Analytical Chemistry Commons^™

Determination Of The Structure Of Sphingomyelin By Tandem Mass Spectrometry And Matrix - Assisted Laser Desorption/Ionization, Antonio Ganios

Williams Honors College, Honors Research Projects

Mass spectrometry is a method that uses masses to determine the structure of a compound. This is completed by first charging the compound until it is a cation or anion, and then its molecular weight can be determined by measuring a mass to charge ratio. The focus of this study was determination of sphingomyelin’s structure. The purpose of this was that sphingomyelin has been shown to play a critical role in many biological pathways and being able to identify this lipid could prove to be beneficial for preventative medicine. Utilizing electrospray ionization (ESI) Quadruple-Time-of-flight (Q-TOF) mass spectrometry on a Waters …

Characterization Of Pm2.5 From Residential Woodstove Use For Source Apportionment Application, Virginia M. Porden

Graduate Student Theses, Dissertations, & Professional Papers

Results are presented for the comparative analysis of the PM_2.5 (Particulate Matter <2.5 µm) emissions from an EPA certified and a Traditional style wood stove using western larch. A total of 92 Quartz QMA 47mm filters were collected using a BGI PM_2.5 SSC (Sharp Cut Cyclone) sampler from each stove type and analyzed on a gas chromatograph-mass spectrometer against blank and deuterated internal standards. The results were analyzed using a Welch’s t-test (α > 0.05) to statistically differentiate between stove designs for temperature, mass, levoglucosan, resin acids (abietic and dehydroabietic), and polycyclic aromatic hydrocarbons [PAH] (acenaphthene, anthracene, benz(a)anthracene, pyrene, and retene). There was no statistical difference in levoglucosan PM_2.5 mass fraction between the stove types, yielding a mean levoglucosan fraction of 9.25% and 95% confidence interval of 8.43% …

Characterization Of Noncovalent Complexes Of Polyelectrolytes By Mass Spectrometry, Anthony J. Marino

Williams Honors College, Honors Research Projects

Various ions of poly-L-lysine and polystyrene sulfonic acid were successfully observed first within a matrix-assisted laser desorption/ionization mass spectrometer and subsequently in an electrospray ionization mass spectrometer. The successful ionization of these polymers allowed for studies to be performed on the noncovalent interactions between the two. Noncovalent interactions were effectively studied on both instruments, but further quantified using tandem mass spectrometry found within the MALDI system and ion-mobility mass spectrometry found within the electrospray ionization system. As a result of employing the use of ion-mobility, various different stoichiometries and charges of polyelectrolyte complexes could be distinguished.

Creation Of A Portable, 3d-Printable, Iphone-Compatible Spectrophotometer, Elise K. Grasse

Williams Honors College, Honors Research Projects

Spectroscopy is a widely used chemical and medical analysis tool. While spectrophotometers are commonly found in many universities and laboratories, they are not available to all high schools or laboratories in developing countries. The objective of this project was to design a high-quality, 3D-printable, iPhone-compatible spectrophotometer that uses a cell phone camera and interface to collect data. The created 3D-print file will be available to anyone with access to a 3D printer which are increasingly found in many laboratories and schools across the country. A low cost pre-printed kit will also be made for those without access to a 3D …

Electronic Structures And Electronic Spectra Of All-Boron Fullerene B40, Rongxing He, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

This study is motivated by the recent discovery of the first all-boron fullerene analogue, a B₄₀ cluster with D_2d point-group symmetry, dubbed borospherene (Nat. Chem., 2014, 6, 727). Insight into the electronic structures and spectral properties of B₄₀ is timely and important to understand the borospherene and the transition from open-ended plate or ribbon-like structures to a hollow-cage structure at B₄₀. Optimized geometries of borospherene B₄₀ for both the ground state and the first excited state allow us to compute spectral properties including UV-vis absorption, infrared (IR) and Raman spectra. Highly resolved absorption and …

Research-Based Implementation Of Peer Instruction: A Literature Review, Trisha Vickrey, Kaitlyn Rosploch, Reihaneh Rahmanian, Matthew Pilarz, Marilyne Stains

