Generation of ATP by chloroplasts through solvent perturbation.

A two-stage method was discovered for generating ATP by chloroplasts in the dark at constant pH through solvent perturbation. With cold acetone as the perturbing solvent, the yield of ATP was found to increase with the volume percent of acetone in the first stage medium. The results are difficult to explain in term of the proton gradient model, but is consistent with the conventional model of prior water formation and subsequent ATP generation.     

Purification of bull sperm hyaluronidase by concanavalin-A affinity chromatography.

A new method for obtaining highly purified hyaluronidase (hyaluronate glycanohydrolase EC 3.2.1.25) in high yield is described. Bull seminal plasma was fractionated with (NH4)2 SO4 and the 30 to 65% saturation fractions were applied to a DEAE-cellulose column. The first protein peak contained hyaluronidase, beta-N-acetylglucosaminidase and beta-glucuronidase. The latter two enzymes were separated by gel filtration on Sephadex G-200. The hyaluronidase was further purified by a Concanavalin-A Sepharose 4B affinity column. By gradient elution with alpha-methyl-D-glucoside a fraction which had a specific activity of 1998 units/mg protein (57 942 National Formulary Standard units/mg protein) was obtained. The highly purified enzyme showed one major protein band on acrylamide gel electrophoresis at pH 4.3. The purified hyaluronidase did not show any beta-glucuronidase or beta-N-acetylglucosaminidase activities. The percent yield of purified hyaluronidase calculated on the basis of total activity was ten times higher than by any pervious method [Yang, C.H. and Srivastava, P.N. (1975) J. Biol. Chem. 250, 79-83].     

Inhibition of bull and rabbit sperm enzymes by alpha-chlorohydrin.

High concentrations of alpha-chlorohydrin were found to inhibit hyaluronidase, beta-glucuronidase, and aryl sulphatases in bull and rabbit spermatozoa, but not acrosin and neuraminidase. Preincubation of the enzyme and alpha-chlorohydrin was essential to achieve the maximum inhibition which was irreversible.     

Influence of clay minerals on sorption of bacteriolytic enzymes

Myxobacteria presumably produce extracellular bacteriolytic enzymes when they are growing in soil. In order to study their ecological significance, adsorption experiments were performed with lytic enzymes produced byMyxococcus virescens in casitone media. Different soils as well as montmorillonite and kaolinite can rapidly adsorb the bacteriolytic but not the proteolytic enzymes. About 1 gm of montmorillonite per liter of cell-free culture solution is enough for the adsorption of 97% of the bacteriolytic enzymes. The adsorption per unit weight is about 100 times greater on montmorillonite than on kaolinite. About 40% of the adsorbed enzymes can be eluted with solutions of high pH or high ionic strength. The only desorbed bacteriolytic enzyme is the alanyl-∈-N-lysine endopeptidase.     

Single-cell transcriptomic atlas of primate cardiopulmonary aging

Aging is a major risk factor for many diseases,especially in highly prevalent cardiopulmonary comorbidities and infectious diseases including Coronavirus Diseas...     

SARS-CoV-2 envelope protein causes acute respiratory distress syndrome (ARDS)-like pathological damages and constitutes an antiviral target

Cytokine storm and multi-organ failure are the main causes of SARS-CoV-2-related death. However, the origin of excessive damages caused by SARS-CoV-2 remains largely unknown. Here we show that the SARS-CoV-2 envelope (2-E) protein alone is able to cause acute respiratory distress syndrome (ARDS)-like damages in vitro and in vivo. 2-E proteins were found to form a type of pH-sensitive cation channels in bilayer lipid membranes. As observed in SARS-CoV-2-infected cells, heterologous expression of 2-E channels induced rapid cell death in various susceptible cell types and robust secretion of cytokines and chemokines in macrophages. Intravenous administration of purified 2-E protein into mice caused ARDS-like pathological damages in lung and spleen. A dominant negative mutation lowering 2-E channel activity attenuated cell death and SARS-CoV-2 production. Newly identified channel inhibitors exhibited potent anti-SARS-CoV-2 activity and excellent cell protective activity in vitro and these activities were positively correlated with inhibition of 2-E channel. Importantly, prophylactic and therapeutic administration of the channel inhibitor effectively reduced both the viral load and secretion of inflammation cytokines in lungs of SARS-CoV-2-infected transgenic mice expressing human angiotensin-converting enzyme 2 (hACE-2). Our study supports that 2-E is a promising drug target against SARS-CoV-2.Subject terms: Cell death, Molecular biology     

Environmental filtering rather than dispersal limitation dominated plant community assembly in the Zoige Plateau

Identifying the mechanisms that underlie the assembly of plant communities is critical to the conservation of terrestrial biodiversity. However, it is seldom measured or quantified how much deterministic versus stochastic processes contribute to community assembly in alpine meadows. Here, we measured the decay in community similarity with spatial and environmental distance in the Zoige Plateau. Furthermore, we used redundancy analysis (RDA) to divide the variations in the relative abundance of plant families into four components to assess the effects of environmental and spatial. Species assemblage similarity liner declined with geographical distance (p < .001, R ² = .6388), and it decreased significantly with increasing distance of total phosphorus (TP), alkali‐hydrolyzable nitrogen (AN), available potassium (AK), nitrate nitrogen (NO₃ ⁺–N), and ammonia nitrogen (NH₄ ⁺–N). Environmental and spatial variables jointly explained a large proportion (55.2%) of the variation in the relative abundance of plant families. Environmental variables accounted for 13.1% of the total variation, whereas spatial variables accounted for 11.4%, perhaps due to the pronounced abiotic gradients in the alpine areas. Our study highlights the mechanism of plant community assembly in the alpine ecosystem, where environmental filtering plays a more important role than dispersal limitation. In addition, a reasonably controlled abundance of Compositae (the family with the highest niche breadth and large niche overlap value with Gramineae and Cyperaceae) was expected to maintain sustainable development in pastoral production. These results suggest that management measures should be developed with the goal of improving or maintaining suitable local environmental conditions.