Fast x-Ray dispersive spectroscopy allowed by the dispersive geometric shows three transitions in the kinetics of 5mM carbonylhemoglobin denaturation. The CO detachment at low pH(2.6) is preceeded by CO bending due to the protonation (pH-5.6), and later by protein unfolding (pH-3.3) Only a few detection systems have been achieved to compete the creditable performance of synchrotron radiation so...

When transglutaminase is heated at temperatures above 40 degrees C, it loses its activity according to a two-step mechanism [Nury, Meunier & Mouranche (1989) Eur. J. Biochem. 180, 161-166]: N----X(TD)----D However, the nature of the molecular events responsible for the irreversible denaturation is still unknown. Investigation of the effects of dithiothreitol and 5,5'-dithiobis-2-nitrobenzoate o...

Sso7d from the thermoacidophilic archaebacterium Sulfolobus solfataricus is a small globular protein with a known three-dimensional structure. Inspection of the structure reveals that Phe31 is a member of the aromatic cluster forming the protein hydrophobic core, whereas Trp23 is located on the protein surface and its side chain exposed to the solvent. The thermodynamic consequences of the subs...

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 req...

The denaturation of ribonuclease A by guanidine hydrochloride, lithium bromide, and lithium chloride and by mixed denaturants consisting of guanidine hydrochloride and one of the denaturants lithium chloride, lithium bromide, and sodium bromide was followed by difference spectral measurements at pH 4.8 and 25 degrees C. Both components of mixed denaturant systems enhance each other's effect in ...

A nucleoside aminohydrolase was prepared in 60-fold relative purity from the nonparticulate fraction of mouse kidney by denaturation at 60”, fractionation with (NH&S04, treatment with alumina gel Cr (pH 7.5), and dialysis in 0.02 M acetate buffer (pH 4.5). The’ optimal pH was 6.5. Cytidine, deoxycytidine, and I-/3-D-arabinofuranosylcytosine were deaminated, and the respective K, values were 7.5...

Human serum albumin (HSA) is an important protein that carries variety of substances like some hormones and drugs in blood. Pharmacological studies of the interaction of many drugs and HSA are reported during several decades, specially recently years. Interaction of cortisol and fluoxetine hydrochloride (FLX) (as a common anti-stress drug) with HSA (as their carrier in blood) has been studied s...

Non-nucleosidic DNA monomers comprising partially protonated amines at low pH have been designed and synthesized. The modifications were incorporated into DNA oligonucleotides via standard DNA phosphoramidite synthesis. The ability of cationic modifications to stabilize palindromic DNA hairpins and parallel triplexes were evaluated using gel electrophoresis, circular dichroism and thermal denat...

Lactoperoxidase (LPO) is a structurally complex and stable mammalian redox enzyme. Here we aim at evaluating the influence of ionic interactions and how these intertwine with the structural dynamics, stability and activity of LPO. In this respect, we have compared LPO guanidinium hydrochloride (GdmCl) and urea denaturation pathways and performed a detailed investigation on the effects of pH on ...

We studied the irreversible thermal denaturation of chymopapain, a papain-related cysteine proteinase. It was found that this process follows simple first-order kinetics under all conditions tested. Rate constants determined by monitoring ellipticity changes at 220 or 279 nm are essentially identical, indicating that denaturation involves global unfolding of the protein. Enthalpies (DeltaH(doub...