Poster Session for GSS 2017

Poster Session Abstracts

P1

Next Steps in Engineering E. coli Erythromycin Production

Lei Fang and Blaine Pfeifer

University at Buffalo, Department of Chemical Engineering

Erythromycin has been widely used to against bacterial infections. Instead of using the original producing host Saccharopolyspora erythraea (S. erythraea), here we harness Escherichia coli (E. coli) as an expression surrogate due to the relative ease of genetic manipulation. A recent version of the production system features five plasmids hosting large (~55 kb) heterologous expression pathway.1 In this work, we’ve improved the strain stability by rearranging the expression pathway. Two bacterial artificial chromosomes(BAC) were employed rather than our previous five plasmids to reduce cell metabolic burden and improve efficiency. We also improved erythromycin titers by accumulating the common deoxysugar intermediate TDP-4-keto-deoxyglucose. Additionally, an E. coli multidrug efflux pump (MacAB) was overexpressed to further elevated erythromycin titer. Finally, six heterologously expressed deoxysugars were studied to biosynthesize erythromycin analogous in this study.

 

P2

A Materials Genome Approach to Dielectric Design: Approaching the Band Gaps of Metal Oxides in Metal Organic Frameworks

Shamima Nasreen, Gregory M. Treich, Matthew L. Baczkowski, Arun K. Mannodi-Kanakkithodi, Aaron Baldwin, Sydney K. Scheirey, Ramamurthy Ramprasad, Yang Cao, and Gregory A. Sotzing

University of Connecticut, Department of Chemistry

Advances in electrical properties and improvements in dielectric constants of materials have been reported by introducing metal organic frameworks (MOF) in the form of organometallic compounds with metal-oxygen bonds in organic polymers. While metal oxides have high dielectric constants, they suffer from lower band gaps compared to some organic polymers. By incorporating metal-oxygen bonds into the mainchain of polymers, high band gaps characteristic of polymers are maintained, while the dielectric constants have been shown to approach those of the metal oxides.  Here, a series of zinc (Zn, 3d-block) and cadmium (Cd, 4d-block) aliphatic coordination complex polyesters with varying numbers of methylene spacer(s), 1 to 8, are synthesized and characterized for their dielectric properties. The rational design of these materials are motivated by Density Functional Theory (DFT) computations of the electronic, ionic and total dielectric constant contributions, along with structural prediction and local enviroment. Dielectric constants, ε, for Zn- and Cd-systems range from ca. 3.2-4.6 and ca. 3.9-6.4, respectively, with strong correlation to DFT computations. Furthermore, these systems approach the dielectric constants of ZnO(8.5) and CdO (6.2), while nearly doubling the band gaps from ca. 3 to as high as ca. 5.5 ± 0.12 eV. These initial studies give insight into the potential advantages and future prospect for more expansion of chemical space for energy storage applications.

P3

Nano low density lipoprotein particles containing cholesterol conjugated HSP27 inhibitor as a drug delivery vehicle for ovarian cancer treatment.

Laila Alhadad and Bin Su

Cleveland State University, Department of Chemistry

Recently, low density lipoproteins recognized to be nano-carriers with a size of 20-27nm for targeted drug delivery for cancer therapy. Targeting cancer cells by drugs is often characterized by low selectivity. Therefore, natural and synthetic delivery systems discovered for improving the selectivity of anti-cancer drugs to tumor tissues. In addition, LDL nano-particles are biocompatible, biodegradable and can carry both hydrophobic and hydrophilic drugs. Endogenous low density lipoprotein vehicle the anticancer drugs to the cells, which over-expressed LDL-preceptors. LDL has therefore been proposed as a potential carrier for chemotherapeutic agents. Based on that, In our research group we synthesized two potent anti-cancer agents encapsulate them into nano-LDL particles to mimic the native LDL particles when we treat ovarian cancer. Our data showed that our agents have strong activity for cells' growth inhibition with and without LDL encapsulation suing both MTT and DLS Assays.

P4

Modeling Electron-Hole Relaxation Across Heterostrcuture Interfaces

Brendan Smith and Alexey Akimov

University at Buffalo, Department of Chemistry

The separation of charge in a semiconductor material is a key aspect in the functionality of many solar based applications such as photocatalytic and photovoltaic cells.  In order to achieve the goal of a reliable, efficient, and clean energy system, the underlying processes which cause and are affected by the separation of charge must be fully understood.  In this work, we look to model the recent results from the Watson group, for the rate of charge transfer across a the Pb0.33V2O5/CdSe heterostructure interface. We examine the rates of electron / hole relaxation across the Pb0.33V2O5/CdSe and V2O5/CdSe structures.

