Twisted Bethe equations from a twisted S-matrix

All-loop asymptotic Bethe equations for a 3-parameter deformation of AdS5/CFT4 have been proposed by Beisert and Roiban. We propose a Drinfeld twist of the AdS5/CFT4 S-matrix, together with c-number diagonal twists of the boundary conditions, from which we derive these Bethe equations. Although the undeformed S-matrix factorizes into a product of two su(2|2) factors, the deformed S-matrix cannot be so factored. Diagonalization of the corresponding transfer matrix requires a generalization of the conventional algebraic Bethe ansatz approach, which we first illustrate for the simpler case of the twisted su(2) principal chiral model. We also demonstrate that the same twisted Bethe equations can alternatively be derived using instead untwisted S-matrices and boundary conditions with operatorial twists.Comment: 42 pages; v2: a new appendix on sl(2) grading, 2 additional references, and some minor changes; v3: improved Appendix D, additional references, and further minor changes, to appear in JHE

The Bound State S-matrix of the Deformed Hubbard Chain

In this work we use the q-oscillator formalism to construct the atypical (short) supersymmetric representations of the centrally extended Uq (su(2|2)) algebra. We then determine the S-matrix describing the scattering of arbitrary bound states. The crucial ingredient in this derivation is the affine extension of the aforementioned algebra.Comment: 44 pages, 3 figures. v2: minor correction

Monte Carlo Analysis of Neck Linker Extension in Kinesin Molecular Motors

Kinesin stepping is thought to involve both concerted conformational changes and diffusive movement, but the relative roles played by these two processes are not clear. The neck linker docking model is widely accepted in the field, but the remainder of the step – diffusion of the tethered head to the next binding site – is often assumed to occur rapidly with little mechanical resistance. Here, we investigate the effect of tethering by the neck linker on the diffusive movement of the kinesin head, and focus on the predicted behavior of motors with naturally or artificially extended neck linker domains. The kinesin chemomechanical cycle was modeled using a discrete-state Markov chain to describe chemical transitions. Brownian dynamics were used to model the tethered diffusion of the free head, incorporating resistive forces from the neck linker and a position-dependent microtubule binding rate. The Brownian dynamics and chemomechanical cycle were coupled to model processive runs consisting of many 8 nm steps. Three mechanical models of the neck linker were investigated: Constant Stiffness (a simple spring), Increasing Stiffness (analogous to a Worm-Like Chain), and Reflecting (negligible stiffness up to a limiting contour length). Motor velocities and run lengths from simulated paths were compared to experimental results from Kinesin-1 and a mutant containing an extended neck linker domain. When tethered by an increasingly stiff spring, the head is predicted to spend an unrealistically short amount of time within the binding zone, and extending the neck is predicted to increase both the velocity and processivity, contrary to experiments. These results suggest that the Worm-Like Chain is not an adequate model for the flexible neck linker domain. The model can be reconciled with experimental data if the neck linker is either much more compliant or much stiffer than generally assumed, or if weak kinesin-microtubule interactions stabilize the diffusing head near its binding site

Hepatoprotective and Antioxidant Effects of Argyreia Speciosa in Rats

The present study has been designed to evaluate the liver protective and in-vivo antioxidant role of Ethanolic extract (EtAS) and Ethyl acetate extract (EAAS) of roots of Argyreia speciosa, an important ‘rasayana’ herb in Indian System of medicine, in CCl4-induced hepatotoxicity and oxidative stress in rats. Animals were treated with EtAS and EAAS at doses of 200 mg and 400 mg / kg body weight p.o. along with CCl4 (0.7 ml / kg in olive oil, 1:1 v/v i.p. on every alternate days) for seven days. Serum biochemical parameters such as SGOT, SGPT, ALP, cholesterol, total and direct bilirubin were determined. Antoixidant status in liver was determined by measuring the activities of Super oxide dismutase (SOD), Catalase and Peroxidase. Histopathological study of isolated liver specimens was also carried out to know the protection offered by the extracts. There was a significant rise in the levels of serum GOT, GPT, and ALP and other biochemical parameters, decrease in the levels of SOD, Catalase and Peroxidase after administration of CCl4. Suspensions of EtAS and EAAS (200 and 400 mg/ kg) successfully prevented the alterations of these effects in rats (p< 0.001). Histopathological examination demonstrated that CCl4 treated group induces ballooning degeneration and centrilobular necrosis. Groups treated with EtAS and EAAS showed recovery on ballooning degeneration and centrlobular bridging necrosis was occasionally present. Data also showed that these extracts possessed strong antioxidant activity, and were comparable to Silymarin, a well known liver protecting herbal formulation

