Effect of Amino Acid Coinclusion on the Complexation of Pyrene with β-Cyclodextrin

Abstract

The possibility of amino acids acting as ternary complexation agents for the binding of pyrene with -cyclodextrin ( -CD) was investigated. UV-vis absorption measurements combined with steady-state and time-resolved fluorescence studies were employed to characterize ternary complex formation. From the 18 amino acids tested it was determined that tryptophan, leucine, phenylalanine, methionine, and isoleucine form ternary complexes. The first three also significantly enhance the association constant of pyrene with -CD. Amino acids are less efficient than alcohols in enhancing the association constants of host-guest complexes, but a higher degree of steric constraint in the complexes including these zwitterionic molecules was observed. In addition, two types of pyrene--CD complexes were shown to exist, which were assigned to complexes with 1:1 and 1:2 pyrene: -CD stoichiometries.

Sensitizing of pyrene fluorescence by β-cyclodextrin-modified TiO2 nanoparticles

“…The association constants obtained from fluorescence spectra are same order as values from the absorption spectra in the present work and values reported for anthracene-9-carboxylic acid/colloidal TiO 2 system [37] and over all equilibrium constant for the pyrene b-CD complex [38]. It is noticed that the association constants evaluated from fluorescence data are more acceptable than those from UV-vis absorption data, because the analytical error by correction of background spectra as carried out on absorption spectra is not necessary to take into consideration on fluorescence spectra.…”

Cell-penetrating Peptides with Intracellular Actin-remodeling Activity in Malignant Fibroblasts

“…(R/W)16 could influence in the same way pyrene fluorescence through binding to lower affinity sites. This quenching would not be surprising because it has been shown that pyrene could be quenched by Trp or Arg (33,34), the two amino acids that compose (R/W)16. The fact that no similar quenching was observed when the peptide was added to preformed F-actin observation could simply indicate a slight conformational change of the protomer upon F-actin formation in the presence of (R/W)16.…”

Molecular‐Recognition and Binding Properties of Cyclodextrin‐Conjugated Polyrotaxanes

“…[18] Herein, all three pyrene species, that is, pyrene free in solution and bound to b-CD with 1:1 and 1:2 stoichiometries, were present. It is noteworthy that no excimer emission was observed, and this excludes the possibility of b-CD complexes containing two pyrene molecules.…”