The amphipathic membrane proteins associated with gangliosides: The Paul-Bunnell antigen is one of the gangliophilic proteins

Two amphipathic protein fractions soluble in organic solvents as well as in water have been isolated from the ganglioside fraction of bovine erythrocyte membranes by successive chromatography in chloroform-methanol mixture on DEAE-Sephadex, silicic acid, and α-hydroxypropylated Sephadex G50 (LH60) columns. These two fractions contained a similar low molecular weight protein but with distinctively different amino acid composition. One of these proteins has been characterized by having a strong Paul-Bunnell antigen activity and had a binding affinity to ganglioside. A similar protein without Paul-Bunnell antigen activity was isolated as the major ganglioside-associated protein.     

Partial specific volumes and interactions with solvent components of α-globulin fromSesamum indicum L. in urea and guanidine hydrochloride

The interaction of α-globulin with urea/guanidine hydrochloride was investigated by determining the apparent partial specific volumes of the protein in these solvents. The apparent partial specific volumes were determined both under isomolal and isopotential conditions. The preferential interaction parameter with solvent components calculated were 0.08 and 0.1 g of urea and guanidine hydrochloride respectively per g protein. In both the cases the interaction was not preferential with water. The total binding of denaturant to α-globulin was calculated both for urea and guanidine hydrochloride and the correlation between experimentally determined number of mol of denaturant bound per mol of protein and the total number of peptide bonds and aromatic amino acids were found to be in excellent agreement with each other. The changes in volume upon transferring α-globulin from a salt solution to 8 M urea and 6 M guanidine hydrochloride were also calculated. This work was done at the Biochemistry Department, Brandeis University, Waltham, Massachusetts 02254, USA.     

Seasonal patterns in water use and leaf turnover of different plant functional types in a species-rich woodland,south-western Australia

Woodlands in south-western Australia are evergreen and transpire throughout the year despite the long, hot and dry summers of the Mediterranean climate. Results from a case study in a species-rich Banksia woodland are used to discuss the ecological and physiological properties that appear to be essential features of this and similar communities. Tree, shrub and perennial herbaceous species with long-lived leaves dominate the community, whereas winter-green herbaceous species with short-lived leaves constitute a minor group. The total leaf area index is therefore reasonably constant in all seasons. Leaf area index is low and canopies are open, causing good coupling between the vegetation and the atmosphere, and making stomatal control an effective regulator of transpiration. Mean maximum (winter) stomatal conductances were high at approximately 300 mmol m^–2 s^–1. Deep-rootedness allows the dominant species to access soil moisture throughout the unsaturated zone, and down to the capillary fringe of the saturated zone. Shrubs and herbs with shallow roots experience greater drought stress during summer. Rates of community evapotranspiration are limited by leaf area index in the wet season, and further reduced by stomatal closure in the dry season. Deep-rooted plants appear to decrease their stomatal conductance before the development of severe drought stress. Such conservative behaviour, possibly related to plant hydraulic constraints, is a contributing factor to the limited seasonality in community water use.     

Which physical and structural factors of liposome carriers control their drug-loading efficiency?

The correlation between structural and physical properties of lipid membrane and its drug-loading efficiency were studied. The properties of bilayer were altered by incorporation of several lipidic modifiers: cholesterol, oleic acid, methyl oleate, and pegylated lipid. By using the molecular probe technique it was demonstrated that the membrane properties, such as micropolarity, microviscosity and free volume were considerably changed by incorporation of the modifiers. The partitioning of two different porphyrins between the bulk aqueous phase and the modified liposomes was studied using the fluorescence methods, and liposome-binding constants were determined. It was found that cholesterol reduced the partitioning of both porphyrins into liposomal bilayer. On the contrary, the incorporation of methyl oleate and pegylated lipid causes a pronounced increase in the value of the binding constants of both porphyrins. It was concluded that the free volume rather than hydrophobicity of bilayer is a governing factor in the solute partitioning into lipid bilayers.     

Shoot anatomy and secretory structures in Hypericum species (Hypericaceae)

The anatomy and ultrastructure of internodes, leaves and petals were compared in Hypericum elegans, H. inodorum, H. olympicum, H. forrestii and two genotypes of H. perforatum. Internode anatomy was variable between species with respect to the structure of the cortical and pith parenchyma, including the presence of secretory reservoirs. Also, the secondary growth was more extensive in shrubs, i.e. H. inodorum and H. forrestii. In leaves, phloem secretory reservoirs were formed in all species, mesophyll secretory reservoirs were absent only in H. elegans and internal nodules were present only in H. elegans and H. perforatum. The petals differed between species in the mesophyll structure and the occurrence and location of secretory structures. The phloem secretory reservoirs lacked sheaths, whereas these were distinct in the mesophyll reservoirs. Other ultrastructural traits of the reservoirs were similar in all the species studied, with the exception of the leucoplast ultrastructure. In internal nodules, the inner cells vs. sheath cells differed in the number of vesicles and other membranous structures and plastid ultrastructure. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 163 , 70–86.     

