Enthalpies of transfer for proteins from aqueous to water-alcohol solutions: A test for models of residues exposed to solvent
✍ Scribed by M. Y. Schrier; G. Defoster; E. E. Schrier; M. Starzak
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1986
- Tongue
- English
- Weight
- 851 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The enthalpies of transfer of proteins from aqueous solution to alcohol-water solutions are used as probes of solvent-accessible surface for these proteins. Enthalpies of transfer to 10 wt% ethanol solutions are determined calorimetrically for the native proteins ribonuclease A, lysozyme, and ovalbumin. Ribonuclease A and lysozyme are reduced and carboxamidomethylated to produce configurations in which interior residues of the native protein are exposed to the solvent; enthalpies of transfer are determined for these species. These data are then compared with enthalpies of transfer for the constituent amino acids of the proteins. The enthalpies of transfer for the residues are used to generate a maximal enthalpy of transfer that can be compared with the enthalpies of transfer for the reduced, carboxamidomethylated proteins. The residue amino acid enthalpies are coupled with probabilities that each residue is an exterior residue to predict an enthalpy of transfer for the native protein that can be compared with the observed enthalpy. The probabilities developed by Wertz and Scheraga and Lee and Richards, and Chothia are then compared on their ability to predict the native enthalpies of transfer for the protein. The Wertz-Scheraga model gives the better fit of this data in all cases.