Exploring physical and chemical properties in new multifunctional indium-, bismuth-, and zinc-based 1D and 2D coordination polymers.

Main group element coordination polymers (MGE-CPs) are important compounds for the development of multifunctional materials. However, there has been a shortage of studies regarding their structural, optical, catalytic, mechanical, and antibacterial properties. This work presents an exhaustive study of a set of crystalline MGE-CPs obtained from bismuth and indium metals and iminodiacetate, 1,2,4,5-benzenetetracarboxylate, and 2,2'-bipyridine as building blocks. An in-depth topological analysis of the networks was carried out. Additionally, nanoindentation studies were performed on two representative low-dimensional compounds in order to find the relationships between their structural features and their intrinsic mechanical properties (hardness and elasticity). The solid-state photoluminescence (SSPL) properties were also studied in terms of excitation, emission, lifetimes values, and CIE chromaticites. Moreover, the heterogeneous catalytic activities of the compounds were evaluated with the cyanosilylation reaction using a set of carbonylic substrates under solvent-free conditions. Finally, the inhibitory effect of the Bi-CPs on the growth of microorganisms such as Escherichia coli, Salmonella enterica serovar Typhimurium, and Pseudomonas aeruginosa, which are associated with relevant infectious diseases, is reported.

Inhibition of peroxidase and catalase activities and modulation of hydrogen peroxide level by inositol phosphoglycan-like compounds.

Inositol phosphoglycan-like compounds are produced by the hydrolysis of the membrane bound glycosyl phosphoinositides. Besides being short term mediators of insulin action, they inhibit peroxidases and catalase, increasing the concentration of cellular hydrogen peroxide. Although high concentrations of hydrogen peroxide are toxic, moderate increases of its basal level are signals for different metabolic pathways. The inhibitor, localized in the cytosol of the cell, acts on peroxidases and catalase of the same tissue (homologous action) and of other tissues or organisms (heterologous action). The inositol phosphoglycan-like compound inhibits peroxidases with different prosthetic groups, i.e. containing iron such as: thyroid peroxidase, lactoperoxidase, horseradish peroxidase, soy bean peroxidase; and containing selenium such as glutathione peroxidase and 2-cys peroxiredoxin with no prosthetic group. Besides peroxidases, the inositol phosphoglycan-like compound inhibits catalase, another heme enzyme. The inhibition kinetics demonstrates a noncompetitive effect. The site of action is not the prosthetic group, given that the inhibitor does not produce any effect on the peak in the Soret region in the presence or absence of hydrogen peroxide. In conclusion, the inositol phosphoglycan-like compound is the general inhibitor of peroxidases and catalase involved in the modulation of hydrogen peroxide level that acts in different metabolic pathways as a signal transducer.

Sublethal effects of ultraviolet A radiation on Enterobacter cloacae.

We report the sublethal effects of ultraviolet A (UVA) on Enterobacter cloacae in comparison with those produced in Escherichia coli. UVA-induced sublethal effects were investigated in either bacterial membrane and at tRNA level. Limited dependence on oxygen concentration for photoinduced inhibition of biochemical membrane functions and low levels of oxidative damage during the irradiation period were found in En. cloacae. On the other hand, ultraviolet spectroscopy and reversed-phase HPLC analysis of hydrolysed tRNA showed that radio induced damage to tRNA is similar in En. cloacae and E. coli. Nevertheless, growth delay induced by UVA in En. cloacae was shorter than that found in E. coli submitted to the same experimental conditions. A limited post-irradiation ppGpp accumulation and the absence of any influence of the membrane damage on the growth delay extent seem to be responsible for the shortness of this effect in En. cloacae. Most of the differences between En. cloacae and E. coli could be attributed to an increased ability of En. cloacae to overcome oxidative stress during UVA exposure.

Oxidative stress and defence mechanisms of the freshwater cladoceran Daphnia longispina exposed to UV radiation.

The aim of the present study is to evaluate the occurrence of oxidative stress in the cladoceran Daphnia longispina exposed to UV-A and UV-B radiation. The activity of antioxidant enzymes and lipid peroxidation markers is investigated and the protective action of ascorbic acid determined. Results show differences in the lethality radioinduced by UV-A and UV-B. Both UV-A and UV-B exposure cause an important increase in malonaldehyde (MDA) concentration and catalase activity. Ascorbic acid addition reduces the MDA concentration, indicating that the oxidative stress caused by either UV-A or UV-B radiation can be controlled by antioxidants. The increase of the antioxidant enzymes may be a response mechanism to oxidative stress.

Pseudomonas aeruginosa UV-A-induced lethal effect: influence of salts, nutritional stress and pyocyanine.

