Multiwavelength spectrophotometric determination of acidity constants of some azo dyes.

A multiwavelength spectrophotometric titration method was applied to study the acidity constants of some azo dyes in water. The UV-vis absorption spectra of azo dye solutions were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants, spectral profiles, concentration diagrams and also the number of components have been calculated.

Electrophysiological studies of malaria parasite-infected erythrocytes: current status.

The altered permeability characteristics of erythrocytes infected with malaria parasites have been a source of interest for over 30 years. Recent electrophysiological studies have provided strong evidence that these changes reflect transmembrane transport through ion channels in the host erythrocyte plasma membrane. However, conflicting results and differing interpretations of the data have led to confusion in this field.

Simulation of DNA electrophoresis through microstructures.

The dependence of the mobility of DNA molecules through an hexagonal array of micropillars on their length and the applied electric field was investigated and it was found that mobility is a nonmonotonic function of their length. Results also revealed that the size dependence of the DNA mobility depends on the applied electric field and there is a crossover around E approximately 25 V/cm for the mobility of lambda-DNA and T4-DNA. These observations are explained in terms of the diffusion process inside the structure affected by the solvent and are modeled using the Langevin and its corresponding Fokker-Planck equations.

Membrane-protein stability in a phospholipid-based crystallization medium.

Protein stability is a crucial factor to consider when attempting to crystallize integral membrane proteins. Cubic phase, or in meso, lipid-bilayer crystallization media are thought to provide native-like environments that should facilitate membrane protein crystallization by helping to stabilize the native protein conformation for the duration of the crystallization process. While excellent crystals of bacteriorhodopsin (bR) and other Halobacterial rhodopsins have been obtained in lipid-bilayer gels formed with monoglycerides, success remains elusive in the general application of such media to other membrane proteins.

Left hemispheric lateralization of brain activity during passive rhythm perception in musicians.

The nature of hemispheric specialization of brain activity during rhythm processing remains poorly understood. The locus for rhythmic processing has been difficult to identify and there have been several contradictory findings. We therefore used functional magnetic resonance imaging to study passive rhythm perception to investigate the hypotheses that rhythm processing results in left hemispheric lateralization of brain activity and is affected by musical training.

What high-deductible plans look like: findings from a national survey of employers, 2005.

This paper documents the availability, enrollment, premiums, and cost sharing for high-deductible health plans that are offered with a health reimbursement arrangement (HRA) or are health savings account (HSA)-qualified plans. Almost 4 percent of employers that offer health benefits offer one of these arrangements in 2005, covering about 2.4 million workers.

Crystal structures of bR(D85S) favor a model of bacteriorhodopsin as a hydroxyl-ion pump.

Structural features on the extracellular side of the D85S mutant of bacteriorhodopsin (bR) suggest that wild-type bR could be a hydroxyl-ion pump. A position between the protonated Schiff base and residue 85 serves as an anion-binding site in the mutant protein, and hydroxyl ions should have access to this site during the O-intermediate of the wild-type bR photocycle. The guanidinium group of R82 is proposed (1) to serve as a shuttle that eliminates the Born energy penalty for entry of an anion into this binding pocket, and conversely, (2) to block the exit of a proton or a related proton carrier.

Specificity of anion binding in the substrate pocket of bacteriorhodopsin.

The structure of the D85S mutant of bacteriorhodopsin with a nitrate anion bound in the Schiff base binding site and the structure of the anion-free protein have been obtained in the same crystal form. Together with the previously solved structures of this anion pump, in both the anion-free state and bromide-bound state, these new structures provide insight into how this mutant of bacteriorhodopsin is able to bind a variety of different anions in the same binding pocket. The structural analysis reveals that the main structural change that accommodates different anions is the repositioning of the polar side chain of S85.

Crystal structure of the bromide-bound D85S mutant of bacteriorhodopsin: principles of ion pumping.

