The interactions of retinoids with retinol-binding protein. A resonance Raman spectroscopic study

We have measured the pre-resonance Raman spectrum of retinal, retinoic acid and retinol in dilute CCl4 solutions and when bound to the bovine-serum retinol-binding protein. The comparison reveals that the binding interaction does not involve any specific interactions of the head group and/or the polyene chain with a particular protein residue. The data indicate hydrogen bonding of bound retinal's head-group oxygen to water, as well as some torsional angle change of its polyene chain upon binding.