1. catalytic incorporation of polyolefins into functionalized (polar
1. Catalytic Incorporation of Polyolefins into Functionalized (polar and non-polar) Block Copolymers
Dylan J. Walsh, Eric Su, Damien Guironnet* University of Illinois at Urbana-Champaign We develop a general methodology to produce HDPE, LLDPE and PP block copolymers and a 3-miktoarm star through a series of catalytic reactions. The methodology can quantitatively access three common controlled polymerizations: coordinative Ring Opening Polymerization (cROP), anionic Ring Opening Polymerizations (aROP), Atom Transfer Radical Polymerization (ATRP) (Scheme 1). The quantitative conversion of polyolefins into block copolymers ensures no homopolymer is generated, establishing the effectiveness of the transformation. Additionally, the range of monomers accessible by controlled polymerizations makes this system a powerful platform to generate a wide range of polyolefin containing materials. Scheme 1. Generalized route for block copolymer synthesis
2. Solventless Hard Soft Acid Base Chemistry: A Match Made in Heaven
Lianna Nina Trankina, James Mack University of Cincinnati High speed ball milling (HSBM) is a solvent-free technique that has reaction principles that are still not fully understood. Acid-base chemistry was tested by reacting a hydrogen donating group (alcohol) with an electron accepting group (base) and proceeding with a nucleophilic substitution on an electrophile (alkyl halide). Incorporating the hard soft acid base theory as the driving force, the metal ions in the base pairs were altered and the favorability of the metal and counter ion pair was examined. The findings have a significant implication for the use of weak bases in solvent free conditions.
3. FINITE-DIFFERENCE TIME-DOMAIN (FDTD) MODELING OF LIPOSOME BASED SUBSTRATES FOR SURFACE ENHANCED RAMAN SPECTROSCOPY (SERS) Zohre Gorunmez, Ian Bruzas, William Lum, Laura B. Sagle, and Thomas L. Beck. University of Cincinnati SERS has been shown to be one of the most sensitive techniques for molecular level detection due to the existence of plasmonic substrates. It has been established that the electromagnetic mechanism (EM) provides the main contribution to SERS enhancement due to the normal Raman spectroscopy arising from coupling of both the incident and re-emitted fields. The FDTD technique has been developed to provide numerical solutions to Maxwell’s time-dependent curl equations in order to provide modeling capabilities for EM enhancement of SERS. Therefore, we apply this method to the liposome-based, highly enhancing SERS substrates to investigate their contributions to SERS.
4. Photodynamic Inactivation of Staphylococcus aureus (MRSA) Using Hybrid Photosensitizer Based on Amphiphilic Block Copolymer Functionalized Gold Nanoparticles
Niranga Wijesiri, Tevhide Ozkaya Ahmadov, Peng Wang, Xinjun Yu, Neil Ayres* and Peng Zhang* University of Cincinnati, Department of Chemistry Multidrug-resistance Staphylococcus aureus (MRSA) has become one of the serious bacterial disease in both hospital and community. Herein, we develop a novel hybrid photosensitizer based on thiol-modified amphiphilic block copolymer, poly (N-isopropylacrylamide-block-styrene), stabilized gold nanoparticles. The hybrid photosensitizing molecules displayed enhanced singlet oxygen generation via light illumination and showed outstanding photodynamic inactivation against MRSA, with an enhanced killing efficiency up to ~6 orders of magnitude. Herein, these novel hybrid photosensitizers can be used as an efficient singlet oxygen generation substrates for the photodynamic inactivation of MRSA.
5. Development of New Cobalt Pincer Complexes for Catalytic Applications Yingze Li, Jeanette A. Krause, and Hairong Guan* Department of Chemistry, University of Cincinnati, Cincinnati, OH Replacing precious-metal-based catalysts with those derived from cheaper and more abundant metals is a major goal of sustainable chemistry. To this end, we have synthesized several novel cobalt pincer complexes bearing a bis(phosphinite)-based pincer (or POCOP-pincer) ligand and bis[(2-dicyclohexylphosphino)methyl]pyrrole (or PNPCy-pincer) ligand. Preliminary catalytic studies suggest that these (POCOP)Co complexes are active catalysts for the hydrosilylation of organic carbonyl compounds. The (PNP)Co complexes are catalytically reactive for the hydrogenation of benzyl nitrile and benzaldehyde.
6. Shape Memory Polymer Foam for Potential Aneurysm Treatment Qinyuan Chai, and Neil Ayres Department of Chemistry, University of Cincinnati, Cincinnati, OH Covalently crosslinked shape memory polymer networks were successfully synthesized using a two-step strategy. First, a lactose functionalized diamine was dissolved in DCM and reacted with excess isophorone diisocyanate (IPDI). Then, poly (ethylene glycol) (PEG) and 1,1,1-tris(hydroxymethyl)ethane (triol) comonomers were added to the prepolymer solution to increase the polymer chain flexibility and crosslink the polymer chains respectively. The polymerization reaction was performed at 80 °C and transparent films were obtained. The glass transition temperature can be tuned by changing the amount of PEG added, using this strategy a glass transistion temperature of 37 °C was obtained. The polymers were prepared as foams using the solvent casting particulate leaching (SCPL) method. The pore morphology can be tuned by the salt particle size and the amount of water added to the salt when making the template. The foams retained excellent shape memory properties after deprotection of acetyl groups on the lactose units and subsequent sulfation. The complex modulus measured from dynamic mechanical analysis (DMA) showed a dependence on pore morphology. Platelet adhesion tests on the sulfated foams proved the feasibility of using these materials for potential blood-contacting applications, including aneurysm embolization.
7. Vapochromic Pt(II) Polymorphs Nathaniel M. Barker, Amie E. Norton, Jamison Reifstek, Mahmood K. Abdolmalek, Jeanette A. Krause, and William B. Connick Vapochromic materials are known to undergo a district color change when exposed to vapors of specific organic compounds. These materials are potentially useful in sensing applications. This presentation describes the preparation and vapochromic properties of a Pt(II) complex with a polypridyl ligand. The complex forms two polymorphs, both of which are vapochromic. Characterization by XRPD, single crystal diffraction, emission, SEM, and optical imaging will be discussed.
