A pulsed NMR study of lipids,bound water and sodium ions in macroscopically-oriented lecithin/water lyotropic liquid crystal model membrane systems

The temperature and orientation dependence of pulsed NMR ‘free induction decay’ signals have been studied in detail for lipid bilayers macroscopically-oriented between glass slides. Results for the lipid molecules (¹H, ³¹P), bound water (²H₂O) and ions dissolved in the aqueous phase (²³Na) are presented. Bilayers of egg-lecithin, dimyristoyl lecithin and potassium oleate have been investigated. In the liquid crystal phase all the signals, including those from bound water and ions exhibit a |3 cos²? ? 1| dependence on orientation of the bilayer normal to the magnetic field. In the case of DML samples, some orientation dependence of both ¹H and ²H signals persists in the gel phase, indicating that the lipid molecules retain a degree of reorientational freedom about their long axes in this phase. At the gel-liquid crystal transition the ²H quadrupole spittings undergo a discontinuous change. Results are interpreted in terms of a model in which water molecules are bound to individual lipid head groups and reorient with them, while sodium ions are located in the aqueous channel between bilayers.     

The measurement of subnanosecond fluorescence decay of flavins using time-correlated photon counting and a mode-locked Ar ion laser.

A system is described consisting of a mode-locked Ar ion laser and time-resolved photon-counting electronics. The system is capable of measuring fluorescence lifetimes in the subnanosecond time domain. The Ar ion laser is suitable for the excitation of flavins, since the available laser wavelengths encompass the first absorption band of the yellow chromophore. Due to the high radiation density and the short pulse, both the time and wavelength resolution of the fluorescence of very weakly emitting compounds can be measured. Experiments have been described for flavin models exhibiting single and multiple modes of decay. In these examples lifetimes were determined both from deconvolved decay curves and from direct analysis of the tail of the curve, where no interference of the exciting pulse is encountered. Both determinations showed very good agreement. Due to the highly polarized laser light the decay of the emission anisotropy could be measured directly after the exciting pulse. In principle, fast rotational motions might be detected. An anisotropy measurement conducted with a flavoprotein with a noncovalently attached FAD is presented.     

Early molecular events in the interaction of enveloped viruses with cells

The fluorescence depolarization of 1,6-diphenyl-hexatriene was used to study the dynamic properties of the hydrophobic regions of the lipid envelopes of ortho- and paramyxoviruses as well as of the Rous sarcoma virus and of the membrane lipids of susceptible and nonsusceptible cells.The systems investigated where active and inactive influenza viruses, and NDV virus acting on chick embryo fibroblasts and Rous sarcoma virus acting on susceptible (C/E) and nonsusceptible (C/B) chicken-cell.Polarization degrees and mean rotational correlation times of DPH embedded in viral lipids were significantly higher than those of DPH in the cell membranes, due to a higher rigidity of the virus envelopes. When suspensions of labelled viruses and unlabelled cells or unlabelled viruses and labelled cells were mixed, a characteristic change of the fluorescence polarization degrees with time was observed. This behaviour was ascribed to a label transfer from virus to cell membranes or vice versa.While the rate constants of label transfer from virus to cells and cells to virus were about the same for the penetrating viruses the rate constants of label release from inactive virus to cells were much larger than for the migration in the opposite direction.     

Anoxia can increase the rate of decay for cnidarian tissue: Using Actinia equina to understand the early fossil record

An experimental decay methodology is developed for a cnidarian model organism to serve as a comparison to the many previous such studies on bilaterians. This allows an examination of inherent bias against the fossilisation of cnidarian tissue and their diagnostic characters, under what conditions these occur, and in what way. The decay sequence of Actinia equina was examined under a series of controlled conditions. These experiments show that cnidarian decay begins with an initial rupturing of the epidermis, followed by rapid loss of recognisable internal morphological characters. This suggests that bacteria work quicker on the epidermis than autolysis does on the internal anatomy. The data also show that diploblastic tissue is not universally decayed more slowly under anoxic or reducing conditions than under oxic conditions. Indeed, some cnidarian characters decay more rapidly under anoxic conditions than they do under oxic conditions. This suggests the decay pathways acting may be different to those affecting soft bilaterian tissue such as soft epidermis and internal organs. What is most important in the decay of soft polyp anatomy is the microbial community, which can be dominated by oxic or anoxic bacteria. Different Lagerstätte, even of the same type, will inevitably have subtle difference in their bacterial communities, which among other factors, could be a control on soft polyp preservation leading to either an absence of compelling soft anthozoans (Burgess Shale) or an astonishing abundance (Qingjiang biota).     

