Matthew A Tarr

University of New Orleans, New Orleans, Louisiana, United States

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Publications (37)104.48 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Progress has been made in using human serum albumin nanoparticles (HSAPs) as promising colloidal carrier systems for early detection and targeted treatment of cancer and other diseases. Despite this success, there is a current lack of multi-functional HSAP hybrids that offer combinational therapies. The size of the HSAPs has crucial importance on drug loading and in vivo performance and has previously been controlled via manipulation of pH and cross-linking parameters. Gold nanomaterials have also gained attention for medicinal use due to their ability to absorb near-infrared light, thus offering photothermal capabilities. In this study, the desolvation and cross-linking approach was employed to encapsulate gold nanorods, nanoparticles, and nanoshells into HSAPs. Incorporation of gold nanomaterials caused some changes in HSAP sizes, but the general size trends remained. This encasement strategy facilitated size-controlled HSAPs, in the range of 100-300 nm, loaded with gold nanostructures; providing composite particles which incorporate photothermally active components.
    Journal of Microencapsulation 08/2014; · 1.57 Impact Factor
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    ABSTRACT: In order to assess the impact of sunlight on oil fate, Macondo Well Oil from the Deepwater Horizon (DWH) rig was mixed with pure water and irradiated with simulated sunlight. After irradiation, the water-soluble organics (WSO) from the dark and irradiated samples were extracted and characterized by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Liquid-liquid extraction yielded two fractions from dark and irradiated water/oil mixtures: acidic WSOs (negative-ion electrospray (ESI)), and base/neutral WSOs (positive-ion ESI) coupled to FT-ICR MS to catalogue molecular-level transformations that occur to Macondo-derived WSOs after solar irradiation. Such direct measure of oil phototransformation has not been previously reported. The most abundant heteroatom class detected in the irradiated WSO acid fractions correspond to molecules that contain five oxygens (O5), while the most abundant acids in the dark samples contain two oxygen atoms per molecule (O2). Higher-order oxygen classes (O5 – O9) were abundant in the irradiated samples, but < 1.5 % relative abundance in the dark sample. The increased abundance of higher-order oxygen classes in the irradiated samples relative to the dark samples indicates that photooxidized components of the Macondo crude oil become water-soluble after irradiation. The base/neutral fraction showed decreased abundance of pyridinic nitrogen (N1) concurrent with an increased abundance of N1Ox classes after irradiation. The predominance of higher-order oxygen classes indicates that multiple photochemical pathways exist that result in oxidation of petroleum compounds.
    Journal of Hazardous Materials 08/2014; Accepted. · 3.93 Impact Factor
  • Sourav Chakraborty, Yang Cai, Matthew A. Tarr
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    ABSTRACT: Low density lipoprotein (LDL) is a major cholesterol carrier in human blood. Oxidations of apolipoprotein B-100 (apo B-100, LDL protein) could be pro-atherogenic and play critical roles in early stages of plaque formation in the arterial wall. The structure of apo B-100 is still poorly understood, partially due to its size (550 KDa, 4563 amino acids). To gain an insight into LDL structure, we mapped the regions of apo B-100 in human LDL which were prone to oxidation using peroxynitrite and hypochlorite as probes. In this study, LDL was incubated with various concentrations of peroxynitrite and sodium hypochlorite in bicarbonate buffer. The LDL protein apo B-100 was delipidated, denatured, alkylated and subjected to tryptic digestion. Tryptic peptides were analyzed employing liquid chromatography – tandem mass spectrometry (LC-MS/MS). Database search was performed against the apo B-100 database (P04114) using “SEQUEST” algorithm to identify peroxynitrite and hypochlorite mediated oxidations markers nitrotyrosine, nitrotryptophan, hydroxy-tryptophan and 3-chlorotyrosine. Several site specific oxidations were identified in apo B-100 after treatment of intact LDL particles with the oxidants. We hypothesize that these regions could be accessible to oxidant and critical for early events in atherosclerotic plaque deposition.This article is protected by copyright. All rights reserved