P5

Photoelectrochemical Study of Mid-Gap State Mediated Photocathodic Performance of CdSe Quantum Dot/β-Pb0.33V2O5 Heterostructures

Nuwanthi Suwandaratne and David F. Watson

University at Buffalo, Department of Chemistry

Solar hydrogen production through photoelectrochemical (PEC) water splitting is a clean and efficient way to address ever-increasing energy demand. Here, we demonstrate CdSe/ β-Pb0.33V2O5 heterostructure as a promising candidate for PEC water-splitting. The intercalation of Pb2+ ions in the crystal structure of V2O5 nanowires (NWs) gives rise to mid-gap states which lie energetically slightly positive of the water oxidation potential (1.23 V vs NHE), and have a significant overlap with the valence band (VB) of CdSe quantum dots (QDs). To investigate the role of mid-gap states, we performed photocurrent measurements on CdSe/V2O5 (no mid-gap states) and CdSe/ β-Pb0.33V2O5 photocathodes  focusing on proton reduction half reaction. CdSe/ β-Pb0.33V2O5 photocathode exhibited an enhanced photocurrent density of ~ 10 μAcm-2 at 0 V vs reversible hydrogen electrode (RHE) at low pH, compared to, ~ 4 μAcm-2 for CdSe/ V2O5 with similar loading of QDs under Xe lamp illumination (45 mW). Moreover, CdSe/ β-Pb0.33V2O5 showed good stability with no drop of photocurrent within first 20 min of stability measurements, compared to, 10 min for CdSe/ V2O5 at 0 V vs RHE.  Importantly, bare β-Pb0.33V2O5 and β-V2O5 nanowire showed no measurable photocurrent, indicating that direct photoreduction of protons by electrons in conduction band (CB) of β-Pb0.33V2O5 and V2O5 does not occur. These results are consistent with the mechanism where, the mid-gap states of β-Pb0.33V2O5 NWs accept photogenerated holes from VB of CdSe QDs, thus increasing separation of charge carriers and allowing electrons located in CB of CdSe QDs to reduce protons to molecular hydrogen.

 

P6

Microwave-Assisted Electrospray Ionization (µAESI)

Maria Rivera, Jaime Orejas Ibanez, Andrew Schwartz, and Steven Ray

University at Buffalo, Department of Chemistry

The electrospray ionization (ESI) source is one of the most prolific soft ionization methods, owing to its capability to produce intact ions of large, labile molecules directly from solution. One of the most crucial steps in ESI is the formation of ions from the droplets created by the Taylor cone, which occurs when high voltage induces charge carriers accumulation at a liquid surface resulting in a free-jet liquid expansion.  Once charged droplets are formed, free ions must be produced from their surface in order for analysis by mass spectrometry (MS) to occur, a step is thought to involve aspects of coulombic repulsion/explosion (Rayleigh explosion) and solvent evaporation.  As a consequence, many ESI sources employ heated interfaces or heated gas streams to encourage rapid solvent evaporation.  Recently, our laboratory has developed a novel method to study the effect of microwave electromagnetic fields at a frequency of 2.45 GHz upon the ESI process.  The introduction of microwave fields near the tip of an ESI needle is accomplished by using a novel waveguide structure to focus microwave energy in a very small and controlled volume.  As microwave radiation is absorbed, it induces very rapid evaporation through dielectric heating, modifying the features of the Taylor cone and affecting process such as droplet generation, ionization efficiency, stability, and fragmentation.  Here, we examine microwave-assisted electrospray ionization (µAESI) as a means to explore the mechanisms of ion generation, searching for methods to expand the capabilities of ESI through alterations in the fragmentation patterns or chemical reaction processes.

P7

Mechanistic Study of the Ring-Closing Metathesis Step in the Ring Expansion of Cyclopentene

Synthia Gratia, William S. Karnofel, and Steven T. Diver

University at Buffalo, Department of Chemistry

Atmospheric pressure glow discharge plasmas have attracted great interest to be used as spectrochemical sources for chemical analysis. Many reasons support this fact: simplicity of generation, low operation costs, potential portability and sometimes even competitive analytical features compared to established techniques. A group of these discharges make use of a liquid electrode to generate a plasma. The compounds present in the liquid are capable of reaching the most active parts of the plasma where they can be atomized, excited and/or ionized. The Solution Cathode Glow Discharge (SCGD) is one example of them and has been used as an effective source for atomic emission spectroscopy based elemental analysis with interesting figures of merit. The SCGD is typically powered by direct current continuous electrical supply of about 1 kV potential and 80 mA current intensity, leading to an attractive power consumption of ~80 W and offering competitive analytical capabilities. With the aim of pushing further its analytical capabilities, in our lab we have developed an experimental set-up capable of producing short time pulses (~ a hundred of ns) of increased applied potential and current, leading to a more energetic plasma with instantaneous power peaks above 500 W. The effect of these pulses on the optical emission spectrum generated by the plasma will be discussed.