Department of Chemistry: Faculty Publications

Current instructional reforms in undergraduate science, technology, engineering, and mathematics (STEM) courses have focused on enhancing adoption of evidence-based instructional practices among STEM faculty members. These practices have been empirically demonstrated to enhance student learning and attitudes. However, research indicates that instructors often adapt rather than adopt practices, unknowingly compromising their effectiveness. Thus, there is a need to raise awareness of the research-based implementation of these practices, develop fidelity of implementation protocols to understand adaptations being made, and ultimately characterize the true impact of reform efforts based on these practices. Peer instruction (PI) is an example of an evidence-based instructional …

New Insight Into The Helium-Induced Damage In Max Phase Ti3Alc2 By First-Principles Studies, Yiguo Xu, Xiaojing Bai, Xianhu Zha, Qing Huang, Jian He, Kan Luo, Yuhong Zhou, Timothy C. Germann, Joseph S. Francisco, Shiyu Du

Department of Chemistry: Faculty Publications

In the present work, the behavior of He in the MAX phase Ti3AlC2 material is investigated using first-principle methods. It is found that, according to the predicted formation energies, a single He atom favors residing near the Al plane in Ti3AlC2. The results also show that Al vacancies are better able to trap He atoms than either Ti or C vacancies. The formation energies for the secondary vacancy defects near an Al vacancy or a C vacancy are strongly influenced by He impurity content. According to the present results, the existence of trapped He atoms in primary Al vacancy can …

Communication: Spectroscopic Consequences Of Proton Delocalization In Ochco+, Ryan C. Fortenberry, Qi Yu, John S. Mancini, Joel M. Bowman, Timothy J. Lee, T. Daniel Crawford, William F. Klemperer, Joseph S. Francisco

Department of Chemistry: Faculty Publications

Even though quartic force fields (QFFs) and highly accurate coupled cluster computations describe the OCHCO⁺ cation at equilibrium as a complex between carbon monoxide and the formyl cation, two notable and typical interstellar and atmospheric molecules, the prediction from the present study is that the equilibrium C_∞v structure is less relevant to observables than the saddle-point D_∞h structure. This is the conclusion from diffusion Monte Carlo and vibrational self-consistent field/virtual state configuration interaction calculations utilizing a semi-global potential energy surface. These calculations demonstrate that the proton “rattle” motion (ν₆) has centrosymmetric delocalization of the …

Structural And Optical Properties Of Cobalt Slanted Nanopillars Conformally Coated With Few-Layer Graphene, Peter M. Wilson, Alexey Lipatov, Daniel Schmidt, Eva Schubert, Mathias Schubert, Alexander Sinitskii, Tino Hofmann

Department of Chemistry: Faculty Publications

Optical characterization of anisotropic multicomponent nanostructures is generally not a trivial task, since the relation between a material’s structural properties and its permittivity tensor is nonlinear. In this regard, an array of slanted cobalt nanopillars that are conformally coated with few-layer graphene is a particularly challenging object for optical characterization, as it has a complex anisotropic geometry and comprises several materials with different topologies and filling fractions. Normally, a detailed characterization of such complex nanostructures would require a combination of several microscopic and spectroscopic techniques. In this letter, we demonstrate that the important structural parameters of these graphene-coated sculptured thin …

Few-Layer Titanium Trisulfide (Tis3) Field-Effect Transistors, Alexey Lipatov, Peter M. Wilson, Mikhail Shekhirev, Jacob D. Teeter, Ross Netusil, Alexander Sinitskii

Department of Chemistry: Faculty Publications

Titanium trisulfide (TiS₃) is a promising layered semiconductor material. Several-mm-long TiS₃ whiskers can be conveniently grown by the direct reaction of titanium and sulfur. In this study, we exfoliated these whiskers using the adhesive tape approach and fabricated few-layer TiS₃ field-effect transistors (FETs). The TiS₃ FETs showed an n-type electronic transport with roomtemperature field-effect mobilities of 18-24 cm²V^-1s^-1 and ON/OFF ratios up to 300. We demonstrate that TiS₃ is compatible with the conventional atomic layer deposition (ALD) procedure for Al₂O₃. ALD of alumina on TiS3 …

