Finding Thermal and Conformational Stability of Iron Storage Nanocage Protein ,Ferritin by Circular Dichroism

Abstract

Ferritin is a globular intracellular protein complex that stores iron and release it in a controlled way.The folded state is stabilized mainly by tight packing of over 80% of the peptide groups and non-polar side chains.This is the structure that can be determined in crystals by x-ray crystallography .The stability of protein is simply the difference in gibbs free energy , ∆G,between the folded(Gf) and unfolded(Gu) state .The larger and more positive the ∆Gu the more stable the protein to denaturation. ∆GU=GU-GF For many proteins,equilibrium unfolding induced by chemical denaturants urea and guanidine chloride (GdnHcl) is much better suited for quantification of stability because the salts bind to amide amide back bone of the protein in such a way as to stabilized unfolded protein.CD is the difference in the absorption of L-CPL and R-CPL and occurs when a molecule contains one or more chiral chromophores.A molecule that absorbs LCP and RCP is optically active or chiral.Ferritin is highly stable at 95deg celcius and so it is called thermostable protein.No conformational changes occur when we applied high temperature but when we treated the protein with high concentration of Guanidinium Hcl its loses its stability and unfolds fully at 8M.