Acetylation of Replication Protein A (RPA) Improves its DNA Binding Property

poster abstractGenome maintenance is critical for cellular survival and growth. Replication Protein A (RPA), a single-strand DNA (ssDNA) binding protein, is vital for various aspects of genome maintenance such as replication, recombination, repair and checkpoint activation. RPA binding to ssDNA protects it from degradation by cellular nucleases, prevents secondary structure formation and from illegitimate recombination. Within the cell, RPA is subject to many post-translational modifications including phosphorylation, SUMOylation and ribosylation. These modifications regulate the activity of RPA with DNA and other binding partners. RPA has been reported to be also modified by acetylation. We found that human RPA (hRPA) can be in vitro acetylated by p300, an acetyl transferase (AT). To study the effect of this modification on its ssDNA binding function, we made use of electro-mobility gel shift assay (EMSA) and bio-layer interferometry (BLI) technology. Using various length oligos, we tested the binding property of unmodified and acetylated RPA. Our results showed that acetylation of RPA increased its binding affinity compared to unmodified RPA. Interestingly, the acetylated form was also able to bind more stably to shorter length oligos compared to the unmodified form. This suggests that the acetylation of RPA improves its ssDNA binding function. This alteration in its enzymatic activity would have significant implications in maintenance of genome fidelity since improved DNA binding function of RPA will protect the genome from both endogenous and exogenous stresses. Additionally, using mass spectrometry analysis we have identified the lysine residues that get modified by the acetyl group both in vitro and in vivo. We are currently studying the factors that trigger this post-translational modification in the cell

Quality of work life, work motivation, job satisfaction and ethical behaviour

Ethical behaviour ensures employees follow organisational social norms in the conduct of their tasks and assignments. But studies have been somewhat silent on the individual-level factors influencing this positive work behaviour, especially in an African public sector context. Further, the contextual factors impacting ethical behaviour at work are yet to be fully known. Therefore, the study examined the relationship between quality of work life and work motivation on ethical behaviour given job satisfaction as a contextual factor. The study collected data from 191 mid-level employees in the Delta State Ministry of Health in Nigeria, and subjected same data to the PLS-SEM analytical procedure. The results demonstrated that job satisfaction and ethical behaviour are positively related, job satisfaction mediates quality of work life and work motivation relationship with ethical behaviour, and quality of work life relationship with ethical behaviour is mediated by work motivation and job satisfaction sequentially. The study concluded that the link between quality of work life and work motivation on ethical behaviour can be explained by the mediational mechanism of job satisfaction. The results imply that public organisations can support ethical behaviour when certain individual-level (psychological) factors are well positioned and managed to achieve desirable outcomes

PERCEIVED ORGANISATIONAL SUPPORT AND ORGANISATIONAL TRUST LINK TO INNOVATIVE WORK BEHAVIOUR BY THE MEDIATION OF TACIT KNOWLEDGE SHARING

The aim of this study is to determine how perceived organisational support and organisational trust affect innovative work behaviour through the mediation mechanism of tacit knowledge sharing in a public organisation context in Nigeria. Using the cross-sectional research design, data were randomly collected from 258 employees from the Delta State Ministry of Health, which was subjected to the partial least square (PLS) analytical procedure for hypothesis testing. The PLS analysis results suggested that while tacit knowledge sharing mediates perceived organisational support and organisational trust link to innovative work behaviour, it also mediates perceived organisational support link to innovative work behaviour sequentially with organisational trust as an antecedent. The study concluded that perceived organisational support and organisational trust prediction of innovative work behaviour can be explained by tacit knowledge sharing. The study puts forward important practical implications for organisations/management to follow in effectuating the linkages among the constructs in a meaningful and coherent manner

THE EFFECT OF TACIT KNOWLEDGE SHARING ON KNOWLEDGE QUALITY TO IMPROVE EMPLOYEE EFFECTIVENESS IN A PUBLIC SERVICE ORGANIZATION

This study aimed to examine how tacit knowledge sharing directly and indirectly affects employee effectiveness in a public sector organization, focusing on the role of knowledge quality as a mediating factor. Empirical studies on the outcomes of tacit knowledge sharing remain limited, especially in a public sector organizational context. This cross-sectional study involved obtaining data from 145 healthcare professionals working in the Delta State Ministry of Health in Nigeria and subjecting this data to analysis using the partial least square method. The study found that tacit knowledge sharing and knowledge quality effects on employee effectiveness were positive and significant. Furthermore, knowledge quality mediated the significant and positive effect of tacit knowledge sharing on employee effectiveness. The study concluded that enhancing knowledge quality can achieve an optimal relationship between tacit knowledge sharing and employee effectiveness. 

