PubMed Health⌕ Search

Biomedical subjects

C C Contaxis

Publications and source records attributed to C C Contaxis.

12 recordsLinked to original sources
PubMed1983

Free energy changes in lysozyme denaturation.

Previous work has shown that native lysozyme (N) is completely denatured by the addition of guanidinium chloride (conformation D) but that partially denatured conformations appear in other denaturants. Conformation I appears when LiClO4 is added to the protein, and conformation II is caused by heating. We have now determined the apparent free energy changes for the reversible processes between N and the three unfolded conformations and for the process between II and D. This allows us to estimate the apparent free energy changes for a process between any two of these four conformations.

Animals↗
PubMed1981

Free energy changes in alpha-lactalbumin denaturation.

Previous work has shown that native alpha-lactalbumin (N) is completely denatured by the addition of guanidine hydrochloride (conformation D) but that partially denatured conformations appear in other denaturants. In particular, conformation I appears when the pH is lowered from 5.5 to 2.2 (I2.2) or when LiClO4 is added at pH 5.5 (I5.5). We have now determined the free energy changes for the processes N leads to I5.5, N leads to D5.5, and I2.2 leads to D2.2. We have also estimated the maximum value of the free energy change for the process N leads to I.22, and this allows us to estimate the changes for all conformational changes between any two of these five conformations.

Animals↗
PubMed1977

The thermal denaturation of bovine cardiac G-actin.

The thermal denaturation of bovine cardiac G-actin has been studied by ultraviolet difference spectroscopy and circular dichroism between pH 7.5 and 10.5. As with proteins previously studied, thermal unfolding is incomplete compared with unfolding by urea or GuHCl. However, the same conformational change is observed over the pH range studied, and the available evidence indicates it is a two-state transition. Thermodynamic analysis of the data shows that deltaHo and deltaSo are strongly dependent on the temperature, that deltaCp is 1300 cal deg-1 mol-1, and that G-actin has a temperature of maximum stability near -5 degrees C.

Actins↗
PubMed1975

A study of the unfolding of the inhibited subtilisin in guanidine hydrochloride.

Inhibited subtilisin (Subtilism Carlsberg; Subtilopeptidase A) is unfolded in the presence of 7 M guanidine hydrochloride. The unfolding reaches a maximum in approximately 6 min at 20C at pH 8.0. This is demonstrated by an increase of the mean residue ellipticity at 222 nm from -8.02 x 10-3 to -1.72 x 10-3 deg. cm-2/decimole. The unfolding is partially reversible and this reversibility is favoured by lower concentrations of enzyme. The fact that the refolding process is not complete may be attributed to either the demonstrated self association of the denatured enzyme or to interference of non-covalently bound autolysis peptides.

Chromatography, Gel↗
PubMed1971

Studies on protein multimers. The association-dissociation behaviour of -galactosidase in glycerol.

1. The effect of glycerol on the association-dissociation behaviour of beta-galactosidases from Escherichia coli is described. Two strains, K12 and ML308, were used as sources of enzyme. The conditions used, involving glycerol at a concentration of 90%, result in dissociation of the active 540000-dalton form to inactive structural subunits of 135000 daltons. 2. A pH-dependent process, assumed to be cyclic in mechanism, allows reassociation to an active form indistinguishable from the initial protein. 3. The apparently identical structural subunits, if produced in the presence of EDTA, were found to give rise to two electrophoretically distinguishable species. 4. Enzymes from both strains of E. coli can be distinguished electrophoretically but exhibit the same behaviour in glycerol. 5. A scheme of the association-dissociation is presented that is consistent with the behaviour observed and that has some predictive value.

Edetic Acid↗