8. Reactivity of Nickel Complexes Bearing a HN(CH2CH2PiPr2)2 Ligand Nadeesha P. N. Wellala, John Luebking, Jeanette A. Krause and Hairong Guan* Department of Chemistry, University of Cincinnati, Cincinnati, OH. Compared to the chemistry of palladium, iridium, ruthenium, cobalt and iron, nickel complexes bearing a HN(CH2CH2PR2)2 ligand are relatively unexplored. A series of these nickel complexes were thus synthesized. Protonation of nickel-bromide, nickel-phenyl, nickel-methyl and nickel-hydride complexes were studied under various reaction conditions. Oxidation and catalytic activities of nickel-bromide complex supported by [N(CH2CH2PiPr2)2]- ligand were also investigated. Stoichiometric studies of cationic nickel-hydride complexes were carried out as well to explore their potential in catalysis.
9. Comparison of solid state and solution photoreactivity of a tertiary alkyl azide
Upasana Banerjee,† Sujan K. Sarkar,† Jeanette A. Krause,† Manabu Abe,‡ and Anna D. Gudmundsdottir*,† †Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States ‡Department of Chemistry, Graduate School of Science, Hiroshima University, Hiroshima 739-8526, Japan
Solid state photoreactions are unique because they tend to much more selective than their counterparts in solutions. Thus, they have potential use in synthetic applications. However, to better understand how the crystal lattice controls the solid state reactivity it is necessary to elucidate solid state reaction mechanism and correlate the solid state kinetics with the crystal lattice. We report the first detection of a tertiary triplet alkylnitrene 2 in solution, solid state and in cryogenic matrices. Triplet alkylnitrene 2 is stable at cryogenic temperatures and thus it can be identified using ESR, UV-Vis, and IR spectroscopy. The D (1.58 cm-1) value obtained from ESR spectroscopy indicates that the unpaired electron are delocalized on the nitrogen atom in 2 and as expected for triplet alkylnitrenes. Irradiation of tertiary azide 1 in solution resulted in formation of products 6 and 7. Laser flash photolysis of 1 in solution confirmed that these products are formed from triplet nitrene 2. In comparison, solid state photolysis of 1 resulted in product 3. Laser flash photolysis of nanocrystals of 1 made it possible to identify the solid state mechanism, also goes through triplet alkylnitrene formation. The triplet alkylnitrenes in the solid state cannot rotate to form solution products. Density functional theory (DFT) calculations were performed to support the proposed reaction mechanism and to support the characterization of the excited states and intermediates.
10. High Resolution, Accurate Mass Spectrometry of Modified RNAs
Peter A. Lobue and Patrick A. Limbach Department of Chemistry, University of Cincinnati RNA modification patterns have been implicated in many important human diseases. To achieve a more complete understanding of RNA modifications and their role in disease, new analytical tools capable of complex sample analysis are needed. As a first step towards this goal, a tandem mass spectrometer method using data-dependent acquisition has been developed on the high resolution, accurate mass Waters Synapt G2S mass spectrometer. Using the parameters developed on this instrument, the LC-MS/MS method was capable of detecting and confirming modified tRNA sequences in a complex digest sample. The MS data and features of the method will be presented.
11. Kinetic Effects of Crystal Packing on the Dimerization of 1,4-Naphthoquinone and its derivatives. Dylan Shields, Sujan Sarkar, Jeanette Krause, Anna Gudmundsdottir Department of Chemistry, University of Cincinnati Abstract: Solid-state photochemical reactions have been shown to be useful synthetic tools for their remarkable stereo and regiospecificity. Decreased solvent use also gives these reactions green chemistry appeal. One of the limitation of using solid-state photoreactions in synthetic applications is understanding how the crystal lattice controls the reactivity. Until recently, elucidation of solid-state reactions has been limited to structure reactivity correlations. With the aid of laser flash photolysis of nanocrystals in water slurry it is possible to determine solid-state kinetics, which makes it possible to correlate the kinetics with the structure. We have investigated dimerization of 1,4-naphthoquinone derivatives in the solid-state, which has allowed us to determine how the crystal packing of a molecule influence the solid-state kinetics of product formation. The correlation was established through X-ray crystallography of the 1,4-naphthoquinone derivatives and their transient kinetics spectroscopy.
12. Liposome-Nanoparticle Substrates for Surface Enhanced Raman Spectroscopy Russell Anthony, William Lum, Ian Bruzas, and Dr. Laura B. Sagle University of Cincinnati, Department of Chemistry, Cincinnati, Ohio, 45220, United States Raman scattering is an inefficient optical phenomenon that occurs when incident photons in-elastically scatter from an atom or molecule. Surface-enhanced Raman Scattering (SERS) spectroscopy uses noble metal surfaces such as Au to greatly increase Raman scattering thus producing a highly sensitive and selective technique, which can analyze single molecules (SM). In order to create more biologically compatible SERS substrates, we propose to encapsulate probe molecules into liposomes to mimic the native environment. As proof of concept, crystal violet was encapsulated into biotinylated liposomes, the liposomes are tethered to a gold surface and finally gold nanoparticles are bound to maximize the signal.
13. Azido Modified NTP as Chemical Handles for Multiplex Analysis of tRNA Digestion Products Kayla Borland and Patrick A. Limbach Department of Chemistry, University of Cincinnati
Liquid chromatography tandem mass spectrometry (LC-MS/MS) is the gold standard in transfer ribonucleic acid (tRNA) modification identification and mapping. A common practice in LC-MS/MS in the field of proteomics is the use of multiplexing, which allows multiple biological samples to be analyzed simultaneously. We are exploring the use of poly adenosine polymerase (PAP), which – under optimized conditions – can add one 2’ azido modified nucleotide to the 3’-terminus of tRNA digest products. The addition of this azido-modified nucleotide can allow for the use of click chemistry to uniquely tag each sample. Here we report preliminary studies focused on click reaction conditions.
