Functionalization of a protein surface with per‐ O ‐methylated β ‐cyclodextrin

Per‐O‐methylated β‐cyclodextrin (CD) bearing an iodoacetamide group at the 6‐position was synthesized to functionalize protein surfaces. Bovine serum albumin (BSA) was quantitatively modified with the CD derivative by the S N 2 reaction of iodoacetamide with a cysteine residue (Cys34) on the BSA surface. The resultant CD‐functionalized BSA (BSA‐CD) spontaneously dimerized upon addition of an anionic tetraarylporphyrin (TPPS) through the supramolecular 1:2 complexation between TPPS and CD on the protein surface. The BSA‐CD/TPPS complex further complexed with ferric protoporphyrin IX (hemin) in the hydrophobic pockets of albumin to form a hemin/BSA‐CD/TPPS ternary complex in which static fluorescence quenching occurred owing to intramolecular electron transfer from the photoexcited TPPS to hemin. © 2011 Wiley Periodicals, Inc. Biopolymers 97: 11–20, 2012.