    Proteomics 08/2014; · 4.43 Impact Factor
  • Phoebe Z Ray, Matthew A Tarr
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    ABSTRACT: Sunlight exposed oil films on seawater or pure water produced substantial amounts of hydroxyl radical as a result of irradiation. Oil was collected from the surface of the Gulf of Mexico following the Deepwater Horizon spill and exposed to simulated sunlight in thin films over water. Photochemical production of hydroxyl radical was measured with benzoic acid as a selective chemical probe in the aqueous layer. Total hydroxyl radical formation was studied using high benzoic acid concentrations and varying exposure time. The total amount of hydroxyl radical produced in 24h irradiations of thin oil films over Gulf of Mexico water and pure water were 3.7×10(-7) and 4.2×10(-7)moles respectively. Steady state concentrations of hydroxyl radical were measured using a competition kinetics approach. Hydroxyl radical concentrations of 1.2×10(-16) to 2.4×10(-16)M were observed for seawater and pure water under oil films. Titanium dioxide (TiO2) nanomaterials were added to the system in an effort to determine if the photocatalyst would enhance oil photodegradation. The addition of TiO2 nanoparticles dramatically changed the observed formation rate of hydroxyl radical in the systems with NP water at pH 3, showing increased formation rate in many cases. With photocatalyst, the steady state concentration of radical decreased, predominantly due to an increase in the hydroxyl radical scavenging rate with oxide present. This study illustrates that oil is a strong and important source of hydroxyl radical when exposed to sunlight. The fate of oil and other dissolved species following oil spills will be heavily dependent on the formation and fate of hydroxyl radical.
    Chemosphere 01/2014; · 3.14 Impact Factor
  • Phoebe Z. Ray, Matthew A. Tarr
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    ABSTRACT: Photochemical production of singlet oxygen from thin oil films over seawater and pure water was measured with furfuryl alcohol as a selective chemical probe. Oil was collected from the surface of the Gulf of Mexico following the Deepwater Horizon spill and from other sources. The loss of furfuryl alcohol and the formation of 6-hydroxy(2H)pyran-3(6H)-one were monitored. Total singlet oxygen formation was studied using high furfuryl alcohol concentrations and varying exposure time. The total amount of singlet oxygen produced in 1 hour irradiations of thin oil films (100 mg, 60 microns thick) over Gulf of Mexico water and pure water were 1.9 ± 0.4 × 10-5 and 1.6 ± 0.3 × 10-5 mol, respectively. After initial tests were performed, titanium dioxide (TiO2) nanomaterials were added to the system in two different concentrations to study the effects of singlet oxygen formation in the presence of a photocatalyst. The addition of TiO2 nanoparticles did not significantly change the observed formation rate of singlet oxygen. Steady state concentrations of photoproduced singlet oxygen were also determined and found to be near 1 × 10-12 M in water under thin films of oil, which is considerably greater than values previously observed for pure seawater. This study illustrates that oil is a source of singlet oxygen when exposed to sunlight. The fate of oil and other dissolved species will be heavily dependent on the formation and reaction of singlet oxygen in thin oil films on water.
