The Binding of Sodium Dodecyl Sulfate to Lysozyme in Aqueous Solutions

The binding mode of sodium dodecyl sulfate to lysozyme and the accompanying structural change of lysozyme by binding have been investigated by means of the binding isotherm, the precipitation curve, and the CD spectra in pure water, NaCl, and borate buffer solutions. The precipitation phenomena could be explained in terms of the neutralization of the net charge of lysozyme due to dodecyl sulfate-ion binding. The analysis of the binding isotherms by the use of the BET equation gave the site number of the first layer corresponding to the positively charged residues at the pH studied. The conformational change from the β-structure to the α-helix has been observed in the second-layer binding. The environmental change of the side-chain residues has also been observed.