Friday May 5th – Presentations

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EXAMINATION OF CONTAMINATED ENVIRONMENTAL WATERS BY MICROBIAL SOURCE TRACKING

Melanie J. Beazley

Department of Chemistry, University of Central Florida, Orlando FL 32816-2366, USA

05:45 PM
to 06:05 PM
Environmental

Protection of our natural waters from pollution is critical to maintaining clean drinking water supplies and healthy habitats for aquatic organisms. Assessment of the sources of contamination to waterbodies is important for developing effective mitigation strategies. Chemical and microbial indicators can be used to determine exposure of natural waters to human and animal contamination. Recalcitrant chemical compounds, such as sucralose (an artificial sweetener) and pharmaceuticals, have been suggested as indicators for wastewater contamination of natural waters. Pathogenic bacteria released from the fecal material of humans and animals cause illness and pose major health hazards when present in drinking water. Fecal bacteria enter natural waters through urban runoff that carries human and animal waste, leaky septic systems, and runoff from agricultural and farm systems. Distinguishing the source of fecal bacteria is important for developing strategies for mitigation of these contaminants. This presentation will examine a microbial source tracking study using genetic biomarkers specific to the fecal material of human, dog, bird, and cow found in Central Florida and to use that method to analyze environmental waters within Orange County. Additionally, the waters will be analyzed for sucralose and pharmaceuticals as supplemental indicators of human wastewater contamination.

Natural Product Inspired Synthetic Medicinal Chemistry: Functional and Complexity Driven Discoveries

Robert W. Huigens III

University of Florida

05:45 PM
to 06:10 PM
Organic Chemistry

Various natural products, such as taxol, morphine and vancomycin, play a prominent role in medicine due to their ability to modulate biological targets critical to human disease.  Our lab has two natural product inspired synthetic medicinal chemistry programs, driven by the function of phenazine antibiotics and the structural complexity of select indole alkaloids.  Each program aims to address major biomedical problems, including: (1) the discovery of therapeutically relevant small molecules capable of eradicating surface-attached bacterial biofilms and (2) enhancing the chemical diversity of screening libraries used to drive drug discovery in high throughput screening campaigns.  Our first program aims to target bacterial biofilms, which contain specialized persister cells that are metabolically dormant and demonstrate high antibiotic tolerance towards every class of conventional antibiotic.  These biofilms are the underlying cause of chronic and recurring bacterial infections.  We have discovered that the marine phenazine antibiotic 2-bromo-1-hydroxyphenazine is a tunable molecular scaffold that provides access to highly potent antibacterial agents that are able to eradicate drug-resistant and antibiotic-tolerant bacterial biofilms.  Our second program is aimed at the rapid generation of highly diverse and complex small molecules, which we access through short synthetic sequences motivated by the dramatic alteration of the inherent complex ring system of various indole alkaloids.  We recently reported a new tryptoline ring distortion approach from yohimbine, an indole alkaloid with a complex fused ring system.  From these and other efforts, we have generated a library of >180 complex and diverse small molecules, which are producing an array of interesting hit compounds in diverse disease areas that will be presented.

MECHANISMS OF ACTIVATED HUMAN GLUCOKINASE DISEASE VARIANTS

Shawn M. Sternisha and Brian G. Miller

Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306

05:45 PM
to 06:05 PM
Biochemistry / Chem Bio.

Human glucokinase (GK) acts as the body’s primary glucose sensor and plays a critical role in glucose homeostatic maintenance. GK is being actively pursued as a therapeutic target for diabetes. Gain-of-function mutations in the glk gene result in hyperactive enzyme variants that cause persistent hyperinsulinemic hypoglycemia. Past biochemical and biophysical studies support the postulate that activated disease variants can be segregated into two mechanistically distinct classes.  In α-type activation, GK displays an increased affinity for glucose and the 1H-13C HMQC spectrum of 13C-Ile labeled enzyme resembles the glucose-bound state. Conversely, in β-type activation glucose affinity is largely unchanged and the 1H-13C spectrum reveals no change in the enzyme structure. Here, we use a combination of viscosity variation studies, chemical quench-flow, and hydrogen-deuterium exchange mass spectrometry to uncover the mechanistic basis for both activation types. Our work elucidates the molecular basis of GK disease variants and provides insights into the nature of GK’s unique kinetic cooperativity.