    Journal of Photochemistry and Photobiology A: Chemistry. 01/2014;
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    ABSTRACT: In this paper we describe the fabrication and characterization of new liposome encapsulated quantum dot-fluorescence resonance energy transfer (FRET)-based probes for monitoring the enzymatic activity of phospholipase A2. To fabricate the probes, luminescent CdSe/ZnS quantum dots capped with trioctylphosphine oxide (TOPO) ligands were incorporated into the lipid bilayer of unilamellar liposomes with an average diameter of approximately 100 nm. Incorporating TOPO capped quantum dots in liposomes enabled their use in aqueous solution while maintaining their hydrophobicity and excellent photophysical properties. The phospholipid bilayer was labeled with the fluorophore NBD C6-HPC (2-(6-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl-1-hexa decanoyl-sn-glycero-3-phosphocholine). The luminescent quantum dots acted as FRET donors and the NBD dye molecules acted as FRET acceptors. The probe response was based on FRET interactions between the quantum dots and the NBD dye molecules. The NBD dye molecules were cleaved and released to the solution in the presence of the enzyme phospholipase A2. This led to an increase of the luminescence of the quantum dots and to a corresponding decrease in the fluorescence of the NBD molecules, because of a decrease in FRET efficiency between the quantum dots and the NBD dye molecules. Because the quantum dots were not attached covalently to the phospholipids, they did not hinder the enzyme activity as a result of steric effects. The probes were able to detect amounts of phospholipase A2 as low as 0.0075 U mL(-1) and to monitor enzyme activity in real time. The probes were also used to screen phospholipase A2 inhibitors. For example, we found that the inhibition efficiency of MJ33 (1-hexadecyl-3-(trifluoroethyl)-sn-glycero-2-phosphomethanol) was higher than that of OBAA (3-(4-octadecyl)benzoylacrylic acid).
    Analytical and Bioanalytical Chemistry 10/2013; · 3.66 Impact Factor
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    ABSTRACT: The photochemical behavior of Deepwater Horizon oil collected from the surface of the Gulf of Mexico was studied. Thin oil films on water were subjected to simulated sunlight, and the resulting chemical and optical changes were observed. Polycyclic aromatic hydrocarbons (PAHs) showed substantial photodegradation, with larger PAHs being more rapidly decomposed. About 60% of the fluorescence at the excitation and emission maxima was observed with 12h of simulated solar irradiation equivalent to approximately 3d of sunlight. Synchronous scan fluorescence measurements showed 80-90% loss of larger PAHs with 12h of simulated solar irradiation. Absorbance of the oil decreased by only 20% over the same time period. Alkanes showed no significant photochemical losses. After irradiation, the toxicity of water in contact with the oil significantly increased, presumably due to the release of water soluble photoproducts that were toxic. Photocatalyst addition resulted in enhanced degradation rate for PAHs, and toxicity of the aqueous layer was altered in the presence of photocatalysts added to the oil film. Photochemistry is an important pathway for degradation of large PAHs, which are typically resistant to biodegradation.
    Chemosphere 10/2013; · 3.14 Impact Factor
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    ABSTRACT: The surface of superparamagnetic silica coated iron oxide (Fe3O4@SiO2) nanoparticles was functionalized with a disulfide bond linked N-hydroxysuccinimidyl (NHS) ester group in order to develop a method for labeling primary amines in peptides/proteins. The nanoparticle labeled proteins/peptides formed after NHS ester reaction with the primary amine groups were isolated using a magnet without any additional purification step. Nanoparticle moieties conjugated to peptides/proteins were then trimmed by cleavage at the disulfide linker with a reducing agent. The labeled peptides were analyzed by LC-MS/MS to determine their sequences and the sites of NHS ester labeling. This novel approach allowed characterization of lysine residues on the solvent accessible surface of native bovine serum albumin. Low cost, rapid magnetic separation, and specificity towards primary amine groups make NHS ester coated Fe3O4@SiO2 nanoparticles a potential labeling probe to study proteins on living cell surfaces.
    Bioconjugate Chemistry 08/2013; · 4.58 Impact Factor
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    ABSTRACT: Vertically aligned Au–TiO2 core–shell nanowires were synthesized by using a two step method. Au nanowires were first synthesized using a galvanostatic constant current electrodeposition technique. A shell of anatase TiO2 was subsequently grown on the Au nanowires using pulsed laser deposition. The core–shell nanostructures were then characterized using electron microscopy, electron diffraction, and X-ray diffraction techniques. The results showed that the wires were highly aligned and well separated. Dye sensitized solar cells were then fabricated using the core–shell nanowire arrays as photoanode, N535 dye as the sensitizer and I3−/I− as the redox electrolyte. The Au nanowires inside the highly crystalline TiO2 anatase nanoshell provided a direct conduction path and improved transport for electrons between the TiO2 and the conducting substrate. This efficient electron conduction out of the oxide semiconductor enhanced the current generation as well as the power conversion efficiency of the cell. The influence of the TiCl4 post-treatment on Au–TiO2 core–shell nanowire electrodes is investigated and compared to nontreated films. Cell efficiencies are improved, due to higher photocurrents as a result of this post-treatment. Optical effects of the metal nanowire may have also contributed to improved performance.
