Resonance energy transfer between tryptophan-214 in human serum albumin and acrylodan, prodan, and promen

It has been proposed that acrylodan (6-acryloyl-2-dimethylaminonaphthalene) and prodan (6-propionyl-2-dimethylaminonaphthalene) bind to site I of human serum albumin, whereas promen (6-propionyl-2-methoxynaphthalene) binds to site II of this carrier protein. Because human albumin contains only one single tryptophan, at position 214, it has been possible to measure the distances from this amino-acid residue to each of the three probes by nonradiative energy transfer. The distances calculated, 2.97 +/- 0.10 nm, 3.14 +/- 0.11 nm, and 2.62 +/- 0.17 nm, respectively, confirm the locations previously proposed for all three probes.