Isiah M. Warner

Molecular fluorescence, phosphorescence, and chemiluminescence spectrometry

Department of Chemistry, University of Louisville, Louisville, Kentucky 40208, Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, Department of Chemistry, Winston-Salem State University, Winston-Salem, North Carolina 27110, Department of Chemistry, Nanoscience and Nanotechnology Institute and the Optical Science and Technology Center, University of Iowa, Iowa City, Iowa 52242, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, Department of Chemistry and Biochemistry, Southern Illinois University, Carbondale, Illinois 62901-4409, Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, and Department of Chemistry, University of Delaware, Newark, Delaware 19716

Changing the Culture of Science Education at Research Universities

Universities must better recognize, reward, and support the efforts of researchers who are also excellent and dedicated teachers. Professors have two primary charges: generate new knowledge and educate students. The reward systems at research universities heavily weight efforts of many professors toward research at the expense of teaching, particularly in disciplines supported extensively by extramural funding (1). Although education and lifelong learning skills are of utmost importance in our rapidly changing, technologically dependent world (2), teaching responsibilities in many STEM (science, technology, engineering, and math) disciplines have long had the derogatory label “teaching load” (3, 4). Some institutions even award professors “teaching release” as an acknowledgment of their research accomplishments and success at raising outside research funds.

Combined polymerized chiral micelle and γ-cyclodextrin for chiral separation in capillary electrophoresis

A combination of a polymerized chiral micelle, poly(sodium N-undecylenyl-D-valinate) [poly(D-SUV)] and gamma-cyclodextrin (gamma-CD) is used for the first time for chiral separation in capillary electrophoresis. A simple theory is presented to rationalize the synergistic effect of the enantioselectivity obtained by use of poly(D-SUV) and gamma-CD in combination. A mixture of four enantiomeric pairs is successfully resolved by use of this combination. The resolutions of the enantiomers using this approach are far superior to those obtained by use of either poly(D-SUV) or gamma-CD alone. In addition, the effects of the antipode (L-SUV), gamma-CD concentration, buffer concentration, organic solvents, and urea concentration on the resolution are also examined.

Seminaphthofluorones are a family of water-soluble, low molecular weight, NIR-emitting fluorophores

A readily accessible new class of near infrared (NIR) molecular probes has been synthesized and evaluated. Specific fluorophores in this unique xanthene based regioisomeric seminaphthofluorone dye series exhibit a combination of desirable characteristics including (i) low molecular weight (339 amu), (ii) aqueous solubility, and (iii) dual excitation and emission from their fluorescent neutral and anionic forms. Importantly, systematic changes in the regiochemistry of benzannulation and the ionizable moieties afford (iv) tunable deep-red to NIR emission from anionic species and (v) enhanced Stokes shifts. Anionic SNAFR-6, exhibiting an unusually large Stokes shift of ≈200 nm (5,014 cm−1) in aqueous buffer, embodies an unprecedented fluorophore that emits NIR fluorescence when excited in the blue/green wavelength region. The successful use of SNAFR-6 in cellular imaging studies demonstrates proof-of-concept that this class of dyes possesses photophysical characteristics that allow their use in practical applications. Notably, each of the new fluorophores described is a minimal template structure for evaluation of their basic spectral properties, which may be further functionalized and optimized yielding concomitant improvements in their photophysical properties.

Highly Efficient Extraction of Phenolic Compounds by Use of Magnetic Room Temperature Ionic Liquids for Environmental Remediation

A hydrophobic magnetic room temperature ionic liquid (MRTIL), trihexyltetradecylphosphonium tetrachloroferrate(III) ([3C(6)PC(14)][FeCl(4)]), was synthesized from trihexyltetradecylphosphonium chloride and FeCl(3) · 6H(2)O. This MRTIL was investigated as a possible separation agent for solvent extraction of phenolic compounds from aqueous solution. Due to its strong paramagnetism, [3C(6)PC(14)][FeCl(4)] responds to an external neodymium magnet, which was employed in the design of a novel magnetic extraction technique. The conditions for extraction, including extraction time, volume ratio between MRTIL and aqueous phase, pH of aqueous solution, and structures of phenolic compounds were investigated and optimized. The magnetic extraction of phenols achieved equilibrium in 20 min and the phenolic compounds were found to have higher distribution ratios under acidic conditions. In addition, it was observed that phenols containing a greater number of chlorine or nitro substituents exhibited higher distribution ratios. For example, the distribution ratio of phenol (D(Ph)) was 107. In contrast, 3,5-dichlorophenol distribution ratio (D(3,5-DCP)) had a much higher value of 6372 under identical extraction conditions. When compared with four selected traditional non-magnetic room temperature ionic liquids, our [3C(6)PC(14)][FeCl(4)] exhibited significantly higher extraction efficiency under the same experimental conditions used in this work. Pentachlorophenol, a major component in the contaminated soil sample obtained from a superfund site, was successfully extracted and removed by use of [3C(6)PC(14)][FeCl(4)] with high extraction efficiency. Pentachlorophenol concentration was dramatically reduced from 7.8 μg mL(-1) to 0.2 μg mL(-1) after the magnetic extraction by use of [3C(6)PC(14)][FeCl(4)].

