EFFECT OF REDUCTIVE ALKYLATION ON TRANSFERRIN CONFORMATION AND PHYSICOCHEMICAL PROPERTIES

Lauryl moieties were linked to the lysine epsilon-amino groups of native transferrin using lauryl aldehyde and sodium cyanoborohydride. The level of derivatization, determined by amino acid analysis, was 50 and 100%, according to the decrease in lysine content. The protein was titrated with 8-anilino-1-naphthylsulphonic acid and changes in fluorescence intensity, lambda(max) and polarization were determined. The intrinsic fluorescence of the protein was determined as a function of the phospholipids' content. The ability of derivatized transferrin to destabilize bilayers was checked using carboxyfluorescein loaded liposomes. The surface activity and the interaction with monolayers were determined for both proteins and compared with the same values before derivatization. The binding of native and derivatized transferrin to bilayers was determined at different phospholipid to protein ratios and found to be highly dependent on the hydrophobicity of protein. The results show that derivatization induces a new structure, the alkyl chains being located inside the protein core. No strong differences were found between 50 and 100% derivatized transferrin.