14. Synthesis of a pyridyl disulfide functionalized RAFT copolymer for conjugation with Polypropylene fumarate through thiol-ene click reactions. Mario Perera, Neil Ayres Department of Chemistry, University of Cincinnati Poly(N,N-dimethyl aminoethyl methacrylate-co-pyridyldisulfide ethyl methacrylate) (poly(DMAEMA-co-PDSMA) was synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The number average molecular weight (Mn= 7800 g/mol) and dispersity (Đ= 1.3) were determined using gel permeation chromatography and the PDSMA content in the polymer was determined using the 1H nuclear magnetic resonance (NMR) spectroscopy. Post polymerization modifications reduced the pyridyl disulfide groups to thiols using (tris(2-carboxyethyl)phosphine) (TCEP), this was confirmed by the disappearance of the pyridyl protons in the 1H NMR spectra. Thiol-ene click reactions are an efficient tool for polymer synthesis and modification. Polypropylene fumarate (PPF) is a hydrophobic polyester that has been investigated as a potential scaffold material for bone tissue engineering. In this work, thiol-ene click reactions were attempted as a strategy to graft PPF with modified poly(DAMAEMA-co-PDSMA). However the expected copolymer was unable to be isolated. Control thiol-ene reactions of PPF with propane thiol and diethyl fumarate with modified poly(N,N-dimethyl acrylamide) were successfully performed, and the 1H and 13C NMR spectroscopy confirmed the products. Hence, this study proves that polymer/polymer thiol-ene reactions are not an appropriate strategy to conjugate PPF and poly(DAMAEMA-co-PDSMA). We speculate that this is due to a combination of steric and reptation effects.
15. Quantitative SERS measurement of trichloroethylene with Au-core/Ag-shell nanoparticles
Zhao Yu, Yan Zhou, Peng Zhang* Department of Chemistry, University of Cincinnati, OH 45221, United States Abstract: Trichloroethylene (TCE) has been used for cleaning and degreasing metal-based equipment, and it is known to be a human carcinogen. Surface-enhanced Raman scattering (SERS) is introduced to determine the concentration of TCE in water. We use Au-core/Ag-shell nanoparticles with 4-mercaptophenylboronic acid (4MPBA) as embedded internal reference as a new strategy to measure TCE with a high sensitivity. 4-mercaptopyridine (4-MPy) can react with TCE through Fujiwara Reaction. We monitor the consumption of 4-MPy by the SERS signals change of Au@4MPBA@Ag nanoparticles to determine the concentration of TCE in water indirectly.
16. Fenton Chemistry of Acetophenones in Water: Evidence of Ipso Substitution
Jennifer L. Meyer1, Richard P. Hotz1, Allan R. Pinhas2 1Department of Chemistry, Mount St. Joseph University 2Department of Chemistry, University of Cincinnati
Using Fenton’s reagent, the coupling of two radicals formed by hydrogen atom abstraction from the -carbon of acetophenone, in its keto form, results in the generation of a 1,4-diketone. However, because the enol form predominates under acidic conditions in water, the major reaction products derive from attack of the hydroxyl radical on the aromatic ring. A small percentage of these compounds, including phenol, are formed by ipso substitution. Identification of ipso substitution products from several substituted acetophenones and possible mechanisms for their formation will be presented.
17. Comparing Photosensitization of Azido-Butyrophenone Derivatives using UV Light and Acetophenone as a Built-in Triplet Sensitizer and Visible Light and Inorganic Photocatalysts
DeVonna M. Gatlin, Anntonette Perry, Anna D. Gudmundsdóttir* Department of Chemistry, University of Cincinnati Photocatalyst make it possible to use visible light for sustainable organic photosynthesis. To explore the difference between the inorganic photocatalyst and built-in triplet sensitizer, we investigated the photoreactivity of alkyl azide 1. Photolysis of alkyl azide 1 with UV light above 300 nm, results in product A through formation of triplet alkylnitrenes intermediates. Irradiation with 400 nm light and photocatalyst X also yields the same product presumably through the same mechanism as UV irradiation. However, photolysis with photocatalyst Y (with 460 nm irradiation) results in product B. We will use theoretical calculations and transient spectroscopy to further understand how the photoreactivity differ for each photocatalyst.
18. Synthesis of Iron and Cobalt Complexes and Their Application toward Hydrogenation
Reactions Huiguang Dai, Hairong Guan Department of Chemistry, University of Cincinnati First row transition metals, such as iron, cobalt, nickel and copper, are drawing more attention for catalytic applications in the past decade, due to their earth-abundancy, environmentally benign, and versatility toward various transformations. Among those transformations, hydrogenation is important to generate alcohols, amines and other fundamental building blocks with dihydrogen as clean reductant. In our group, we synthesized iron and cobalt complexes and particles, which were employed for homogeneous or heterogeneous hydrogenation catalysts toward carboxylic esters, amides, nitriles, aldehydes and ketones. Mechanistic study and computational calculation were also carried out to understand the reaction in details and help to improve catalytic performance.
19. ROS responsive self-cyclization for hydroxyl radical detoxification Jing Liu, Eddie J. Merino Department of Chemistry, University of Cincinnati Reactive oxygen species are biologically important highly reactive species. Hydroxyl radical is especially bad since it reacts indiscriminately with biomolecules. I am designing novel antioxidants that selectively respond to hydroxyl radical over other forms of ROS. These new antioxidants can possible prevent cell damage. I will show the synthesis and design of new antioxidants. Two molecules, called AP1 and AP2, were made with each synthesis being six steps. I then examined reactivity of both and found AP2 to be selectively oxidized by hydroxyl radical. Biological tests are under way and show the potential of AP2.
20. Photosensitization of α-azidoacetophenone using Ru-metal complex as a photocatalyst Nayera Abdelaziz, and Anna D. Gudmundsdottir*,† †Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States Photochemistry is useful for synthesizing strained molecules. Most organic compounds do not absorb visible light, but photocatalysts which are transition metal complexes make it possible to use visible light to carry out photoreaction. The ability to use visible light for carrying out photoreactions is important as either sun light or by environmental friendly LEDs, can be used as the light source. Our group previously reported the first detection of triplet alkylnitrenes in solution by laser flash photolysis of α-azidoacetophenone derivatives which have a built-in triplet sensitizer. Here we report the photosensitization of α-azidoacetophenone using [Ru(bpz)3][BF6]2., as a catalyst. We will compare whether the photocatalyst gives the same results as triplet sensitizer. We will compare photoreactivity obtained with triplet sensitizer and photocatalyst by preforming transient spectroscopy, product studies and theoretical calculations.
21. TOXIC METAL ACCUMULATION IN SELENIUM SUPPLEMENTED AQUAPONICS SYSTEMS. Christopher Yap, Skyler W. Smith, Megan Schmale, Julio A. Landero Figueroa, and Joseph A. Caruso. University of Cincinnati, Chemistry Department, 312 College Dr., Crosley Tower Room 404, Cincinnati, OH 45221; [email protected]. Aquaponics is an integrated technique that combines aquaculture and hydroponics using a re-circulating water system. Compared to traditional aquaculture methods, aquaponics potentially provides sustainable food production while conserving freshwater. The aim of this research was to find the optimal level of selenium, an essential antioxidant, for Nile tilapia via feed supplementation and track its accumulation in tilapia, basil and beans by using ICP-MS. Selenium accumulation in all system components followed the supplementation pattern with a level of approximately 1 ppm demonstrating the most optimal fish growth among our 3 systems. Toxic metal accumulation and water quality will also be presented.
