A molecular dynamics study of the bee venom melittin in aqueous solution, in methanol, and inserted in a phospholipid bilayer

The structural properties of melittin, a small amphipathic peptide found in the bee venom, are investigated in three different environments by molecular dynamics simulation. Long simulations have been performed for monomeric melittin solvated in water, in methanol, and shorter ones for melittin inserted in a dimyristoylphosphatidylcholine bilayer. The resulting trajectories were analysed in terms of structural properties of the peptide and compared to the available NMR data. While in water and methanol solution melittin is observed to partly unfold, the peptide retains its structure when embedded in a lipid bilayer. The latter simulation shows good agreement with the experimentally derived 3J-coupling constants. Generally, it appears that higher the stability of the helical conformation of melittin, lower is the dielectric permittivity of the environment. In addition, peptide-lipid interactions were investigated showing that the C-terminus of the peptide provides an anchor to the lipid bilayer by forming hydrogen bonds with the lipid head group

Economic efficiency of mechanised fishing in Tamil Nadu – a case study in Chennai

A study was conducted to analyse the economic efficiency of mechanised fishing in Chennai in Tamil Nadu along the east coast of India. The craft and gear combinations over the years witnessed dramatic changes on account of the huge cost of fishing, duration and depth of operations and maintenance. The mechanised gillnetters showed tremendous increase among the fishing fleet in Chennai mainly due to their assured returns and consistent marketing margin. The present study specifically compares the economic efficiency of mechanised gillnet units and trawlers operating from Chennai. Average operating cost and net income per day for the multiday (MD) gillnetters were `17,757 and 6,613 whereas in the case of multiday trawlers, the operating cost and net income per day were `18,095 and `3,219, respectively. Targeted tuna fishing and better price realisation in the value chain have contributed to better performance of gillnet units. The higher fuel requirement observed for MD trawlers as compared to MD gillnetters is attributed to long distance travelling and the use of mechanical power for propulsion as well as for fishing. The study found that efficiency measures in terms of labour, capital and fuel have established the supremacy of mechanised gillnetters

The nomenclature and conformational analysis of lipids and lipid analogs

Lipids form an essential part of the biomembrane and it is of paramount importance to study their conformational aspects. It is found that the present methods of nomenclature for lipids are totally inadequate for describing these diverse amphipathic molecules. Further the existing methods are incompatible in terms of assignment of the absolute configuration. A systematic method for the naming of lipids which is rationally extendible to a wide class of amphipaths is described. The conformational features of the natural glycerolipids as well as a synthetic amphipath containing a glutamic acid moiety known to undergo interesting phase transitions, have been examined in detail using the framework of the current nomenclature system. The implications of the conformational flexibility of these molecules on assemblies of these systems is touched upon

A molecular dynamics study of the bee venom melittin in aqueous solution, in methanol, and inserted in a phospholipid bilayer

ISSN:0175-7571ISSN:1432-101

Interaction of the Disaccharide Trehalose with a Phospholipid Bilayer: A Molecular Dynamics Study

The disaccharide trehalose is well known for its bioprotective properties. Produced in large amounts during stress periods in the life of organisms able to survive potentially damaging conditions, trehalose plays its protective role by stabilizing biostructures such as proteins and lipid membranes. In this study, molecular dynamics simulations are used to investigate the interaction of trehalose with a phospholipid bilayer at atomistic resolution. Simulations of the bilayer in the absence and in the presence of trehalose at two different concentrations (1 or 2 molal) are carried out at 325 K and 475 K. The results show that trehalose is able to minimize the disruptive effect of the elevated temperature and stabilize the bilayer structure. At both temperature, trehalose is found to interact directly with the bilayer through hydrogen bonds. However, the water molecules at the bilayer surface are not completely replaced. At high temperature, the protective effect of trehalose is correlated with a significant increase in the number of trehalose-bilayer hydrogen bonds, predominantly through an increase in the number of trehalose molecules bridging three or more lipid molecules

Not Available

Not AvailableA study was conducted to analyse the economic efficiency of mechanised fishing in Chennai in Tamil Nadu along the east coast of India. The craft and gear combinations over the years witnessed dramatic changes on account of the huge cost of fishing, duration and depth of operations and maintenance. The mechanised gillnetters showed tremendous increase among the fishing fleet in Chennai mainly due to their assured returns and consistent marketing margin. The present study specifically compares the economic efficiency of mechanised gillnet units and trawlers operating from Chennai. Average operating cost and net income per day for the multiday (MD) gillnetters were `17,757 and 6,613 whereas in the case of multiday trawlers, the operating cost and net income per day were `18,095 and `3,219, respectively. Targeted tuna fishing and better price realisation in the value chain have contributed to better performance of gillnet units. The higher fuel requirement observed for MD trawlers as compared to MD gillnetters is attributed to long distance travelling and the use of mechanical power for propulsion as well as for fishing. The study found that efficiency measures in terms of labour, capital and fuel have established the supremacy of mechanised gillnetters.Not Availabl

Lower Ionospheric Response to IMP Polarity Reversals

273-276Noon measurements of radio wave absorption in the ionosphere available at Colombo, Waltair and Kokubunji over long periods of time are employed in the study of the effect of IMF polarity reversals on the lower ionosphere at tropical and middle latitudes. Nearly 60% of the reversals are found to give rise to modest enhancements in absorption. This percentage is a little higher for positive to negative reversals as compared to that for negative to positive events. Mesospheric heating due to increased geomagnetic activity following a reversal is suggested as the possible mechanism behind absorption enhancements

Dependence of Frequency Power Law Exponent of Ionospheric Radiowave Absorption on Solar Zenith Angle

43-46study of the effect of the solar zenth angle on the frequency power law exponent derived from simultaneous vertical incidence multifrequency ionospheric absorption measurements available from a number of low and midlatitude stations has shown that the exponent, in fact, increases when deviative absorption becomes relatively more significant compared to nondeviative absorption. A numerical simulation using a double x-Chapman type absorbing zone yielded results identical to the experimental observation. It is suggested that in the formula L = A/(f+fL)m (solar zenith angle constant), widely used in such studies, neither A nor m remains independent of the solar zenith angle