Role of organic acids in the formation of the ionic composition in developing glycophyte leaves

The ionic composition in the leaves of some glycophyte plants (Phaseolus vulgaris L., Lycopersicon esculentum L., and Amaranthus cruentus L.) was studied during leaf development. Plants were grown in a stationary hydroponic culture; a growth medium contained equimolar concentrations of inorganic ions (NO ₃ ^? , Cl^?, SO ₄ ^2? , H₂PO ₄ ^? , K⁺, Ca²⁺, Mg²⁺, and Na⁺) equal to 5 mg-equiv./l for each ion. In the juvenile leaf, the main ions were K⁺ and water-soluble anions of organic acids represented mainly by di-and tricarboxylic acids in kidney bean and tomato and oxalic acid in amaranth. An increase in the total amount of organic anions, coinciding with the accumulation of bivalent cations, was registered in leaves of glycophytes during their development. Mature and senescing leaves of tomato and kidney bean accumulated mainly di-and tricarboxylic acid salts with the prevalence of Ca²⁺ ions. In amaranth leaves, the formation of water-insoluble (acid-soluble) oxalate pool containing Ca²⁺ ions (mature leaves) or Ca²⁺ and Mg²⁺ ions (senescing leaves) was registered. The priority role of the metabolism of organic acids in the formation of the ionic composition of glycophyte leaves during their development is discussed. It is supposed that the species-specific ionic composition of glycophyte leaves at different developmental stages is due mainly to the pattern of carbon metabolism causing the accumulation either of di-and tricarboxylic acids or oxalic acid.     

A study of steroid hydroxylation activity of Curvularia lunata mycelium

It has been demonstrated that the mycelium of Curvularia lunata at the end of the logarithmic growth phase displays a maximal 11-hydroxylase activity towards cortexolone (4-6 g/l) used for transformation as a microcrystalline suspension in phosphate buffer. The mycelium at a later stage of fungal growth displays an elevated 14-hydroxylase activity, necessary for generation of 14-hydroxyandrostenedione. The effects of different forms of substrate added to the reaction mixture, age and concentration of mycelium, and fungal clones tolerant to salts of heavy metals (0.35-0.5%) were studied to remove the side 14-hydroxylation, accompanying the main cortexolone transformation. Mycelia of the fungal clones tolerant to Co2+ and Cu2+ displayed a weak hydroxylase activity or its complete absence and an elevated content of melanin, the biosynthesis of which is intensified under adverse conditions. The results obtained suggest that the transformation of steroids by the studied C. lunata strain is a detoxication of foreign compounds.     

Direct amidation of poly(gamma-glutamic acid) with benzylamine in dimethyl sulfoxide

Partially benzylamidated, amphipathic poly(gamma-glutamic acid) (BzPGA) was synthesized from poly(gamma-glutamic acid) (PGA) and benzylamine by direct amidation in dimethyl sulfoxide (DMSO). Benzylamine and PGA were heated in DMSO for 1 to 26 h at temperatures between 110 and 130 degrees C, producing derivatives of various degrees of benzylamidation as a function of the reaction time and temperature. Neither any carboxyl-activating agent nor catalyst is needed for the reaction to proceed. After purification by dialysis, the product was identified by 1H and 13C 1D and 2D NMR in DMSO-d(6). BzPGA prepared by the new direct amidation method was identical to that obtained with a conventional carbodiimide-mediated reaction in water. The one-pot amidation procedure described in the present article can probably be applied to the synthesis of amides from other amines and carboxylic acids.     

Supplementation with Sucrosomial® iron leads to favourable changes in the intestinal microbiome when compared to ferrous sulfate in mice

BioMetals - Iron deficiency is one of the most common nutritional deficiencies worldwide and is often treated with oral iron supplements. However, commonly used supplements, including those based...     

