A DFT study on the adsorption of benzodiazepines to vermiculite surfaces

Journal of Molecular Modeling - Widespread use of pharmaceuticals such as benzodiazepines has been resulting over the last decades in the dissemination of residues of these compounds in the...     

Determination of lecithin:cholesterol acyltransfer in mouse plasma and the influence of mercaptoethanol and sulphydryl blocking agents on its activity.

1. The cholesterol esterifying activity in mouse plasma has been identified as lecithin:cholesterol acyltransferase (LCAT) on the basis of stoichiometric data, predominant transfer of polyunsaturated fatty acids, wide pH optimum and inhibition of esterification by phospholipase A2 and sulphydryl blocking agents. The esterifying activity differed from that present in plasma of man, rat and other species since it was partially inhibited by mercaptoethanol and other thiols. 2. Stoichiometric correlations between unesterified cholesterol, lecithin and lysolecithin were not exact, suggesting possible involvement of other enzymes in the overall esterification process during in vitro incubation of mouse plasma. 3. The initial rate of cholesterol esterification was determined by in vitro incubation of mouse plasma, whose cholesterol had been labelled by prior in vivo injection of 3H-mevalonic acid. The mean rate was 281 +/- 74 nmol/ml/hr (mean +/- S.D., n = 12) and correlated with unesterified cholesterol concentration (r = 0.73, P less than 0.01).     

Fluorescent membrane probes’ behavior in lipid bilayers: insights from molecular dynamics simulations

Fluorescence spectroscopy and microscopy have been used as tools to study membrane biophysics for decades now. Because phospholipids are non-fluorescent, the use of extrinsic membrane probes in this context is commonplace. Two major points of concern arise regarding this matter, namely the incomplete understanding of the probe behavior inside the bilayer and the perturbation of the latter resulting from probe incorporation. To this effect, molecular dynamics (MD) simulations, by providing detailed atomic-scale information, represent a valuable way to characterize the location and dynamics of bilayer-inserted membrane probes, as well as the magnitude of perturbation they induce on the host lipid structure, and several important classes of reporter molecules have been studied in recent years. This article reviews the state of the art of MD simulations of bilayer-inserted fluorescent probes, focusing on the information that has been obtained from previous studies and hinting at future perspectives in this rapidly emerging field.     

Mechanisms of energy dissipation in peanut under water stress

Effect of drought on the mechanisms of energy dissipation was evaluated in two-month-old Arachis hypogaea cvs. 57–422, 73–30, and GC 8–35. Plants were submitted to three treatments: control (C), mild water stress (S1), and severe water stress (S2). Photosynthetic performance was evaluated as the Hill and Mehler reactions. These activities were correlated with the contents of the low and high potential forms of cytochrome (cyt) b ₅₅₉, plastoquinone, cyt b ₅₆₃, and cyt f. Additionally, the patterns of carotenoids and chlorophylls (Chls), as well as the alterations of Chl a fluorescence parameters were studied. Under mild water stress the regulatory mechanism at the antennae level was effective for 57–422 and GC 8–35, while in the cv. 73–30 an overcharge of photosynthetic apparatus occurred. Relative to this cv., under S1 the stability of carotene and the dissipative cycle around photosystem (PS) 2 became an important factor for the effective protection of the PS2 reaction centres. The cyclic electron flow around PS1 was important for energy dissipation under S1 only for the cvs. 57–422 and 73–30.     

Changes in Photosynthetic Performance of Ceratonia Siliqua in Summer

Photosynthetica - In carob tree (Ceratonia siliqua) radiant energy saturated net photosynthetic rate (P N) during summer was about 10 % of the spring values. This was accompanied by a reduction in...     

Modified Pseudomonas agar: new differential medium for the detection/enumeration of Pseudomonas aeruginosa in mineral water.

Pseudomonas aeruginosa has been implicated as a foodborne and waterborne pathogen and is now considered a primary infectious agent. In the present study, the survival of P. aeruginosa inoculated in mineral water was evaluated by drop counts on Pseudomonas Agar Base (PAB), PAB with CN supplement X107, PAB with cetrimide, PAB with nalidixic acid, and these media with added FeSO(4). Initial counts, before starvation, were the same in all media tested. Following this period, P. aeruginosa became sensitive to PAB with added cetrimide. The addition of FeSO(4) did not improve the recovery of stressed P. aeruginosa but gave colonies a typical dark brown colour being easily differentiated from other species that can grow at 42 degrees C. The modified Pseudomonas agar medium was also tested with several P. aeruginosa strains, other species of Pseudomonas, and other genera. Only P. aeruginosa strains (pyocyanin positive) produced the typical colonies. Our results demonstrate that Pseudomonas agar with ferrous sulphate, used for the differentiation of P. aeruginosa colonies, and nalidixic acid, used as an inhibitor of Gram-positive bacteria, might be a useful medium for the detection of injured P. aeruginosa in mineral water.     

T-20 and T-1249 HIV fusion inhibitors' structure and conformation in solution: a molecular dynamics study.

Fusion of the HIV envelope with the target cell membrane is a critical step of the HIV entry into the target cell. Several peptides based on the C-region of HIV gp41 have been used in clinical trials as possible HIV fusion inhibitors. Among these are T-1249 and T-20 (also known as enfurvitide). Despite recent works, a detailed molecular picture of the inhibitory mechanism of these molecules is still lacking. These peptides are usually depicted as alpha-helices by analogy with the structure of the sequence of the gp41 protein with which they are homologous. However, structures like these would be highly unstable in solution and thus would not explain, by themselves, the ability that the two fusion inhibitors have to become solvated by water and also interact effectively with cell membranes. To this effect, extensive molecular dynamics simulations were carried out to investigate the structure and conformational behavior of T-1249 and T-20 in water, as well as shorter homologous peptides CTP and 3f5, which show no inhibitory action. We found that the studied inhibitors have no stable structure in solution in the time scale studied. Additionally, the solvent accessible area varies significantly during the simulation. Our findings suggest that these peptides may assume not only one, but several possible sets of structures in solution, some of which more adequate to interact with the solvent, whereas others might be better suited to interact with cell membranes. Interestingly, and in accordance with published experimental studies, we verified that T-1249 displays considerably larger alpha-helical structure than T-20. Taking into account a recent study with design peptides with increased helicity, it is possible that this feature may be related to the increased inhibiting efficiency of T-1249 relative to that of T-20.     

Chromosomal mapping, gene structure and characterization of the human and murine RAB27B gene

Background  

Rab GTPases are regulators of intracellular membrane traffic. The Rab27 subfamily consists of Rab27a and Rab27b. Rab27a has been recently implicated in Griscelli Disease, a disease combining partial albinism with severe immunodeficiency. Rab27a plays a key role in the function of lysosomal-like organelles such as melanosomes in melanocytes and lytic granules in cytotoxic T lymphocytes. Little is known about Rab27b.