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Muscat, Oman

Sultan Qaboos University, located in Al Khoudh in the Muscat Governorate, is the only public university in the Sultanate of Oman.Most students entering the university are selected based on their performance in high school final examinations. Student enrollment has grown from 500 in 1986 to more than 10,000 in 2005. More than half of the students live off campus due to space constraints. It currently has around 15,357 students of which 7,942 are female students and 7,415 are male students. Wikipedia.

The ability of site I of human serum albumin (HSA) to bind medium sized molecules is important for the distribution, metabolism, and efficacy of many drugs. Herein, we show that this binding site has the ionization ability that may alter the drug structure during the process of its delivery. We reveal this ability by employing 2-(2′-hydroxyphenyl)benzoxazole (HBO) as a pH sensitive probe. Binding of HBO in site I is studied here at physiological pH 7.2 using steady-state and lifetime spectroscopic measurements, molecular docking and molecular dynamics (MD) simulation methods. The complex photophysics of HBO and the unique fluorescence signature of its anionic form indicate that, upon binding with HSA, the molecule exists in equilibrium between the anionic and the syn-keto forms. The position of HBO inside the binding site was determined experimentally by measuring the fluorescence quenching of W214, the sole tryptophan residue in HSA. The ionization degree of HBO inside the binding site was estimated to be close to the ionization degree of HBO in an aqueous solution of pH 10. This was concluded by comparing the fluorescence behavior of bound HBO to that of HBO in different solvents and in aqueous solutions of different pH values. Molecular docking and MD simulations show that HBO binds in site I close to W214, confirming the experimental results, and pinpoint the dominant role of hydrophobic interactions in the binding site. The formation of the anionic form is proposed to be due to through-space interaction between the OH group of HBO and both R222 and I290 with a binding mode similar to that of warfarin in site I. Comparison of the results with those of HBO mixed with key amino acids in solution indicates the importance of through-space interaction in the formation of the anion, similar to enzymatic reactions. © the Owner Societies 2012.

The complex photophysics of 2-(2′-hydroxyphenyl)benzoxazole (HBO), 2-(2′-hydroxyphenyl)benzimidazole (HBI), and 2-(2′-hydroxyphenyl) benzothiazole (HBT) in different media makes them suitable as fluorescent probes to study the nature of binding sites in macromolecular systems. In this work, we investigate the spectroscopy of the three benzazole derivatives (HBXs) in different solvents and in human serum albumin (HSA) in order to understand the binding mechanism in subdomain IIA of HSA which has the ability to host a large variety of natural and pharmaceutical compounds. The three probes are found to specifically bind close to W214, the sole tryptophan residue in HSA, in a mode similar to that of the binding of the anticoagulant drug warfarin. The current results show that the structural differences between the three HBX molecules did not produce any measurable effects when binding with HSA. In particular, the change in planarity of the molecular backbone, from a perfectly planar and more rigid structure (HBO) to a twisted structure (HBI) and a flexible structure (HBT) has no effect on the mode of binding. Also, the strength of the intramolecular hydrogen bonds in HBXs (HBO > HBT > HBI) is shown not to intervene with the ability of HSA to ionize the ligands via through-space interaction with polar amino acid residues, similar to enzymatic reactions. The results emphasize the nature of HSA as a versatile and indiscriminate receptor, capable of binding a variety of ligands by adapting its binding pockets. In this regard, binding of HBXs, and other structurally similar ligands, in subdomain IIA is best described by the induced-fit model in which considerable flexibility of the binding site is necessary for molecular recognition. The results also point to the high affinity of the warfarin binding pocket (within subdomain IIA) for binding versatile molecular structures including several drugs. This affinity stems from the flexibility of the amino acids forming the binding pocket. © The Royal Society of Chemistry 2013.

Masters K.,Sultan Qaboos University
Medical Teacher | Year: 2013

Background: Edgar Dale's Pyramid of Learning and percentages of retained learning are cited in educational literature in a range of disciplines. The sources of the Pyramid, however, are misleading. Aims: To examine the evidence supporting the Pyramid and the extent to which it is cited in medical education literature. Methods: A review of literature (1946-2012) based on a search utilising Academic Search Complete, CINAHL, Medline and Google Scholar conducted from September to November 2012. Results: A total of 43 peer-reviewed medical education journal articles and conference papers were found. While some researchers had been misled by their sources, other authors' interpretations of the citations did not align with the content of those citations, had no such citations, had circular references, or consulted questionable sources. There was no agreement on the percentages of learning retention, in spite of many researchers' citing primary texts. Discussion and conclusion: The inappropriate citing of the Pyramid and its associated percentages in medical education literature is widespread and continuous. This citing undermines much of the published work, and impacts on research-based medical education literature. While the area of learning/teaching strategies and amount of retention from each is an area for future research, any reference to the Pyramid should be avoided. © 2013 Informa UK Ltd.

El-Shafey E.I.,Sultan Qaboos University
Journal of Hazardous Materials | Year: 2010

A carbonaceous sorbent was prepared from rice husk via sulfuric acid treatment. Sorption of Zn(II) and Hg(II) from aqueous solution was studied varying time, pH, metal concentration, temperature and sorbent status (wet and dry). Zn(II) sorption was found fast reaching equilibrium within ∼2 h while Hg(II) sorption was slow reaching equilibrium within ∼120 h with better performance for the wet sorbent than for the dry. Kinetics data for both metals were found to follow pseudo-second order model. Sorption rate of both metals was enhanced with temperature rise. Activation energy, E a, for Zn(II) sorption, was ∼13.0 kJ/mol indicating a diffusion-controlled process ion exchange process, however, for Hg(II) sorption, E a was ∼54 kJ/mol indicating a chemically controlled process. Sorption of both metals was low at low pH and increased with pH increase. Sorption was much higher for Hg(II) than for Zn(II) with higher uptake for both metals by rising the temperature. Hg(II) was reduced to Hg(I) on the sorbent surface. This was confirmed from the identification of Hg 2Cl 2 deposits on the sorbent surface by scanning electron microscopy and X-ray diffraction. However, no redox processes were observed in Zn(II) sorption. Sorption mechanism is discussed. © 2009 Elsevier B.V. All rights reserved.

The aim of this study was to demonstrate a novel method for measuring the effects of toxicants on the behavior of groups of unmarked fish. Ctrax is an open source Python-based machine vision program that was originally designed to track fruit flies (Drosophila). The effects of the fish anaesthetic quinaldine sulfate on the behavior of groups of 10 unmarked Arabian killifish (Aphanias dispar) in a small arena were measured. Ctrax was able to identify and track the X-Y coordinates of the individual fish over 1. min recording periods. The data was analyzed using specifically written Matlab (The Mathworks™) toolboxes and the effects of quinaldine sulfate on absolute swimming velocity, forward swimming velocity, rate of change in orientation and distance to wall were calculated. Additionally the effects of quinaldine sulfate on path tortuosity were also measured. Ctrax has significant benefits over other available technologies for tracking the 2-dimensional coordinates of fish. In particular the software is open source and thus freely available, it is accurate, requires only simple easily available equipment and able to track potentially large groups of fish (possibly >50) while maintaining their individual identities. © 2011 Elsevier Ltd.

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