Binding and Activation of Alkenes by Zn(II), Cd(II), and Hg(II) Complexes: A Theoretical Investigation

Christine Greene, Patrick K. Grudzien, and John T. York

Stetson University

05:45 PM
to 06:05 PM
Inorganic Chemistry

The divalent group 12 metal ions are widely used to catalyze reactions of unsaturated C–C bonds, with the formation of metal–π-complexes commonly proposed as important intermediates. Despite these proposals, little experimental evidence exists to support the stability and reactivity of such adducts for the group 12 metals.  To shed light on the stability and potential reactivity of these intermediates, we have used density functional theory to investigate the bonding and activation of alkenes by Zn2+, Cd2+, and Hg2+ in a series of [M(L)(η2–C2H4)]n+ complexes (where L = a variety of N-donor ligands). Structural and vibrational analyses predict an activated ethylene C=C bond with all three metals, with the degree of activation enhanced by the use of neutral bidentate ligands . Bond energy decomposition analysis (EDA) shows that metal–ethylene interaction energies are favorable for all complexes studied and even more favorable than for many experimentally-isolated copper(I) analogues. Both EDA and natural bond orbital (NBO) analysis indicate that ethylene(π)→[M(L)]n+ electron donation dominates Dewar-Chatt-Duncanson bonding in these complexes, while electrostatic and orbital stabilization provide roughly equal contributions to the overall metal–ethylene bond stabilization. Molecular orbital analysis predicts that the electrophilic reactivity of the metal-bound ethylene moiety would be significantly enhanced due to substantial stabilization of its π*- and π-orbitals. These findings support reported experimental results and provide new insight into the use of group 12 metals as catalysts in important organic transformations.

Controlled Drug Delivery through an Ion Exchange Membrane

Demetra Maria Pantelis, Juliette Experton, Charles R. Martin

University of Florida Department of Chemistry, Gainesville, FL 32611

05:45 PM
to 06:05 PM
Analytical Chemistry

Applying a current through a synthetic membrane is used to enhance the delivery rate of ionic drugs. However, a precise quantification of the amount of drug delivered requires knowing what fraction of that current is carried by the drug ion. We have developed a device to electrochemically induce membrane drug delivery through an ion selective membrane. This device was used to transport a surrogate drug anion, nitrate, to a receiver solution while applying a voltage across the membrane. The delivery rate scaled with the voltage applied across the membrane and dissipated when an equilibrium state was reached. At equilibrium, we have shown that a precisely quantifiable amount of drug can be delivered. We also have shown experimentally, and proven theoretically, that our membrane drug delivery prototype turns itself off when a predetermined amount of drug has been delivered. This suggests that dosage-controlled and selective drug delivery can be obtained using our proposed device.

HIGHLY DISPERSIBLE        CORE-SHELL Ag@TiO2 NANOPARTICLES FOR NON-PHOTOCHEMICAL DEGRADATION OF METHYL PARATHION

Somayeh Talebzadeh Farooji,1 Clémence Queffélec,2 Florian Forato,2 Bruno Bujoli,2 Scott A. Trammell,3 and D. Andrew Knight

1Chemistry Department, Florida Institute of Technology, Melbourne, FL 32901
2Université de Nantes, Laboratoire CEISAM, UMR CNRS 6230, Nantes, France.
3Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC 20375

06:05 PM
to 06:25 PM
Materials Chemisry

Highly water-dispersible core-shell Ag@TiO2 nanoparticles were prepared and were shown to be catalytically active for the rapid degradation of the organothiophosphate pesticide methyl parathion (MeP). Formation of degradation product, p-nitrophenolate was monitored at pH=8 using UV-Vis spectroscopy, and 31P NMR spectroscopy confirmed that hydrolysis is the predominant pathway for substrate breakdown under non-photocatalytic conditions. We have demonstrated that the unique combination of TiO2 with silver nanoparticles is required for catalytic hydrolysis with good recyclability. This work represents the first example of MeP degradation using TiO2 doped with AgNP under mild and ambient conditions. The analysis of catalytic data and a proposed dark mechanism for MeP hydrolysis using core-shell Ag@TiO2 will be presented.

