Invited Talk (Chemistry)

Proteins conformational stability

prof. Marián Antalík, DrSc. Institute of Chemistry,
PF UPJŠ, Košice, Slovakia

Abstract

Proteins are complex biopolymers created from 20 different amino acids connected by peptide bonds to polypeptide chain. Proteins` 3D structure depends on the composition of these amino acids as well as surroundings solvent molecules and special ligands (cofactors) and they adopt essentially unique conformations under physiological conditions. Functional native structure of the proteins comprise huge amount of different interaction as hydrogen bonds, ionic pairs, van der Waals bonds and hydrophobic interactions. After the synthesis of polypeptide chain in the ribosomes in appropriate conditions spontaneous folding of proteins are observed to native conformation.

The stability of proteins against changes in the temperature as well as in the chemical conditions of the solvent is only marginal. A typical magnitude order of the free energies of unfolding is approximately 20-50 of kJ/mol. The reason for a rather small free energy difference of proteins between their native and denatured state is due to the fact that the entropic contribution and the enthalpic contribution to the folding process almost cancel. Both contributions are large, but have opposite signs. The natural solvent for proteins is water, but it is always mixed with salts and other compounds which influence the ionic strength, the pH values, chemical affinity to certain molecular groups on the protein surface. All these properties have a strong influence on proteins` stability; they can induce unfolding to denatured state or folding to the native state.

In some cases the denatured states can be irreversible associated to aggregate states with severe consequences concerning certain health problems as neurodegenerative diseases - Alzheimer´s, Parkinson´s and Creutzfeldt- Jacob´s disorder.