Near-Infrared Fluorescent NanoGUMBOS for Biomedical Imaging

Herein, we report on near-infrared (NIR) fluorescent nanoparticles generated from an emergent class of materials we refer to as a Group of Uniform Materials Based on Organic Salts (GUMBOS). GUMBOS are largely frozen ionic liquids, although the concept is more general and is also easily applied to solid ionic materials with melting points in excess of 100 degrees C. Nanoparticles based on GUMBOS (nanoGUMBOS) derived from a NIR fluorophore are prepared using a reprecipitation method and evaluated for in vivo fluorescence imaging. Due to their uniformity, single-step preparation, and composite nature, nanoGUMBOS help to resolve issues with dye leakage problems innate to alternate cellular stains and unlock a myriad of applications for these materials, highlighting exciting possibilities for multifunctional nanoGUMBOS.

Cyclodextrin-induced fluid solution room-temperature phosphorescence from acenaphthene in the presence of 2-bromoethanol

Abstract A 1:1 stoichiometric ratio and a formation constant of 130 1 mol −1 were obtained for the binary inclusion complex between acenaphthene and β-cyclodextrin (CD). On addition of 2-bromoethanol, effective quenching of the fluorescence emission and enhancement of the room-temperature phosphorescence (RTP) of acenaphthene is observed. The use of 2-bromoethanol as an external “heavy atom” to obtain room-temperature phosphorescence in fluid solutions is discussed. The RTP emission from acenaphthene included in β-CD was optimized and characterized. The apparent formation constant of the ternary associate was determined to be 880 1 mol −1 by the use of RTP enhancement in the presence of 1% 2-bromoethanol. The data indicate a ternary association between acenaphthene, β-CD and the bromo alcohol. The use of sodium sulfite, for chemical deoxygenation, to obtain RTP emission from a non-heavy atom-containing luminophor is shown to be feasible. The kinetics of the deoxygenation reaction were established and a photochemical catalytic effect on the reaction was demonstrated.

Lanthanide Complexes as Fluorescent Indicators for Neutral Sugars and Cancer Diagnosis

Simple water-soluble lanthanum and europium complexes are effective at detecting neutral sugars as well as glycolipids and phospholipids. In solutions at physiologically relevant pH the fluorescent lanthanum complex binds neutral sugars with apparent binding constants comparable to those of arylboronic acids. Interference from commonly occurring anions is minimal. The europium complex detects sialic acid-containing gangliosides at pH 7.0 over an asialoganglioside. This selectivity is attributed, in large part, to the cooperative complexation of the oligosaccharide and sialic acid residues to the metal center, based on analogous prior studies. In MeOH, lysophosphatidic acid (LPA), a biomarker for several pathological conditions including ovarian cancer, is selectively detected by the europium complex. LPA is also detected via a fluorescence increase in human plasma samples. The 2-sn-OH moiety of LPA plays a key role in promoting binding to the metal center. Other molecules found in common brain ganglioside and phospholipid extracts do not interfere in the ganglioside or LPA fluorescence assays.

Determination of pharmacologically active compounds in root extracts of Cassia alata L. by use of high performance liquid chromatography

A simple high performance liquid chromatography (HPLC) method was developed and validated for the determination of six phenolic compounds, five anthraquinones (rhein, aloe-emodin, emodin, chrysophanol and physcion) and a flavonoid (kaempferol), in root extracts from Cassia alata L. Solid-phase extraction, using C(18) cartridges, was used to remove interfering substances from the root extracts. The extracts were analyzed on a C(18) column using an isocratic mobile phase which consisted of acetonitrile, methanol, and 10mM aqueous ammonium acetate (25:55:20, v/v). Identification of the analytes was performed by use of standards and on-line mass spectrometric detection using atmospheric pressure chemical ionization. The concentration of the phenolic compounds in the root extracts was determined using HPLC with ultraviolet detection at 260nm. The limits of detection obtained for the anlytes were in the range of 0.23-4.61ppm. The overall R.S.D. precision values (intra- and inter-day) for the retention times and peak-areas were lower than 0.16 and 2.10%, respectively. In addition, the recovery of the developed method for the analysis of these phenolic compounds was determined, and ranged from 81.2+/-4.3 to 106+/-2%.

Enantiomeric separations by use of polymeric surfactant electrokinetic chromatography

This review surveys the enantiomeric separation of drugs by electrokinetic chromatography using polymeric chiral surfactant pseudostationary phases. These phases have recently been shown to provide better mass transfer and increased rigidity and stability than regular micelles in micellar capillary electrophoresis. Characterization of the polymeric chiral surfactants is presented. Solution interactions of the pseudostationary phases via thermodynamics and fluorescence probe studies are evaluated. Also, case studies of enantiomeric separation of drugs using a single amino acid surfactant and the synergistic effect of the addition of gamma-cyclodextrin to the buffer is discussed. The use of dipeptide surfactants for chiral drug separations is described as well.