Are ABA,ethylene or their interaction involved in the response of leaf growth to soil water deficit? An analysis using naturally occurring variation or genetic transformation of ABA production in maize

The role of abscisic acid (ABA) and its possible interaction with ethylene in mediating leaf elongation response to soil water deficit are a matter of controversy. To address this question, we used a set of maize genotypes with various levels of ABA either due to natural variability or to genetic transformation targeted on NCED/VP14, a key enzyme of ABA synthesis. The transgenic lines yielded less strong phenotypes than available mutants, making it possible to use them under normal growing conditions. We focused on leaf elongation during night periods in order to avoid the confounding effect of ABA on leaf water status. Our results suggest that over a wide range, internal ABA level (measured in both leaf extracts or xylem sap) has no clear effect on leaf elongation response to soil water deficit, except in the case of an antisense line presenting the strongest reduction in ABA accumulation that showed a slight maintenance of leaf elongation during water deficit. Leaf ethylene production rate was variable and not related to water deficit except in the ABA-deficient transgenic lines where it was increased by water deficit on average but not systematically. Moreover, variability in ethylene production rate was not linked to variability in elongation rate. Our results thus suggest that neither ABA nor ethylene seems to play a major role in the control of leaf elongation response to soil water deficit.     

Estimation of temperature and precipitation from morphological characters of dicotyledonous leaves

The utility of regression and correspondence models for deducing climate from leaf physiognomy was evaluated by the comparative application of different predictive models to the same three leaf assemblages. Mean annual temperature (MAT), mean annual precipitation (MAP), and growing season precipitation (GSP) were estimated from the morphological characteristics of samples of living leaves from two extant forests and an assemblage of fossil leaves. The extant forests are located near Gainesville, Florida, and in the Florida Keys; the fossils were collected from the Eocene Clarno Nut Beds, Oregon. Simple linear regression (SLR), multiple linear regression (MLR), and canonical correspondence analysis (CCA) were used to estimate temperature and precipitation. The SLR models used only the percentage of species having entire leaf margins as a predictor for MAT and leaf size as a predictor for MAP. The MLR models used from two to six leaf characters as predictors, and the CCA used 31 characters. In comparisons between actual and predicted values for the extant forests, errors in prediction of MAT were 0.6°-5.7°C, and errors in prediction of precipitation were 6-89 cm (=6-66%). At the Gainesville site, seven models underestimated MAT and only one overestimated it, whereas at the Keys site, all eight models overestimated MAT. Precipitation was overestimated by all four models at Gainesville, and by three of them at the Keys. The MAT estimates from the Clarno leaf assemblage ranged from 14.3° to 18.8°C, and the precipitation estimates from 227 to 363 cm for MAP and from 195 to 295 cm for GSP.     

The management of rice straw,fertilisers and leaf litters in rice cropping systems in Northeast Thailand.

The maintenance of soil organic matter (SOM) and the balancing of nutrient flows into and out of the rainfed rice cropping systems in Northeast Thailand is of paramount importance to arresting the decline in soil fertility and crop yields. A system where small applications of leaf litters from locally grown trees are applied annually to rice paddy soils prior to transplanting is described. The annual application of 1500 kg/ha of Cajanus cajan, Acacia auriculiformis, Phyllanthus taxodifolius and Samanea saman for five seasons resulted in increases in rice grain yield of 48, 35, 32 and 23% above the no-leaf litter control, respectively. Average annual nutrient inputs from the leaf litters, in kg/ha, ranged from 62.7 N, 3.9 P, 17.9 K, and 3.5 S for Cajanus cajan to 24.5 N, 1.5 P, 8.1 K and 2.0 S for Acacia auriculiformis. Nutrient balances, determined by the difference between the inputs (fertiliser and added leaf litters) and outputs (grain and straw) indicated net positive N and P balances of up to 457 and 60 kg/ha. respectively, after five seasons of leaf litter applications. Sulfur and potassium balances resulted in net deficits of up to −3 and −52 kg S and K/ha, respectively, where no leaf litter was applied and rice straw was removed following harvest. Calculated apparent nutrient recoveries reflected the decomposition rate of the added residues and were highest for P and K, reflecting their higher soil residual value than mobile nutrients such as N and S. Sustainable farming systems will require that crop yields are stable through the maintenance of soil fertility and the balance of nutrients in the system. This revised version was published online in June 2006 with corrections to the Cover Date.