Synthesis of Silver Nanoparticles and Evaluation of Antimicrobial Activity Using the Aqueous Extract of Pterodon emarginatus Seeds.

The decline in research for new antimicrobials, combined with the rise in bacterial resistance, has become a critical issue that is expected to worsen over time. As an alternative, health sciences have integrated materials engineering to develop new bioactive compounds through the interaction of nanoparticles with plant-derived compounds. These compounds offer advantages such as high bioavailability and low cost, exemplified by , a plant native to the Brazilian Cerrado.

Beta glucosidase from Bacillus polymyxa is activated by glucose-6-phosphate.

Optimization of cellulose enzymatic hydrolysis is crucial for cost effective bioethanol production from lignocellulosic biomass. Enzymes involved in cellulose hydrolysis are often inhibited by their end-products, cellobiose and glucose. Efforts have been made to produce more efficient enzyme variants that are highly tolerant to product accumulation; however, further improvements are still necessary.

A general RNA motif for cellular transfection.

We have developed a selection scheme to generate nucleic acid sequences that recognize and directly internalize into mammalian cells without the aid of conventional delivery methods. To demonstrate the generality of the technology, two independent selections with different starting pools were performed against distinct target cells. Each selection yielded a single highly functional sequence, both of which folded into a common core structure.

Evolved streptavidin mutants reveal key role of loop residue in high-affinity binding.

We have performed a detailed analysis of streptavidin variants with altered specificity towards desthiobiotin. In addition to changes in key residues which widen the ligand binding pocket and accommodate the more structurally flexible desthiobiotin, the data revealed the role of a key, non-active site mutation at the base of the flexible loop (S52G) which slows dissociation of this ligand by approximately sevenfold. Our data suggest that this mutation results in the loss of a stabilizing contact which keeps this loop open and accessible in the absence of ligand.

Kinetic and mechanistic analysis of the Escherichia coli ribD-encoded bifunctional deaminase-reductase involved in riboflavin biosynthesis.

Riboflavin is biosynthesized by most microorganisms and plants, while mammals depend entirely on the absorption of this vitamin from the diet to meet their metabolic needs. Therefore, riboflavin biosynthesis appears to be an attractive target for drug design, since appropriate inhibitors of the pathway would selectively target the microorganism. We have cloned and solubly expressed the bifunctional ribD gene from Escherichia coli, whose three-dimensional structure was recently determined.

Kinetic and structural analysis of bisubstrate inhibition of the Salmonella enterica aminoglycoside 6'-N-acetyltransferase.

Aminoglycosides are antibacterial compounds that act by binding to the A site of the small 30S bacterial ribosomal subunit and inhibiting protein translation. Clinical resistance to aminoglycosides is generally the result of the expression of enzymes that covalently modify the antibiotic, including phosphorylation, adenylylation, and acetylation. Bisubstrate analogs for the aminoglycoside N-acetyltransferases are nanomolar inhibitors of Enterococcus faecium AAC(6')-Ii.

Bisubstrate inhibition: Theory and application to N-acetyltransferases.

Bisubstrate inhibitors represent a potentially powerful group of compounds that have found significant therapeutic utility. Although these compounds have been synthesized and tested against a number of enzymes that catalyze sequential bireactant reactions, the detailed theory for predicting the expected patterns of inhibition against the two substrates for various bireactant kinetic mechanisms has, heretofore, not been presented. We have derived the rate equations for all likely sequential bireactant mechanisms and provide two examples in which bisubstrate inhibitors allow the kinetic mechanism to be determined.

The kinetic mechanism of AAC3-IV aminoglycoside acetyltransferase from Escherichia coli.

The aminoglycoside 3-N-acetyltransferase AAC(3)-IV from Escherichia coli exhibits a very broad aminoglycoside specificity, causing resistance to a large number of aminoglycosides, including the atypical veterinary antibiotic, apramycin. We report here on the characterization of the substrate specificity and kinetic mechanism of the acetyl transfer reaction catalyzed by AAC(3)-IV. The steady-state kinetic parameters revealed a narrow specificity for the acyl-donor and broad range of activity for aminoglycosides.

Functional shikimate dehydrogenase from Mycobacterium tuberculosis H37Rv: purification and characterization.

Tuberculosis (TB) poses a major worldwide public health problem. The increasing prevalence of TB, the emergence of multi-drug-resistant strains of Mycobacterium tuberculosis, the causative agent of TB, and the devastating effect of co-infection with HIV have highlighted the urgent need for the development of new antimycobacterial agents. Analysis of the complete genome sequence of M.

Cloning and expression of functional shikimate dehydrogenase (EC 1.1.1.25) from Mycobacterium tuberculosis H37Rv.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, continues to be one of the deadliest diseases in the world. TB resurged in the late 1980s and now kills more than 2 million people a year. Possible factors underlying the reemergence of TB are the high susceptibility of human immunodeficiency virus-infected persons to the disease, the proliferation of multi-drug-resistant (MDR) strains, patient noncompliance in completing the standard "short-course" therapy, and decline of health care systems.