Dilatometric and refractometric studies of the helix—coil transition of poly‐L‐glutamic acid in aqueous solution

摘要: The helix—coil transition of poly-L-glutamic acid (PGA) in aqueous solutions was followed by volume changes, ΔV, and also differential refractive indices, Δn. increase ΔV or decrease Δn upon mixing the sodium salt PGA with dilute HCl gave three straight lines between pH 7 4, two breaks corresponding to zone observed other physical methods. For reaction: COO− + H+ CO-OH, per mole bound 11.4 11.1 ml. 0.01 0.2M NaCl solutions, respectively. An additional conformational change about 0.5–1 amino residue for coil helix, after taking electrostatic interaction into consideration. This probably due release water hydration at amide linkages when polypeptide is converted α-helix, even occurrence voids chain as a result imperfect packing atoms, although origin this still not fully understood present time. changes calculated from assuming constant polarizability polymer found be higher association reaction than those mentioned above. On hand, fair agreement direct measurements.