ENERGY TRANSFER IN TRITON X-405 MICELLES: THE EFFECTS OF TEMPERATURE AND BRIJ 35

–Energy transfer from the phenyl groups of micellar Triton X-405 (TX-405) to solubilized pyrene molecules has been measured at a range of temperatures and in the presence of different polyoxyethylene 23 lauryl ether (Brij 35) concentrations. Increases in temperature lead to elimination of water from the outer, wet, micelle layer and an inward movement of associated pyrene. The addition of Brij also leads to a reduction in polarity of the microenvironment of pyrene. However, sensitization is observed even at high Brij concentrations. The donor/acceptor separation caused by the introduction of Brij proceeds slowly, continuing for several minutes after its addition to micellar TX-405.     

Influence of fluorinated alcohols on cyclodextrin: Pyrene complexation

An investigation of the effect of fluorinated alcohols on complexation between pyrene and - and -cyclodextrin (CD) in aqueous solution is reported. Using fluorescence spectrophotometric analysis, pyrene I/III vibronic band ratios were monitored upon the addition of CD, both in the absence and presence of fluorinated alcohols, as well as in the presence of their nonfluorinated alcohol analogs. The fluorinated alcohols studied were 2,2,2-trifluoroethanol and 2,2,3,3,3-pentafluoro-1-propanol. In aqueous solution, the alcohols were found to have no effect on the pyreneI/III ratio in the absence of CD, but a strong effect when CD was present. For -CD, the stoichiometry of the CD/pyrene complex was found to be predominantly 2 : 1, whereas for -CD it was 1 : 1. Apparent complexation equilibrium constants for the CD/pyrene complexes in the absence and presence of the alcohols were calculated by use of nonlinear regression analysis. Interactions between the alcohols and CDs were also investigated using¹H and¹⁹F NMR techniques.     

Energy transfer in benzalkonium chloride micelles

The energy transfer process from the excited phenyl group of micellar benzalkonium chloride (BAC) to solubilized anthracene is described. NMR studies show the solubilization site of the anthracene to be near the phenyl group in the BAC micelles. The system gives an energy transfer efficiency of 0.741 and the donor-acceptor separation is 41.4 A.     

Complexation of ephedrine withβ-cyclodextrin: An NMR spectroscopy study

This study focuses on the inclusion complex of ephedrine with -CD. The association of -CD and ephedrine has been examined using¹H NMR and circular dichroism. The systematic shifts of the proton resonances of the phenyl moiety of ephedrine and that of the protons located inside the -CD cavity, provide evidence of intracavity inclusion. Two-dimensional ROESY show preferential localization of ephedrine in close proximity with protons located inside the -CD cavity. The systematic variation of circular dichroism spectra with increasing concentration of -CD is used to estimate the apparent formation constant.Emory University School of Medicine, Atlanta, GA 30322, U.S.A.     

Spectroscopic analysis and drug-binding studies of the CNBr fragments of human serum albumin

Three large fragments (A, B and C) of human serum albumin (HSA) were produced by cyanogen bromide digestion of HSA in order to investigate the specific binding sites. The fragments were isolated by use of gel filtration, followed by high performance ion exchange chromatography. The isolated fragments were examined by use of UV/Vis, steady-state fluorescence, and circular dichroism spectroscopy. The study was extended to examine the interactions of bilirubin and two anionic drugs, warfarin and naproxen, with HSA and the three fragments. The primary bilirubin binding site on HSA molecule appeared to be located between fragment A and fragment C. The results also suggest the binding sites of the two anionic drugs to mosy likely be located in fragment C of HSA molecule.     

Spectral characterization ofβ-Cyclodextrin : Triton X-100 complexes

The spectral characteristics of the surfactant, Triton X-100, in the absence and presence of-cyclodextrin have been examined. The fluorescence of Triton X-100 is concentration dependent and is markedly enhanced in the presence of-cyclodextrin. Analysis of the variations in the excitation-emission profiles of the surfactant with concentration suggests excimer emission at concentrations above the critical micelle concentration (CMC). Nuclear magnetic resonance (NMR) spectroscopy suggests that the phenyl group is included inside the CD cavity while a portion of the ethylene oxide chain extends outside the cavity. Benesi-Hildebrand type equations were derived to determine the stoichiometry and to estimate the formation constant of the CD: S_f complex.     

Spectroscopic effects of organized media on a cyanine dye/pyrene derivative

The absorption and fluorescence spectra of a cyanine dye/pyrene derivative are studied in the presence of-cyclodextrin, Brij 35, cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). Benesi-Hildebrand type equations are used to estimate the apparent association constant of the dye/cyclodextrin complex. In addition, an estimate of the dimerization constant for the dye is examined.