Biotechnological Production Of 1,2,4-Butanetriol: An Efficient Process To Synthesize Energetic Material Precursor From Renewable Biomass, Yujin Cao, Wei Niu, Jiantao Guo, Mo Xian, Huizhou Liu

Department of Chemistry: Faculty Publications

1,2,4-Butanetriol (BT) is a valuable chemical with extensive applications in many different fields. The traditional chemical routes to synthesize BT suffer from many drawbacks, e.g., harsh reaction conditions, multiple steps and poor selectivity, limiting its industrial production. In this study, an engineered Escherichia coli strain was constructed to produce BT from xylose, which is a major component of the lignocellulosic biomass. Through the coexpression of a xylose dehydrogenase (CCxylB) and a xylonolactonase (xylC) from Caulobacter crescentus, native E. coli xylonate dehydratase (yjhG), a 2-keto acid decarboxylase from Pseudomonas putida (mdlC) and …

Fine-Tuning Interaction Between Aminoacyl-Trna Synthetase And Trna For Efficient Synthesis Of Proteins Containing Unnatural Amino Acids, Nanxi Wang, Tong Ju, Wei Niu, Jiantao Guo

Department of Chemistry: Faculty Publications

By using a directed evolution approach, we have identified aminoacyl-tRNA synthetase variants with significantly enhanced activity for the incorporation of unnatural amino acids into proteins in response to the amber nonsense codon in bacteria. We demonstrated that the optimization of anticodon recognition of tRNA by aminoacyltRNA synthetase led to improved incorporation efficiency that is unnatural amino acid-specific. The findings will facilitate the creation of an optimized system for the genetic incorporation of unnatural amino acids in bacteria.

A Comparison Of Energy-Resolved Vibrational Activation/Dissociation Characteristics Of Protonated And Sodiated High Mannose N-Glycopeptides, Forouzan Aboufazeli, Venkata Kolli, Eric D. Dodds

Department of Chemistry: Faculty Publications

Fragmentation of glycopeptides in tandem mass spectrometry (MS/MS) plays a pivotal role in site-specific protein glycosylation profiling by allowing specific oligosaccharide compositions and connectivities to be associated with specific loci on the corresponding protein. Although MS/MS analysis of glycopeptides has been successfully performed using a number of distinction dissociation methods, relatively little is known regarding the fragmentation characteristics of glycopeptide ions with various charge carriers. In this study, energy-resolved vibrational activation/ dissociation was examined via collision-induced dissociation for a group of related high mannose tryptic glycopeptides as their doubly protonated, doubly sodiated, and hybrid protonated sodium adduct ions. The doubly …

Stretchable Conductive Composites For Use In Soft Devices, Joshua Aaron Lessing, Stephen A. Morin, George M. Whitesides

Department of Chemistry: Faculty Publications

An elastically-deformable, conductive composite using elastomers and conductive fibers and simple fabrication procedures is provided. Conductive elastomeric composites offer low resistance to electrical current and are elastic over large (>25%) extensional strains. They can be easily interfaced/built into structures fabricated from elastomeric polymers.

Apparatus, Systems, And Methods For Modular Soft Robots, Stephen A. Morin, Sen Wai Kwok, Robert F. Shepherd, George M. Whitesides

Department of Chemistry: Faculty Publications

Apparatus, Systems, and methods for providing modular soft robots are disclosed. In particular, the disclosed modular soft robot can include a flexible actuator having a plurality of molded flexible units. Each molded flexible unit can include a mechanical connector configured to provide a physical coupling to another molded flexible unit, and the plurality of molded flexible units are arranged to form an embedded fluidic channel. The modular soft robot can also include an inlet coupled to the embedded fluidic channel, where the inlet is configured to receive pressurized or depressurized fluid to inflate or deflate a portion of the flexible …

Recyclable Magnetite Nanoparticle Catalyst For One-Pot Conversion Of Cellobiose To 5-Hydroxymethylfurfural In Water, Anuja Bhalkikar, Zane C. Gernhart, Chin Li Cheung