Phosphorous Speciation in Lake Silver Water Column and Sediment

Kathleen McCormac and Melanie J. Beazley

Department of Chemistry, University of Central Florida, Orlando FL 32816-2366, USA

06:05 PM
to 06:25 PM
Environmental

The chemical speciation of phosphorus (P) in freshwater lakes controls the bioavailability of P to aquatic organisms including algae, and ultimately affects the occurrence of large algal blooms. In lakes with high sedimentation rates, P may become quickly buried and subsequently deplete the availability of reactive P within the water column. The objective of this study was to determine the speciation of P in a central Florida lake water column and sediment in order to understand the seasonal controls that affect P bioavailability. Water and sediment samples were collected in May, July, and November 2016 representing spring, summer, and fall, respectively. The primary forms of P speciation include soluble (bioavailable), adsorbed to particulates, precipitated in minerals, and incorporated within organics. Sediments in Lake Silver included shallow, sandy/silty fractions containing a high percentage of adsorbed P and deeper, muddy fractions containing a higher organic P fraction. Preliminary analyses indicate that the adsorption of P to particle surfaces is the primary controlling factor affecting P bioavailability in Lake Silver sediments, particularly during the summer months when plant and algae productivity is highest.

Unexpected Reactivity of Trimetallic Cu-chalcogenide Clusters Towards Small Molecule Substrates

Brian J. Cook, Gianna N. Di Francesco, Leslie J. Murray

Chemistry Laboratory Building, Department of Chemistry, Center for Catalysis, University of Florida

06:05 PM
to 06:25 PM
Inorganic Chemistry

Multi-metallic clusters are often employed in biological systems to facilitate electron transfer and assist in the activation of strong bonds in small molecules. Recently, we have synthesized and fully characterized a pair of chalcogenide-bridged tricopper complexes LCu33-E)  (E = S, Se),   models of Cuz clusters in N2O reductase (where L is a cyclophane featuring three b-diketiminate arms). Both complexes can be reduced by one electron to afford the S=1/2 M[LCu33-E)], where M = Cp*2Co+, K(THF)n+, (18-crown-6)K(THF)2+. The unpaired electron is delocalized over the {Cu33-E} cluster, with the DFT suggesting that the electron density residing mostly on E donor. Remarkably, these radical anion complexes function as reductants towards a variety of small molecule substrates, including CO2, to regenerate the neutral starting reagent, LCu33-E).  Ongoing mechanistic and electrochemical studies for CO2­ reduction, including the role of the counter-cation, will be discussed.

Development of a Cryogenic Linear Ion Trap for the Structural Elucidation of Unknown Metabolites

Adam P. Cismesia, Nicolas C. Polfer

Gainesville, FL for both

06:05 PM
to 06:25 PM
Analytical Chemistry

The structural identification of unknown metabolites via MS/MS is constrained by the standards included in MS/MS databases.1 Infrared (IR) ion spectroscopy provides detailed chemical information based on the vibrational modes of an analyte. Room temperature methods of IR spectroscopy, such as infrared multiple photon dissociation (IRMPD) spectroscopy, is relatively easy to implement in commercial mass spectrometers, however, it suffers from limited resolution.2,3  In contrast, cryogenic techniques, such as infrared predissociation (IRPD) spectroscopy, offer enhanced resolution, but there are considerable challenges in both instrumentation and methodology to overcome before the technique becomes analytically useful. 4,5  Experimental strategies to overcome sensitivity constraints, poor overall duty cycle, and extensive acquisition time of the experiment are intimately tied to the development of a mass-selective cryogenic trap. Here, we discuss the construction and operation of a cryogenic linear ion trap (LIT) in terms of performing IR predissociation spectroscopy.

 

(1)          J. Chromatogr. A. 2014, 1353, 99-105.

(2)          Int. Rev. Phys. Chem. 2009, 28, 481-515.

(3)          Chem. Soc. Rev. 2011, 40, 2211-2221.

(4)          J. Am. Chem. Soc. 2011, 133, 6440-6448.

(5)          J. Am. Soc. Spectrom. 2016, 27, 757-766.

 

Drug Candidate Discovery: Targeting Bacterial Topoisomerase I Enzymes for Novel Antibiotic Leads

Shayna Sandhaus, Yuk-Ching Tse-Dinh

Florida International University

06:05 PM
to 06:25 PM
Biochemistry / Chem Bio.