P8

Electrospray Ionization Zoom Time-of-Flight Mass Spectrometry

Christopher Brais, Jonas B. Metternich, and Steven J. Ray

University at Buffalo, Department of Chemistry

Zoom time-of-flight mass spectrometry (zoom-TOFMS) is a new technique that can provide additional functionality to a traditional time-of-flight mass spectrometry (TOFMS) instrument. Zoom-TOFMS improves resolution, increases repetition rate, increases duty cycle, and improves signal-to-noise ratios for a specific window of mass-to-charges (m/z) by isolating and analyzing only the targeted m/z range of the entire mass spectrum.  The technique is particularly interesting because it can be easily retrofit to existing TOFMS instruments, as only a few simple architectural and electrostatic modifications are required.  Traditional TOFMS relies on using constant energy acceleration (CEA) to impart equal energy to ions of equivalent m/z via a pulsed electric field. In contrast, zoom-TOFMS employs constant momentum acceleration (CMA). With CMA, the acceleration voltage pulse is shortened and terminated before the fastest moving ion leaves the acceleration region.  In this way, all ions will acquire equivalent momentum (but m/z dependent energies).  A new zoom-TOFMS ion focusing strategy uses CMA to achieve improved focus over a window of m/z while excluding all other ions.  The ion focusing strategies employ the conventional TOFMS instrument architecture, allowing both TOFMS and zoom-TOFMS to be combined in a single instrument; the two modes of operation selected as required.  Here, a commercial mass spectrometer (Micromass/Waters® LCT Classic ESI-TOFMS) is modified for zoom-TOFMS mode operation.  Ion flight simulations made using computer simulation (SIMION®) investigate the focusing capabilities of CMA coupled with electrospray ionization (ESI) TOFMS.  The practical experimental capabilities of this instrument technique are examined here, and current performance evaluated.


P9

1,3-Diaxial Steric Control of Hoveyda-Grubbs Type Catalyst Initiation Rates

Zackary Gregg, Justin Griffiths, and Steven Diver

University at Buffalo, Department of Chemistry

Since the discovery of the first-generation Grubbs catalyst in 1992, a spectrum of novel ruthenium metathesis catalysts has been developed. Although there is much literature on the topic, efforts to fine-tune novel systems and better characterize existing ruthenium olefin metathesis catalyst systems are underway. Our efforts involve probing the initiation rates of Hoveyda-Grubbs second generation catalysts containing cyclohexoxybenzylidenes  to determine the effects of 1,3-diaxial strain.

P10

Design, Simulation, and Construction of a Distance-of-Flight Mass Spectrometer

Andrew Schwartz, Kelsey Williams, Darryl Lopez, and Steven Ray

University at Buffalo, Department of Chemistry

The synthesis of a stereochemically pure triene was used as a mechanistic probe to evaluate the validity of an alkyne-first pathway for the ring expanding ene-yne metathesis. The ring expanding ene-yne metathesis is an intermolecular reaction between a terminal alkyne and a cycloalkene, such as cyclopentene, promoted by the Grubbs catalyst. The triene was prepared through a seven step sequence employing a cross ene-yne metathesis and a stereoselective allylic transposition through an Ireland-Claisen rearrangement. The triene reacted with the Grubbs catalyst under typical ring expansion conditions, which produced the cycloheptadiene in excellent yield. The experiments support the validity of an alkyne-first mechanism by clearly identifying that the putative penultimate intermediate provides the product of the metathesis cascade. 

P11

Involvement of Lipids in Cellular Proliferation in MCF-7 Breast Cancer Cells

Isin Tuna Sakallioglu, Jeanne Danes, Jonna Frasor, and G. Ekin Atilla-Gokcumen

University at Buffalo, Department of Chemistry

Mammalian lipidome consists of thousands of lipid species. This diversity introduces a challenge in studying the individual lipid structures in complex matrices. Development of high-resolution mass spectrometry techniques with improved sensitivity in the past decades now enables us to characterize lipids in cellular extracts. De novo lipogenesis (DNL) regulates the expression of key lipogenic genes involved in fatty acids and cholesterol biosynthesis. High DNL activity is also associated with tumor growth, proliferation and invasion of cancer cells since it supplies lipids for membrane synthesis and signaling events. Sterol regulatory element binding protein (SREBP) is a known transcriptional regulator of DNL genes, therefore inhibiting activation of SREBP is a potential target for perturbing cellular growth in cancers. In this study, we used fatostatin to deactivate SREBP. Fatostatin is a non-sterol synthetic molecule that inhibits golgi translocation of SREBP through binding to SREBP cleavage-activating protein (SCAP). We inhibited DNL in a hormone dependent breast cancer cell line (MCF-7). We studied the phenotypic alterations induced by fatostatin and investigated the subsequent effects on the cellular lipidome using untargeted LC-MS-based lipidomics. We showed that fatostatin treatment causes significant changes in lipid composition in MCF-7 and efforts to analyze these changes at the molecular level are ongoing. Characterization of specific lipid species that change with fatostatin treatment will help to elucidate the involvement of lipid biosynthetic pathways in cellular proliferation.

