Degradation of hyaluronan by ultrasonication in comparison to microwave and conventional heating

Hyaluronan (hyaluronic acid, HA) was depolymerised by ultrasonication (US), microwave irradiation (MW) and conventional heating (CH), and the effect of pH and oxidants was investigated. The degradation was followed by viscometry and size exclusion chromatography coupled with low-angle light scattering. The results demonstrated that depolymerisation of HA by US leveled off to a limiting molecular mass, and the degradation was significantly enhanced by acidic and alkaline pH only in the presence of oxidants. In contrast to US, the course of depolymerisation by MW was strongly pH-dependent, and the degradation rate increased with decreasing pH. The expected enhancement of depolymerisation by MW in comparison to CH was marked only at very short heating time at pH <4. The NMR and FTIR spectral analyses indicated that HA in the whole M_w-range studied retained almost the backbone of the parent polysaccharide independently on the degradation method used. At harsh degradation conditions (long-term treatments, particularly at acidic pH or alkaline pH and in presence of oxidants) the depolymerisation was accompanied by destruction of both constituent sugar residues and formation of unsaturated structures detectable by UV-absorption at 230–240 and 260–270 nm. US-assisted oxidative degradation under mild reaction conditions was shown to be the most appropriate procedure to reduce the molecular mass of HA to 100 kDa without significant chemical modification of the polysaccharide.     

Genotypic control of the speed of development inArabidopsis thaliana (L.)Heynh. lines obtained from natural populations

Sixteen early, medium late, and late homozygote lines ofArabidopsis thaliana, obtained from three natural populations, were crossed with a common check variety S 96. The speed of development was expressed by the value log (x+y), wherex stands for the number of days after which flower primordia appear, andy for the number of leaves in the rosette. The experiments were caried out under conditions which emphasized the differences in the speed of development. We assessed the degree of dominancy, heritability on the basis of F₁ and F₂ variance, and analyzed F₂ distributions. It was established that some of the investigated lines differ from the variety S 96 in one pair of dominant genes or genes with incomplete dominancy for late flowering, other in two pairs of genes with complementary effects, and that the variety S 96 probably also contains other alleles causing late flowering inhibited by some type of epistasis. Even though the most important part is always played by one or two pairs of genes with high dfficiency, genes with lower efficiency often take part in the process; in some lines the genes with high efficiency could not be established.     

Interpretation of the last‐glacial vegetation of eastern‐central Europe using modern analogues from southern Siberia

Aim Interpretation of fossil pollen assemblages may benefit greatly from comparisons with modern palynological and vegetation analogues. To interpret the full‐ and late‐glacial vegetation in eastern‐central Europe we compared fossil pollen assemblages from this region with modern pollen assemblages from various vegetation types in southern Siberia, which presumably include the closest modern analogues of the last‐glacial vegetation of central Europe. Location Czech and Slovak Republics (fossil pollen assemblages); Western Sayan Mountains, southern Siberia (modern pollen assemblages). Methods Eighty‐eight modern pollen spectra were sampled in 14 vegetation types of Siberian forest, tundra and steppe, and compared with the last‐glacial pollen spectra from seven central European localities using principal components analysis. Results Both full‐ and late‐glacial pollen spectra from the valleys of the Western Carpathians (altitudes 350–610 m) are similar to modern pollen spectra from southern Siberian taiga, hemiboreal forest and dwarf‐birch tundra. The full‐glacial and early late‐glacial pollen spectra from lowland river valleys in the Bohemian Massif (altitudes 185–190 m) also indicate the presence of patches of hemiboreal forest or taiga. Other late‐glacial pollen spectra from the Bohemian Massif suggest an open landscape with steppe or tundra or a mosaic of both, possibly with small patches of hemiboreal forest. Main conclusions Our results are consistent with the hypothesis that during the full glacial and late glacial, the mountain valleys of the north‐western Carpathians supported taiga or hemiboreal forest dominated by Larix, Pinus cembra, Pinus sylvestris and Picea, along with some steppic or tundra formations. Forests tended to be increasingly open or patchy towards the west (Moravian lowlands), gradually passing into the generally treeless landscape of Bohemia, with possible woodland patches in locally favourable sites.     

Annotated chromosome counts of czechoslovak plants (31–60) (Materials for “Flóra ČSSR”—3)

Chromosome counts of the following 30 taxa (106 populations) are given:Betonica officinalis (2n=16);Bidens frondosus (2n=48);Calamagrostis arundinacea (2n=28+0–2B);Dianthus carthusianorum subsp.latifolius (2n=30);Festuca gigantea (2n=42, 42+2B);Hypericum perforatum (2n=32);Koeleria macrantha (2n=28);Kohlrauschia prolifera (2n=30);Lilium martagon (2n=24+0–2B);Melica ciliata (2n=18);Poa remota (2n=14);Ranunculus polyanthemos (2n=16);R. sardous subsp.sardous (2n=16);Roegneria canina (2n=28+0–1B);Rudbeckia laciniata (2n=76);Scabiosa canescens (2n=16);Serratula tinctoria (2n=22);Seseli elatum subsp.heterophyllum var.beckii (2n=18);S. hippomarathrum (2n=20);Thlaspicaerulescens caerulescens subsp.tatrense (2n=14);Trifolium alpestre (2n=16);T. avense (2n=14);T. medium (2n=79, 80+0–2B, 82);T. rubens (2n=16);Veronica officinalis subsp. alpestris (2n=36);Vincetoxicum hirundinaria (2n=22);Vulpia bromoides (2n=14);Zerna benekenii (2n=28)Z. monoclada (2n=28+0–8B);Z. ramosa (2n=42). Remarks on taxonomy, nomenclature and chorology for some of these taxa are given.     