The global community is facing a crisis—antibiotics are often ineffective due to the emergence of multi-drug resistant bacterial pathogens. The need for new antibiotics acting against novel bacterial cell targets is dire. Bacterial topoisomerase I (TopoI) is an attractive target for new antibiotics, since it should be vulnerable to bactericidal topoisomerase poison inhibitors in every bacterium, and its function is known to be required for the survival of certain bacterial pathogens including Mycobacterium tuberculosis. Selective and potent inhibitors of bacterial TopoI can be useful as new antibiotic leads. Bacterial TopoI relaxes supercoiled DNA by using its active-site tyrosine residue to attack the phosphodiester backbone of the DNA, forming a covalent intermediate and cleaving one strand of the DNA. It then passes the other strand through the break and rejoins the DNA to increase the DNA linking number by one. Catalytic inhibitors of topoisomerase I may prevent the enzyme from binding or cleaving the DNA, while poison inhibitors can stabilize the DNA-enzyme covalent intermediate, thus causing the accumulation of DNA breaks, leading to bacterial cell death. This project seeks novel inhibitors of bacterial topoisomerase I in various bacterial strains of global health significance. Two main assays are used to find antibacterial compounds that target TopoI—an enzyme inhibition assay (a gel-based assay that monitors the formation of relaxed DNA in the presence of inhibiting compounds), and a growth inhibition assay (an assay that monitors the growth of bacteria in the presence of topoisomerase inhibitors). Several promising compounds have been found from various screens that inhibit bacterial TopoI well, and are able to prevent bacterial cell growth. Many of the discovered compounds are effective against M. tuberculosis topoisomerase I, and can prevent the growth of M. smegmatis, a non-pathogenic homolog of M. tuberculosis. The use of diverse approaches such as in silico docking studies and mixture-based compound screening has been successful at finding novel inhibitors of bacterial topoisomerase I, and may bring us one step closer to new and effective antibiotics.

AApeptides as a scaffold for the discovery of bioactive molecules

Jianfeng Cai*

Department of Chemistry, CHE 205, University of South Florida, 4202 E. Fowler Ave, Tampa, FL 33647

06:10 PM
to 06:35 PM
Organic Chemistry

The identification and development of sequence-specific peptidomimetics is of significance in bioorganic chemistry and chemical biology. A new class of peptidomimetics termed "AApeptides" was recently developed by our group. The synthesis of AApeptides can be conveniently achieved on the solid phase. Similar to other peptidomimetics, AApeptides are resistant to proteolytic degradation, and possess limitless potential to introduce chemically diverse functional groups. Moreover, they are able to fold into well-defined secondary and tertiary structures. The functions of AApeptides have also been recently explored, including rational design of AApeptides for the mimicry of the primary and secondary structure of bioactive peptides, and combinatorial library for the discovery of potential molecular probes and drug leads.

Can we leverage equilibrium thermodynamics to unlock new well-defined polymeric materials?

Dr. Goutam Palui, William Neary, Stefan Brits, Michele Bohlmann, Aaron Kendrick, and Prof. Justin G. Kennemur

Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306

06:25 PM
to 07:00 PM
Materials Chemisry

Recent success in low ring strain cycloalkenes towards ring opening metathesis polymerization (ROMP) has been achieved. Once considered a negative attribute towards obtaining well-defined materials at high conversions, we have shown that a strategic approach towards leveraging the thermodynamics of this equilibrium polymerization can afford polymers with living-like conditions and at high yields. Synthetic aspects, characterization, and potential utility of these materials will be discussed.

Cooperative-Binding Split Aptamer Assays for Rapid, Specific and Ultra-Sensitive Detection of Small-molecule Targets in Biofluid samples

Haixiang Yu, Juan Canoura, Bhargav Guntupalli and Yi Xiao*

Department of Chemistry and Biochemistry, Florida International University, 11200 SW 8th Street, Miami, FL, 33199. *Corresponding author: yxiao2@fiu.edu

