Computer simulations of the interaction of human immunodeficiency virus (HIV) aspartic protease with spherical gold nanoparticles: implications in acquired immunodeficiency syndrome (AIDS).

The interaction of gold nanoparticles (AuNP) with human immune-deficiency virus aspartic protease (HIVPR) is modelled using a regime of molecular dynamics simulations. The simulations of the 'docking', first as a rigid-body complex, and eventually through flexible-fit analysis, creates 36 different complexes from four initial orientations of the nanoparticle strategically positioned around the surface of the enzyme. The structural deviations of the enzymes from the initial x-ray crystal structure during each docking simulation are assessed by comparative analysis of secondary structural elements, root mean square deviations, B-factors, interactive bonding energies, dihedral angles, radius of gyration (R g), circular dichroism (CD), volume occupied by C α , electrostatic potentials, solvation energies and hydrophobicities.

Bacterial diguanylate cyclases: structure, function and mechanism in exopolysaccharide biofilm development.

The ubiquitous bacterial cyclic di-guanosine monophosphate (c-di-GMP) emerges as an important messenger for the control of many bacterial cellular functions including virulence, motility, bioluminescence, cellulose biosynthesis, adhesion, secretion, community behaviour, biofilm formation and cell differentiation. The synthesis of this cyclic nucleotide arises from external stimuli on various signalling domains within the N-terminal region of a dimeric diguanylate cyclase. This initiates the condensation of two molecules of guanosine triphosphate juxtaposed to each other within the C-terminal region of the enzyme.

Arginine metabolising enzymes as targets against Alzheimers' disease.

Even though the accumulation of arginine and the deposit of aggregated Aβ-peptides (senile plaques) in the brain of an Alzheimer patient are classic points of evidence in the neuropathology of the disease considerable dispute remains on their method of formation. One acceptable mechanism to initiate events is a 'seed' aggregation of free monomeric peptides into toxic soluble amyloid oligomers and subsequently into deposits of insoluble fibrils. Since all of these events take place in the brain astrocytes it suggests an interference between arginine-metabolising enzymes and the Aβ-peptides.

Interaction of nanoparticles with arginine kinase from Trypanosoma brucei: kinetic and mechanistic evaluation.

Arginine kinase is not only absent from mammalian hosts but is critical to the survival of trypanosomes under stressful conditions and consequently its inhibition may lead to an effective treatment for trypanosomiasis. The His-tagged enzyme was cloned from Trypanosoma brucei genomic DNA, expressed in Escherichia coli BL21 DE3 cells and purified on a Ni-affinity column and by FPLC on a Superdex 200 HR. The enzyme had a specific activity of 2.

Multiple fold increase in activity of ferroxidase-apoferritin complex by silver and gold nanoparticles.

Unlabelled: The effect of silver (Ag) and gold (Au) nanoparticles on the ferroxidase activity of apoferritin showed a 110-fold increase in specific activity and a 9-fold increase over the control at the respective molar ratios of Au-apoferritin and Ag-apoferritin nanoparticles (NPs) of 500:1 and 1000:1. Typical color change, from pale yellow to brown, occurred when apoferritin was mixed with AgNO(3) or AuCl(3) followed by sodium borohydride to afford respective metal-apoferritin NP complexes in a ratio of between 250:1 and 4000:1. These complexes were characterized by ultraviolet-visible inductively coupled plasma-optical emission spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and energy-dispersive x-ray spectroscopy.

Ferroxidase activity of apoferritin is increased in the presence of platinum nanoparticles.

The ferroxidase activity of horse spleen apoferritin (HSAF) is increased by nine-fold in the presence of platinum nanoparticles. HSAF was mixed with varying concentrations of K2PtCl4 followed by a 20-fold concentration of sodium borohydride to afford Pt:HSAF nanoparticle complexes in a ratio of between 1:250 and 1:4000. Typical colour changes, from colourless or pale yellow to brown, occurred that were dependent on the amount of platinum present.

Spectrofluorimetric analysis of the interaction of amyloid peptides with neuronal nitric oxide synthase: implications in Alzheimer's disease.

Background: The deposition of aggregated β-amyloid peptide senile plaques and the accumulation of arginine within the astrocytes in the brain of an Alzheimer's patient are classic observations in the neuropathology of the disease. It would be logical, in the aetiology and pathogenesis, to investigate arginine-metabolising enzymes and their intimate association with amyloid peptides.

Methods: Neuronal nitric oxide synthase (nNOS) was isolated, purified and shown, through fluorescence quenching spectroscopy and fluorescence resonance energy transfer (FRET), to interact with structural fragments of Aβ(1-40) and be catalytic towards amyloid fibril formation.

Association of β-amyloid peptide fragments with neuronal nitric oxide synthase: Implications in the etiology of Alzheimers disease.