We report the crystal structure of a bromide-bound form of the D85S mutant of bacteriorhodopsin, bR(D85S), a protein that uses light energy rather than ATP to pump halide ions across the cell membrane. Comparison of the structure of the halide-bound and halide-free states reveals that both displacements of individual side-chain positions and concerted helical movements occur on the extracellular side of the protein. Analysis of these structural changes reveals how this ion pump first facilitates ion uptake deep within the cell membrane and then prevents the backward escape of ions later in the pumping cycle.

PVC-membrane ion-selective bulk optode for Ag+ ion based on hexathia-18-crown-6 and 1,2-benzo-3-octadecanoylimino-7-diethylaminophenoxazine.

A silver-selective optode membrane incorporating hexathia-18-crown-6 for cation recognition and a lipophilic chromoionophore 1,2-benzo-3-octadecanoylimino-7-diethylaminophenoxazine for transduction has been prepared. The PVC membrane composition was optimized to result in the largest working concentration range. The response range of the proposed optode is 5.

Crystallization of membrane proteins from media composed of connected-bilayer gels.

The use of hydrated-lipid gels in which the bilayer is an infinitely periodic (or at least continuous), three-dimensional structure offers a relatively new approach for the crystallization of membrane proteins. While excellent crystals of the Halobacterial rhodopsins have been obtained with such media, success remains poor in extending their use to other membrane proteins. Experience with crystallization of bacteriorhodopsin has led us to recognize a number of improvements that can be made in the use of such hydrated-gel media, which may now prove to be of general value for the crystallization of other membrane proteins.

In vivo electrotransfer of the cardiotrophin-1 gene into skeletal muscle slows down progression of motor neuron degeneration in pmn mice.

Among all vectors designed for gene therapy purposes, adenovirus appears to be the most efficient in vivo vehicle to transduce the broadest spectrum of cellular targets. However, the deleterious immunogenicity of this viral vector impedes its use in chronic diseases. Non-viral vectors, such as naked DNA, are attractive alternatives for safety and technical issues, such as scale-up production.

New attractor states for synchronous activity in synfire chains with excitatory and inhibitory coupling.

In a feedforward network of integrate-and-fire neurons, where the firing of each layer is synchronous (synfire chain), the final firing state of the network converges to two attractor states: either a full activation or complete fading of the tailing layers. In this article, we analyze various modes of pattern propagation in a synfire chain with random connection weights and delta-type postsynaptic currents. We predict analytically that when the input is fully synchronized and the network is noise free, varying the characteristics of the weights distribution would result in modes of behavior that are different from those described in the literature.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) modulates lactogenic hormone-mediated differentiation and gene expression in HC11 mouse mammary epithelial cells.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mammary gland carcinogen in cooked meat. Using the HC11 mouse mammary epithelial cell line, a well-characterized model for hormone-mediated differentiation, we examined whether PhIP altered the expression of genes regulated by lactogenic hormones dexamethasone, insulin, and prolactin (DIP). When HC11-Lux cells (stably transfected with a beta-casein promoter luciferase construct) were cultured in DIP-containing medium, PhIP (100 microM) enhanced luciferase activity 11-fold over that observed in DIP medium alone.

Structure of an early intermediate in the M-state phase of the bacteriorhodopsin photocycle.

The structure of an early M-intermediate of the wild-type bacteriorhodopsin photocycle formed by actinic illumination at 230 K has been determined by x-ray crystallography to a resolution of 2.0 A. Three-dimensional crystals were trapped by illuminating with actinic light at 230 K, followed by quenching in liquid nitrogen.

Cobalt(II)-selective membrane electrode based on a recently synthesized benzo-substituted macrocyclic diamide.

A PVC-membrane electrode based on a recently synthesized 18-membered macrocyclic diamide is presented. The electrode reveals a Nernstian potentiometric response for Co2+ over a wide concentration range (2.0 x 10(-6)-1.

Crystal structure of the D85S mutant of bacteriorhodopsin: model of an O-like photocycle intermediate.

