A passive auxiliary circuit with interphase transformer applied in 12-pulse converters to provide clean power utility interface
- Authors: Shih, Der-Chun , Young, Chung-Ming , Whiteley, Chris G
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67095 , vital:29031 , https://doi.org/10.1080/02533839.2016.1230029
- Description: publisher version , This paper proposes a passive auxiliary circuit which can be added to an interphase transformer (PAC + IPT) configuration to reduce the total harmonic distortion (THD) existing in 12-pulse diode rectifier converter systems at AC mains. The proposed PAC + IPT compensation method is a simple structure, with low power consumption and requires no extra DC power supply. We present the theoretical analysis of the proposed topology that lessens the total harmonic distortion (THD) and evaluate the dynamic simulation results on a 12-pulse converter system and a 3-kW laboratory prototype. Both the simulation and the experimental results show that the proposed PAC + IPT compensation method can improve the power quality and provide a clean power utility interface of AC line input currents for a conventional 12-pulse diode rectifier converter.
- Full Text: false
- Date Issued: 2016
Alzheimer’s disease: making sense of the stress
- Authors: Whiteley, Chris G
- Date: 2016
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/67072 , vital:29029 , http://www.smgebooks.com/alzheimers-disease/chapters/ALZD-16-08.pdf
- Description: publisher version , To facilitate a deep understanding of the mechanisms involved in neurodegeneration and Alzheimer’s disease fundamental knowledge is required about the action and function of enzymes in the brain that not only metabolise arginine (neuronal nitric oxide synthase) but are closely associated with oxidative (superoxide dismutase; catalase; glutathione peroxidase) and/or nitrosative stress. In particular the focus extends towards enzymes that contribute to amyloid peptide aggregation and senile plaquedeposits (fibrillogenesis). Of special importance are the glycine zipper regions within these amyloid peptides, especially Aβ25-29 and Aβ29-33 (that contains two isoleucine residues) and the pentapeptide Aβ17-21 (that contains two phenylalanines), each generated by enzymatic cleavage of the intramembrane amyloid precursor protein. Use of antisense-sense technology has identified regions in each enzyme that are capable of binding with the amyloid peptides. After an initial inhibition of each enzyme there is an oligomerisation into soluble fibrils which accumulate and eventually precipitate. The use of nanoparticles do not just prevent but reverse the formation of these fibrils either by disrupting the binary adduct – enzyme-Aβ-peptide- or by reaction with, and therefore deplete, Aβ-monomers in solution and so block potential aggregation sites on the enzyme itself. Future therapy towards Alzheimer’s disease should target the C-terminal region of the amyloid precursor protein and substitute hydrophobic residues for the glycine amino acids within the glycine zipper region.
- Full Text:
- Date Issued: 2016
Computer simulations of the interaction of human immunodeficiency virus (HIV) aspartic protease with spherical gold nanoparticles: implications in acquired immunodeficiency syndrome (AIDS)
- Authors: Whiteley, Chris G , Lee, Duu-Jong
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67083 , vital:29030 , https://doi.org/10.1088/0957-4484/27/36/365101
- Description: publisher version , 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. Normalisation of the data narrows the selection from the initial 36 to one 'final' probable structure. It is concluded that, after computer simulations on each of the 36 initial complexes incorporating the 12 different biophysical techniques, the top five complexes are the same no matter which technique is explored. The significance of the present work is an expansion of an earlier study on the molecular dynamic simulation for the interaction of HIVPR with silver nanoparticles. This work is supported by experimental evidence since the initial 'orientation' of the AgNP with the enzyme is the same as the 'final' AuNP-HIVPR complex generated in the present study. The findings will provide insight into the forces of the binding of the HIVPR to AuNP. It is anticipated that the protocol developed in this study will act as a standard process for the interaction of any nanoparticle with any biomedical target.
- Full Text: false
- Date Issued: 2016
Docking of HIV protease to silver nanoparticles
- Authors: Whiteley, Chris G , Shing, C-Y , Kuo, C-C , Lee, Duu-Jong
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67105 , vital:29032 , https://doi.org/10.1016/j.jtice.2015.10.029
- Description: publisher version , This interaction of silver nanoparticles (AgNP) with human immune-deficiency virus aspartic protease (HIVPR) is examined by molecular dynamics simulation using the Colores (Situs) package and biophysical techniques using UV–vis spectroscopy, dynamic light scattering, transmission electron microscopy and circular dichroism. The ‘docking’ of AgNP with HIVPR creates a complex [AgNP–HIVPR] to initiate a hypochromic time-dependent red-shift for the surface plasmon resonance maximum. MD simulations reflect large perturbations to enzyme conformations by fluctuations of both rmsd and B-factors. Increase in changes to electrostatic potentials within the enzyme, especially, with chain B, suggest hydrophobic interactions for the binding of the AgNP. This is supported by changes to mainchain and sidechain dihedrals for many hydrophobic amino acid including Cys95, Trp6 and Trp42. Circular dichroism spectra reveal disappearance of α-helices and β-sheets and increase in random coil first from chain B then chain A. During initial stages of the interactive simulation the enzyme is conformational flexible to accommodate the AgNP, that docks with the enzyme under a cooperative mechanism, until a more stable structure is formed at convergence. There is a decrease in size of the HIVPR–AgNP complex measured by changes to the gyration radius supporting evidence that the AgNP associates, initially, with chain B.