06:25 PM
to 07:00 PM
Analytical Chemistry

Sensors employing split aptamers that reassemble in the presence of a target can achieve excellent specificity, but the accompanying reduction of target affinity mitigates any overall gains in sensitivity. We have generated a split cocaine-binding aptamer that incorporates two binding domains, such that target binding at one domain greatly increases the affinity of the second domain. We for the first time have developed a split aptamer that achieves enhanced target-binding affinity through cooperative target binding. We experimentally demonstrate that the resulting cooperative-binding split aptamer (CBSA) exhibits higher target binding affinity and is far more responsive in terms of target-induced aptamer assembly compared to the single-domain parent split aptamer (PSA) from which it was derived. Using this CBSA, we achieved specific, ultra-sensitive, one-step fluorescent detection of cocaine within fifteen minutes at concentrations as low as 50 nM in 10% saliva without signal amplification. To achieve an ultra-sensitive detection of small-molecule targets, we employed Exonuclease-assisted target recycling (EATR) strategy along with fluorophore/quencher modified, or AuNP-conjugated CBSA fragments to amplify CBSA-target binding events. Our results showed that by in simply introducing EATR into CBSA binding assay, the sensitivity of fluorescence assay has been enhanced by 50 folds in urine samples, or a clear red-to-blue color change was clearly observed in the saliva samples containg 2 μM of cocaine after 20 minutes. It is clear that the CBSA-based assays represent a robust and sensitive means for detection of small-molecule targets in actual clinical samples.

 

Mapping specificity landscapes of RNA-protein interactions by high throughput sequencing

Michael E. Harris1, Hsuan-Chun Lin1, Jing Zhao1, Courtney N. Niland2, and Eckhard Jankowsky2

1Department of Chemistry, University of Florida
2Department of Biochemistry, Case Western Reserve University

06:25 PM
to 06:45 PM
Biochemistry / Chem Bio.

RNA-binding proteins (RBPs) are typically involved in non-equilibrium cellular processes, and specificity can arise from differences in ground state, transition state or product states of the binding reactions for alternative RNAs. We used newly developed high throughput methods to measure and analyze the RNA association kinetics and equilibrium binding affinity for all possible sequence combinations in precursor tRNA binding site of C5, the essential protein subunit of Escherichia coli ribonuclease P. The results show that the RNA sequence specificity of C5 arises due to favorable RNA-protein interactions that stabilize the transition state for association and bound ES complex. Specificity is further impacted by unfavorable RNA structure involving the C5 binding site in the ground state. The results illustrate a comprehensive quantitative approach for analysis of RNA binding specificity, and show how both RNA structure and sequence preferences of an essential protein subunit direct the specificity of a ribonucleoprotein enzyme.

Titanium Based Isoreticular Metal-Organic Frameworks for Photocatalytic Reduction of CO2 under Blue Light

Fernando J. Uribe-Romo,1* Matthew W. Logan,1 Suliman Ayad,2 Jeremy D. Adamson,1 Tristan Dilbeck,2 Kenneth Hanson,2

1 Department of Chemistry, University of Central Florida, 4111 Libra Dr. Rm. 251 PSB, Orlando, FL 32816-2366, USA.
2 Department of Chemistry, Florida State University, 95 Chieftan Way Rm. 118 DLC, Tallahassee, FL 32306-4390, USA.

06:25 PM
to 07:00 PM
Inorganic Chemistry

The gradual accumulation of carbon dioxide (CO2) is considered a large contributing factor in the overall increase of global temperature in recent years due to human activity. In this work, a systematic approach was taken to functionalize a series of metal-organic frameworks (MOFs) isoreticular to MIL-125-NH2 to act as photocatalyts in the transformation of CO2 into reduced carbon in solar fuels. The prepared materials display a reduction in optical band gap correlated to inductive effects from increasing N-alkyl substituents chain lengths (from methyl to heptyl). We found that secondary N-alkyl substitution (isopropyl, cyclopentyl and cyclohexyl) display larger apparent quantum yields that of the primary analogues in the photoreduction of CO2 under irradiation with blue LED light. This demonstrates a promising new type of candidate materials for next generation visible-light photocatalyst constructed from earth abundant elements.