Color image-based shape reconstruction of multi-color objects under general illumination conditions

Humans have the ability to infer the surface reflectance properties and three-dimensional shape of objects from two-dimensional photographs under simple and complex illumination fields. Unfortunately, the reported algorithms in the area of shape reconstruction require a number of simplifying assumptions that result in poor performance in uncontrolled imaging environments. Of all these simplifications, the assumptions of non-constant surface reflectance, globally consistent illumination, and multiple surface views are the most likely to be contradicted in typical environments. In this dissertation, three automatic algorithms for the recovery of surface shape given non-constant reflectance using a single-color image acquired are presented. In addition, a novel method for the identification and removal of shadows from simple scenes is discussed.In existing shape reconstruction algorithms for surfaces of constant reflectance, constraints based on the assumed smoothness of the objects are not explicitly used. Through Explicit incorporation of surface smoothness properties, the algorithms presented in this work are able to overcome the limitations of the previously reported algorithms and accurately estimate shape in the presence of varying reflectance. The three techniques developed for recovering the shape of multi-color surfaces differ in the method through which they exploit the surface smoothness property. They are summarized below:• Surface Recovery using Pre-Segmentation - this algorithm pre-segments the image into distinct color regions and employs smoothness constraints at the color-change boundaries to constrain and recover surface shape. This technique is computationally efficient and works well for images with distinct color regions, but does not perform well in the presence of high-frequency color textures that are difficult to segment.iv• Surface Recovery via Normal Propagation - this approach utilizes local gradient information to propagate a smooth surface solution from points of known orientation. While solution propagation eliminates the need for color-based image segmentation, the quality of the recovered surface can be degraded by high degrees of image noise due to reliance on local information.• Surface Recovery by Global Variational Optimization - this algorithm utilizes a normal gradient smoothness constraint in a non-linear optimization strategy, to iteratively solve for the globally optimal object surface. Because of its global nature, this approach is much less sensitive to noise than the normal propagation is, but requires significantly more computational resources.Results acquired through application of the above algorithms to various synthetic and real image data sets are presented for qualitative evaluation. A quantitative analysis of the algorithms is also discussed for quadratic shapes. The robustness of the three approaches to factors such as segmentation error and random image noise is also explored

The Effect of Implantation Temperature and Ionizing Radiation on the Microstructure of Ion Implanted Sapphire

Single crystalline specimens of aluminum oxide (Al2O3) were irradiated with boron, nitrogen and iron ions at room temperature and 1000oC to fluences of 1×1017 B+/cm2, 3×1016 N+/cm2 and 1×1017 Fe+/cm2 respectively with 150 keV of energy. Following irradiation, the structures were examined by several experimental techniques: transmission electron microscopy (TEM), Rutherford backscattering - ion channeling (RBS-C) spectroscopy, optical absorption measurements, x-ray diffraction (XRD) technique, and x-ray photoelectron spectroscopy (XPS). The samples implanted at room temperature were then annealed for one hour at 1000oC in a reducing (Ar-4%H2) gas and the microstructures examined. The implantation temperature significantly influenced the microstructure of the implanted samples. The room temperature boron-implanted microstructure consists of the typical black spot radiation damage, which differs from the microstructural features observed at 1000oC. Cross-sectional TEM micrograph for the nitrogen-implanted at room temperature reveals a band of bubbles or voids; whereas the 1000oC N-implanted specimen exhibits a different type of black spot radiation damage generally ascribed to defect clusters. The microstructure of the iron-implanted sapphire at room temperature contains black spot damage clusters and small (1-2 nm) precipitates at depths greater than about 25 nm. The sample implanted with iron at 1000°C contains particles of iron as large as 50 nm and no evidence of black spot radiation damage. These iron particles were identified as α-Fe. The microstructures for all three species implanted into sapphire at room temperature followed by annealing in Ar-4% H2 for one hour at 1000°C were quite different from the as-implanted ones. None contained black-spot damage or interstitial defect clusters, but all contained evidence for small second phase particles. The annealing promoted the recombination of point defects and defect clusters and allowed the system to move toward the equilibrium phase compositions. The lattice disorder as measured by RBS-C was greater for iron and boron implantation at room temperature than at 1000°C, but higher for nitrogen-implanted at 1000°C. The highest lattice disorder was produced by the iron implantation and is attributed to the higher density of displacements in the cascades. The optical absorption measurements indicate the presence of oxygen vacancies and defect clusters involving oxygen vacancies. The number of F-type centers was highest for boron-implanted at 1000° C. The depth-dependent microstructures of the irradiated specimens, the energy deposited (elastic and inelastic) as a function of depth from the surface, the range of implanted species, and the defect production were modeled using the transport and range of ions in materials (TRIM) program. The results of the model showed that the ionizing component of the irradiation did not noticeably affect the microstructures. The ENSP ratios {(dE/dx)e/(dE/dx)n} obtained from the TRIM simulations did not differ significantly for the three species through the range where significant displacements occurred. The range of boron-implanted into sapphire is more than that for nitrogen and iron. Iron has the shortest range. The density of vacancy (and interstitial) production is much higher for the Fe than for the B or N. The number of Al vacancies produced at all positions along the range is greater than the concentration of O vacancies