22. Detection of Post-Transcriptional RNA Modifications in the Radioresistant Bacterium Deinococcus radiodurans R1 Ruoxia Zhao, Balu Addepalli, Patrick A. Limbach* Department of Chemistry, Rieveschl Laboratories for Mass Spectrometry, University of Cincinnati, Cincinnati, OH 45221
The bacterium Deinococcus radiodurans is one of the most ionizing radiation resistant families of bacteria discovered to date. D. radiodurans has extraordinary resistance to all reactive oxygen species (ROS)-generating agent including desiccation, ionizing radiation, UV radiation, mitomycin C and so on. In order to understand whether transfer RNAs (tRNAs) are modified differently when D. radiodurans are exposed to ionizing radiation (IR), the modified nucleosides in control D. radiodurans and D. radiodurans with different extent of IR (60Co) have been analyzed by Reverse-Phase High Performance Liquid Chromatography Mass Spectrometry (RP-HPLC-MS/MS). RNA modification mapping is conducted by utilizing a base-specific ribonuclease (RNase T1) to cleave a larger RNA into smaller digestion products (oligonucleotides). The location and identity of nucleotides and modified nucleotides can be determined by using of a DNA-based exclusion list which enhances data dependent RP-HPLC-MS/MS detection method. Determining the modified RNA sequence will increase the understanding of structure-function relationships of RNAs.
23. Quantification of Volatile Organic Compounds in hookah condensed smoke produced from Different Heat Sources
Patricia Chu, Julio A. Landero University of Cincinnati Hookah tobacco smoking is currently on the rise worldwide. It is commonly believed to be safer than smoking cigarettes, and the lack of regulations in the US can be perceived as a reaffirmation of this. However, previous research have shown that hookah smoke contains toxic compounds such as polycyclic aromatic compounds (PAHs). PAHs are a class of volatile organic compounds (VOCs) produced when organic matter is heated under low oxygen conditions. These compounds are highly toxic, carcinogenic at low levels. The maximum temperature of the hookah tobacco preparation and the heating element position within the hookah head can result in different rates of PAHs production and volatilization. Previous research in the lab show that using either an electric heat source or charcoal will produce the VOCs within the distillate collected for analysis. The objective of this research is to quantify the amount of VOCs in both sources to compare them to cigarettes, after cryo-condensing of the smoke. The HPLC-FLD detection of PAHs under different heat sources after a 30 min smoking session will be presented.
24. Verification of methylated Inosine in Bacillus subtilis tRNA.
Christina Psihountas, Collin Wetzel, and Patrick A. Limbach Department of Chemistry, Rieveschl Laboratories for Mass Spectrometry, University of Cincinnati, Cincinnati, OH 45221 Transfer Ribonucleic Acids (tRNAs) have more modified bases than the other species of RNA. Modifications can serve one of three purposes in tRNA: 1) provide stability to the tRNA structure, 2) assist with anticodon-codon fidelity, and 3) serve as determinants to aminoacyl tRNA synthetase. Liquid chromatography tandem mass spectrometry (LC-MS/MS) is the current method for detecting and characterizing modifications. A previous analysis of Bacillus subtilis showed methylated Inosine (m1I or Im) present at position 73 in some tRNAs. This finding is currently being verified through nucleoside detection and oligonucleotide sequencing of B. subtilis tRNA with LC-MS/MS.
25. New Tripodal Ligands with α-Hydroxy Acid Groups and Their Photoactivity Alena Moore1, Aubrey Malott1, Aleksander Thomas1, Michael J. Goldcamp1, and Michael J. Baldwin2 (1) Wilmington College, Wilmington, OH 45177 (2) University of Cincinnati, Cincinnati, OH 45221 Alpha-hydroxy acid (AHA) groups can bind Fe(III) and release it as Fe(II) after photolysis. A new ligand has been synthesized by adding AHA groups to a nitrilotriacetate framework. Coordination of Fe(III) may create a cage with a photochemical “lock.” The Fe(III) complex shows production of CO2, a product of photochemical AHA cleavage. CO2 produced has been quantified by MS and is significantly greater than that of the photolysis of free ligand or complexes of other metals. We are exploring structural characterization of metal complexes of this ligand and the synthesis of ligands with longer AHA “arms.”
26. Metal Complexes of Ligands with α-Hydroxy Acid Donor Groups Alex Saunders1, Michael J. Goldcamp1, Jeanette Krause2, and Michael J. Baldwin2 (1) Wilmington College, Wilmington, OH 45177 (2) University of Cincinnati, Cincinnati, OH 45221 Photo-initiated release of an active species could be useful in many applications. Ligands containing an α-hydroxy acid group have been shown to bind Fe(III) and release it as Fe(II) after photolysis. The ligand AHA-PYR was synthesized by reaction of pyridine-carboxaldehyde with 4-amino-2-hydroxybutanoic acid to form the imine. X-ray crystal structures of the Cu(II) and Zn(II) complexes show 1-D coordination polymers, with the mono-deprotonated ligand. UV-vis analysis of the deprotonation of the copper shows that further deprotonation can occur. Structures of complexes with more metals are being pursued, as are variations to the organic substituents of the AHA-PYR ligand.
27. Bioinspired Tripodal Amine Chelates Containing α-hydroxy Acids and α-hydroxy Amides and Photochemistry of their Metal Complexes
Jennifer E. Vernia and Michael J. Baldwin University of Cincinnati α-hydroxy acids found in photoactive siderophores can be incorporated into organic compounds, mimicking the strong binding affinity and photoactive properties of iron-siderophore complexes. A series of α-hydroxy acid (AHA) containing compounds with a tripodal amine motif has been synthesized. Varying the functional groups attached to the non-AHA arms of the tripodal amine allows for studies of metal complex structure, stability and photochemistry. The iron complexes of siderophores that contain α-hydroxy amides also show photoactivity. New α-hydroxy amide containing chelates have been synthesized, and their iron complexes are photoactive. The choice of amine added to AHA allows for expansion of applications.