Food web structure changes with elevation but not rainforest stratum

Changes in species richness along elevational gradients are well documented. However, little is known about how trophic interactions between species and, in particular, the food webs that these interactions comprise, change with elevation. Here we present results for the first comparison of quantitative food webs in forest understorey and canopy along an elevational gradient. Replicate quantitative food webs were constructed for assemblages involving 23 species of cavity‐nesting Hymenoptera and 12 species of their parasitoids and kleptoparasites in subtropical rainforest in Australia. A total of 1589 insects were collected using trap nests across 20 plots distributed at sites ranging from 300 to 1100 m a.s.l. Insect abundance, insect diversity and parasitism rate generally decreased with increasing elevation. Food web structure significantly changed with elevation. In particular, weighted quantitative measures of linkage density, interaction evenness, nestedness (weighted NODF) and potential for enemy mediated interactions (PAC) decreased with increasing elevation, and network specialisation (H₂′) increased with increasing elevation, even after controlling for matrix size; but there was no change in weighted connectance. Changes in forest type and temperature along the elevational gradient are likely to be, at least partly, responsible for the patterns observed. We found no significant differences in insect abundance, insect diversity or parasitism rate between canopy and understorey. Furthermore, there were no differences in food web structure between strata. These results contribute further evidence to studies revealing changes in food web structure along natural environmental gradients and provide information that can potentially be used for predicting how communities may respond to climate change.     

Sequential unfolding of the hemolysin two‐partner secretion domain from Proteus mirabilis

Protein secretion is a major contributor to Gram‐negative bacterial virulence. Type Vb or two‐partner secretion (TPS) pathways utilize a membrane bound β‐barrel B component (TpsB) to translocate large and predominantly virulent exoproteins (TpsA) through a nucleotide independent mechanism. We focused our studies on a truncated TpsA member termed hemolysin A (HpmA265), a structurally and functionally characterized TPS domain from Proteus mirabilis. Contrary to the expectation that the TPS domain of HpmA265 would denature in a single cooperative transition, we found that the unfolding follows a sequential model with three distinct transitions linking four states. The solvent inaccessible core of HpmA265 can be divided into two different regions. The C‐proximal region contains nonpolar residues and forms a prototypical hydrophobic core as found in globular proteins. The N‐proximal region of the solvent inaccessible core, however, contains polar residues. To understand the contributions of the hydrophobic and polar interiors to overall TPS domain stability, we conducted unfolding studies on HpmA265 and site‐specific mutants of HpmA265. By correlating the effect of individual site‐specific mutations with the sequential unfolding results we were able to divide the HpmA265 TPS domain into polar core, nonpolar core, and C‐terminal subdomains. Moreover, the unfolding studies provide quantitative evidence that the folding free energy for the polar core subdomain is more favorable than for the nonpolar core and C‐terminal subdomains. This study implicates the hydrogen bonds shared among these conserved internal residues as a primary means for stabilizing the N‐proximal polar core subdomain.     

Tracing the genetic origin of Europe's first farmers reveals insights into their social organization

Farming was established in Central Europe by the Linearbandkeramik culture (LBK), a well-investigated archaeological horizon, which emerged in the Carpathian Basin, in today''s Hungary. However, the genetic background of the LBK genesis is yet unclear. Here we present 9 Y chromosomal and 84 mitochondrial DNA profiles from Mesolithic, Neolithic Starčevo and LBK sites (seventh/sixth millennia BC) from the Carpathian Basin and southeastern Europe. We detect genetic continuity of both maternal and paternal elements during the initial spread of agriculture, and confirm the substantial genetic impact of early southeastern European and Carpathian Basin farming cultures on Central European populations of the sixth–fourth millennia BC. Comprehensive Y chromosomal and mitochondrial DNA population genetic analyses demonstrate a clear affinity of the early farmers to the modern Near East and Caucasus, tracing the expansion from that region through southeastern Europe and the Carpathian Basin into Central Europe. However, our results also reveal contrasting patterns for male and female genetic diversity in the European Neolithic, suggesting a system of patrilineal descent and patrilocal residential rules among the early farmers.