    RSC Advances 04/2012; 2(9):3791-3800. · 3.71 Impact Factor
  • Gayatri Sahu, Scott W. Gordon, Matthew A. Tarr
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    ABSTRACT: Dye sensitized solar cells (DSSCs) have been widely studied as alternatives for generation of electricity from sunlight due to their efficiency and cost effectiveness. Increasing the electron transport out of the metal oxide is important in achieving higher efficiency. Enhancing light absorption can also improve cell efficiency. The motive of this work was to synthesize and use Au–TiO2 core-shell nanowires as anode materials in DSSCs in order to increase cell efficiency by enhancing electron transport out of the oxide and/or increasing light collection efficiency. TiO2nanotubes were first grown in alumina templates using a sol–gel method. Goldnanowires were subsequently grown in the pores of these tubes by electrodeposition. Resulting nano-structured arrays were characterized using electron microscopy and diffraction techniques; the results show that the wires were highly aligned and well separated. The current–voltage (J–V) behavior for the Au–TiO2 core-shell nanowire based DSSCs was compared to the J–V data for TiO2nanotube based DSSCs, indicating substantial improvements upon incorporation of the Au core nanowires. TiCl4 treatment of the Au–TiO2 core-shell nanowire structures resulted in further efficiency improvements.
    RSC Advances 12/2011; 2(2):573-582. · 3.71 Impact Factor
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    ABSTRACT: Conditions for the detection of three odd-electron cholesterol oxidation peaks were determined and these peaks were shown to be artifacts of the matrix-assisted laser desorption time of flight (MALDI-TOF) process. Matrix choice, solvent, laser intensity and cholesterol concentration were systematically varied to characterize the conditions leading to the highest signals of the radical cation peaks, and it was found that initial cholesterol solution concentration and resultant density of solid cholesterol on the MALDI target were important parameters in determining signal intensities. It is proposed that hydroxyl radicals, generated as a result of laser irradiation of the employed 2,5-dihydroxybenzoic acid (DHB) matrix, initiate cholesterol oxidation on the MALDI target. An attempt to induce the odd-electron oxidation peaks by means of adding an oxidizing agent succeeded using an acetonitrile solution of DHB, cholesterol, and cumene hydroperoxide. Moreover, addition of free radical scavengers reduced the abundances of some oxidation products under certain conditions. These results are consistent with the mechanism of oxidation proposed herein involving laser-induced hydroxyl radical production followed by attack on neutral cholesterol. Hydroxyl radical production upon irradiation of dithranol matrix may also be responsible for generation of the same radical peaks observed from cholesterol in dithranol by an analogous mechanism.
    Journal of the American Society for Mass Spectrometry 04/2011; 22(4):659-69. · 3.59 Impact Factor
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    Sourav Chakraborty, Matthew A Tarr
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    ABSTRACT: A novel thioureido naphthalene derivative was synthesized and characterized. The compound proved itself as an effective fluoride sensor with respect to selectivity and sensitivity. In acetonitrile, the fluorescence intensity increased by 40-fold with the addition of 5 equiv. of fluoride. Fluorescence intensity did not substantially change with other halides, suggesting that the thioureido protons interact strongly with fluoride but not with other halides. The enhanced fluorescence is due to increased quantum efficiency of the fluoride complex.Key words: fluoride sensing, thioureido compound, fluorescence.
