INTERACTION OF TRYPTOPHAN AND N-ACETYLTRYPTOPHANAMIDE WITH DODECYLPENTAOXYETHYLENEGLYCOL ETHER MICELLES

Through the fluorimetric determination of the critical micellar concen tration of dodecylpentaoxyethyleneglycol ether and sodium dodecylsulfa te, we have investigated the interaction of the zwitterionic tryptopha n and its uncharged analogue N-acetyl-L-tryptophanamide with micelles in terms of binding constants. This could be useful to monitor protein interaction with different membrane-like environments using the intri nsic tryptophan fluorescence. The weakest interaction took place betwe en tryptophan and sodium dodecylsulfate, while the strongest one occur red between N-acetyl-L-tryptophanamide and dodecylpentaoxyethyleneglyc ol ether. This suggests that micelle head groups control the interacti on, but the polar moiety bringing the fluorophore also seems to play a role. The unexpected lack of interaction between tryptophan and dodec ylpentaoxyethyleneglycol ether is also discussed. (C) 1997 Elsevier Sc ience B.V.