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East Jerusalem, Palestine

Al-Quds University is a Palestinian university with campuses in Jerusalem, Abu Dis, and al-Bireh. It was founded in 1984 , but its official constitution was written in 1993 when Mohammed Nusseibeh, its first Chancellor and Chancellor of the College of Science and Technology, announced its formation. Wikipedia.

Dembitsky V.M.,Hebrew University of Jerusalem | Al Quntar A.A.A.,Hebrew University of Jerusalem | Al Quntar A.A.A.,Al-Quds University | Srebnik M.,Hebrew University of Jerusalem
Chemical Reviews | Year: 2011

Bacteria communicate with one another via production, detection, and response to secreted chemical signal molecules called autoinducers. Organic chemists have long been interested in natural products, and their investigations have contributed to many advances in chemistry, especially the total synthesis of complex boron-containing molecules with many chiral centers. Gram-positive and Gram-negative bacteria can produce species specific signal to communicate within species. The functions controlled by QS are varied and reflect the needs of a particular species of bacteria to inhabit a given niche. Siderophores are small, high-affinity metal chelating compounds secreted by bacteria, fungi, and grasses. Complexes of boron with sugars or/or sugar alcohols are utilized as nutritional supplements, with the carbohydrate portion being selected to provide a relatively high boron-sugar association constant of at least 250 and preferably 500 or more. Source

A mechanistic study using ab initio and DFT calculation methods on the intramolecular ring-closing of enol ethers 1Z, 1E, and 2 (Kirby's enzyme models for aldolase and isomerase) has revealed that proton transfer is the rate determining step and involves two stages: re-organization of the global minimum structure (having the lowest enthalpic energy and a relatively long distance between the two reactive centers, r) to a more organized ground state conformation (having the smallest r distance among all the conformations), and a second stage by which the proton is transferred from the organized state to the corresponding transition state. The energy needed for the first stage to occur is dependent on the rotation barrier for the proton to be in proximity to the CC double bond carbon (proximity effects), whereas, that needed for the second step is largely affected by the strain energies of the reactant and the corresponding product. In addition, it was found that the oxocarbocation intermediate involved in the proton transfer is unstable and undergoes ring-closing to the corresponding product with zero activation energy. Further, the calculated DFT effective molarities (EM) for 1Z, 1E, and 2 were found to correlate strongly with experimental EM values. © 2010 Elsevier Ltd. All rights reserved. Source

Karaman R.,Al-Quds University
Tetrahedron Letters | Year: 2010

Using density functional theory (DFT) at the B3LYP level with the 6-31G(d,p) basis set, a general equation is derived relating activation energy with the distance between the two reactive centers (rGM), and the hydrogen-bonding angle (αGM) in an intramolecular proton transfer process. The strong correlation between the values of rGM and αGM with the activation energy, ΔG‡, which reflects the experimental reaction rate, provides an excellent tool to predict reaction rate based on calculated geometrical parameters for a certain system (ΔH‡, ΔG‡ vs rGM and αGM). The slope of the equation can be used as an indicator of the mode by which the two reacting centers orchestrate in an intramolecular process. © 2010 Elsevier Ltd. All rights reserved. Source

Fanun M.,Al-Quds University
Journal of Colloid and Interface Science | Year: 2010

Water/sucrose laurate/ethoxylated mono-di-glyceride/ethanol/peppermint oil microemulsion systems were formulated and characterized using electrical conductivity, dynamic viscosity, nuclear magnetic resonance, dynamic light scattering, small angle X-ray scattering and cryogenic transmission electron microscopy. The solubilization capacity of water in the oil is dependent on the surfactants and ethanol/oil mixing ratios (w/w). Static percolation phenomena were observed in these systems, and the water volume fraction percolation threshold was determined. A progressive transformation of the water-in-oil to bicontinuous and inversion to oil-in-water microemulsions occurs upon dilution with water, which was revealed by the determination of the diffusion coefficients of both oil and water inside the microemulsions. The diffusion coefficients of the surfactants at the interface of the microemulsions increase with increasing water volume fraction. The periodicity of the microemulsions increases linearly with increasing water volume fraction. In addition, the correlation length increases with water volume fraction to a certain value then decreases. Cryo-TEM images of the oil-in-water microemulsions revealed the presence of spheroidal droplets of up to 12 nm diameter. © 2009 Elsevier Inc. All rights reserved. Source

Karaman R.,Al-Quds University
Tetrahedron Letters | Year: 2010

DFT and ab initio calculation results for proton transfer reactions in Kirby's acetals reveal that the mechanism proceeds via efficient intramolecular general acid catalysis (IGAC) and not through a 'classical' general acid catalysis mechanism (GAC). Further, they show that the driving force for the proton transfer efficiency is the proximity of the two reactive centers (r) and the attack angle (α), and the rate of the reaction is linearly correlated with r 2 and sin (180° - α). Acetals with short r values and with α values close to 180° (forming a linear H-bond) are more reactive due to the development of strong hydrogen bonds in their global minimum, transition state, and product structures. © 2010 Elsevier Ltd. All rights reserved. Source

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