Crystal structures are reported for the D85S and D85S/F219L mutants of the light-driven proton/hydroxyl-pump bacteriorhodopsin. These mutants crystallize in the orthorhombic C222(1) spacegroup, and provide the first demonstration that monoolein-based cubic lipid phase crystallization can support the growth of well-diffracting crystals in non-hexagonal spacegroups. Both structures exhibit similar and substantial differences relative to wild-type bacteriorhodopsin, suggesting that they represent inherent features resulting from neutralization of the Schiff base counterion Asp85.

Protective effects of cardiotrophin-1 adenoviral gene transfer on neuromuscular degeneration in transgenic ALS mice.

Amyotrophic lateral sclerosis (ALS) is mainly a sporadic neurodegenerative disorder characterized by loss of cortical and spinal motoneurons. Some familial ALS cases (FALS) have been linked to dominant mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1). Transgenic mice overexpressing a mutated form of human SOD1 with a Gly93Ala substitution develop progressive muscle wasting and paralysis as a result of spinal motoneuron loss and die at 5 to 6 months.

Multiple-point variance analysis for optimal adjustment of a monitoring network.

The selection of sampling sites is one of the major tasks in the design of a monitoring network. Many environmental networks suffer from either insufficient information or redundant information. This study presents a new, effective algorithm that addresses the issues of insufficient and reduction information.

Characterization of conditions required for X-Ray diffraction experiments with protein microcrystals.

The x-ray exposure at which significant radiation damage occurs has been quantified for frozen crystals of bacteriorhodopsin. The maximum exposure to approximately 11-keV x-rays that can be tolerated for high-resolution diffraction experiments is found to be approximately 10(10) photons/microm(2), very close to the value predicted from limits that were measured earlier for electron diffraction exposures. Sample heating, which would further reduce the x-ray exposure that could be tolerated, is not expected to be significant unless the x-ray flux density is well above 10(9) photons/s-microm(2).

Strontium-selective membrane electrodes based on some recently synthesized benzo-substituted macrocyclic diamides.

Eight different recently synthesized macrocyclic diamides were studied to characterize their abilities as strontium ion carriers in PVC membrane electrodes. The electrode based on 1,13-diaza-2,3;11,12-dibenzo-4,7,10-trioxacyclopentadecane-14,15-dione exhibits a Nernstian response for Sr(2+) ions over a wide concentration range (1.0 × 10(-)(1)-3.

Effects of muscimol or homotaurine on sleep-wake states in alcohol-dependent rats during withdrawal.

Sleep-wake states were studied following withdrawal in 36 adult male wistar alcohol-dependent rats, after chronic administration of ethanol (10 g/kg/24 h) for 13 days. In the light phase of the withdrawal day, 12 alcohol-dependent rats received muscimol (0.25 mg/kg), 12 received homotaurine (140 mg/kg), and 12 received 0.

Stability of brain content of magnesium in experimental hypomagnesemia.

Magnesium is important in cerebral function. If there is a deficiency and neurological symptoms accrue, we hypothesised that Mg2+ deficiency causes neurological symptoms by decreasing the level of Mg2+ in cerebral tissue. The content of magnesium was determined in 12 brain structures in magnesium-deficient rats.

Secondary structure of the outer membrane proteins OmpA of Escherichia coli and OprF of Pseudomonas aeruginosa.

When purified without the use of ionic detergents, both OmpA and OprF proteins contained nearly 20% alpha-helical structures, which disappeared completely upon the addition of sodium dodecyl sulfate. This result suggests that the proteins fold in a similar manner, with an N-terminal, membrane-spanning beta-barrel domain and a C-terminal, globular, periplasmic domain.

Effects of alcohol dependence on shock-induced fighting: action of muscimol and homotaurine.

We have applied the electroshock-induced fighting behavior to the study of experimental alcohol dependence. Adult Wistar rats were intoxicated chronically with ethanol (10 g/kg/24 h) for 13 days. Electroshock-induced fighting behavior was studied during chronic intoxication and withdrawal in comparison with normal rats receiving a water-carbohydrate solution isocaloric to ethanol.