Neuronal nitric oxide synthase (nNOS) was purified on DEAE-Sepharose anion-exchange in a 38% yield, with 3-fold recovery and specific activity of 5 µmol.min(-1).mg(-1).

Advances in aerobic granule formation and granule stability in the course of storage and reactor operation.

Aerobic granulation is drawing increasing global interest in a quest for an efficient and innovative technology in wastewater treatment. Developed less than two decades ago, extensive research work on aerobic granulation has been reported. The instability of the granule, which is one of the main problems that hinder practical application of aerobic granulation technology, is still to be resolved.

Arginine metabolising enzymes as therapeutic tools for Alzheimer's disease: peptidyl arginine deiminase catalyses fibrillogenesis of beta-amyloid peptides.

The accumulation of arginine in the cerebrospinal fluid and brains of patients suffering from acute neurodegenerative diseases like Alzheimer's disease, point to defects in the metabolic pathways involving this amino acids. The deposits of neurofibrillary tangles and senile plaques perhaps as a consequence of fibrillogenesis of beta-amyloid peptides has also been shown to be a hallmark in the aetiology of certain neurodegenerative diseases. Peptidylarginine deiminase (PAD II) is an enzyme that uses arginine as a substrate and we now show that PAD II not only binds with the peptides Abeta(1-40), Abeta(22-35), Abeta(17-28), Abeta(25-35) and Abeta(32-35) but assists in the proteolytic degradation of these peptides with the concomitant formation of insoluble fibrils.

Stereological assessment of extracellular polymeric substances, exo-enzymes, and specific bacterial strains in bioaggregates using fluorescence experiments.

This review addresses the introduction of fluorescent molecular tags into exo-enzymes and extra polymeric substances of bioaggregates and the use of confocal laser scanning microscopy (CLSM) to map their role, purpose and quantitative description of the biological processes they undertake. Multiple color staining coupled with CLSM and fluorescent in situ hybridisation (FISH) and flow cytometry have identified the individual polymeric substances, whether they are proteins, lipids, polysaccharides, nucleic acids or antibodies, as well as the microorganisms in the bioaggregate. Procedures are presented for simultaneous multicolor staining with seven different fluorochromes - SYTOX Blue for nucleic acids; Nile red for lipids; Calcofluor white [CW] for beta-polysaccharides; concanavalin A [Con A] for alpha-poly-saccharides; fluorescein-isothiocyanate [FITC] for proteins; SYTO 63 for live microbial cells and Calcium Green for monitoring calcium levels in the microbial cells.

Bioreduction of platinum salts into nanoparticles: a mechanistic perspective.

A mechanism for the bioreduction of H2PtCl6 and PtCl2 into platinum nanoparticles by a hydrogenase enzyme from Fusarium oxysporum is proposed. Octahedral H2PtCl6 is too large to fit into the active region of the enzyme and, under conditions optimum for nanoparticle formation (pH 9, 65 degrees C), undergoes a two-electron reduction to PtCl2 on the molecular surface of the enzyme. This smaller molecule is transported through hydrophobic channels within the enzyme to the active region where, under conditions optimal for hydrogenase activity (pH 7.

Arginine deiminases: therapeutic tools in the etiology and pathogenesis of Alzheimer's disease.

There is, at present, no definitive pre-mortem diagnostic tool for Alzheimer's disease, (AD) which relates to a poor understanding of its etiology. Brains of AD patients contain large amounts of the toxic plaque-forming beta-amyloid1-42 fragment in addition to elevated concentrations of the amino acid L-arginine. This work proposes that lowering levels of arginine in the astrocytes surrounding amyloid plaques may serve as a therapeutic tool in this neurodegenerative disorder.

Recovery of rhodium(III) from solutions and industrial wastewaters by a sulfate-reducing bacteria consortium.

A quantitative analysis of the rate of removal of rhodium(III) by a resting sulfate-reducing bacteria (SRB) consortium under different initial rhodium and biomass concentrations, pH, temperature, and electron donor was studied. Rhodium speciation was found to be the main factor controlling the rate of its removal from solution. SRB cells were found to have a higher affinity for anionic rhodium species, as compared to both cationic and neutral species, which become abundant when speciation equilibrium was reached.

Acetamidoquinone and acetamidohydroxy derivatives as inhibitors for both dihydroxyacetamido epoxidase and dehydrogenase.

A series of monohydroxy and dihydroxyacetanilides, acetamidoquinones and bromoacetamidoquinones have been synthesised and tested as substrates and/or inhibitors of highly purified dihydroxyacetamido epoxidase (DHAE) and dihydroxy acetamido dehydrogenase (DHADH) from Streptomyces LL-C10337. None was found to act as substrates but many selectively inhibit the enzymes. Kinetic analysis has shown that all the compounds act as reversible competitive inhibitors with respect to the substrates 2,5-dihydroxyacetanilide and 2,3-epoxy-1,4-benzoquinone-5-acetanilide.