The presence of NaCl in plating media shows an important protection against the Pseudomonas aeruginosa UV-A-induced lethal effect, contrasting with the known sensitizing action of salts on UV-A-irradiated Escherichia coli cells. MgSO4 exhibits a similar protection, but lower concentrations than for NaCl are needed to achieve the same effect. NaCl protection from lethal effects involves an osmotic mechanism, while MgSO4 could act by a different process. On the other hand, when cells grown in a complete medium are then incubated for 20 min in a synthetic medium and irradiated with UV-A, a very marked protection is obtained. This protection is dependent on protein synthesis, since treatment with tetracycline, during the nutritional stress, blocks its induction. These results offer a new example of cross-protection among different stressing agents. In our experimental conditions, natural phenazines of P. aeruginosa are not present in the cells, ruling out the possibility that these pigments act as photosensitizers. Conversely, pyocyanine (the major phenazine produced by this microorganism) prevents the UV-A killing effect in a concentration-dependent way when present in the irradiation media. Finally, UV-A irradiation induces, as in E. coli, the accumulation of guanosine tetraphosphate and guanosine pentaphosphate, although the physiological meaning of this finding has yet to be determined.

Ultraviolet-B lethal damage on Pseudomonas aeruginosa.

Pseudomonas aeruginosa has shown an increased sensitivity compared with that of Escherichia coli and Enterobacter cloacae, when they were exposed to 0.4 kJ/m2 of ultraviolet-B radiation. The rapid decay in cell viability observed in Pseudomonas aeruginosa after the irradiation was influenced by factors such as culture media and the presence of pyocyanine during the irradiation. The radioinduced lethal damage could be prevented by photoreactivating treatment, indicating that pyrimidine dimer formation was the mechanism causing bacterial death. The results indicate that several environmental conditions may act as protective agents against ultraviolet-B-induced damage.

Lethal effect induced in Pseudomonas aeruginosa Exposed to Ultraviolet-A radiation.

Ultraviolet-A (365 nm, 120 kJ/m2/h) exposure caused cell death in Pseudomonas aeruginosa at doses at which Escherichia coli cell viability was not affected. We have not found that UVA induced growth delay or any other sublethal effect. Irradiated suspensions of P. aeruginosa showed a marked reduction in membrane-bound succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) activities. Succinate-driven respiration and several nutrient transport systems were also inhibited. Whereas SDH and LDH activities were independent of the irradiation conditions, cell viability, respiration and transport systems were protected when irradiation was performed in an N2 atmosphere. A similar protective effect was observed when cells were grown in media containing glycerol or when preirradiation bacterial growth was carried out at 30 degrees C (instead of 37 degrees C). Results suggest that UVA induces a differential damaging effect on several biochemical functions of P. aeruginosa. The UVA- induced photodamage may fall into two categories: indirect damage mediated by oxygen (cell killing and inhibition of respiration and transport systems) and direct damage to SDH and LDH (apparently not oxygen dependent). These enzymes and leucine transport appear not to be involved in the lethal effect described herein because they were altered despite viability-preserving conditions

UV-A oxidative damage modified by environmental conditions in Escherichia coli.

The effect of sublethal fluences (50-200 kJ m-2) of UV-A radiation (320-400 nm) in bacterial cells is a transient growth inhibition related to photo-modified tRNA and is associated with changes in membrane structure and function. Higher UV-A fluences result in cell death due to the production of reactive oxygen species, so far undetected at sublethal doses. Oxidative mechanisms of toxicity induced by 120 kJ m-2 UV-A radiation can be recorded by ultra-weak chemiluminescence, useful in quantifying oxidative reactions. When Escherichia coli was exposed to UV-A stress at a fluence rate equivalent to that of the Sun in the biosphere (33 W m-2), chemiluminescence levels were proportional to the photodamage. Chemiluminescence and photo-damage are linearly proportional and dependent on environmental conditions of the cells. It is postulated that in addition to tRNA photo-modification, UV-A alters the membrane structure of E. coli by oxidative damage, since changes in the membrane structure under different environmental conditions play a key role in the cell's response to UV-A injury.

Peptidoglycan hydrolases in an autolytic mutant of Salmonella typhimurium.

Two peptidoglycan hydrolases were isolated from the autolytic mutant Salmonella typhimurium DA361 (envD). One of them, resistant to penicillin, was found free in the supernatant of partially purified envelopes sedimented by ultracentrifugation, and the other bound to the envelopes proved to be sensitive to the antibiotic. Both were able to hydrolyse in vitro high molecular weight non-specific peptidoglycan isolated from E. coli W7 labelled with [14C]diaminopimelic acid. Similar enzymatic activities were separated also from S. typhimurium DA362 (envD+) a non-lytic isogenic pair of the above and from the wild type strain LT-2. All of the hydrolytic activities reported here were strongly inhibited when DNA was added to the assay systems. The peptidoglycan hydrolases isolated from the autolytic mutant suffered a competitive inhibition while those from the non-lytic strains were apparently inhibited in uncompetitive modal relationship. It is postulated that the inhibitory effect may bear affinity with the preservation of DNA sites of attachment to cell membranes sustaining peptidoglycan structure and functions.

