturally possess strong reductive TCA cycle have been rarely studied to produce these chemicals, except for succinic acid, due to their dependence on fumarate reduction to transport electrons for ATP synthesis. In this study, malic acid (MA), a dicarboxylic acid of industrial importance, was selected as a target chemical for mass production using Mannheimia succiniciproducens, a rumen bacterium possessing a strong reductive branch of the TCA cycle. The metabolic pathway was reconstructed by eliminating fumarase to prevent MA conversion to fumarate. The respiration system of M. succiniciproducens was reconstructed by introducing the Actinobacillus succinogenes dimethylsulfoxide (DMSO) reductase to improve cell growth using DMSO as an electron acceptor. Also, the cell membrane was engineered by employing Pseudomonas aeruginosa cis-trans isomerase to enhance MA tolerance. High inoculum fed-batch fermentation of the final engineered strain produced 61 g/L of MA with an overall productivity of 2.27 g/L/h, which is the highest MA productivity reported to date. The systems metabolic engineering strategies reported in this study will be useful for developing anaerobic bioprocesses for the production of various industrially important chemicals.     

Cryopreservation of immature spring wheat zygotic embryos using an abscisic acid pretreatment

Spring wheat (Triticum aestivum L.) zygotic embryos were successfully cryopreserved, without the addition of exogenous cryoprotectants, using only an abscisic acid (ABA) pretreatment. Optimum survival was obtained when embryos were cultured in vitro for 10 days on semisolid Murashige and Skoog (MS) nutrient medium supplemented with 0.5 mg/L (±) ABA prior to cryopreservation. The embryos resumed growth within three days when returned to MS medium devoid of ABA but containing 2mg/L 2,4-dichlorophenoxyacetic acid. The embryogenic calli produced from these embryos exhibited normal plant regeneration on auxin-free media. Changes in dw/fw ratio, as well as the esterified fatty acid and sucrose concentrations correlated positively with the development of tolerance to cryopreservation.NRCC Publication No. 33519     

The Potential Efficacy of Glycyrrhizic Acid and Its Nanostructure Against Brown Rot of Peach fruits

Production of peaches (Prunus persica (L.) Batsch) for both local market and export is increasing each year in Egypt. Brown rot disease, caused by Monilinia laxa and Monilinia fructigena, is considered one of the most important postharvest rots affecting peaches in Egypt and economic losses are increasing. Antifungal activity of glycyrrhizic acid nanoparticles (GA-NPs) and glycyrrhizic acid (GA) at 0.2 and 0.4 mmol/L was investigated as a control for both these brown rot pathogens on peach fruits in both in vitro and in vivo studies. In the in vitro studies, GA-NPs were the most effective as shown by the ability to decrease linear growth of both brown rot pathogens in potato dextrose agar (PDA) amended with 0.4 mmol/L GA-NPs. Micrographs of M. fructigena exposed to 0.4 mmol/LGA showed mycelial deformations, nodule formation, detachment of the cell wall, shrinkage and inhomogeneous cytoplasmic materials with large vacuoles. Mycelium of M. laxa exposed to 0.4 mmol/ LGA-NPs resulted in thinner and distorted hyphae, nodule formation, cell wall thinning, and swellings. The GANPs and GA treatments improved fruit quality by maintaining firmness and total soluble solids (TSS). GA-NPs were more effective in decreasing decay incidence than their bulk material. The 0.4 mmol/L GA-NPs completely inhibited the disease on naturally infected peach fruits for both seasons of 2018 and 2019. Furthermore, 0.4 mmol/L GA-NPs reduced the disease incidence in inoculated fruits by 95 (M. laxa) and 88% (M. fructigena) in 2018 season and 96 (M. laxa) and 85% (M. fructigena) in 2019 season. In conclusion, GA-NPs could enhance the resistance of peaches against brown rot caused by M. laxa and M. fructigena.     

D-amino acid levels in human physiological fluids

Plasma, urine, cerebrospinal fluid (CSF), and amniotic fluid were examined to determine whether free D-amino acids were present and if so at what levels. It was found that D-amino acids exist in all physiological fluids tested, but that their level varied, considerably. The lowest levels of D-amino acids were usually found in amniotic fluid or CSF (almost always <1% of the corresponding L-amino acid). The highest levels were found in urine (usually tenth percent to low percent levels). Pipecolic acid seemed to be different from the other amino acids tested in that it was excreted primarily as the D-enantiomer (often >90%). Correspondingly high levels of D-pipecolic acid were not found in plasma. Some of the trends found in this work seemed to be analogous to those found in a recent rodent study. © 1993 Wiley-Liss, Inc.