GEOMETRICAL ANALYSIS OF STRUCTURAL-CHANGES IN IMMUNOGLOBULIN DOMAINS TRANSITION FROM NATIVE TO MOLTEN STATE

Molecular dynamics simulation (300, 320, 340 K) performed on the Fab ( Kol) fragment of immunoglobulin G revealed that the structural changes associated with relaxation of peptides after their release from the s tabilized by the tertiary interaction native conformation may be consi dered characteristic of the transition from native to molten state. Th e configuration of peptide chains at temperatures close to melting, li berated from the constraints associated with tertiary packing, was fou nd to deviate toward helical rather than extended forms. The direction of the shift is diagonal on the Phi-Psi map. The torsional angles ten d to concentrate in the C-eq(7) region, and some leak to the alpha(R) area. The geometrical parameters designed to describe the configuratio n of the peptide chain in Fab fragment also confirmed that during melt ing the peptides generally moved toward helical form.