Biochemical and phenotypical correction of an envelope mutant of Salmonella typhimurium.

Salmonella typhimurium DA 361 bears an env D1 mutation with the following abnormal phenotypical and biochemical characteristics: a) it autolyses at stationary phase in nutrient broth; b) it grows in chains of short rods; c) it is a poor maltose fermenter and d) it has a diphosphatidylglycerol (DPG) content twice as high than its isogenic non-lytic pair DA 362 (env D+) and LT2, of which both are derivatives. Growth of DA 361 in the presence of 400 mM ethanol leads on a 50% decrease of DPG level, thereby equalling its PG/DPG ratio with those of the control strain. Consequently, a correction on the other phenotypical and biochemical anomalies are induced since the DA 361 strain decreases its autolytic activity, ferments normally maltose and appear as rods undifferentiated from DA 362.

Glycosidases in the rat uterus during the oestrus cycle.

Seven acid glycosidases activities have been measured in normal rat uterus during the oestrus cycle. It has been observed that alpha-fucosidase, alpha-mannosidase, beta-galactosidase, alpha-galactosidase, aryl sulfatase, acid phosphatase and hexosaminidase activities changed cyclically during the oestrus cycle. From onward oestrus to metaoestrus the enzyme activities are in their highest level, but then decline slightly towards the resting one, as the cycle progresses. It is possible that changes in glycosidases content bear a lysosomal relationship, since it is known the increase in the lysosome content of the uterus during the oestrus and metaoestrus. The increased enzyme content could be related to uterus glycoproteins secretion and degradation during the normal oestrus cycle.

Glycosidases from the rat uterus.

Six glycosidase activities were detected in homogenates of the rat uterus by using the p-Nitrophenyl-glycoside as substrate. The enzyme activities were separated by Sephadex G-200 column chromatography. The uterus contained alpha-galactosidase, beta-galactosidase and N-acetylglucosaminidase activity which had a similar pH optima of 4.4, whereas the pH optimum for beta-fucosidase was found to be of 4.4 - 4.6. The alpha-mannosidase activity showed two peaks of maximal activity at pH 5.0 and pH 6.0. The uterus contained two forms of the alpha-L-fucosidase activity separable by Sephadex G-200 which had a pH optima of 4.4 - 4.6 (form I) and pH 5.0 (form II). The glycosidases differed in heat stability, Km values and other several characteristics, which suggests that each enzyme apparently did not show any cross-contamination.

Glycosidases in the rat uterus during the oestrus cycle.

Seven acid glycosidases activities have been measured in normal rat uterus during the oestrus cycle. It has been observed that alpha-fucosidase, alpha-mannosidase, beta-galactosidase, alpha-galactosidase, aryl sulfatase, acid phosphatase and hexosaminidase activities changed cyclically during the oestrus cycle. From onward oestrus to metaoestrus the enzyme activities are in their highest level, but then decline slightly towards the resting one, as the cycle progresses. It is possible that changes in glycosidases content bear a lysosomal relationship, since it is known the increase in the lysosome content of the uterus during the oestrus and metaoestrus. The increased enzyme content could be related to uterus glycoproteins secretion and degradation during the normal oestrus cycle.

Glycosidases from the rat uterus.

Six glycosidase activities were detected in homogenates of the rat uterus by using the p-Nitrophenyl-glycoside as substrate. The enzyme activities were separated by Sephadex G-200 column chromatography. The uterus contained alpha-galactosidase, beta-galactosidase and N-acetylglucosaminidase activity which had a similar pH optima of 4.4, whereas the pH optimum for beta-fucosidase was found to be of 4.4 - 4.6. The alpha-mannosidase activity showed two peaks of maximal activity at pH 5.0 and pH 6.0. The uterus contained two forms of the alpha-L-fucosidase activity separable by Sephadex G-200 which had a pH optima of 4.4 - 4.6 (form I) and pH 5.0 (form II). The glycosidases differed in heat stability, Km values and other several characteristics, which suggests that each enzyme apparently did not show any cross-contamination.

Carbohydrate utilization by the avian oviduct during the laying cycle.

In the present work the carbohydrate utilization by the avian oviduct during the egg formation was studied. The pattern obtained for total hexose, fucose, hexosamines, sialic acid, fructose and sulphate demonstrated that in the domestic fowl's oviduct the isthmus and the shell gland secrete the precursors for the protein carbohydrate substance of the mammillae and shell matrix and may contribute during the shell formation with the substrates necessary for the metabolic energy of the organ. The infundibulum only participates as a donor for the metabolic energy.