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Keywords:

  • albumin;
  • cyclodextrin;
  • porphyrin;
  • protein self-assembly;
  • supramolecular chemistry

Abstract

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 SN2 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.