- Full Text: false
- Date Issued: 2016
Cleaning fouled membranes using sludge enzymes
- Authors: Melamane, Xolisa L , Pletschke, Brett I , Leukes, Winston D , Whiteley, Chris G
- Date: 2003
- Language: English
- Type: text
- Identifier: vital:6480 , http://hdl.handle.net/10962/d1006242
- Description: Maintenance of membrane performance requires inevitable cleaning or "defouling" of fouled membranes. Membrane cleaning using sludge enzymes, was investigated by first characterising ostrich abattoir effluent for potential foulants, such as lipids, proteins and polysaccharides. Static fouling of polysulphone membranes using abattoir effluent was also performed. Biochemical analysis was performed using quantitative and qualitative methods for detection of proteins on fouled and defouled membranes. The ability of sulphidogenic proteases to remove proteins adsorbed on polysulphone membranes and capillary ultrafiltration membranes after static fouling, and ability to restore permeate fluxes and transmembrane pressure after dynamic fouling was also investigated. Permeate volumes were analysed for protein and amino acids concentrations. The abattoir effluent contained 553 μg/ml of lipid, 301 μg/ml of protein, 141 μg/ml of total carbohydrate, and 0.63 μg/ml of total reducing sugars. Static fouled membranes removed 23.4percent of proteins. Defouling of dynamically fouled capillary ultrafiltration membranes using sulphidogenic proteases was successful at pH 10, 37°C, within 1 h. Sulphidogenic protease activity was 2.1 U/ml and Flux Recovery (FR percent) was 64 percent.
- Full Text:
- Date Issued: 2003
Accelerated sludge solubilisation under sulphate reducing conditions: the effect of hydrolytic enzymes on sludge floc size distribution and EPS composition
- Authors: Akhurst, P , Rose, Peter D , Whiteley, Chris G , Pletschke, Brett I
- Date: 2002
- Language: English
- Type: Conference paper
- Identifier: vital:6455 , http://hdl.handle.net/10962/d1010430
- Description: Extracellular polymeric substances (EPS) are the construction materials for microbial aggregates such as biofilms, flocs and sludge, and greatly contribute to the structural integrity of sludge flocs in wastewater treatment processes. The loss of integrity of the sewage sludge floc is believed to be due to enhanced hydrolysis of important structural components such as lignin, protein and cellulose in the sludge floc matrix. The mechanism of enhanced sludge floc fracture, due to the action of enzymes hydrolysing these structural components, remains a key element in our understanding of how the floc integrity in systems utilising a sulphate reducing system is compromised. A range of relatively non-specific exogenous enzymes (ß-glucosidase, cellulase, proteases: trypsin, pronase E and chymotrypsin) were added to a sulphidogenic bioreactor- (containing both sulphate reducing bacteria (SRB) and a methanogenic bacterial system) and a (control) methanogenic bioreactor sample, and the effect of these enzymes on sludge floc size (diameter) distribution and EPS composition was investigated. Sludge samples from the bioreactors were examined under bright field and differential interference contrast light microscopy. Proteolytic and glucohydrolytic activity of the enzymes were monitored using standard enzyme assaying techniques, and Bradford, Somogyi-Nelson, and total carbohydrate assays were performed to establish the composition of the EPS (after extraction with 3% (v/v) glutaraldehyde and Sephacryl S-400 size exclusion chromatography). Sludge flocs present in the sulphidogenic environment of the sulphidogenic bioreactor were found to have smaller diameters than their counterparts present in the methanogenic bioreactor. The addition of hydrolytic (i.e. proteolytic and glycohydrolytic) enzymes resulted in an increased rate of matrix hydrolysis, leading to increased rates of floc fracture and deflocculation. The presence of ß-glucosidase, cellulase, and proteases naturally residing within the sludge floc was confirmed. We propose that the addition of commercially available enzymes may be prohibitively costly on a large scale, and that the activity of the enzymes naturally residing within the floc matrix be optimised or enhanced. As the bulk of the EPS was shown to be composed of mainly polysaccharides, we propose that by increasing the activity of the naturally occurring ß-glucosidases residing within the floc matrix, the process of deflocculation may be enhanced. As sulphide has been shown to increase the activity of this very important key enzyme, we propose that this is one of the contributing factors why sludge solubilisation is accelerated under sulphate reducing conditions.
- Full Text:
- Date Issued: 2002