28. TiO2-Based Solid Phase Extraction and HPLC-Coupled Mass Spectrometry for the Detection of 2’-O-methylmodifications in RNA
Manasses Jora, Robert Ross, and Patrick Limbach Department of Chemistry, University of Cincinnati, Cincinnati, OH Modifications present in the RNA sequence may affect its stability, structure, function, and translation. Variations in modification patterns in an organism is of great interest owing to their relationship to diseases and syndromes. Modifications present in the sugar are typically less abundant and, consequently, more difficult to be detected. The goal of this work was to optimize a TiO2-based method for the enrichment of 2’-O-ribomodifications, and use it to increase detection of 2’-O-modfied nucleosides by LC-MS/MS. The results qualify the method as a powerful tool to be used in conjunction to LC-MS/MS for 2’-O-methylmodifications detection in RNA.
29. Bacterial Detection Based on Localized Surface Plasmon Resonance of Functionalized Gold Nanoparticles
Michael E. Smith, Niranga Wijesiri, Peng Zhang Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221–0172 USA The emergence of multi–drug–resistant bacteria has generated significant interest to develop on–site, fast, sensitive, and reliable detection methods in order to safeguard public health. Herein, we present results of a bacterial detection scheme that exploits changes in the localized surface plasmon resonance (LSPR) of functionalized gold nanoparticle solutions that arise from interactions with bacterial cell surfaces. The detection scheme exhibited successful, yet irreproducible results for proof of concept studies, and unsuccessful results for bacterial detection. These results are likely due to pH variations in un–buffered sample solutions.
30. Methodology development for the synthesis of end-functionalized polyolefins
Michael Hyatt, Alexander Horn, Damien Guironnet University of Illinois at Urbana Champaign
Functionalized polyolefins are an important class of materials, but are difficult to produce in a controlled manner. One method to synthesize these materials is the chain transfer polymerization using early transition metals, but is inhibited by electron rich heteroatoms. Since late transition metals are more stable towards heteroatoms, we have developed a chain transfer polymerization using a Brookhart diimine palladium catalyst with silanes as the chain transfer agent. The rate of chain transfer was investigated as well as certain key intermediates. Future work will include using modified silanes to directly introduce functional groups onto the end of the polymer chain.
31. Characterization of Reactive Intermediates in the Photo Reactivity of Vinyl and Arylic
Azides. Onyinye Osisioma, Bruce Ault, Anna D Gudmundsdottir Department of Chemistry, University of Cincinnati Vinyl azides have been studied in the past as possible precursors for triplet vinylnitrenes and served as starting points in the sustainable synthesis of complex heterocycles by visible light catalysis. Aryl azides have important applications as photo-linkers through intermolecular insertion reactions associated with triplet reactivity. We studied the photoreactivity of vinyl azide 1 to explain the triplet sensitization of vinyl azides to form triplet nitrenes. We hypothesized that direct irradiation of vinyl azide 1 would yield the azirine through a triplet vinylnitrene intermediate. Irradiation of 1 in argon matrices resulted in azirine 2, presumably through concerted reaction of the singlet excited state of vinyl azide 1. In comparison, long wavelength irradiation of azirine 2 formed ketenimine 3, whereas short wavelength irradiation resulted in formation of ylide 4. We propose that ketenimine 3 is formed from a triplet vinylnitrene intermediate. Density functional theory calculations were used to support the reaction mechanism of vinyl azide 1. Product studies on aryl azide 5 indicate temperature dependence which allows us to contrast singlet and triplet reactivity. We have also detected the formation of a long-lived intermediate by laser flash photolysis from azide 5 with low reactivity with oxygen. We will further investigate sensitization of aryl azide 5 using available inorganic catalysts to determine the mechanism of sensitization.
32. Interactions of Avobenzone with model POPC lipid membrane, investigated using Molecular Dynamics and Neutron Reflectometry
Andrew Eisenhart1, Marzieh Mirzamani2, Frank Heinrich3, Anna D. Gudmundsdottir1, Thomas L. Beck1, Harshita Kumari2 1Department of Chemistry, University of Cincinnati, Cincinnati, OH; 2James L. Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH; 3NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD
Avobenzone (1-(4-Methoxyphenyl)-3-(4-tert-butylphenyl)propane-1,3-dione) is commonly used as an active ingredient in modern broad-spectrum sunscreens as a UV absorbing molecule, due to its ability to absorb UVA radiation it is an attractive species to many sunscreen manufacturers. In our research we have explored the interactions of Avobenzone with skin, modeled using POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine). Neutron Reflectometry has been used to define the density of Avobenzone inside the membrane and these results are corroborated with molecular dynamic simulations. Using these simulations we have reported the free-energy changes associated with Avobenzone, and the Avobenzone-TBC complex, as a function of locatio. Additionally we report the mobility of Avobenzone molecules inside the membrane by calculating the diffusion constants of Avobenzone in a populated membrane.
33. Understanding the Chemical Energetics behind an 8000M Mixer/mill Joel Andersen, James Mack University of Cincinnati, Cincinnati, OH, USA. Mechanochemistry is a solventless approach to conducting chemical reactions. However, the nature of energy transformations during mechanochemical reactions is poorly understood. To better understand this process, the effect of variables such as temperature, operating frequency, and reaction-vessel hardness on various Diels Alder reactions are being investigated. The results suggest an intriguing re-thinking of the way we commonly perceive the Arrhenius equation. Significant impacts on selectivity are expected as an outcome of this work.
34. Presence of organic molecule: PAHS occurred during hookah smoking
Aida Gueye, Julio A. Landero University of Cincinnati Hookah smoking which happens to be a new trend of smoking tobacco using a smoking apparatus has gotten to be known and used everywhere. This method of smoking has been studied to be collecting some volatile organic compounds that are similar to the one found in tobacco but said to be lower in quantity and less toxic. In order to certify the results of the previous study done, a hookah project will be done by using 3 different heat sources such as 2 types of tobacco, and an electric heat source as well as a hookah apparatus and tobacco. By running the experiment each heat source will be providing a quantity of volatile organic compounds which will be used to compare them from one another. After comparing the results of organic compound collected during the condensation of the vapor used to determine to the quantity of the PAHS, a comparison will be made with cigarette smoking to show that hookah smoking is less toxic than cigarette smoking.
