The conserved disulfide bond of human tear lipocalin modulates conformation and lipid binding in a ligand selective manner

► Disulfide reduction promotes the plasticity for the hairpin CD. ► The time constant of binding kinetics for NBD cholesterol is decreased 3 fold. ► However, the time constant of binding kinetics for NBD C12-HPC is only slightly decreased. ► Disulfide reduction promotes conformational changes to favor binding the bulky ligand.