Repulsive interactions between uncharged bilayers. Hydration and fluctuation pressures for monoglycerides.

Pressure versus distance relations have been obtained for solid (gel) and neat (liquid-crystalline) phase uncharged lipid bilayers by the use of x-ray diffraction analysis of osmotically stressed monoglyceride aqueous dispersions and multilayers. For solid phase monoelaidin bilayers, the interbilayer repulsive pressure decays exponentially from a bilayer separation of approximately 7 A at an applied pressure of 3 x 10(7) dyn/cm2 to a separation of approximately 11 A at zero applied pressure, where an excess water phase forms. The decay length is approximately 1.3 A, which is similar to the value previously measured for gel phase phosphatidylcholine bilayers. This implies that the decay length of the hydration pressure does not depend critically on the presence of zwitterionic head groups in the bilayer surface. For liquid-crystalline monocaprylin, the repulsive pressure versus distance curve has two distinct regions. In the first region, for bilayer separations of approximately 3-8 A and applied pressures of 3 x 10(8) to 4 x 10(6) dyn/cm2, the pressure decays exponentially with a decay length of approximately 1.3 A. In the second region, for bilayer separations of approximately 8-22 A and applied pressures of 4 x 10(6) to 1 x 10(5) dyn/cm2, the pressure decays much more gradually and is inversely proportional to the cube of the distance between bilayers. These data imply that two repulsive pressures operate between liquid-crystalline monocaprylin bilayers, the hydration pressure, which dominates at small (3-8 A) bilayer separations, and the fluctuation pressure, which dominates at larger bilayer separations (greater than 8 A) and strongly influences the hydration properties of the liquid-crystalline bilayers.(ABSTRACT TRUNCATED AT 250 WORDS)     

X-ray diffraction observations of chemically skinned frog skeletal muscle processed by an improved method.

Whole frog sartorius muscles can be chemically skinned in approximately 2 h by relaxing solutions containing 0.5% Triton X-100. The intensity and order of the X-ray diffraction pattern from living muscle is largely retained after such skinning, indicating good retention of native structure in fibrils and filaments. Best X-ray results were obtained using a solution with (mM): 75 K acetate; 5 Mg acetate; 5 ATP; 5 EGTA; 15 K phosphate, 2% PVP, pH 7.0. Equatorial X-ray patterns showed that myofibrils swell after detergent skinning, as also observed after mechanical skinning. This swelling could be reversed by adding high molecular weight colloids (PVP or dextran) to the extracting solution. By finding the colloid osmotic pressure needed to restore the in vivo interfilament spacing (3% PVP, 4 X 10(4) mol wt) the swelling pressure was estimated as 35 Torr in a standard KCl-based relaxing solution. The swelling pressure and the extent of swelling were less than acetate replaced chloride as the major anion. Detergent-skinned muscle lost the constant-volume relation between sarcomere length and lattice spacing seen in intact muscle. Changes in A band spacing were paralleled by changes in I and band-Z line spacing at a constant sarcomere length. After detergent skinning, I1,0 rose while I1,1 fell, a change in the relaxing direction. Since raising the calcium ion concentrations from pCa 9 to PCa 6.7 was without effect on equatorial or axial X-ray patterns, we concluded that these intensity changes were not due to calcium-dependent cross-bridge movement but rather to disordering of thin filaments in the A band.     

Genetic variation in the carbonic anhydrase isozymes of macaque monkeys. I. The radioimmunosorbent assay

A radioimmunosorbent technique is described which is capable of independently detecting both isozymes of carbonic anhydrase, CA I and CA II, in concentrations as low as 1 ng/ml. The technique is used to quantitate the different electrophoretic variants of red cell CA I as well as levels of CA II in the pig-tailed macaque, Macaca nemestrina.Supported by U.S. Public Health Service research grant GM-15419.U.S. Public Health Service Predoctoral Trainee (GM-71-14).     

Pig slurry acidification,separation technology and thermal conversion affect phosphorus availability in soil amended with the derived solid fractions,chars or ashes

Aims

The aim was to study effects of slurry acidification, separation technology and thermal processing on the availability of P in soil amended with the solid fraction of pig slurry.

Methods

Acidified and non-acidified slurry were separated using different technologies: screw press (SCR), decanting centrifuge (DEC) and drainage after chemical pretreatment (CHE). Solids and pyrolysed (400 °C or 600 °C, char) or combusted (625 °C, ash) solids were applied to two soils, with triple superphosphate (TSP) as a reference. Soil P availability was determined over 12 weeks using diffusive gradients in thin films (DGT).

Results

The initial availability of P from DEC and CHE solids was similar to TSP in both soils. After 6 weeks no significant difference was observed between DEC solids and DEC chars. Acidification did not significantly affect P availability in the solids-amended soils over time, but it did affect P availability with the thermally processed materials.

Conclusions

Application of separated pig slurry solids generally increased soil P availability initially, but declining with time, indicating soil P fixing reactions. Chars and ashes on the other hand showed lower initial P availability, but remained constant or increased slightly with chars yielding P availability similar to solids after 12 weeks.

     

Effects of <Emphasis Type="Italic">Penicillium bilaii</Emphasis> on maize growth are mediated by available phosphorus

Background and aims

Functional traits are promising indicators of global changes and ecosystem processes. Trait responses to environmental conditions have been examined widely in vascular plants. In contrast, few studies have focused on soil lichens and mosses composing biocrusts. We aimed to evaluate the potential of biocrust tissue traits as indicators of changes in climate and soil properties.

Methods

Isotope ratios and nutrient content in biocrust tissue were analyzed in 13 Mediterranean shrublands along an aridity gradient. Differences in tissue traits between biocrust groups (lichens and mosses), and relationships between tissue traits and climatic and soil variables were examined.

Results

Lichens and mosses differed in δ¹³C, δ¹⁵N and N content, indicating distinct physical and physiological attributes. Tissue traits correlated strongly with numerous climatic variables, likely due to a modulator effect on biocrust water relations and metabolism. We found contrasting responses of lichen and moss traits to climate, although they responded similarly to soil properties. Overall, the most responsive trait was δ¹⁵N, suggesting this trait is the best to reflect integrated processes occurring in the atmosphere and soil.

Conclusions

Biocrust tissue traits arise as cost-effective, integrative ecological indicators of global change drivers in Mediterranean ecosystems, with potential applications in response-effect trait frameworks.

     

Solubilization of enzymes and nucleic acids in hydrocarbon micellar solutions

The present state of the field of biopolymers solubilized in apolar solvents via reverse micelles is reviewed. First, an extensive discussion of the physical and chemical properties of reverse micelles is presented. Particular attention is devoted to the nature of water in the water pools of reverse micelles; to the structure and shape of the micellar aggregates; and to the dynamic properties of the reverse micelles. In the second part of the paper, the mechanism of solubilization of proteins and nucleic acids in hydrocarbon reverse micelles is discussed. Spectroscopic data, mostly circular dichroism and fluorescence, are reviewed in order to clarify the conformational changes which the biopolymers undergo upon their uptake into the micellar environment and determine the location of the biopolymers inside the reverse micelles. Data from neutron scattering, light scattering, ultracentrifugation, and electron microscopy of the protein-containing micelles are reviewed and discussed with the aim of illustrating the structure of the micellar aggregates containing the biopolymer as guest molecules. The activity of enzymes and nucleic acids is discussed, with emphasis on the influence upon the chemical reactivity brought about by the micellar parameters. Finally, a brief review of the applications and potentialities of biopolymer-containing reverse micelles is presented.