35. Amount of Volatile Organic Compounds Smoke Produces from Various Heat Source Bintou Thiam, Julio A. Landero University of Cincinnati Hookahs are water pipes used to smoke with tobacco that comes in different flavors. Although many think it is less harmful, hookah smoking has many of the same health risks as cigarette smoking. The charcoal used to heat the tobacco can raise health risks by producing high levels of carbon monoxide, metals, and cancer-causing chemicals. Researchers have shown and proven that hookah smoke contains toxic compounds that are produced when heated under low oxygenic conditions. Such compounds are known as Polycyclic Aromatic Compounds (PAHs) which are a class of volatile organic compounds (VOCs). The temperature of the hookah preparation and the heating element position can affect the rates of the PAHs production and volatilization. The purpose of this lab is to gather the amount of VOCs, after the cryo-condensing of the smoke, in the electric heat source and both of the charcoals used the hookah in order to compare them to cigarettes.
36. Normal Mode Analysis of Conformational Changes in the ClpP Peptidase
Qi Wang1, Riina Tehver2 and George Stan1,* 1. Department of Chemistry, University of Cincinnati, OH 45221. 2. Department of Physics and Astronomy, Denison University. Granville, OH 43023. Caseinolytic proteases are molecular machines composed of an ATPase and a peptidase. The ClpP peptidase comprises two stacked heptameric rings enclosing a spherical chamber with 14 protease active sites. Recent studies hypothesize that the degraded proteins are released through equatorial pores. In this work, a normal mode analysis method is used to study the conformational changes of the monomer and tetradecamer of ClpP. We observed a large deformation of the axial loop and handle domains in the monomer normal modes, while the allosteric transitions of the tetradecamer are mainly contributed by conformational changes of the handle region. Our results support a model that ClpP releases degraded peptides through the equatorial regions.
37. Computational Studies of Dynamic Collaboration between ClpB and co-factor DnaK during Protein Disaggregation Yu-Hsuan Shih1, Shannon M. Doyle2, Andrea N. Kravats2, Joel R. Hoskins2, Sue Wickner2 and George Stan1 1Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221 2Laboratory of Molecular Biology, NCI, NIH, Bethesda, MD 20892 Aggregates, which are known to deteriorate the cell functions under stress environments, can be rescued by a set of chaperone nanomachines such as ClpB ATPase and co-factor DnaK. The mechanism of ClpB and DnaK is controlled by ATP-driven large conformational changes, initiating the disaggregation process during protein quality control. How ClpB and DnaK interact and collaborate during binding events is unclear. We investigated dynamic interactions between ClpB and DnaK by applying the molecular dynamics (MD) simulations. Our computational studies are consistent with biochemical experiments as well as suggesting potential residues important for ClpB and DnaK interaction.
38. Exploring Microtubule Breaking Mechanisms Using Large Scale Molecular Simulations
Nan Jiang, Ruxandra I. Dima Department of Chemistry, University of Cincinnati Microtubules (MTs), polymerized from dimer units, are the main cytoskeletal filaments. The reorganization of MTs is often initiated by removing dimers through mechanical destruction by motor enzymes. Those enzymes convert chemical energy from ATP hydrolysis into mechanical work. Previous experimental work suggests that lattice defects act as active spots for those enzymes. We investigate the mechanical behavior leading to the crushing of MTs using molecular dynamic simulations. Our study provides molecular details of the MT breaking pathways as well as the distribution of mechanical forces needed to break the lattice. Our results strongly support the proposal that defects represented by lattice vacancies are important in MT crushing, as the force needed to break a filament with vacancies is much lower than the one required to break an intact one.
39. Formation of new Transition metal complexes containing two α-hydroxy acid moieties
Ahmed Elshewy, Michael J. Baldwin Department of Chemistry, University of Cincinnati To sequester iron, bacteria biosynthesize molecules called siderophores that bind Fe(III) very strongly. Some siderophores are photochemically active. These all have an α-hydroxy acid related functional group. A series of new two α-hydroxy acids-containing chelates inspired by photoactive marine siderophores, along with their transition metal complexes are being synthesized and characterized structurally and photochemically. These new chelate structures are being designed to accommodate two different metal sites including one photo active iron site and a second variable metal site.
40. Effect of Force Directionality on ClpB-mediated Unfolding Mechanisms of GFP and superfolder GFP Rui Jiang and George Stan University of Cincinnati Protein disaggregation and degradation by the ClpB nanomachine, a member of the HSP100 ATPase family, are crucial to prevent lethal protein fibrillization and maintain cellular homeostasis. We study the molecular mechanisms of ClpB-mediated disaggregation by using computer simulations of threading Green Fluorescent Protein (GFP) and superfolder GFP substrates through the central pore of ClpB. We find similar unfolding pathways of GFP as in experiments and coarse-grained simulations. We also find that in the unrestrained case mimicking in vivo action, GFP is oriented along with the direction of weaker mechanical resistance, leading to a lower critical force and faster unfolding.
41. Photoactive uranyl complexes of α-hydroxy acid chelates Mark A. Chrisman, Jeanette A. Krause, Michael J. Baldwin Department of Chemistry, University of Cincinnati Uranyl complexes were formed with the 3,5-diCl-Sal-AHA and 3,5-di-t-butyl-Sal-AHA chelates which formed photoactive dimers. These dimers produce UIV upon photoreduction. While the uranyl complexes form as dimers they share similar binding to the FeIII Sal-AHA complexes with each ligand binding to two metal centers. The organic photoproducts are similar to that found to occur upon photolysis of the FeIII Sal-AHA complexes rather than what is typical of uranyl ion in organic solvent. The complex is able to photoreduce methyl viologen under anaerobic conditions.
42. Mechanistic Studies of Iridium Pincer Complexes Using Flow Chemistry J. Carl Schultz, Damien Guironnet Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign Iridium pincer catalysts offer high selectivity in the dehydrogenation of alkanes to α-olefins, but due to their co-solubility with the formed product they are challenging to use in continuous processes. Herein, we undertake to study these catalysts in a two-phase flow reactor which allows an unsupported catalyst to be retained in a liquid phase while a volatile substrate is continuously fed and removed as vapor. Various iridium pincer complexes have been synthesized and are undergoing mechanistic studies under reaction conditions.