    Canadian Journal of Chemistry 02/2011; 85(2):153-156. · 0.96 Impact Factor
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    ABSTRACT: The paper describes the development of highly sensitive particle-based fluorescence resonance energy transfer (FRET) probes that do not use molecular fluorophores as donors and acceptors. In these probes, CdSe/ZnS luminescent quantum dots (QDs) were capped with multiple histidine-containing peptides to increase their aqueous solubility while maintaining their high emission quantum yield and spectral properties. The peptide-modified QDs (QD-His) were covalently attached to carboxyl-modified polystyrene (PS) microspheres to form highly emitting PS microspheres (QD-PS). Gold nanoparticles (AuNPs) were then covalently attached to the QD-PS surface to form AuNP-QD-PS composite microspheres that were used as FRET probes. Attachment of AuNPs to QD-PS completely quenched the QD emission through FRET interactions. The emission of QD-PS was restored when the AuNPs were removed from the surface by thiol ligand displacement. The new AuNP-QD-PS FRET platform is simple to prepare and highly stable, and it opens many new possibilities for carrying out FRET assays on microparticle-based platforms and in microarrays. The versatility of these assays could be greatly increased by replacing the linkers between the QDs and AuNPs with ones that selectively respond to specific cleaving agents or enzymes.
    Journal of the American Chemical Society 02/2011; 133(7):2028-30. · 10.68 Impact Factor
  • Sourav Chakraborty, Yang Cai, Matthew A Tarr
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    ABSTRACT: Human low-density lipoprotein (LDL) is a major cholesterol carrier in blood. Elevated concentration of low-density lipoprotein, especially when oxidized, is a risk factor for atherosclerosis and other cardiac inflammatory diseases. Past research has connected free radical initiated oxidations of LDL with the formation of atherosclerotic lesions and plaque in the arterial wall. The role of LDL protein in the associated diseases is still poorly understood, partially due to a lack of structural information. In this study, LDL was oxidized by hydroxyl radical. The oxidized protein was then delipidated and subjected to trypsin digestion. Peptides derived from trypsin digestion were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Identification of modified peptide sequences was achieved by a database search against apo B-100 protein sequences using the SEQUEST algorithm. At different hydroxyl radical concentrations, oxidation products of tyrosine, tryptophan, phenylalanine, proline, and lysine were identified. Oxidized amino acid residues are likely located on the exterior of the LDL particle in contact with the aqueous environment or directly bound to the free radical permeable lipid layer. These modifications provided insight for understanding the native conformation of apo B-100 in LDL particles. The presence of some natural variants at the protein level was also confirmed in our study.
    Analytical Biochemistry 09/2010; 404(2):109-17. · 2.58 Impact Factor
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    ABSTRACT: Micro RNAs (miRNAs) represent a family of small ribonucleic acids (RNAs) that are post-transcriptional regulators of messenger RNA (mRNA) complexity. Brain cells maintain distinct populations of miRNAs that support physiologically normal patterns of expression, however, certain miRNA abundances are significantly altered in neurodegenerative disorders such as Alzheimer's disease (AD). Here we provide evidence in human neural (HN) cells of an aluminum-sulfate- and reactive oxygen species (ROS)-mediated up-regulation of an NF-kappaB-sensitive miRNA-146a that down-regulates the expression of complement factor H (CFH), an important repressor of inflammation. This NF-kappaB-miRNA-146a-CFH signaling circuit is known to be similarly affected by Abeta42 peptides and in AD brain. These aluminum-sulfate-inducible events were not observed in parallel experiments using iron-, magnesium-, or zinc-sulfate-stressed HN cells. An NF-kappaB-containing miRNA-146a-promoter-luciferase reporter construct transfected into HN cells showed significant up-regulation of miRNA-146a after aluminum-sulfate treatment that corresponded to decreased CFH gene expression. These data suggest that (1) as in AD brain, NF-kappaB-sensitive, miRNA-146a-mediated, modulation of CFH gene expression may contribute to inflammatory responses in aluminum-stressed HN cells, and (2) underscores the potential of nanomolar aluminum to drive genotoxic mechanisms characteristic of neurodegenerative disease processes.
