Thermodynamic stability of ribonuclease A in alkylurea solutions and preferential solvation changes accompanying its thermal denaturation: a calorimetric and spectroscopic study.


Abstract

The effect of methylurea, N,N'-dimethylurea, ethylurea, and butylurea as well as guanidine hydrochloride (GuHCl), urea and pH on the thermal stability, structural properties, and preferential solvation changes accompanying the thermal unfolding of ribonuclease A (RNase A) has been investigated by differential scanning calorimetry (DSC), UV, and circular dichroism (CD) spectroscopy. The results show that the thermal stability of RNase A decreases with increasing concentration of denaturants and the size of the hydrophobic group substituted on the urea molecule. From CD measurements in the near- and far-UV range, it has been observed that the tertiary structure of RNase A melts at about 3 degrees C lower temperature than its secondary structure, which means that the hierarchy in structural building blocks exists for RNase A even at conditions at which according to DSC and UV measurements the RNase A unfolding can be interpreted in terms of a two-state approximation. The far-UV CD spectra also show that the final denatured states of RNase A at high temperatures in the presence of different denaturants including 4.5 M GuHCl are similar to each other but different from the one obtained in 4.5 M GuHCl at 25 degrees C. The concentration dependence of the preferential solvation change delta r23, expressed as the number of cosolvent molecules entering or leaving the solvation shell of the protein upon denaturation and calculated from DSC data, shows the same relative denaturation efficiency of alkylureas as other methods. Study holds ProTherm entries: 5459, 5460, 5461, 5462, 5463, 5464, 5465, 5466, 5467, 5468, 5469, 5470 Extra Details: thermal and solvent denaturation; UV spectroscopy

Submission Details

ID: soPpY7953

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:30 p.m.

Version: 1

Publication Details
Poklar N;Petrovcic N;Oblak M;Vesnaver G,Protein Sci. (1999) Thermodynamic stability of ribonuclease A in alkylurea solutions and preferential solvation changes accompanying its thermal denaturation: a calorimetric and spectroscopic study. PMID:10211829
Additional Information

Number of data points 24
Proteins Ribonuclease pancreatic ; Ribonuclease pancreatic
Unique complexes 1
Assays/Quantities/Protocols Experimental Assay: Tm buffers:None: -, ionic:: , pH:7.0 ; Experimental Assay: dHcal buffers:None: -, ionic:: , pH:7.0 ; Experimental Assay: Tm ionic:: , buffers:None: -, pH:7.0 ; Experimental Assay: dHvH buffers:None: -, ionic:: , pH:7.0 ; Experimental Assay: Tm buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:3.5 ; Experimental Assay: dHcal buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:3.5 ; Experimental Assay: Tm pH:3.5, buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M ; Experimental Assay: dHvH buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:3.5 ; Experimental Assay: Tm buffers:glycine-HCl: 0.1 M/0.1 M, pH:3.0, ionic:NaCl: 0.1 M ; Experimental Assay: dHcal buffers:glycine-HCl: 0.1 M/0.1 M, pH:3.0, ionic:NaCl: 0.1 M ; Experimental Assay: Tm buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:3.0 ; Experimental Assay: dHvH buffers:glycine-HCl: 0.1 M/0.1 M, pH:3.0, ionic:NaCl: 0.1 M ; Experimental Assay: Tm buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:2.0 ; Experimental Assay: dHcal buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:2.0 ; Experimental Assay: Tm buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:2.0 ; Experimental Assay: dHvH buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:2.0 ; Experimental Assay: Tm buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:1.5 ; Experimental Assay: dHcal buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:1.5 ; Experimental Assay: Tm buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:1.5 ; Experimental Assay: dHvH buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:1.5 ; Experimental Assay: Tm buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:1.1 ; Experimental Assay: dHcal pH:1.1, buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M ; Experimental Assay: Tm buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M, pH:1.1 ; Experimental Assay: dHvH pH:1.1, buffers:glycine-HCl: 0.1 M/0.1 M, ionic:NaCl: 0.1 M
Libraries Mutations for sequence KETAAAKFERQHMDSSTSAASSSNYCNQMMKSRNLTKDRCKPVNTFVHESLADVQAVCSQKNVACKNGQTNCYQSYSTMSITDCRETGSSKYPNCAYKTTQANKHIIVACEGNPYVPVHFDASV
Sequence Assay Result Units