Non-covalent and coordination interactions in Cu(II) systems with uridine, uridine 5'-monophosphate and triamine or tetramine as biogenic amine analogues in aqueous solutions

Reactions of metallation and non-covalent interactions have been studied in ternary systems of Cu(II) ions with uridine, uridine 5'-monophosphate and diamines or triamines. It has been found that in metal-free systems the reaction centres of the nucleoside with the polyamine are the donor nitrogen atoms N(3) and protonated -NH(x) groups of the amines. In comparison to systems with adenosine or cytidine, the pH range of complex formation is shifted towards higher values. It is a consequence of significantly higher basicity of uridine and in agreement with the ion-ion, ion-dipole interaction model assumed. Formation of molecular complexes of uridine 5'-monophosphate with polyamines at a low pH is the result of activity of the phosphate group which plays the role of a negatively charged reaction site. Non-covalent interactions interfere in processes of bioligand metallation. Centres of weak interactions are simultaneously binding sites of metal ions. In protonated Cu(Urd)(PA)H(x) complexes, coordination has been found to involve the N(3) atom from the nucleoside and two donor nitrogen atoms from the polyamine (PA). In the heteroligand species Cu(Urd)(PA), despite deprotonation of all amine groups, one of these groups is located outside the inner coordination sphere. In complexes with uridine-5'-monophosphate, the phosphate group is active in metallation. Moreover, in certain coordination compounds this group is engaged in non-covalent interactions with PA molecules, despite binding Cu ions, as has been shown on the basis of equilibrium and spectral studies.     

Infection of clover by plant growth promoting Pseudomonas fluorescens strain 267 and Rhizobium leguminosarum bv. trifolii studied by mTn5-gusA

Plant growth promoting Pseudomonas fluorescens strain 267, isolated from soil, produced pseudobactin A, 7-sulfonic acid derivatives of pseudobactin A and several B group vitamins. In coinoculation with Rhizobium leguminosarum bv. trifolii strain 24.1, strain 267 promoted clover growth and enhanced symbiotic nitrogen fixation under controlled conditions. To better understand the beneficial effect of P. fluorescens 267 on clover inoculated with rhizobia, the colonization of clover roots by mTn5-gusA marked bacteria was studied in single and mixed infections under controlled conditions. Histochemical assays combined with light and electron microscopy showed that P. fluorescens 267.4 (i) efficiently colonized clover root surface; (ii) was heterogeneously distributed along the roots without the preference to defined root zone; (iii) formed microcolonies on the surface of clover root epidermis; (iv) penetrated the first layer of the primary root cortex parenchyma and (v) colonized endophytically the inner root tissues of clover.     

Protein phosphorylation/dephosphorylation in the inner membrane of potato tuber mitochondria

Dioxins invade the body mainly through the diet, and produce toxicity through the transformation of aryl hydrocarbon receptor (AhR). An inhibitor of the transformation should therefore protect against the toxicity and ideally be part of the diet. We examined flavonoids ubiquitously expressed in plant foods as one of the best candidates, and found that the subclasses flavones and flavonols suppressed antagonistically the transformation of AhR induced by 1 nM of 2,3,7,8-tetrachlorodibenzo-p-dioxin, without exhibiting agonistic effects that transform AhR. The antagonistic IC(50) values ranged from 0.14 to 10 microM, close to the physiological levels in human.     

Prediction of protein cleavage sites by the barley cysteine endoproteases EP-A and EP-B based on the kinetics of synthetic peptide hydrolysis

Hordeins, the natural substrates of barley (Hordeum vulgare) cysteine endoproteases (EPs), were isolated as protein bodies and degraded by purified EP-B from green barley malt. Cleavage specificity was determined by synthesizing internally quenched, fluorogenic tetrapeptide substrates of the general formula 2-aminobenzoyl-P(2)-P(1)-P(1)'-P(2)' 1-tyrosine(NO(2))-aspartate. The barley EPs preferred neutral amino acids with large aliphatic and nonpolar (leucine, valine, isoleucine, and methionine) or aromatic (phenylalanine, tyrosine, and tryptophan) side chains at P(2), and showed less specificity at P(1), although asparagine, aspartate, valine, and isoleucine were particularly unfavorable. Peptides with proline at P(1) or P(1)' were extremely poor substrates. Cleavage sites with EP-A and EP-B preferred substrate sequences are found in hordeins, their natural substrates. The substrate specificity of EP-B with synthetic peptides was used successfully to predict the cleavage sites in the C-terminal extension of barley beta-amylase. When all of the primary cleavage sites in C hordein, which occur mainly in the N- and C-terminal domains, were removed by site-directed mutagenesis, the resulting protein was degraded 112 times more slowly than wild-type C hordein. We suggest that removal of the C hordein terminal domains is necessary for unfolding of the beta-reverse turn helix of the central repeat domain, which then becomes more susceptible to proteolytic attack by EP-B.     

