Halophilic proteins and the influence of solvent on protein stabilization

Competition between protein-solvent and protein-protein interactions is arguably the most important contributing factor to polypeptide folding in general. A study of halophilic proteins, correlating their stability and solution structures in different conditions, focuses on the effects of a high salt solvent. A mechanism is proposed to explain how these proteins have adapted to such an extreme environment.     

Very low density lipoprotein. Fate of phospholipids, cholesterol, and apolipoprotein C during lipolysis in vitro.

In this study we have determined the fate of phospholipids, cholesterol, and apolipoprotein C during lipolysis of rat plasma very low density lipoprotein (rat VLDL). The experiment was carried out in vitro with lipoprotein lipase purified from bovine milk, VLDL labeled with [(14)C]palmitate, [(3)H]cholesterol, [(32)P]phospholipids, and (125)I-labeled apolipoprotein C and in plasma-devoid systems. Triglyceride hydrolysis ranged between 0 and 98.6%. [(32)P]Phospholipids, unesterified [(3)H]cholesterol, and (125)I-labeled apolipoprotein C were removed from the VLDL (d < 1.019 g/ml) during lipolysis. About one-third of the [(32)P]phosphatidylcholine was hydrolyzed to lysolecithin, and was transferred to the fraction d > 1.21 g/ml. The other two-thirds of the phospholipids were removed unhydrolyzed, mainly to the fraction d 1.04-1.21 g/ml. With the progression of the lipolysis, unesterified [(3)H]cholesterol was removed from VLDL at increasing rates, predominantly to the fraction d 1.04-1.21 g/ml. (125)I-Labeled apolipoprotein C removed from the VLDL partitioned between the fraction of d 1.04-1.21 g/ml and d > 1.21 g/ml. Negative-staining electron microscopy of the fraction d 1.04-1.21 g/ml (containing phospholipids, unesterified cholesterol, and apolipoprotein C) revealed many discoidal lipoproteins. [(3)H]Cholesteryl esters remained associated with the VLDL even when 70-80% of the triglycerides were hydrolyzed. These observations suggest that during in vitro lipolysis of VLDL, surface constituents leave the lipoprotein concomitantly with the hydrolysis of core triglycerides. The process of removal of surface constituents is independent of the presence of an acceptor lipoprotein and may occur in the form of a surface-fragment particle. -Eisenberg, S., and T. Olivecrona. Very low density lipoprotein. Fate of phospholipids, cholesterol, and apolipoprotein C during lipolysis in vitro.     

Properties of the foot inhibitor from hydra

Summary A substance was isolated from crude extracts of hydra that inhibits foot regeneration. This substance, the foot inhibitor, has a molecular weight of 500 daltons. It is a hydrophilic molecule, slightly basic in character and it has no peptide bonds. The pruified substance acts specifically and at concentrations lower than 10^–7 M. At this low concentration only foot and not head regeneration is inhibited. Hydra are sensitive to purified foot inhibitor between the second and eight hour after initiation of foot regeneration by cutting. In normal animals the foot inhibitor is most likely produced by nerve cells. A substance with similar biological and physico-chemical properties is found in other coelenterates.     

A new species of Eugenia (Myrtaceae) from Venezuela

Eugenia mcvaughii is described from a forest remnant of the Jardin Botánico of Caracas, Venezuela. Found also in the hills adjacent to Caracas, it may be considered as an endemic species of the Interior Coastal Cordillera.