Protonation and electronic structure of 2,6-dichlorophenolindophenolate during reduction. A theoretical study including explicit solvent

Protonation in the two-electron/two-proton reduction processes of 2,6-dichlorophenolindophenolate (DCIP) is investigated combining density functional theory (DFT) and molecular dynamics (MD) methods. DCIP (anion), DCIP^?– (radical anion), and DCIP^2? (dianion) are considered, including the electronic structure analysis from the prospective of quantum theory of atoms and molecules (QTAIM). It is shown that oxygen on the indophenolate moiety and nitrogen are the first and/or the second proton acceptor sites and their energetic order depends on the total charge of the system. MD simulations of differently charged species interacting with the solvent molecules have been performed for methanol, water, and oxonium cation (H₃O⁺). Methanol and water molecules are found to form only hydrogen bonds with the solute irrespective of its charge. The calculated pK_a values show that the imino group of DCIPH^? is a weaker acid than water. While in the case of DCIP (and DCIP^?–) plus oxonium cation, proton transfer from the solvent to the solute was evidenced for both aforementioned acceptor sites. In addition, MD simulations of bulks containing 15 and 43 molecules of water around the DCIP molecule have been performed, revealing the formation of 2–4 hydrogen bonds.

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Graphical Abstract 2,6-Dichlorophenolindophenolate interacts with solvent molecules (water, oxonium cation and methanol). Hydrogen transfer and electronic structure are studied by DFT and molecular dynamics methods

     

The potential pitfalls of using 1,1-diphenyl-2-picrylhydrazyl to characterize antioxidants in mixed water solvents

Approaching living systems, aqueous solutions are appropriate to characterize antioxidants, whereas the frequently used standard 1,1-diphenyl-2-picrylhydrazyl (DPPH) is insoluble in water. Therefore, mixed water-ethanol solvents were investigated using the electron paramagnetic resonance (EPR) spectroscopy. Two forms of DPPH were identified: at higher ethanol ratios a quintet spectrum characteristic of solutions, and at lower ratios, a singlet spectrum typical for solid DPPH, were found. Mixed solvents with 0-50% (v/v) water reproduced the same antioxidant equivalent points well and the reaction rate between DPPH and the antioxidant may increase considerably with increasing water ratios, as demonstrated using vitamin E as an antioxidant. But at still higher water ratios (70-90% (v/v)) the antioxidant activities dropped, since a part of the DPPH in the aggregated form does not react sufficiently with the antioxidants. Characteristics of the most common antioxidants were determined in ethanol or its 50% (v/v) aqueous solution.     

Correlation of cardio-ankle vascular index, ten-year risk assessment and other atherosclerosis risk factors

The aim of the study was to assess correlation of atherosclerosis severity as determined by two different methods of screening for atherosclerosis: (A) measurement of the cardio-ankle vascular index-CAVI by use of the VaseraVS-1500 vascular screening device, and (B) Framingham scale scoring. 52 subjects (28 male and 24 female) were enrolled in the study. Classification of study subjects into four quartiles based on theoretically calculated 10-year risk according to Framingham scale (medians: 1%, 3%, 4% and 15%) confirmed the risk increase to be associated with a statistically significant increase in CAVI, age and total cholesterol, and a statistically significant decrease in HDL-cholesterol (p < 0.001 all). Spearman correlation coefficients showed a statistically significant correlation of 10-year risk with CAVI (p = 0.0242; r = 0.4494). Study results suggested that simultaneous determination of CAVI and 10-year risk might prove justified. They are not contradictory, the more so, these two parameters showed a significant positive correlation. This test panel yields comprehensible, implying all the possible consequences and highly motivating information that may stimulate the person for lifestyle modification.     

Comparison of the effect of individual saturated and unsaturated fatty acids on cell growth and death induction in the human pancreatic beta-cell line NES2Y

We tested the effects of various types of fatty acids, differing in the degree of saturation and in the cis/trans configuration of the double bond, on the growth and viability of NES2Y cells (a human pancreatic beta-cell line). We found that during a 48-hour incubation period, saturated fatty acids, i.e. palmitic and stearic acids, at a physiologically relevant concentration of 1 mM and higher concentrations induced death of the beta-cells while their counterpart unsaturated fatty acids, i.e. palmitoleic and oleic acids, did not induce cell death at concentrations up to 3 mM. We also found that unsaturated elaidic acid with a trans double bond exerted significant inhibition of growth of the beta-cells at a concentration approximately ten times lower, i.e. 0.1 mM vs. 1 mM, than counterpart oleic acid with a cis double bond. This is the first direct evidence that a trans unsaturated fatty acid is significantly more effective in inhibiting beta-cell growth than a counterpart cis unsaturated fatty acid. Furthermore, we newly demonstrated that beta-cell death induced by saturated fatty acids is related to significant increase of caspase-2 activity (2 to 5-fold increase) but not to caspase-3 activation. The growth-inhibiting effect of saturated fatty acids at concentrations lower than death-inducing concentrations correlates with certain increase of caspase-2 activity.