Theory of Nucleosome Corkscrew Sliding in the Presence of Synthetic DNA Ligands

Histone octamers show a heat-induced mobility along DNA. Recent theoretical studies have established two mechanisms that are qualitatively and quantitatively compatible with in vitro experiments on nucleosome sliding: Octamer repositiong through one-basepair twist defects and through ten-basepair bulge defects. A recent experiment demonstrated that the repositioning is strongly suppressed in the presence of minor-groove binding DNA ligands. In the present study we give a quantitative theory for nucleosome repositioning in the presence of such ligands. We show that the experimentally observed octamer mobilities are consistent with the picture of bound ligands blocking the passage of twist defects through the nucleosome. This strongly supports the model of twist defects inducing a corkscrew motion of the nucleosome as the underlying mechanism of nucleosome sliding. We provide a theoretical estimate of the nucleosomal mobility without adjustable parameters, as a function of ligand concentration, binding affinity, binding site orientiation, temperature and DNA anisotropy. Having this mobility at hand we speculate about the interaction between a nucleosome and a transcribing RNA polymerase and suggest a novel mechanism that might account for polymerase induced nucleosome repositioning.Comment: 23 pages, 4 figures, submitted to J. Mol. Bio

Presence of Visceral Larva Migrans in the Urinary Bladder of a Woman in Khorramabad, Iran

The presence of Visceral Larva Migrans (VLM) in a patient is reported. A 57-year- old woman suffering from right upper abdominal and suprapubic pain referred into a clinic in Khorramabad, Lorestan Province, Iran. A cystoscopy was performed and biopsy was taken. The light microscopic study showed a couple of larvae as well as mononuclear inflammatory cell- infiltration. Because occurrence of VLM is potentially problem in rural areas, it is recommended that an educational program to be initiated to prevent and control VLM infection in both rural and urban people. Clinicians also should consider the clinical features of visceral larva migrans

Iodination of Alcohols over Keggin-type Heteropoly Compounds: A Simple, Selective and Expedient Method for the Synthesis of Alkyl Iodides

Different catalysts derived from Keggin-type heteropoly compounds were prepared and their catalytic activities have been compared in the iodination of benzyl alcohol with KI under mild reaction conditions. A high catalytic activity was found over tungstophosphoric acid supported on silica and titania. The effect of catalyst loading, iodine source and the nature of substituents on the aromatic ring of benzyl alcohol were investigated. Finally, several competitive reactions were studied between structurally diverse alcohols. This protocol provides a mild and expedient way for the conversion of various alcohols to their corresponding alkyl iodides with high selectivity.Keywords: Keggin-type Heteropoly Compounds, Supported Catalyst, Alcohols, Alkyl Iodides, Potassium Iodid

Stochastic model for nucleosome sliding in the presence of DNA ligands

Heat-induced mobility of nucleosomes along DNA is an experimentally well-studied phenomenon. A recent experiment shows that the repositioning is modified in the presence of minor-groove binding DNA ligands. We present here a stochastic three-state model for the diffusion of a nucleosome along DNA in the presence of such ligands. It allows us to describe the dynamics and the steady state of such a motion analytically. The analytical results are in excellent agreement with numerical simulations of this stochastic process.With this model, we study the response of a nucleosome to an external force and how it is affected by the presence of ligands.Comment: 10 pages, 8 figures, submitted to Eur. Phys. J.

Organic Thin Film Transistor with Carbon Nanotube Electrodes

The contact resistance between organic semiconductors and metallic electrodesaffectsthe performance of the organic thin film transistor (OTFT) negatively so that it may make thefield effect mobility of charge carrier seem small. In order to reduce the contact resistance weused conducting Carbon Nanotube (CNT) films, which consist of the same element as the basicmaterial of the organic semiconductors, as source or drain electrodes. The measurements oftransistor properties based on pentacene single crystals have been carried out by using both CNTfilm electrodes and metal electrode

Morphological variation of golden mullet, Liza aurata, of southern coasts of the Caspian Sea

Morphological features of Golden mullet (Liza aurata) population in the southern coasts of the Caspian Sea were studied. A total of 228 fish specimens were collected from Bandar Anzali, Kiashahr, Babolsar and Bandar Turkman in Iranian waters. A combination of Truss network, traditional system and few meristic counts were simultaneously applied to the sample set. Statistically high significant morphometric differences were observed between the four L. aurata stocks. Univariate analysis of variance (ANOVA) revealed significant differences between the means of samples for 10 out of 25 standardized morphometric measurements of truss system, 3 out of 7 measurements of traditional morphometric system and also the number of second dorsal fin spines, soft rays of second dorsal fin, total number of pectoral fin rays, soft rays of anal fin, number of squmosum scales and pyloric caeca among meristic counts. Discriminant analysis correctly classified 76% and 70.3% of individuals into their original samples for morphometric features and meristic counts, respectively. Plotting discriminant functions revealed differentiation of the four stocks based on morphometric measurements. The Bandar Anzali stock was isolated from the others, and the Baholsar stock was found to be located between Kiashahr and Bandar Turkman stocks. The pattern of morphological discreetness suggests a direct relationship between the extent of morphological divergence and geographical separation

Wavelength dependent photoelectron circular dichroism of limonene studied by femtosecond multiphoton laser ionization and electron-ion coincidence imaging

Enantiomers of the monoterpene limonene have been investigated by (2+1) resonance enhanced multiphoton ionization and photoelectron circular dichroism employing tuneable, circularly polarized femtosecond laser pulses. Electron imaging detection provides 3D momentum measurement while electron-ion coincidence detection can be used to mass-tag individual electrons. Additional filtering, by accepting only parent ion tagged electrons, can be then used to provide discrimination against higher energy dissociative ionization mechanisms where more than three photons are absorbed to better delineate the two photon resonant, one photon ionization pathway. The promotion of different vibrational levels and, tentatively, different electronic ion core configurations in the intermediate Rydberg states can be achieved with different laser excitation wavelengths (420 nm, 412 nm, and 392 nm), in turn producing different state distributions in the resulting cations. Strong chiral asymmetries in the lab frame photoelectron angular distributions are quantified, and a comparison made with a single photon (synchrotron radiation) measurement at an equivalent photon energy

Study of changes in macro elements Ca, Mg, Na and K in eggs of rainbow trout (Oncorhynchus mykiss) at different incubation stages

We studied rainbow trout eggs requirements to macro elements Ca, Mg, Na and K at different stages of incubation period. The research was carried out at Namroud rainbow trout hatchery center in winter 2005. Two incubators in equal conditions were selected. The first was stocked with approximately 60000 eggs and the second had no eggs. A total of 100 fertilized eggs were sampled and assessed for the elements before introduction of the eggs to the incubator. Weekly samples were taken from the eggs and water of the first and second incubator. The sampled eggs were digested by Tripathi method and concentration of the elements in eggs extract was measured by ICP apparatus. In addition, variation of these elements between input and discharge water of both incubators was investigated