Development of an abiotic laboratory screening test for microbially influenced corrosion

An abiotic laboratory screening test (ALST) was developed that replicated the major corrosion-causing characteristics of several natural biotic environments. The natural biotic environments replicated were a Delaware Bay seawater site, an Arizona well-water system and a Tennessee River fresh-water system. The ALST was designed to produce the following major microbial effects with respect to corrosion: (a) the high oxidizing power of the natural environment, (b) the chloride concentration of the natural environment, and (c) aerobic and anaerobic areas on the specimen surface, as produced by colonies of aerobic and anaerobic microorganisms in the natural biotic environment. The ALST was evaluated by conducting corrosion tests on various materials (platinum electrodes, alloy 400, AL-6XN alloy, and 304L/316L stainless steels). The results obtained were compared with those obtained from the field studies at the natural biotic environment sites. It was found from polarization resistance measurements in the abiotic solution that alloy 400 had a corrosion rate that was in good agreement with that obtained in the Delaware Bay natural biotic water environment. Cathodic polarization behaviors were determined for platinum electrodes, alloy 400, and 304L stainless steel in the abiotic solution. Comparison of these results to those obtained in the field studies in the natural environments showed that the corrosion current densities were somewhat higher in the abiotic solution. The open-circuit potentials (OCP) obtained for the materials in the abiotic solution were significantly higher than those obtained in the natural biotic environments. The visual and microscopic results of the surfaces of the weldments after exposure in the ALST compared favorably with their counter-parts after exposure in the natural biotic water environments. From the results, the developed ALST replicated the natural environments reasonably well. The higher ennoblement and corrosion current densities obtained in the ALST are indications that the developed ALST is a conservative test. If there is no significant accelerated corrosion in the ALST, there will not be significant accelerated corrosion in the natural biotic environment; but if there is significant accelerated corrosion in the ALST, there may or may not be significant accelerated corrosion in the natural biotic environment

Creativity and future time perspective : an investigation of construct validity

The purpose of this study was to investigate the relationship between the cognitive dimensions of Creativity and Future Time Perspective (FTP). An attempt was made to integrate Guilford\u27s cognitive model of creativity with Nurmi\u27s problem solving model of FTP. The sample consisted of 135 female undergraduate students between the ages of 18 - 24 years. Creativity was measured using Guilford\u27s Consequences, and FTP was measured using the Future Problem Solving Tasks (FPST) instrument. Creative thinking was assessed as the number of Obvious and Remote responses and the combined total of these responses (Fluency). Other variables measured were Length of Response Time, GPA and Perceived Likelihood of Event. Results show that Consequences and FPST were significantly correlated on all of the creativity variables considered. Creativity was found to be a stronger predictor of FTP than academic achievement. Remote scores on the Consequences was significantly correlated with GPA while the remote scores on the FPST was not; the Length of Response Time was positively correlated with FPST while likelihood of event was negatively correlated with FPST