    Journal of inorganic biochemistry 06/2009; 103(11):1591-5. · 3.25 Impact Factor
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    ABSTRACT: The ability of hydroxyl radicals to penetrate into liposomal model membranes (dimyristoylphosphatidylcholine) has been demonstrated. Liposomes were prepared and then characterized by digital fluorescence microscopy and dynamic light scattering after extrusion to determine liposomal lamellarity, size, and shape. Hydroxyl radicals were generated in the surrounding aqueous medium using a modified Fenton reagent (hydrogen peroxide and Fe(2+)) with the water-soluble iron chelator EDTA. High and low doses of radical were used, and the low dose was achieved with physiologically relevant iron and peroxide concentrations. Fluorescent probes covalently bound to the membrane phospholipid were used, including two lipophilic pyrenyl probes within the membrane bilayer and one polar probe at the water-membrane interface. Radical reactions with the probes were monitored by following the decrease in fluorescence and by observing oxidation products via matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Differences in the probe position within the membrane were correlated with the reactivity of the probe to assess radical access to the site of the probe. For all probes, reaction rates increased with increasing temperature. Within the membrane bilayer, reaction rates were greater for the probe closest to the membrane-water interface. Cholesterol protected these probes from oxidation. Kinetic models, scavenger studies, and product identification studies indicated that hydroxyl radical reacted directly with the in-membrane probes without the mediation of a secondary radical.
    Free Radical Biology & Medicine 04/2009; 46(10):1376-85. · 5.27 Impact Factor
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    ABSTRACT: Treatment of preformed magnetite nanoparticles with ultrasound in aqueous media with dissolved tetrachloroauric acid resulted in the formation of gold-magnetite nanocomposite materials. These materials maintained the morphology of the original magnetite particles. The loading of gold particles could be controlled by adjusting experimental parameters, including the addition of small amounts of solvent modifiers such as methanol, diethylene glycol, and oleic acid. The nanocomposite materials were magnetic and exhibited optical properties similar to pure gold nanoparticles.
    Ultrasonics Sonochemistry 08/2008; 15(5):891-7. · 3.52 Impact Factor
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    ABSTRACT: Hurricane Katrina in 2005 had a major impact on the university system in the New Orleans area. This paper describes the impact and the recovery efforts of four major universities in New Orleans and tells of the lessons learned during the recovery.
    Journal of Chemical Health and Safety 01/2007; 14(5):15-24.
  • Weixi Zheng, Matthew A Tarr
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    ABSTRACT: Recent research has indicated that ternary complexes can be formed among carboxymethyl-beta-cyclodextrin, certain polycyclic aromatic hydrocarbons (PAHs) (e.g. anthracene and 2-naphthol), and Fe(2+) in aqueous solution. The formation of these ternary complexes has been suggested as the reason for improved reaction efficiency in iron catalyzed Fenton degradation (H(2)O(2)+Fe(2+)-->*OH+OH(-)+Fe(3+)) of PAHs and other pollutants. In the present work, several other cyclodextrins were examined to determine their ability to form similar ternary complexes with 2-naphthol and Fe(2+). Fluorescence and NMR techniques were employed in this study. Results showed that hydroxypropyl-beta-cyclodextrin, beta-cyclodextrin, and alpha-cyclodextrin were able to encapsulate 2-naphthol molecules, but their binding with Fe(2+) was weak. On the contrary, sulfated-beta-cyclodextrin has significant binding with Fe(2+), but it showed little inclusion of 2-naphthol molecules. Consequently, none of these four cyclodextrins formed significant amounts of ternary complexes in aqueous solution. The techniques used in this study provide useful methods for assessing the ability of cyclodextrins to form ternary complexes with guest compounds and metal ions.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 12/2006; 65(5):1098-103. · 1.98 Impact Factor
  • Matthew A. Tarr, Junhua Zhu, Richard B. Cole
    09/2006; , ISBN: 9780470027318