42. Synthesis of Esters from Aldehydes Catalyzed by a Nickel Pincer Hydride Complex
Nathan A. Eberhardt and Hairong Guan Department of Chemistry, University of Cincinnati Synthesis of esters from Aldehydes can be a useful chemical process. Here we describe a POCOP Pincer Nickel Hydride complex that can catalyze the esterification of aldehydes into esters. The process cross esterifies aldehydes with the alcohol present as solvent. A number of alcohols were screened. Amide synthesis, transfer hydrogenation, and acceptorless dehydrogenation were also explored.
Emily Westbrook, Jinnan Zhang, Mike Gazda, Peng Zhang*
University of Cincinnati, Department of Chemistry, Cincinnati, OH 45221-0172 Antibiotic-resistance is one of the three greatest threats to human health with more than 2,000,000 illnesses and 22,000 deaths and billions of dollars in excess spending annually. Our strategy uses silver-enhanced photoactivated nanoparticles for the photoinactivation of bacteria. The patent pending nanoparticles do not involve antibiotics and no new resistance will be incurred. Additionally, they are effective against drug-resistant bacteria and treatment is rapid and broad-spectrum. This project has been funded as a University of Cincinnati Accelerator Project and we are pursuing commercialization of this technology.
44. Efficient Photorelease Achieved by Irreversible Formation of Excited State Intermediates, New Photoremovable Protecting Group
Kosala Thenna Hewa‡, Sivaramakrishnan Muthukrishnan‡, David Lee Phillips†, Anna D. Gudmundsdottir‡
‡Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221. †Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S. A. R.,P. R. China New photoremovable protecting group 1 releases alcohols in high yields. The photorelease of the alcohol takes place in argon and oxygen saturated solutions. We elucidated the mechanism for photorelease using product studies, ultra-fast transient absorption spectroscopy, ultra-fast transient Raman spectroscopy and molecular modeling. Upon irradiation, excited 1 undergoes Intramolecular H abstraction to form singlet excited biradical 2 that then inter system crosses (ISC) to form triplet biradical 2. Triplet biradical 2 undergoes expulsion of N2 to form biradical 3. Biradical 3 undergo lactonization to release methanol and form biradical 4. Intra molecular H transfer of biradical 4 forms final photoproduct 5. The high yield for the photorelease is due to the irreversible formation of intermediate 3 by the expulsion of N2.
45. Mechanistic Investigation on Photochemical Formation of Alkylnitrene in Solution and Cryogenic Matrices from Diazides
Dushanee Sriyarathne, Taha Alhayani, and Anna Gudmundsdottir Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221.
Nitrenes are reactive intermediates that have a monovalent nitrogen atom and can be used in numerous applications, such as photoaffinity labeling and surface modification. Due to the high spin property of nitrenes, it has the potential to be used as building blocks for high spin assemblies. Although, di-nitrenes could be useful for several applications, they have, however, not been studied extensively. Alkylnitrenes are generally formed by exposing azides with built-in triplet sensitizers to light to bypass the singlet reactivity of the azido moiety. In this study, we investigated the triplet reactivity of 2,2-diazido-2,3-dihydroinden-1-one (1). Interestingly, azide 1 can potentially undergo several different photoreactions, α-cleavage, homolytic cleave of one the azide, release of N2 to form nitrenes intermediate, but irradiation of 1 results in formation of only two new photoproducts. To elucidate the reaction mechanism for 1, we relayed on several spectroscopic methods such as, laser flash photolysis (LFP), low temperature UV/vis, matrix isolation and electron spin resonance (ESR) to identify the excited states and intermediates involved. In addition to these methods, we used Gaussian DFT calculations to support the proposed reactions mechanism.
46. Multiplexed, Flexible and Portable Plasmonic Biosensing On-Chip Jie He, George Yoshida, Celeste Bulach, Laura Sagle University of Cincinnati, Chemistry Department, Cincinnati, OH 45221 Localized Surface Plasmon Resonance Based biosensors provide sensitive, label-free, rapid, colorimetric detection. We incorporated nanoparticle arrays into microfluidic and multiplexed devices by combining photolithography and colloidal lithography. This presentation highlights two recent applications. The first involves the fabrication of 96-well glass/PDMS plates fitting into commercial UV-Vis plate readers. We carried out drug screening for the Human Antigen R (HuR) protein. The second application is a point-of-care assay for pathogenic species associated with sexually transmitted disease. In addition, these uniform nanoparticle arrays can be fabricated on flexible polymers. Combining our technology with color analyzing software on the I-Phone enables rapid read-out.
47. A Twin ROS-activated Anti-tumor Agent Haizhou Zhu, Abdulsalam, Safnas, Merino Edward* Department of Chemistry, University of Cincinnati Reactive oxygen species such as superoxide and hydrogen peroxide related to proliferation, differentiation, signaling, and apoptosis of the cell. It is reported that the high concentrations of various ROS is required for tumors compared to healthy tissue. Base on this observation I have designed a novel cytotoxic agent that contains two covalently linked anti-tumor agents. They are both inactive until ROS breaks them apart. Once apart they both activate them and impart a dual mechanism of action. Thus the cancer cells are hit twice when ROS is high.
48. Atomistic simulations of unfolding and translocation of the Immunoglobulin domain I27 in repetitive cycles of the ClpY Biological Nanomachines
Abdolreza Javidialesaadi and George Stan Department of Chemistry, University of Cincinnati, OH 45221, Cincinnati, OH Powerful AAA+ ATPases, such as ClpY, are hexameric biological nanomachines which selectively process abnormal proteins targeted for degradation by unfolding and threading them through a narrow central channel. The molecular details of unfolding and translocation of substrate proteins by these nanomachines have not yet been fully understood. We performed targeted molecular dynamics simulations coupled with repetitive pulling forces of an implicit solvent model of ClpY-mediated unfolding and translocation of an Immunoglobulin protein domain, Titin I27. We find that in vivo-like ClpY-action results in I27 reorientation during the threading, which allows I27 unfolding to proceed by unzipping the C-terminal strand.
49. Reversible addition-fragmentation chain transfer polymerization by microwave reactor
John Hammann, Emily Westbrook, Peng Zhang*
University of Cincinnati, Department of Chemistry, Cincinnati, OH 45221-0172 A microwave reactor procedure was developed to reduce the time of synthesizing polymers compared to conventional heating methods. This was achieved by using a reversible addition-fragmentation chain transfer (RAFT) polymerization in synthesizing poly(methylmethacrylate). The more time spent in the microwave reactor correlated to a higher molecular weight and a greater yield. This reaction protocol has been developed in hopes to aid future research with block copolymer or statistical copolymers.
