Use of a halogenase of hormaomycin biosynthesis for formation of new clorobiocin analogues with 5-chloropyrrole moieties

The depsipeptide antibiotic hormaomycin, which is produced by Streptomyces griseoflavus W-384, contains a 5-chloropyrrole moiety. In the producer strain we identified the gene hrmQ that shows sequence similarity to FADH(2)-dependent halogenases. This gene was cloned and heterologously expressed in Streptomyces roseochromogenes var. oscitans DS12.976, which is the producer of the aminocoumarin antibiotic clorobiocin, which contains a 5-methylpyrrole moiety. For the present experiment, we used a mutant of this strain in which the respective pyrrole-5-methyltransferase had been inactivated. Expression of the halogenase hrmQ in this mutant strain led to the formation of two new clorobiocin derivatives that carried a 5-chloropyrrole moiety. These compounds were isolated on a preparative scale, their structures were elucidated by (1)H NMR spectroscopy and mass spectrometry, and their antibacterial activity was determined. The substrate of HrmQ is likely to be a pyrrole-2-carboxyl-S-[acyl carrier protein] thioester. If this assumption is true, this study presents the first experiment in combinatorial biosynthesis that uses a halogenase that acts on an acyl carrier protein-bound substrate.     

Gold-catalyzed oxide nanopatterns for the directed assembly of Ge island arrays on Si

The heteroepitaxial growth of Ge on Au-patterned Si(001) is investigated using in situ spectromicroscopy. Patterning of a hydrogen-terminated Si surface with a square array of Au dots followed by brief exposure to air leads to the spontaneous, local oxidation of Si. The resulting oxide nanopattern limits the surface migration of Au during annealing up to 600 degrees C, resulting in complete preservation of the Au pattern. Subsequent deposition of Ge induces a redistribution of Au across the surface even as the oxide nanopattern persists. As a result, the oxide pattern drives the growth of Ge islands into an ordered assembly, while Au decorates the surfaces of the Ge islands and modifies their shape.     

Laser-assisted fabrication of biomolecular sensing microarrays

With the aim of obtaining high density biosensing arrays we use pulsed laser deposition to immobilize functional biomolecules on useful surfaces, and micro- and nanopatterning techniques for fabrication of prototype immunosensing bioarrays. We report biological activity tests demonstrating the functional properties of the immobilized proteins and atomic force microscopy characterization of films of nanometric dimensions. Laser-fabricated immunofluorescent arrays are analyzed to check that the intensity and contrast of the sensing sites allow efficient device fabrication. We have also developed an elementary array of heterogeneous reaction sites and tested its performance by simultaneous incubation with the different specific antigens.     

On warm conceptual change: The interplay of text, epistemological beliefs, and topic interest.

The aim of this study was to go further than considering only cognitive factors to extend the understanding of the complex, dynamic underlying knowledge revision processes. Fifth graders were assigned to 2 reading conditions. Participants in 1 condition read a refutational text about light, whereas participants in the other read a traditional text. Within each reading condition, students had more or less advanced beliefs about scientific knowledge (complex and evolving vs. simple and certain), as well as high or low topic interest. Overall findings from pretest to immediate and delayed posttests showed that knowledge revision was affected by several interactions among the variables examined. Students who attained the highest scores at both the immediate and delayed posttests were those who had read the refutational text and had high topic interest, as well as more advanced beliefs about scientific knowledge. In particular, the refutational text was more powerful in prompting a restructuring of alternative conceptions about 2 of the 3 light phenomena examined. In addition, students preferred the innovative text to the traditional textbook text. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Natural antioxidant polyphenols on inflammation management: Anti-glycation activity vs metalloproteinases inhibition