Department of Chemistry: Faculty Publications

Environmentally benign and easily recoverable magnetite nanoparticles (Fe₃O₄ NPs) were demonstrated to catalyze the one-pot conversion of cellobiose, a glucose disaccharide, to 5-hydroxymethylfurfural (5-HMF).Theconversion was achieved in water under hydrothermal conditions.The catalytic activity of Fe₃O₄ NPs surpassed those of iron (II) and iron (III) chlorides in this reaction. Optimized cellobiose conversion reactions catalyzed with Fe₃O₄ NPs gave the highest 5-HMF yields of 23.4 ± 0.6% at 160^∘C for 24 hours. After three reuses, the Fe₃O₄ NP catalyst retained its catalytic activity with similar 5-HMF yields, demonstrating …

Simulation Evidence Of Hexagonal-To-Tetragonal Znse Structure Transition: A Monolayer Material With A Wide-Range Tunable Direct Bandgap, Lei Li, Pengfei Li, Ning Lu, Jun Dai, Xiao Cheng Zeng

Department of Chemistry: Faculty Publications

2D material with tunable direct bandgap in the intermediate region (i.e., ≈2–3 eV) is key to the achievement of high efficiency in visible-light optical devices. Herein, a simulation evidence of structure transition of monolayer ZnSe from the experimental pseudohexagonal structure to the tetragonal structure (t-ZnSe) under lateral pressure is shown, suggesting a possible fabrication route to achieve the t-ZnSe monolayer. The as-produced t-ZnSe monolayer exhibits highly tunable bandgap under the biaxial strains, allowing strain engineering of t-ZnSe’s bandgap over a wide range of 2–3 eV. Importantly, even under the biaxial strain up to 7%, the t-ZnSe monolayer still keeps its …

Cip10 Optimization For 4,4-Methylene Diphenyl Diisocyanate Aerosol Sampling And Field Comparison With Impinger Method, Silvia Puscasu, Simon Aubin, Yves Cloutier, Philippe Sarazin, Huu Van Tra, Sébastien Gagné

Études primaires

4,4-methylene diphenyl diisocyanate (MDI) aerosol exposure evaluation in spray foam insulation application is known as being a challenge because the spray foam application actually involves a fast-curing process. Available techniques are either not user-friendly or are inaccurate or not validated for this application. To address these issues, a new approach using a CIP10M was developed to appropriately collect MDI aerosol in spray foam insulation while being suitable for personal sampling. The CIP10M is a commercially available personal aerosol sampler that has been validated for the collection of microbial spores into a liquid medium. Tributylphosphate with 1-(2-methoxyphenyl)piperazine (MOPIP) was introduced into …

Comparison Between The Asset Ez4 Nco And Impinger Sampling Devices For Aerosol Sampling Of 4,4′-Methylene Diphenyl Diisocyanate In Spray Foam Application, Silvia Puscasu, Simon Aubin, Yves Cloutier, Philippe Sarazin, Huu Van Tra, Sébastien Gagné

Études primaires

4,4′-methylene diphenyl diisocyanate (MDI) aerosol exposure evaluation in spray foam insulation application is known to be a challenge. Current available techniques are either not user-friendly or are inaccurate or are not validated for this application. A new sampler has recently been developed to address the user-friendliness issues with other samplers: the ASSET EZ4-NCO, but the use of this sampler in spray foam insulation applications has not been demonstrated or validated. Because of this, the current work was undertaken to provide a comparison of the ASSET sampler with an impinger method, considered to be the best available method in the context …

Development Of An Extraction Method For The Mass Spectral Analysis Of Organic Gunshot Residue From Clothing, Brent Casper

Theses and Dissertations--Chemistry

This dissertation will focus on the extraction of volatile organic compounds associated with gunshot residue from articles of clothing, followed by analysis with mass spectrometry. During the discharge of a weapon, a cloud of volatile organic gunshot residue (OGSR) is dispersed around a firearm. This will create a high probability of transfer between the OGSR and the clothing of individuals who are near a discharged weapon.

The first part of this dissertation will be the development of a method for removal of volatile OGSR from articles of clothing. Extraction of OGSR will be completed by solid phase microextraction (SPME), followed …