Effect of hydrophobicity degree of polymer particles on lipase immobilization and on biocatalyst performance

Abstract

Many studies describe the advantages of using hydrophobic particles on lipase immobilisation. However, many of these works neglect the effect of other variables of the supports, such as specific area and porosity, on the biocatalyst performance, and do not evaluate the influence of the hydrophobicity level of the particles on the biocatalysts’ activity as a single variable. Thus, the focus of the present work was to evaluate the effect of the hydrophobicity degree of polymeric particles on the biocatalysts’ activities, mitigating the influence of other variables. The study was divided into two steps. Firstly, distinct particles, exhibiting different composition and hydrophobicity levels, were used for the immobilization of a commercial lipase B from Candida antarctica (CAL-B). Then, distinct core-shell polymeric particles presenting different functional compounds on the surface were produced, using as comonomers styrene, divinylbenzene, 1-octene, vinylbenzoate and cardanol. Such particles were subsequently used for CAL-B immobilisation and the performance of the biocatalysts was evaluated on hydrolysis (using p-nitrophenyl laurate, as substrate) and esterification (using ethanol and oleic acid, as substrate) reactions. Based on the screening step, it was observed that for non-porous particles the correlation coefficients between the hydrophobicity level of the supports and the biocatalysts performance, for both hydrolysis and esterification reactions, were very low (0.32 and 0.45, respectively). It highlights that there was no significant correlation between these variables and that, probably, the chemical composition of the polymeric chains affects more significantly the biocatalyst performance. Then, analysing the subsequent stage, it was observed that small changes in the surface composition of the core-shell particles result in significant changes on the textural properties of the supports (specific area ranging from 1.2?m².g^?1 to 18.3?m².g^?1; and contact angles ranging from 71° (hydrophilic particles) to 92° (hydrophobic supports) when polymer films were put in contact with water). Such particles were also employed on CAL-B immobilization and it was noticed that higher correlation coefficients were achieved for hydrolysis (ρ?=?0.53) and esterification (ρ?=?0.74) reactions. Therefore, it is shown that the hydrophobicity degree of such supports starts to affect more effectively the biocatalysts performance when other textural features of the supports become more significant, such as specific area and porosity.     

Hirticrusta gen. nov. segregated from Neofomitella in Polyporaceae (Polyporales)

Taxonomic studies including morphological observations and phylogenetic analyses were conducted on Japanese “uragin-take”, an unidentified species from Amazonia, Brazil and their allies. Phylogenetic analyses using ITS, nrLSU and RPB2 regions revealed that “uragin-take”, Neofomitella polyzonata and the unidentified species formed a monophyletic clade separate from the clade including the other four Neofomitella spp. and that “uragin-take” is conspecific with N. polyzonata. Morphological investigations on authentic specimens revealed that Polyporus subradiatus is a prior name for N. polyzonata. We propose Hirticrusta gen. nov. typified by H. subradiata segregated from Neofomitella, and we erected H. amazonica sp. nov. for the unidentified species. Hirticrusta is characterized by annual to biennial and sessile basidiocarps, semicircular to dimidiate pileus, velutinous to tomentose hairs on pileus surface, buff to brown context with a crustose layer indicated by a dark brown line forming a longitudinal section below the superficial hairs, a trimitic hyphal system, crustose layer composed of parallel and densely arranged brown hyphae and cylindrical basidiospores. The new species, H. amazonica is distinguishable from other polypores by downy and long tomentum on the pileus surface (up to 20 mm thick), brown context with a dark brown layer below the tomentum and round pores (5–7/mm).     

青藏高原草地产量与草畜平衡变化

深入了解青藏高原草地生产力与草畜平衡状态的变化,是青藏高原生态屏障建设和生态环境保护的基础。利用遥感植被指数和叶面积指数产品,基于VIP生态水文过程模型,模拟分析了青藏高原2000—2018年间草地生产力的时空格局,并结合同期农牧业统计资料,分析了青藏高原县域尺度草畜平衡状态的变化。结果表明:青藏高原草地多年平均净初级生产力(NPP)为158.4 g C·m^-2·a^-1;近20年来草地生产力上升趋势明显,显著上升面积的比例为44.7%。气候变暖、降水量增加、草本植物生长期延长和大气CO₂浓度升高是青藏高原草地生产力提高的主要驱动因素。基于草场产量估算的青藏高原平均理论载畜量为1.17 SU·hm^-2,年增长率为0.011 SU·hm^-2。2000年以来青藏高原草地超载情况总体趋于好转,严重超载县的面积比例已降至20%以下,其中超载程度较严重的地区,畜牧业的维持和发展主要依靠作物秸秆补饲。研究结果可为区域农牧业结构调整和生态环境保护提供科学依据。