CALORIMETRIC STUDY OF COLD AND THERMAL DENATURATION OF BOVINE β-LACTOGLOBULIN B

The denaturational behaviour of bovine β-lactoglobulin B has been studied in solutions containing guanidine hydrochloride by differential scanning calorimetry. The experiments have shown that complete peaks of cold denaturation can be recorded also in high concentration of protein solutions. The cold denaturation and the renaturation of the protein are reproducible, but the thermal denaturation is irreversible. The activation energy of thermal denaturation calculated is about 285 kJ/mol.

Synthesis of Isonucleoside-Incorporated Oligonucleotides and Their Binding Abilities with Complementary Sequences

Aim To synthesize isonucleoside-incorporated oligonucleotides and investigatetheir binding abilities with complementary sequences. Methods The synthesis was performed on DNAsynthesizer, and the binding behavior was investigated by thermal denaturation studies. Results Fourkinds of single isonucleoside containing oligonucleotides were synthesized. The results of thermaldenaturation showed that the existence of isonucleoside decreased the stability of duplex, and theeffect was more obvious when the isonucleoside was in the middle of the sequence. No obviousdifference was observed when 6'-OH of isonucleoside was free or was protected by allyl group.Conclusions The existence of isonucleoside in oli-gonucleotide makes chain twist and decreased thestability of duplex.

Analysis of Lattice Size, Energy Density and Denaturation for a One-Dimensional DNA Model

There are several mechanical models to describe the DNA phenomenology. In this work the DNA denaturation is studied under thermodynamical and dynamical point of view using the well known Peyrard-Bishop model. The thermodynamics analysis using the transfer integral operator method is briefly reviewed. In particular, the lattice size is discussed and a conjecture about the minimum energy to denaturation is proposed. In terms of the dynamical aspects of the model, the equations of motion for the system are integrated and the results determine the energy density where the denatura- tion occurs. The behavior of the lattice near the phase transition is analyzed. The relation between the thermodynamical and dynamical results is discussed.

Effects of Selective Biotinylation on the Thermodynamic Stability of Human Serum Albumin

Thermal denaturation and stability of two commercially available preparations of Human Serum Albumin (HSA), differing in their advertised level of purity, were investigated by differential scanning calorimetry (DSC). These protein samples were 99% pure HSA (termed HSA99) and 96% pure HSA (termed HSA96). According to the supplier, the 3% difference in purity between HSA96 and HSA99 is primarily attributed to the presence of globulins and fatty acids. Our primary aim was to investigate the utility of DSC in discerning changes in HSA that occur when the protein is specifically adducted, and determine how adduct formation manifests itself in HSA denaturation curves, or thermograms, measured by DSC. Effects of site specific covalent attachment of biotin (the adduct) on the thermodynamic stability of HSA were investigated. Each of the HSA preparations was modified by biotinylation targeting a single site, or multiple sites on the protein structure. Thermograms of both modified and unmodified HSA samples successfully demonstrated the ability of DSC to clearly discern the two HSA preparations and the presence or absence of covalent modifications. DSC thermogram analysis also provided thermodynamic characterization of the different HSA samples of the study, which provided insight into how the two forms of HSA respond to covalent modification with biotin. Consistent with published studies [1] HSA96, the preparation with contaminants that contain globulins and fatty acids seems to be comprised of two forms, HSA96-L and HSA96-H, with HSA96-L more stable than HSA99. The effect of multisite biotinylation is to stabilize HSA96-L and destabilize HSA96-H. Thermodynamic analysis suggests that the binding of ligands comprising the fatty acid and globulin-like contaminant contributes approximately 6.7 kcal/mol to the stability HSA96-L.

Unfolding and Inactivation of Green Crab (Scylla Serrata) Alkaline Phosphatase during Thermal Denaturation

Enzyme activity is strongly dependent on its conformational integrity. The present paper compares the inactivation and unfolding of green crab (Scylla serrata) alkaline phosphate during thermal denaturation. The results show that inactivation takes place before noticeable conformational changes. This is in general accord with the suggestion previously made by Tsou, indicating that the active site of multi metal enzymes is situated in a region more flexible than the molecules as a whole.

Two Ways of Denaturation Leading to Different Transition States of Fibrinogen

HFG (human fibrinogen) desorbed from a PTFE (polytetrafluoroethylene) surface and thermally denatured HFG were conformationally studied by using FTIR (Fourier transform infrared) spectroscopy. It is shown that some irreversible conformational changes of HFG, including a decrease in the α helix content and an increase in the β structure content, were induced by the PTFE surface adsorption/desorption.This suggests that some α helix structures should transform into β structures.Desorbed HFG was thermally denatured as well as the native HFG under a thermal incubation of 30 min at 73 ℃ .After the same thermal treatment, the α helix content in the thermally denatured desorbed HFG was obviously less than that in the former native HFG.