Gemmules of sponges from a warm lake

1. Two types of gemmules were found, each in a different species of sponge, from the warm monomictic Lake Kinneret: (i) clustered gemmules, sharing the pneumatic layer of the gemmular capsule and resembling gemmules of Eunapius ; (ii) gemmules that develop non-synchronously, containing amphidisc spicules within the gemmular capsule and resembling those of Ephydatia . Algal cells were not detected within either type of gemmule although they exist in the developed sponges.
2. Sponges began producing gemmules in the lake with the onset of lake drawdown and ceased when lake level was minimal. The gemmules hatched when the lake level began to rise.
3. Under experimental conditions gemmules hatched between 13 and 35 °C. Germination was optimal at 20–25 °C. Chilling of young gemmules prior to incubation at 25 °C improved germination rate.
4. The percentage of germinating dry gemmules diminished 4–6 months after their collection from the lake. None germinated after 10 months. Submerged gemmules maintained high viability with ageing (up to 100% germination 18 months after collection). Desiccation influenced gemmule viability over time, by both decreasing the percentage of germinating gemmules and increasing the lag time before onset of germination.
5. Gemmules kept in the dark germinated significantly less than those illuminated for 12 h day     

An enemy of your enemy is your friend: Impact of predators on aggregation behavior of gammarids

Predation pressure may affect many aspects of prey behavior, including forming groups and changes in social interactions. We studied the aggregation behavior of competing gammarids Dikerogammarus villosus and Pontogammarus robustoides (Amphipoda, Crustacea) to check whether they modify their preferences for conspecifics or heterospecifics in response to predator (the racer goby Babka gymnotrachelus) kairomones in the presence or absence of stone shelters (alternative protection source). Both species exhibited preferences toward shelters occupied by conspecifics over empty shelters and conspecifics apart from shelters, suggesting that their aggregation depends not only on habitat heterogeneity, but also on their social interactions. Moreover, gammarids in the presence of shelters (safer conditions) preferred conspecifics over heterospecifics, but predator kairomones made them form aggregations irrespective of species. In the predator presence, P. robustoides increased its aggregation level only in the sheltered conditions, whereas D. villosus exhibited this response only in the absence of shelters, suggesting that this behavior can protect it against predators. Therefore, we tested the antipredator effectiveness of D. villosus aggregations by exposing them to fish predation. Gobies foraged most effectively on immobile single gammarids compared to moving and aggregated individuals. Fish also avoided aggregated prey, confirming the protective character of aggregations. We have demonstrated that the predator presence increases aggregation level of prey gammarids and affects their social behavior by reducing antagonistic interactions and avoidance between competing species. This is likely to affect their distribution and functioning in the wild, where predator pressure is a standard situation.     

New Hydrazides and Hydrazide‐Hydrazones of 2,3‐Dihalogen Substituted Propionic Acids: Synthesis and in vitro Antimicrobial Activity Evaluation

The main aim of this research was the synthesis, spectral identification and in vitro antimicrobial evaluation of new hydrazides and hydrazide‐hydrazones of 2,3‐dihalogen substituted propionic acids. New hydrazides were obtained by the substitution reaction of appropriate ethyl esters of 2,3‐dihalogen substituted propionic acids with hydrazine hydrate. Then obtained hydrazides were subjected to condensation reaction with various aldehydes which yielded with new hydrazide‐hydrazone derivatives. All obtained compounds were identified on the basis of spectral methods (¹H‐NMR, ¹³C‐NMR) and in vitro screened against a panel of bacterial and fungal strains according to EUCAST and CLSI guidelines.     

Polysaccharides and mucin 5AC (MUC5AC) expression in gallbladder mucosa of young patients with gallstones as evaluated by spatial visualization and quantification

The study aimed at examination of tissue expression of polysaccharides and secretory mucin 5AC (MUC5AC) in young patients (up to 25 years of age) with a symptomatic gallstones. For comparison, patients most frequently subjected to cholecystectomy were studied, i.e. patients of approximately 50 years of age with the same diagnosis. In quantitative studies on tissue expression of both mucus components, the modern technique of spatial visualization was applied for the first time. Application of the technique permitted to demonstrate significant positive relationships between expression of glycoproteins (immunocytochemical ABC technique for detection of MUC5AC) and expression of sugar components in mucus (PAS technique) and to confirm suitability of the technique for quantitative appraisal of both histochemical and immunocytochemical reactions. An even higher expression of polysaccharides in the entire mucosa and of MUC5AC was detected in gallbladder epithelium of 50-year-old patients, as compared to young patients with symptomatic gallstones. In the young patients, expression of polysaccharides correlated with inflammatory activity (grading), width of gallbladder wall and PLT level in peripheral blood. A significantly higher expression of polysaccharides in gallbladder epithelium was demonstrated in young patients admitted in the emergency mode to the hospital. These correlations in young patients may suggest a role of both mucus components in pathogenesis of cholelithiasis in this age group. A quantitative appraisal of mucus component expression in the two parts of gallbladder mucosa (epithelium vs. entire mucosa) using spatial visualization technique permitted to more accurately compare production of glycoproteins and of polysaccharides in patients with cholelithiasis and to demonstrate additional correlations of a potential clinical significance.