Peptide N-Amination: A versatile backbone modification for proteomimetic constraint

  1. Juan R. Del Valle

Department of Chemistry, University of South Florida, Tampa, FL 33620

06:35 PM
to 07:00 PM
Organic Chemistry

Backbone amide substitution has a profound impact on the conformation, bioactivity, and proteolytic stability of parent peptides. Although N-alkylation has been extensively employed in peptide SAR campaigns, heteroatomic amide substituents have received far less attention. Here, we describe a novel series of N-amino peptide (NAP) derivatives that mimic β-sheet-like secondary structure and exhibit enhanced resistance to aggregation and proteolysis. Tetrahydropyridazinedione (tpd)-constrained peptides feature a cyclic Ni-Cαi+1 constraint leading to stabilization of extended backbone conformation by NMR and X-ray diffraction. ‘Stitched’β-strand foldamers based on oligomeric tpd constraints thus represent a new class of β-strand mimics readily accessible by conventional SPPS.  We have subsequently investigated the impact of simple NAP modifications on β-sheet stability and β-strand recognition by a variety of biophysical methods. Our results demonstrate, for the first time, that peptide N-amination supports β-sheet conformation despite the presence of a tertiary amide. This non-covalent stabilization is attributed to increased torsional strain, cis amide lone pair repulsion, and intraresidue C6 H-bonding. Development of an efficient electrophilic amination approach toward enantiopure α-hydrazino acids corresponding to each of the primary proteinaceous amino acids further enables rapid ‘NAP scanning’ of lead sequences.

Kinetic and mechanistic investigation on TiO2 photocatalytic degradation of the flame retardant tris (2-chloroethyl) phosphate in aqueous solution

A. M. Abdullah, Kevin O’Shea

 

Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199

06:45 PM
to 07:00 PM
Environmental

Recently, the decontamination of organophosphate flame retardants from aqueous solution has received a considerable interest due of their potential threat to human health and the environment.  We report herein the TiO2 photocatalytic oxidation of the flame retardant, tris-(2-chloroethyl) phosphate (TCEP), from aqueous solution. GC-NPD was used to monitor the disappearance of TCEP concentration during photocatalytic degradation. Our results demonstrate more than 90% of TCEP ([TCEP] <100 µM) is degraded within 1 hour upon irradiation at 350 nm in oxygen-saturated aqueous suspension of TiO2 at ambient temperature.  The degradation follows pseudo first order kinetics with rate constants varying from 0.28 to 0.03 min-1 depending on the initial concentrations over the range of 18– 270 µM. The rate constant for the degradation decreases with increasing initial TCEP concentration, implying the process may be controlled by mass transfer (adsorptiondesorption) at the surface of TiO2. This kinetic behavior is also consistent with the Langmuir-Hinshelwood model implying oxidation occurs at the surface of TiO2. The solution pH does not have a major impact on the degradation from pH 4-9. Mineralization to chloride and phosphate were monitored by IC over 5 hours of extended irradiation and an excellent mass balance was observed for both anions. The degradation decreases by ~ 50% with the addition of an equal amount of the hydroxyl radical scavenger, coumarin, indicating hydroxyl radicals are the main species participating in the degradation mechanism. The diester adducts of TCEP are the primary intermediates identified by NMR.  These results suggest that photocatalytic oxidation will be useful for the decontamination of aqueous solutions contaminated with recalcitrant organophosphate compounds.

FABRIC PHASE SORPTIVE EXTRACTION: A GREEN SAMPLE PREPARATION TECHNIQUE FOR FOOD, PHARMACEUTICAL, ENVIRONMENTAL AND BIOLOGICAL SAMPLES

Abuzar Kabir, PhD; Rodolfo Mesa, BSc; Samantha Rakela; Kenneth G. Furton, PhD

Department of Chemistry and Biochemistry, Florida International University, Miami, FL

06:25 PM
to 06:45 PM
Environmental

Food, pharmaceutical, environmental and biological samples contain high volume of matrix interferents that may interfere with the sample preparation techniques used and require sample pretreatment processes such as filtration, centrifugation, protein precipitation etc., prior to analyte extraction. These extra steps are laborious, time consuming, and may result in significant analyte loss and poor data quality.

Fabric sorptive extraction (FPSE) has been developed to handle samples containing high volume of interferents without any sample pretreatment. The FPSE device utilizes a piece of fabric as the substrate to chemically bind polymeric sorbent (such as polydimethylsiloxane) via sol-gel reaction. The sol-gel sorbent provides unique selectivity towards the target analyte, porous sorbent allows rapid mass transfer of the analyte from the bulk sample for analyte-sorbent interaction and the fabric substrate acts as a bait via hydrophilic/hydrophobic interactions to lure the target analyte(s). As a result, FPSE provides a near exhaustive extraction in a relatively short period.