Rapid Mixing Methods for Exploring the Kinetics of Protein Folding

Information on the time-dependence of molecular species is critical for elucidating reaction mechanisms in chemistry and biology. Rapid flow experiments involving turbulent mixing of two or more solutions continue to be the main source of kinetic information on protein folding and other biochemical processes, such as ligand binding and enzymatic reactions. Recent advances in mixer design and detection methods have opened a new window for exploring conformational changes in proteins on the microsecond time scale. These developments have been especially important for exploring early stages of protein folding

ISOLATION AND CHARACTERIZATION OF SECONDARY METABOLITE FROM HABENARIA INTERMEDIA D.DON FOR EVALUTION OF HEPATOPROTECITVE ACTIVITY AGAINST CARBON TETRACHLORIDE INDUCED LIVER DAMAGE IN ALBINO RATS

 Objective: Isolation and characterization of secondary metabolite from Habenaria intermedia D Don for assessment of hepatoprotecitve activityagainst carbon tetrachloride (CCl4) induced liver damage in albino rats.Methods: The phenolic constituents present in ethanolic fraction of tubers of H. intermedia was isolated by column chromatography usinggradient elution technique. The isolated phenolic compound was characterized by infrared, 1H nuclear magnetic resonance and mass spectralanalysis. The isolated compound was screened for hepatoprotecitve activity against liver toxicity induced in Albino rats by intraperitonealinjection of CCl4. Albino rats weighing 150-200 g were randomly divided in to four groups of six rats each. Group I served as normal control andreceived only 1% tween in distilled water. Group II served as a negative control and received CCl4 in liquid paraffin at the dose of 0.7 ml/kg.p.o.CCl4 on alternate days. Group III and IV were intoxicated with CCl4 0.7 ml/kg.p.o. before the administration of silymarin 100 mg/kg.p.o. andisolated phenolic constituent (gallic acid) in polyethylene glycol at the dose of 25 mg/kg.p.o. respectively. Various liver function biochemicalparameters such as serum glutamic oxaloacetic transaminase (SGOT), serum glutamic-pyruvic transaminase (SGPT); serum bilirubin and totalprotein were assessed before and after treatment to investigate the hepatoprotecitve activity. Histopathology of liver sections of rats treated withisolated phenolic constituents was also studied.Results: It was observed that in CCl4 intoxicated group SGPT, SGOT, serum bilirubin levels were elevated, and the total protein content wasdecreased when compared to the control group. Administration of isolated phenolic constituent at the dose of 25 mg/kg.p.o. reduced thesepathological damages caused by CCl4 intoxication compare to normal, and silymarin treated groups. The results were further supported byhistopathology of isolated phenolic constituent treated rat liver, which showed the presence of normal hepatic cords, absence of necrosis andfatty infiltration.Conclusion: The present study has justified that the isolated phenolic constituent (gallic acid) exhibited significant hepatoprotecitve potential againstCCl4 induced toxicity in Albino rats, thus enabling to expand the spectrum of novel hepatoprotecitve formulations.Keywords: Habenaria intermedia, Gallic acid, Hepatoprotecitve, Carbon tetrachloride toxicity, Silymarin

Early Events During Folding of Wild-type

uring the final stages of folding. The fact that both variants exhibit the same number of kinetic phases with very similar rates confirms that the folding mechanism is not perturbed by the F76W/W140H mutations. However, the Trp at position 76 reports on the rapid formation of a hydrophobic cluster in the N-terminal b-sheet region while the wild-type Trp140 is silent during this early stage of folding. Quantitative modeling of the (un)folding kinetics and thermodynamics of these two proteins versus urea concentration revealed that the F76W/W140H mutation selectively destabilizes the native state relative to WT SNase while the stability of transient intermediates remains unchanged, leading to accumulation of intermediates under equilibrium conditions at moderate denaturant concentrations. q 2004 Elsevier Ltd. All rights reserved. Keywords: protein folding kinetics; stopped-flow; continuous-flow; fluorescence; ANS *Corresponding author Introduction Elucidating early events in the