Solutions of the enzyme luciferase, extracted from Cypridina, were subjected at pH 6.8 to temperatures from 40-55 degrees C. for times up to 24 hours. After the desired exposures samples were cooled rapidly to room temperature, mixed with luciferin, and the first order velocity constants (representing luciferase activity) of the resulting luminescent reactions were determined by a photo electri...

Differential scanning calorimetry was employed to investigate the structure of spinach (Spinacia oleracea) chloroplast membranes. In a low ionic strength Hepes-buffered medium, major calorimetric transitions were resolved at 42.5 degrees C. (A), 60.6 degrees C (B), 64.9 degrees C (C(1)), 69.6 degrees C (C(2)), 75.8 degrees C (D), 84.3 degrees C (E), and 88.9 degrees C (F). A lipid melting trans...

Previous studies of recombinant full-length human apolipoprotein A-V (apoA-V) provided evidence of the presence of two independently folded structural domains. Computer-assisted sequence analysis and limited proteolysis studies identified an N-terminal fragment as a candidate for one of the domains. C-Terminal truncation variants in this size range, apoA-V(1-146) and apoA-V(1-169), were express...

The peripheral subunit-binding domain from the dihydrolipoamide acetyltransferase (E2) component of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus is stably folded, despite its short sequence of only 43 amino acid residues. A 41 residue peptide derived from this domain, psbd41, undergoes a cooperative thermal unfolding transition with a tm of 54 degrees C. This ...

The interaction between bovine serum albumin (BSA) and methyl cinnamate (MC), an strawberry flavor compound, was investigated. We found that BSA and MC form complex with stoichiometry (n) equal 1, driven by system’s entropy increase and enthalpy reduce at pH 7.4, 5.0 and 3.5, with binding constants (Kb) in magnitude of 10 5 L.mol -1 . There was difference in variation of standard enthalpy of co...

In contrast to the implications of the letter by Huang et al. (1), our previous work unambiguously showed that the protein BBL under denaturing conditions is a single, partly unfolded state (one-state folding) rather than a mix of folded and unfolded molecules (two-state folding) (2). This conclusion was based on ultrahigh-resolution single-molecule (sm) FRET experiments (>1 photon per microsec...

Using glucose oxidase and salmon testis-derived DNA molecules, we sought to extend the recently proposed idea of interfacial adsorption denaturation. The surface pressure-time (π-t) isotherm Gibbs monolayer exhibited a rapid increase in pressure relatively prompt transition liquid condensed film. appearance this expansion phase occurred much earlier than that previously identified for lysozyme,...

Thermal denaturation of equinatoxin II (EqTxII) in glycine buffer solutions (pH 1.1, 2.0, 3.0, and 3.5) and in triple distilled water (pH 5.5-6.0) was examined by differential scanning calorimetry, UV and CD spectroscopy and fluorescence emission spectroscopy of the added hydrophobic fluorescent probe ANS. At pH 5.5-6.0 and at temperatures below 60 degrees C, the protein exists in a native stat...

Wheat α-amylase, a multi-domain protein with immense industrial applications, belongs to α+β class of proteins with native molecular mass of 32 kDa. In the present study, the pathways leading to denaturation and the relevant unfolded states of this multi-domain, robust enzyme from wheat were discerned under the influence of temperature, pH and chemical denaturants. The structural and functional...

Denaturation of dilute solutions of ferrimyoglobins at pH 650 and 50’ by a 7to lo-fold molar excess for copper(D) is completely reversible on addition of excess chelating agent. The renaturation reaction exhibits first order kinetics. In the ultracentrifuge, the copper(D)-denatured proteins show little aggregation except for an increase in sedimentation constant for the sperm whale protein from...