Interaction of L-tryptophan with alpha-cyclodextrin: studies with calorimetry and proton nuclear magnetic resonance spectroscopy.
The interaction of L-tryptophan with alpha-cyclodextrin was investigated in a 0.1 M phosphate buffer at pH 7.4 with a LKB 2277 microcalorimeter, using flow mixed mode at 25 degrees C. The thermodynamic parameters for inclusion complex formation obtained are as follows; DeltaG(0) = - 7.03 kJ/mol (K = 17.0), DeltaH(0) = - 9.50 kJ/mol, DeltaS(0) = - 8.3 J/mol K. The driving force for inclusion complex formation was considered to be mainly van der Waals-London dispersion force, and the contribution of hydrogen bonding was secondary in importance. Also, from the measurements of the proton nuclear magnetic resonance spectra and the model building with Corey-Pauling-Koltum atomic models, the probable structures of the complex, together with conformational change of L-tryptophan by complexation, were determined.
Nishijo
J
J
Kobe Pharmaceutical University, Motoyama-kitamachi, Higasinada-ku, Kobe 658-8558, Japan. nishijo@kobepharma-u.ac.jp
Tsuchitani
M
M
D002151:Calorimetry; D003505:Cyclodextrins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D011522:Protons; D014364:Tryptophan / Q000737:chemistry*; D047391:alpha-Cyclodextrins
D003505:Cyclodextrins; D011522:Protons; D047391:alpha-Cyclodextrins; D014364:Tryptophan; C032613:alpha-cyclodextrin