Complex Formation of Adenosine 3',5'-Cyclic Monophosphate with β-Cyclodextrin: Kinetics and Mechanism by Ultrasonic Relaxation

Abstract

Adenosine 3',5'-cyclic monophosphate (cAMP) is a second messenger responsible for a multitude of cellular responses. In this study, we utilized β-cyclodextrin (β-CD) as an artificial receptor with a hydrophobic cavity to elucidate the inclusion kinetics of cAMP in a hydrophobic environment using the ultrasonic relaxation method. The results revealed that the interaction of cAMP with β-CD followed a single relaxation curve as a result of host-guest interactions. The inclusion of cAMP into the β-CD cavity was found to be a diffusion-controlled reaction. The dissociation of cAMP from the β-CD cavity was slower than that of adenosine 5'-monophosphate (AMP). The syn and anti glycosyl conformations of adenine nucleotides are considered to play an important role in formation of the inclusion complex. Taken together, our findings indicate that hydrophobic interactions are involved in the inclusion complex formation of cAMP with β-CD and provide insight into the interactions of cAMP with cAMP-binding proteins.

Ultrasonic Relaxation for Complexation Reaction Between β-Cyclodextrin and Butanoic Acid in Aqueous Solution

“…The more hydrophobic the guest molecule is, the slower the dissociation from the host-guest complex is. The similar trends were found in the system with alcohols, AMP, cAMP, and amines as the guests [6][7][8]13] . These dependences of the rate constants on the hydrophobicity of the guest molecules reflect clearly on the stability of the inclusion complex.…”

“…In this study, we demonstrated that the interaction reactions [6][7][8]13] . A comparison of the results of the dissociated form with those in the undissociated form declares that the rate constant for the ionized guest is smaller than that for the neutral guest.…”

“…Dynamic association and dissociation processes between host and guest are of fundamental importance for certain functions of supramolecular systems. The dynamic properties of the interaction between cyclodextrins and nonelectrolytes have been examined in our series of experimental study by the ultrasonic relaxation method [6][7][8] . These investigations have revealed that the stabilization of the complexes is sensitive to the size of cavity, and to the balance between hydrophobicity and the hydrophilicity of the guest.…”