After the extraction, the device is exposed to a small volume of organic solvent for analyte back-extraction. The analyte solution is then centrifuged to remove particulate materials.

Several recent applications of FPSE for extracting important pharmaceuticals and personal care product residues from environmental water will be presented.

Many body effects in biomolecular ionic interactions

Sameer Varma

Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL-33620, USA

08:30 AM
to 09:05 AM
Biophysical

Molecular insight into ion-driven processes requires a precise knowledge of how the energetics, structures, dynamics of ions differ between hydrated and biomolecule-bound states. While first principles quantum mechanical models can yield reliable estimates for relative binding energies, estimates for thermodynamics and ion-binding response are subject to limitations from conformational sampling and system size. In contrast, molecular mechanics models that do not describe many body effects explicitly can technically get past sampling/system-size issues, but suffer severely from accuracy. Polarizable models are being developed as a compromise between accuracy and efficiency, but are they sufficiently reliable to derive causalities? In general, where do we stand in terms of being able to use molecular simulations to understand selective ion binding to biomolecules, and the response of ion binding to biomolecular function? Here I’ll discuss these issues and potential solutions in the context of our work on potassium channels.

The solubility of bioactive trace elements from aerosols

William M. Landing, Alina Ebling, Rachel Shelley, Peter Morton

Florida State University

08:30 AM
to 09:05 AM
Environmental

Aerosol deposition is an important pathway for the delivery of bioactive trace elements (TE) to the open ocean. Quantifying the solubility of aerosol TE is essential to our understanding of the impacts of atmospheric deposition on marine productivity, yet is confounded by uncertainties with regard to sample storage (time and conditions) and how best to measure solubility. Short-term solubility experiments may not capture some less-reactive fractions that could become soluble over longer time scales in the ocean. The use of an extended seawater leaching scheme requires a supply of fresh, clean surface ocean seawater and is limited to those TE that can be quantified on small volumes of seawater. We will present data on the use of hot, dilute acetic acid (4.5 M) amended with 0.02M hydroxylamine (aka "Berger Leach") to quantify the solubility of a broad suite of TE from aerosol samples collected on the US GEOTRACES North Atlantic Zonal Transect and from Bermuda. The samples were stored both frozen and thawed for up to five years. Solubility from frozen filters using ultrapure water was tested over a 14-month period showing no significant loss of solubility. The Berger Leach was applied to frozen filters (stored 2-5 years) and thawed filters (stored up to 5 years) and showed no significant loss of solubility regardless of storage time or conditions. We conclude that the ultrapure water leach provides a lower limit estimate for aerosol TE solubility while the Berger Leach provides an upper limit estimate, thereby helping to constrain ocean biogeochemical models that include aerosol solubility.

Polymers containing metastable-state photoacids

Yi Liao

Florida Institute of Technology

08:30 AM
to 08:55 AM
PMSE/POLY

Metastable-state photoacid (mPAH) can be used to reversibly alter proton concentration with visible light. Most of its applications reported in the past years used solutions of mPAHs. For the development of photoresponsive material, solid polymers containing mPAHs are often desirable. We studied the behaviours of merocyanine-type and TCF-type mPAHs in polymer films. Results showed that low dark acidity and fast reverse reaction are important for an mPAH to be used in solid polymer materials and the polymer media needs to allow efficient proton transfer. Photochromic films with different colour changes were developed by loading mPAHs and acidochromic dyes into polymer films. Local pH pulses in PBS buffer were demonstrated by irradiating a hydrogel or micro-meter polymer thin film containing an mPAH with visible light. Synthesis of polymers grafted with mPAHs will also be presented.

Exploring Gram-negative bacteria as a source of biologically active natural products and application to the undergraduate research experience

Christine M. Theodore

The University of Tampa

08:30 AM
to 09:05 AM
Natural Products

Compounds from macro marine organisms are thought to be produced by microbial symbionts. Recent literature reviews have shown significant parallels between compounds isolated from macro organisms and non-photosynthetic Gram-negative bacteria (NPGNB). Though these structural parallels exist, little attention has been focused on these NPGNBs. Marine-derived NPGNBs represent an untapped well of potential microbial-produced compounds.  As a proof of concept, sampling of California nearshore sediments gave rise to the discovery of a morphologically interesting Gram-negative bacterium. In addition to four known cyclic depsipeptides (kailiuns B-E) and two new analogues were also isolated and structurally analyzed (kailiuins G and H). Currently, these methods are being adapted to accommodate undergraduate researchers and sampling of Florida Gulf-Coast sediments.