P12

Bimodal ultrasmall nanoparticles for NIR optical and T1 MR imaging

Jossana Damasco, Tymish Ohulchanskyy, Guanying Chen, Hilliard Kutscher, Ferdinand Schweser, and Paras N. Prasad

University at Buffalo, Department of Chemistry

Combining optical and MR imaging in a single contrast agent is a very attractive platform that can be utilized for both molecular and physiological imaging. Nanoparticles allow the design of multimodal imaging agents and confining a large number of paramagnetic ions on the crystal surface result in a higher T1 relaxivity enhancement in comparison with clinical Gd-chelates MR contrast agents. Herein we present the successful synthesis of ultrasmall core-shell nanoparticles (usNPs) tailored for both optical and magnetic resonance imaging. The usNPs consist of three layers: an optically active NaNdF4:Yb10% core, an inert NaYF4 shell, and a thin outer layer of magnetic NaGdF4. The presence of Nd3+ and Yb3+ ions in the inner core of the particle allows the tuning of the optical property to the biological window. Capitalizing on the high absorption band of Nd3+ at 800nm and the very efficient energy transfer between Nd3+ and Yb3+, the particle can be excited at 800nm to yield a strong signal at 980nm. The inert NaYF4 shell serves as barrier to surface quenching, while the water-accessible Gd3+ on the outer shell surface can efficiently promote longitudinal (T1) proton relaxation without significant leaching of Gd3+ from the crystal matrix making the nanoparticles non-toxic. The ultrasmall particle size (sub-5 nm) is beneficial to achieve significantly higher ionic relaxivity and faster clearance than the larger sized nanoparticles. In this study, different ratios of PEG phospholipids (DSPE-PEG(2000) and DSPE-PEG(2000)-NH2) were utilized to render the usNPs water-dispersible and biocompatible with a functionalizable surface. These usNPs reached as high as 84 mM 1 s-1 ionic Gd3+ relaxivity at 3T. Influence of surface coating to the relaxivities and the effect of field strengths were evaluated to gain an insight on the suitable design of nanoparticle contrast agents.

P13

Synthesis of Novel Macrocycles Containing a N-Heterocyclic Carbene

Anibal Davalos and Steven T. Diver

University at Buffalo, Department of Chemistry

The synthesis of versatile N-heterocyclic carbene (NHC) containing macrocycles as ligands for transition metals is presented. NHC ligands are known to impart high thermal endurance to catalytic systems. This is due to the stable NHC-metal bond. The use of NHCs as ligands has been exploited significantly in important metal catalyzed reactions such as olefin metathesis, and cross couplings. New and demanding applications require constant development of new catalytic systems and improvement of the existing ones-mainly by the synthesis of novel ligands. We hypothesize that a macrocyclic ligand will both protect the metal catalyst and impart improved selectivity. Our approach has shown to be a suitable route to obtain macrocycles with different dimensions and functionalities from very similar starting material. Here in we report the progress towards the synthesis of the macrocyclic ligands by a series of cross coupling and ring closing metathesis reactions.

 

P14

Electrical and Optical Emission Properties of a Pulsed Solution Cathode Glow Discharge

 

Jaime Orejas Ibanez, Andrew J. Schwartz, and Steven J. Ray

University at Buffalo, Department of Chemistry

Atmospheric pressure glow discharge plasmas have attracted great interest to be used as spectrochemical sources for chemical analysis. Many reasons support this fact: simplicity of generation, low operation costs, potential portability and sometimes even competitive analytical features compared to established techniques. A group of these discharges make use of a liquid electrode to generate a plasma. The compounds present in the liquid are capable of reaching the most active parts of the plasma where they can be atomized, excited and/or ionized. The Solution Cathode Glow Discharge (SCGD) is one example of them and has been used as an effective source for atomic emission spectroscopy based elemental analysis with interesting figures of merit. The SCGD is typically powered by direct current continuous electrical supply of about 1 kV potential and 80 mA current intensity, leading to an attractive power consumption of ~80 W and offering competitive analytical capabilities. With the aim of pushing further its analytical capabilities, in our lab we have developed an experimental set-up capable of producing short time pulses (~ a hundred of ns) of increased applied potential and current, leading to a more energetic plasma with instantaneous power peaks above 500 W. The effect of these pulses on the optical emission spectrum generated by the plasma will be discussed.