Gregory Nelson

Fluorescence Lifetime Study of Cyclodextrin Complexes of Substituted Naphthalenes

The interactions of α, β, and -γ-cyclodextrins and selected naphthalene derivatives as observed through fluorescence lifetime measurements are discussed in detail. These systems can be quickly characterized with the use of the parameters obtained from experimental fluorescence decay curves. The formation of inclusion complexes can be followed with the appearance of a long-lived fluorophore which contributes to the total fluorescence according to the cyclodextrin concentration. This fluorophore is determined to be an inclusion complex between a naphthalene and cyclodextrin.

The formation of pyrene:cyclomalto-oligosaccharide complexes in the presence of non-ionic surfactants

Abstract Examination of the interactions of pyrene, cyclomalto-oligosaccharides (cyclodextrins), and selected non-ionic surfactants by measurements of fluorescence life-times indicates that ternary complexes are formed. Studies of surface tensiometry indicate that binary complexes occur between cyclodextrins and non-ionic surfactants.

Influence oftert-butyl alcohol on cyclodextrin inclusion complexes of pyrene

The effect oftert-butyl alcohol on complexes of pyrene and various cyclodextrins is investigated. The equilibrium constant for the complexation is derived from the fluorescence decay parameters. A greater than twofold enhancement of pyrene lifetime is observed in the presence oftert-butyl alcohol and β-cyclodextrin or γ-cyclodextrin. As the number of hydroxyl groups decreases, substituted β-cyclodextrins show smaller enhancements to both the fluorescence lifetime and the formation constant. These observations are explained by proposing that alcohol molecules are associated with the inclusion complex. This association increases the apparent hydrophobicity of the cyclodextrin cavity, protects the molecule from collisional quenching and deactivation, and provides additional rigidity to the system.

Cyclodextrin complexes of polyaromatic hydrocarbons in the presence of aliphatic alcohols

Pyrene, as a fluorescence probe, has been used to study the cyclodextrin complexation process in the presence of different alcohols. The complex formation as well as the hydrophobicity of the cyclodextrin interior can be significantly influenced by the introduction of alcohols. The alcoholic alkyl group and the primary and secondary hydroxyl groups of the cyclodextrin proved to be the determining factors in the complex formation.

The Influence of Mobile Phase Alcohol Modifiers on HPLC of Polycyclic Aromatics Using Bonded Phase Cyclodextrin Columns

Abstract Recent studies have shown that formation constants for cyclodextrin inclusion complexes are increased in the presence of certain alcohols. This paper describes a preliminary investigation of the effects of mobile phase alcohol modifiers on HPLC separation of polynuclear aromatics using cyclodextrin bonded phases. Dramatic changes in the chromatography are reported in the presence of alcohol. Some discussion is provided as to how these results may be used to increase the selectivity of HPLC separations using cyclodextrin bonded phases.

Investigation of ternary cyclodextrin complexes by fluorescence spectrometry

Abstract Ternary complexes of cyclodextrin are apparently formed in the presence of saturated alcohols, glycols and acids. The role of third components in these complexes is investigated. Pyrene is used as a probe to determine the degree of compartmentalization, the change in the hydrophobicity of the microenvironment, and the formation constant.

The utility of time-resolved emission spectroscopy in the study of cyclodextrin-pyrene inclusion complexes

The application of time-resolved emission spectroscopy to the characterization of cyclodextrin inclusion complexes of pyrene in the presence of various alcohols is described. Such measurements offer a means of selectively studying the characteristics of inclusion complexes in the presence of uncomplexed pyrene. The fluorescence lifetimes and formation constants of these complexes are enhanced in the presence of alcohols. These enhancements are reportedly due to the formation of pyrene-alcohol-CD ternary complexes.

Analysis of drug binding sites on human serum albumin using multidimensional fluorescence measurements

Abstract Stern-Volmer fluorescence quenching, fluorescence lifetime measurements and fluorescence detected circular dichroism quenching (FDCDQ) are used to investigate the properties of the site I and site II binding areas on human serum albumin (HSA). The binding sites are probed using the site I specific fluorescent markers warfarin, dansylamide, and the site II markers salicyclic acid and naproxen. Two nonionic quenching probes, acrylamide and 2,2,2-trichloroethanol, are used to measure the relative degree of exposure and hydrophobicity of the binding sites. Quenching measurements confirm that the microenvironment of the site I binding area is more hydrophobic than site II. The fluorescence lifetimes for the site I probes increase by an order of magnitude upon binding to HSA. The change in lifetime upon binding and lack of dynamic quenching of the bound fluorophores indicates that the site I and site II binding areas are located in pockets on the protein which are formed as the probes bind. Lifetime measurements in the presence of both quenchers provide evidence that the site II probes bind to two regions of different microenvironment. One of these sites is quenched by acrylamide and does not contribute to the FDCDQ signal. The salicylic acid bound to the second and predominant binding area on HSA which produces the optical activity for the complex is not quenched by acrylamide.

An Inexpensive Intelligent Interface for Coupling a Pra Fluorescence Lifetime Instrument to a Microvax II

ABSTRACT An inexpensive interface which can perform serial and parallel I/O operations necessary for instrument control and data transfer operations using time-correlated single photon counting instrumentation is described. Development of a compatible stepper motor system for controlling peripherals is also provided. This interface was implemented using an inexpensive Z80A based microcomputer.

Optimization of Fluorescence Measurements

Various components of a conventional fluorometer are discussed. Several approaches to optimization of some of these components are discussed by citing specific research examples. The four areas of research that are described include: stabilization of a xenon arc lamp, improvements in sample chemistry, increased detector selectivity, and development of data reduction strategies for complex data. Improvements in the fluorescence measurement process are cited with each example.