ADDITION OF PT(IPR) GROUPINGS TO RU5 CARBIDE, TRIIRON, AND TRIRUTHENIUM DODECACARBONYLS GIVE NEW MULTINUCLEAR PT- RU AND PT- FE CLUSTER COMPLEXES

 

Vincent Zollo Jr.1, Anjaneyulu Koppaka1, Sedigheh Etezadi1, Burjor Captain1.

1. Department of Chemistry, University of Miami, Coral Gables, FL 33124, USA

08:30 AM
to 08:50 AM
Inorganic Chemistry

The reaction of Pt(IPr)(SnBut3)(H), 1 [IPr = N-heterocyclic carbene ligand N,N’-bis-(2,6-(diisopropyl) phenyl)imidazole-2-ylidene], 2 with Ru­55-C)(CO)15, 3, Fe3(CO)12, 4, and Ru3(CO)12, 5, afforded several mixed-metal Pt-Ru and Pt-Fe cluster complexes. The reaction between 1 and 2 in benzene reflux in 1.2:1 (and 2.2:1) ratio afforded monoplatinum-pentaruthenium complexes PtRu­5(IPr)(µ6-C)(CO)15, 6, in 54% (10%) yield, and PtRu­5(IPr)(µ6-C)(CO)14(H)2, 7, in 6% (10%) yield, as well as Pt2Ru5(IPr)(µ6-C)(CO)15, 8, and diplatinum-pentaruthenium Pt2Ru5(IPr)26-C)(CO)15, 9, in 2% (36%) yield. Compound 6 readily reacts with, H2 in room temperature to form 7, while 9 shows dynamic activity in solution with Pt(IPr) ligands exchanging . The reaction of 1 and 3 in benzene at room temperature in a 3:1 ratio, produced two mixed-metal trigonal planar Pt-Fe complexes a monoplatinum-diiron Fe2Pt(IPr)(CO)9, 10, in 20% yield and diplatinum-monoiron FePt2(IPr)2(CO)6, 11, in 2% yield. The carbonylation of 10 shows full consumption to compound 11. In a 3:1 ratio, 1 and 5 were mixed in hexane at reflux temperature affording the trigonal bipyramidal cluster Pt2Ru3(IPr)2(CO)12, 12, in 32% yield. The synthesis, reactivity, and structural characterization of the complexes will be discussed.

1,2,3-Triazoles as versatile directing group for selective sp2 and sp3 C–H activation

Chiyu Wei, Xiaohan Ye, and Xiaodong Shi*

The Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, United States

08:30 AM
to 08:50 AM
Organic Chemistry

Selective C-H functionalization was achieved with designated 1,2,3-triazole acid auxiliary groups under Pd-catalyzed C–H activation conditions. Both sp2 and sp3 C–H bonds were effectively activated, giving the desired products in good yields. This result revealed several successful examples for  for C-H amination, acetoxylation, alkynylation, and olefination using 1,2,3-triazole ligands.

Proton transfer in gas-phase biomolecules probed by infrared ion spectroscopy

Amanda L. Patrick, Ning Zhao, Nicolas C. Polfer

Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611-7200, USA

08:30 AM
to 09:05 AM
Physical Chemistry

Understanding proton transfer is intimately linked with rationalizing the gas-phase fragmentation chemistry of biomolecules in mass spectrometry. This talk aims to explore mechanisms of proton transfers during ionization and controlled gas-phase ion activation. In the ionization studies, the kinetic trapping of solution-phase structures into the gas phase is shown to be dependent on the solvents and energetic considerations in the electrospray source. The systematic studies support a protic bridge-type mechanism which may (or may not) enable proton transfer. In the gas-phase activation studies, UV activation causes distonic cleavage at C-I bonds, triggering subsequent rearrangement chemistry. In all of these studies, the structures of the species of interest are characterized via infrared ion spectroscopy supported by quantum-chemical calculations.