The diet polyphenols are a secondary metabolites of plants able to act on inflammation process. Their anti-inflammatory activity is articulated through several mechanisms that are related to their antioxidative and radical scavengers properties. Our work is focused on a novel approach to inflammatory disease management, based on anti-glycative and matrix metalloproteinases (MMPs) inhibition effects, as a connected phenomena. To better understand these correlation, polyphenols Structure–Activity Relationship (SAR) studies were also reported. The antioxidant polyphenols inhibit the AGEs at different levels of the glycation process in the following ways: (1) prevention of Amadori adduct oxidation; (2) trapping reactive dycarbonyl compounds; (3) attenuation of receptor for AGEs (RAGE) expression. Moreover, several flavonoids with radical scavenging property showed also MMPs inhibition interact directly with MMPs or indirectly via radical scavengers and AGEs reduction. The essential polyphenols features involved in these mechanisms are C2-C3 double bond and number and position of hydroxyl, glycosyl and O-methyl groups. These factors induce a change in molecular planarity interfering with the hydrogen bond formation, electron delocalization and metal ion chelation. In particular, C2-C3 double bond improve the antioxidant and MMPs inhibition, while the hydroxylation, glycosylation and methylation induce a positive and negative correlation, respectively.     

Antimicrobial resistance in food and clinical Aeromonas isolates

This study highlights the incidence of resistance and the presence of plasmids in human and food isolates of Aeromonas in Brazil. A total of 83 Aeromonas spp. strains (28 isolated from human and 55 from fresh lettuce) were studied. Thirty-five were identified as A. hydrophila complex and 48 as A. caviae complex. All strains were shown to be susceptible to imipenem, amikacin, gentamicin, tobramycin and ciprofloxacin by the disk diffusion method. Resistance to antimicrobial agents was observed in strains of both food and clinical origin. The food strains were resistant to ampicillin/sulbactam, cefoxitin and tetracycline, while the clinical strains presented resistance to ampicillin/sulbactam, cefotaxime, ceftazidime, cefoxitin, sulfamethoxazole/trimethoprim, chloramphenicol and tetracycline. The minimal inhibitory concentrations of chloramphenicol, tetracycline and sulfamethoxazole/trimethoprim were tested by agar dilution. Thirteen strains isolated from vegetables were resistant to tetracycline (MIC 16 microg ml-1). Two A. hydrophila strains and one A. caviae strain presented extracromosomal DNA (3 and 15 kb plasmids, respectively). The tetracycline resistance phenotype determinant was related to the 15 kb plasmid according to cure and transformation experiments.     

S100B Protein concentration in milk-formulas for preterm and term infants. Correlation with industrial preparation procedures

Human milk S100B protein possesses important neurotrophic properties. However, in some conditions human milk is substituted by milk formulas. The aims of the present study were: to assess S100B concentrations in milk formulas, to verify any differences in S100B levels between preterm and term infant formulas and to evaluate the impact of industrial preparation at predetermined phases on S100B content. Two different set of samples were tested: (i) commercial preterm (n = 36) and term (n = 36) infant milk formulas; ii) milk preterm (n = 10) and term infant (n = 10) formulas sampled at the following predetermined industrial preparation time points: skimmed cow milk (Time 0); after protein sources supplementation (Time 1); after pasteurization (Time 2); after spray-drying (Time 3). Our results showed that S100B concentration in preterm formulas were higher than in term ones (p < 0.01). In addition, S100B concentrations during industrial preparation showed a significant increase (p < 0.001) at Time 1 followed by a slight decrease (p > 0.05) at Time 2, whereas a significant (p < 0.001) dip was observed at Time 3. In conclusion, S100B showed a sufficient thermostability to resist pasteurization but not spry-drying. New feeding strategies in preterm and term infants are therefore warranted in order to preserve S100B protein during industrial preparation.     

Effects of α-tocopherol and citric acid on the oxidative stability of alimentary poultry fats during storage at low temperatures

The purpose of this study was to investigate the stability of three alimentary poultry fats (goose, duck, and chicken) by natural antioxidants (α-tocopherol and citric acid). This was targeted to extend their shelf life, and to monitor the quality parameters during refrigerated (+4°C) and frozen storage (–20°C). The addition of natural antioxidants in a proportion of 0.1% has extended the shelf life of goose fat stored at +4°C by 90 days; for goose fat stored at –20°C citric acid has prolonged the shelf life by 150 days, while goose fat with α-tocopherol could be stored for more than 480?days at –20°C without spoilage. Polyunsaturated fatty acids and monounsaturated fatty acids content decreased significantly (p < 0.05) after 480 days of chilled storage for fat samples with α-tocopherol. The natural antioxidants provided good protection against oxidation of poultry fats, and these can be used to monitor the oxidation of fats and to predict their shelf life stability.