Hyperoxidation of Peroxiredoxin 6 Induces Alteration from Dimeric to Oligomeric State.

Peroxiredoxins(Prdx), the family of non-selenium glutathione peroxidases, are important antioxidant enzymes that defend our system from the toxic reactive oxygen species (ROS). They are thiol-based peroxidases that utilize self-oxidation of their peroxidatic cysteine (C) group to reduce peroxides and peroxidized biomolecules. However, because of its high affinity for hydrogen peroxide this peroxidatic cysteine moiety is extremely susceptible to hyperoxidation, forming peroxidase inactive sulfinic acid (Cys-SO₂H) and sulfonic acid (Cys-SO₃H) derivatives.

Repeated dose oral toxicity of Trivanga Bhasma in Swiss albino mice.

Trivanga Bhasma, a metallic preparation containing Bhasmas of Naga (lead), Vanga (tin) and Yashada (zinc), was studied for repeated dose toxicity in Swiss albino mice to estimate No Observed Effect Level (NOEL) or No Observed Adverse Effect Level (NOAEL). A total of 80 Swiss albino mice of either sex with an average body weight of 28-30 g were equally divided into four groups (Group I, II, III, and IV). Group I served as control and was given vehicle (honey: water in 2:3 ratio) Group II, III, and IV received Trivanga Bhasma @ 7.

Lymphedematous HIV-associated Kaposi's sarcoma.

Background: Advanced Kaposi's sarcoma is frequently associated with chronic lymphedema (cLO). The histopathological features of lymphedematous HIV-associated KS (KS) are poorly documented and the co-existence of fibroma-like nodules in lymphedematous KS is under-recognized. The aims of this study were to assess the clinicopathological spectrum and diagnostic difficulties associated with lymphedematous KS and to highlight the clinicopathological profile of fibroma-like nodules.

A unique molten globule state occurs during unfolding of cytochrome c by LiClO4 near physiological pH and temperature: structural and thermodynamic characterization.

We have carried out denaturation studies of bovine cytochrome c (cyt c) by LiClO4 at pH 6.0 and 25 degrees C by observing changes in difference molar absorbance at 400 nm (Deltaepsilon400), mean residue ellipticities at 222 nm ([theta]222) and difference mean residue ellipticity at 409 nm (Delta[theta]409). The denaturation is a three-step process when measured by Deltaepsilon400 and Delta[theta]409, and it is a two-step process when monitored by [theta]222.

Stability of proteins in the presence of polyols estimated from their guanidinium chloride-induced transition curves at different pH values and 25 degrees C.

We have recently concluded from the heat-induced denaturation studies that polyols do not affect deltaG(D) degrees (the Gibbs free energy change (deltaG(D)) at 25 degrees C) of ribonuclease-A and lysozyme at physiological pH and temperature, and their stabilizing effect increases with decrease in pH. Since the estimation of deltaG(D) degrees of proteins from heat-induced denaturation curves requires a large extrapolation, the reliability of this procedure for the estimation of deltaG(D) degrees is always questionable, and so are conclusions drawn from such studies. This led us to measure deltaG(D) degrees of ribonuclease-A and lysozyme using a more accurate method, i.

Testing polyols' compatibility with Gibbs energy of stabilization of proteins under conditions in which they behave as compatible osmolytes.

It is generally believed that compatible osmolytes stabilize proteins by shifting the denaturation equilibrium, native state <--> denatured state toward the left. We show here that if osmolytes are compatible with the functional activity of the protein at a given pH and temperature, they should not significantly perturb this denaturation equilibrium under the same experimental conditions. This conclusion was reached from the measurements of the activity parameters (K(m) and k(cat)) and guanidinium chloride-induced denaturations of lysozyme and ribonuclease-A in the presence of five polyols (sorbitol, glycerol, mannitol, xylitol and adonitol) at pH 7.

Effect of polyol osmolytes on DeltaG(D), the Gibbs energy of stabilisation of proteins at different pH values.

Thermal denaturation curves of lysozyme and ribonuclease-A were determined by measuring their far-UV circular dichroism (CD) spectra in the presence of different concentrations of five polyols (sorbitol, glycerol, mannitol, xylitol and adonitol) at various pH values in the range 7.0--1.9.

Counteracting osmolyte trimethylamine N-oxide destabilizes proteins at pH below its pKa. Measurements of thermodynamic parameters of proteins in the presence and absence of trimethylamine N-oxide.

Earlier studies have reported that trimethylamine N-oxide (TMAO), a naturally occurring osmolyte, is a universal stabilizer of proteins because it folds unstructured proteins and counteracts the deleterious effects of urea and salts on the structure and function of proteins. This conclusion has been reached from the studies of the effect of TMAO on proteins in the pH range 6.0-8.