50. Determining the impact of irradiation on melanized radiotrophic fungi with varying metabolic resources Melissa Kelley, Lauren Schultz, Mellie J Paulines, Jahmila Pettis, Balasubrahmanyam Addepalli, Patrick Limbach University of Cincinnati Department of Chemistry Melanin has been found to play a role in the ability of radiotrophic fungi to convert gamma radiation into a metabolic resource. Cryptococcus neoformans and Cladosporium sphaerospermum are able to survive extreme conditions including oxidative stress and radiation exposure. Various effects of metabolic resources have been investigated for their role in melanin production and survivability. Total RNA isolation techniques for the organisms have been optimized. Further work must be performed to determine the effects of the metabolic resources on total RNA and transfer RNA modifications.
51. Enhanced fluorescence with polymer blends embedded in mesoporous silica Emily Westbrook and Peng Zhang*
University of Cincinnati, Department of Chemistry, Cincinnati, OH 45221-0172 Imaging living cells with fluorescent probes has improved our understanding of many biochemical processes. However, cytotoxicity, poor solubility and selectivity, rapid irreversible bleaching and self-quenching of these probes has limited their application. We have demonstrated the enhanced fluorescence of a polymer blend nanodot core embedded in mesoporous silica. A blend of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and polystyrene was nanoprecipitated, and then coated with a mesoporous silica shell. These fluorescent nanoparticles show aqueous solubility, increased fluorescence lifetime and were further surface functionalized with folic acid for improved cell selectivity. These nanoparticles show great potential for use in living cell imaging.
52. Isolation of Pt(IV) complexes capable of reversible 2-electron oxidation/reduction Spencer Hendrickson As the world population continues to grow and countries become more developed, a need for more efficient energy supplies is evident. Reducing the amount of energy needed for chemical reactions would be one of many ways of improving the efficiency of our energy. By using complexes that can undergo two-electron transfer reactions, the efficiency of many reactions may be improved. 2nd and 3rd row transition metal complexes are appealing candidates due to their ability to reversibly undergo two-electron changes in oxidation state. However, not much is known about this interchangeability because the large change in geometry of these reactions tend to be irreversible. This poster will discuss efforts to prepare and study a series of ligand architectures and their respective platinum complexes.
53. Analyzing novel antioxidant molecules for prevention of ROS mediated DNA damage Emma S. Johnson, Safnas F. AbdulSalam, Jing Liu, Haizhou Zhu, Edward J. Merino University of Cincinnati Reactive oxygen species (ROS) are chemically reactive oxygen-containing molecules. Ultraviolet light from the sun damages DNA via ROS, causing a sunburn, which can lead to skin cancer. This study addresses this issue by testing potential antioxidant agents to combat ROS-induced DNA damage to plasmid DNA. We developed two methods to induce a nick in plasmid DNA, one using riboflavin with UV light to produce superoxide and the other a Fenton Reaction to produce hydroxyl radicals. Both methods were optimized to 50% DNA damage. This optimization allowed for the testing of various agents to observe their antioxidant potential.
54. Investigating UV absorption properties of avobenzone complexed with calixarenes Marzieh Mirzamani, Anushree Das, Dr. Arnab Dawn, Dr. Anna Gudmundsdottir, Dr. Harshita Kumari University of Cincinnati Avobenzone (1-(4-Methoxyphenyl)-3-(4-tert-butylphenyl)propane-1,3-dione) is a common UVA absorber used as a sunscreen agent. The exposure to UV light causes avobenzone to degrade causing a reduction in its effectiveness over time. Herein, we will discuss the UV absorption properties of avobenzone and avobenzone with PO3H2-calixarene. UV absorption studies indicate a minimal difference in efficacy between avobenzone and avobenzone with PO3H2-calixarene. However, PO3H2-calixarene is shown to control the rate of degradation of avobenzone.
55. Verification of methylated Inosine in Bacillus subtilis tRNA. Christina Psihountas, Collin Wetzel, and Patrick A. Limbach University of Cincinnati Transfer Ribonucleic Acids (tRNAs) have more modified bases than the other species of RNA. Modifications can serve one of three purposes in tRNA: 1) provide stability to the tRNA structure, 2) assist with anticodon-codon fidelity, and 3) serve as determinants to aminoacyl tRNA synthetase. Liquid chromatography tandem mass spectrometry (LC-MS/MS) is the current method for detecting and characterizing modifications. A previous analysis of Bacillus subtilis showed methylated Inosine (m1I or Im) present at position 73 in some tRNAs. This finding is currently being verified through nucleoside detection and oligonucleotide sequencing of B. subtilis tRNA with LC-MS/MS.
56. Small Molecule Effects on Surfactant Microstructure and Dynamics: A Case Where MD
and NMR Can Drive Understanding in How Partitioning Influences Physical Properties Allison Talley, Reza Javidi, George Stan University of Cincinnati The physical properties of surfactant aggregate structures, for example biological membrane bilayers or consumer cleaning products, are strongly modulated by the presence of small molecules such as cholesterol or flavors/fragrances. The ability to directly measure the partitioning of small molecules in these systems and assess their impact on surfactant microstructure and dynamics is critical for understanding many properties like mechanical strength and curvature or viscosity and stability. Utilizing the nuclear Overhauser effect to determine through space proximity of molecules is a standard technique in systems where global structure is well defined and internal motion is accounted for (as in a folded protein). However, since experimental results cannot discriminate between signals arising from distance or dynamics additional information must be provided for systems where the internal motion plays a role in the NMR signal. Here we present a method where atomistic molecular dynamic simulations provide a way to probe the dynamics of interaction and account for internal motions.
57. Elucidating the Unique Solid State Mechanism for the Photoreactivity of azide 3-Azido-1,3-diphenyl-isobutyrophenone in Crystals
S. Karthik, Jeanette Krause, Anna D. Gudmundsdottir. Department of chemistry, University of Cincinnati, USA Solid state photolysis of 3-Azido-1,3-diphenyl-isobutyrophenone (1) result in formation of isobutyrophenone (2) and benzonitrile (3) in quantitative yields. Products 2 and 3 come from cleavage of the -C-C bond in azide 1. In comparison, photolysis of azide 1 in solution yields 3 different compounds, 4, 5 and 6, that come from cleavage of the azido group. X-ray structure of azide 1 and laser flash photolysis of its nano-crystals make it possible elucidate the solid state reaction mechanism and to explain the solid state photoreactivity.