A study of the occurrence of regulator secondary structures in globular proteins

The distribution of regular secondary structures, viz. α-helices and β-strands, along the length of over 70 properties whose secondary structural details have been reported, has been analysed. The occurrence of these regular structures tends to be a maximum at the N- and C-termini. Our analysis suggests that both these free ends could possibly serve as nucleating centers for secondary structures and could play an important role in the folding of proteins.     

A chemosystematic study of some geraniaceae

The flavonoids of five Geranium, fourteen Erodium and four Monsonia species were studied. Quercetin was the most common aglycone with lesse     

Factors controlling stem cell recirculation. 5. Modification of the effects of endogenous glucocorticoids on CFUs migration in T-deficient mice

It was shown that at a continuously increased level of endogenous glucocorticoids (injection of ACTH) in thymectomized and B mice the degree of inhibition of CFUs migration, that was observed in T-deficient mice without ACTH injection, did not increase. With T-deficiency the stimulatory effect of the hypocorticoid state (adrenalectomy) on the CFUs migration persisted but was less pronounced than in animals with intact thymus.     

THE EFFECTS OF SOLUBILIZATION PROCEDURES ON THE RELEASE AND MOLECULAR STATE OF ACETYLCHOLINESTERASE FROM ELECTRIC ORGAN TISSUE

Abstract— A study was made of the effect of various solubilization procedures on the release of AChE from electric organ tissue of the electric eel and on the molecular state of the enzyme. The procedures employed included homogenization in different ionic media or in the presence of detergents, etuymic treatment and chemical modification. Studies were performed on intact electroplax, tissue homogenates and membrane fractions. The apparent AChE activity of intact cells, homogenates and membrane fractions was shown to be governed by diffusion-controlled substrate and hydrogen ion gradients, generated by AChE-catalyscd hydrolysis, leading to a lower substrate concentration and a lower pH in the vicinity of the particulate enzyme.
Treatment of homogenates with NaCl solutions or with NaCl solutions containing the nonionic detergent Triton X-100 causes release of the native'molecular forms of the enzyme (primarily the 18 S species) which aggregate at low ionic strength. For optimal extraction both high ionic strength (e.g. 1 M-NaCl) and the detergent are needed AChE is also solubilized by treatment of tissue homogenates with trypsin, bacterial protease or collagenase. The first two enzymes caused its release as an 11 S non-aggregating form, while collagenase also produces a minor non-aggregating - 16 S component. Treatment of tissue homogenates with maleic anhydride causes release of AChE as a non-aggregating 18 S species. On the basis of the solubilization experiments it is concluded that the interaction of AChE with the excitable membrane is primarily electrostatic. The possible orientation of the enzyme within the synaptic gap is discussed.     

Electron microscope examination of two plaque variants from a nuclear polyhedrosis virus of the alfalfa looper, Autographa californica

This investigation looks into the ultrastructural differences between plaque variants of the alfalfa looper nuclear polyhedrosis virus. The variants exhibit distinct differences in polyhedra morphology and enveloping of the nucleocapsids.Tissues from larvae infected per os or subcutaneously with virus from one type of plaque always contained virus representative of both plaques. This was not true of the in vitro cultured cells. In those cells, a culture infected with one plaque type always developed infections that were typical of that particular plaque.     

Assessment of uncoupling activity of uncoupling protein 3 using a yeast heterologous expression system.

Uncoupling protein 3L, uncoupling protein 1 and the mitochondrial oxoglutarate carrier were expressed in Saccharomyces cerevisae. Effects on different parameters related to the energy expenditure were studied. Both uncoupling protein 3L and uncoupling protein 1 reduced the growth rate by 49% and 32% and increased the whole yeast O2 consumption by 31% and 19%, respectively. In isolated mitochondria, uncoupling protein 1 increased the state 4 respiration by 1.8-fold, while uncoupling protein 3L increased the state 4 respiration by 1.2-fold. Interestingly, mutant uncoupling protein 1 carrying the H145Q and H147N mutations, previously shown to markedly decrease the H+ transport activity of uncoupling protein 1 when assessed using a proteoliposome system (Bienengraeber et al. (1998) Biochem. 37, 3-8), uncoupled the mitochondrial respiration to almost the same degree as wild-type uncoupling protein 1. Thus, absence of this histidine pair in uncoupling protein 2 and uncoupling protein 3 does not by itself rule out the possibility that these carriers have an uncoupling function. The oxoglutarate carrier had no effect on any of the studied parameters. In summary, a discordance exists between the magnitude of effects of uncoupling protein 3L and uncoupling protein 1 in whole yeast versus isolated mitochondria, with uncoupling protein 3L having greater effects in whole yeast and a smaller effect on the state 4 respiration in isolated mitochondria. These findings suggest that uncoupling protein 3L, like uncoupling protein 1, has an uncoupling activity. However, the mechanism of action and/or regulation of the activity of uncoupling protein 3L is likely to be different.     

Integrating the statistical analysis of spatial data in ecology

In many areas of ecology there is an increasing emphasis on spatial relationships. Often ecologists are interested in new ways of analyzing data with the objective of quantifying spatial patterns, and in designing surveys and experiments in light of the recognition that there may be underlying spatial pattern in biotic responses. In doing so, ecologists have adopted a number of widely different techniques and approaches derived from different schools of thought, and from other scientific disciplines. While the adaptation of a diverse array of statistical approaches and methodologies for the analysis of spatial data has yielded considerable insight into various ecological problems, this diversity of approaches has sometimes impeded communication and retarded more rapid progress in this emergent area. Many of these different statistical methods provide similar information about spatial characteristics, but the differences among these methods make it difficult to compare the results of studies that employ contrasting approaches. The papers in this mini-series explore possible areas of agreement and synthesis between a diversity of approaches to spatial analysis in ecology.