Chemistry Commons^™

Atomistic Details Of Peptide Reversed-Phase Liquid Chromatography From Molecular Dynamics Simulations, Pablo M Scrosati, Lars Konermann

Chemistry Publications

Peptide separations by reversed-phase liquid chromatography (RPLC) are an integral part of bottom-up proteomics. These separations typically employ C18 columns with water/acetonitrile gradient elution in the presence of formic acid. Despite the widespread use of such workflows, the exact nature of peptide interactions with the stationary and mobile phases are poorly understood. Here we employ microsecond molecular dynamics (MD) simulations to uncover details of peptide RPLC. We examined two tryptic peptides, a hydrophobic and a hydrophilic species, in a slit pore lined with C18 chains that were grafted onto SiO₂ support. Our simulations explored peptide trapping, followed by desorption …

Influence Of Magnetic Nanoparticles And Magnetic Stress On An Ionic Liquid Electrospray Source, Kurt Joseph Terhune

Dissertations, Master's Theses and Master's Reports

Two electrospray sources were developed to operate on an ionic liquid ferrofluid; one source was a pressure‑fed capillary electrospray source and the other was a novel electrospray source which used a magnetically‑induced instability to produce a peak from which an electric field could extract electrospray. Multiple characteristics of electrospray operation were examined for both sources using faraday plates/cups, a quartz crystal microbalance, a retarding potential analyzer, and a time-of-flight mass spectrometer. The ILFF electrosprays for a capillary source were shown to operate in a mixed ion/droplet regime. The mass flow of the electrospray beam was primarily transported by larger particles …

Analysis Of Improvised Explosives By Electrospray Ionization - Mass Spectrometry And Microfluidic Techniques, Inge Corbin

FIU Electronic Theses and Dissertations

Improvised explosives may be based on smokeless gunpowder, fertilizers, or inorganic oxidizers such as nitrate (NO3-), chlorate (ClO3-), and perchlorate (ClO4-) salts.

Identification is a priority for the military and law enforcement but due to their varying physical properties and complexity, identification can be challenging. Consequently, three methods have been developed to aid in presumptive and confirmatory detection.

Smokeless powder contains plasticizers, stabilizers, dyes, opacifiers, flash suppressants, and other compounds. Identification of these additives can narrow down or identify the brands of smokeless powder used in a device. Fourteen organic smokeless powder components were identified by capillary electrochromatography (CEC) using …

Application Of Electrospray Ionization Mass Spectrometry For Ionic Liquids And Their Biodegradation Products, Sepideh Rahbarirad

Masters Theses

Ionic liquids (ILs) are organic salts with unique physico-chemical properties and are used as green alternatives to volatile organic solvents. ESI-MS is a sensitive technique to detect these stable, permanent ions. My research focused on (1) Identification of biodegradation products of ionic liquids and (2) Multiplexed tandem MS by modulation of ionization efficiency.

Studies, have demonstrated that ILs are toxic to the environment, which makes their biodegradability an important consideration. In this work, metabolites generated during the biodegradation of 1-butyl-3-methylimidazolium chloride (BMIM), a degradation resistant and commonly used ionic liquid, are identified using high performance liquid chromatography-mass spectrometry (LC-MS).

Multiplexed …

Fabricating Superhydrophobic And Superoleophobic Surfaces With Multiscale Roughness Using Airbrush And Electrospray, Karam N. Almilaji

Theses and Dissertations

Examples of superhydrophobic surfaces found in nature such as self-cleaning property of lotus leaf and walking on water ability of water strider have led to an extensive investigation in this area over the past few decades. When a water droplet rests on a textured surface, it may either form a liquid-solid-vapor composite interface by which the liquid droplet partially sits on air pockets or it may wet the surface in which the water replaces the trapped air depending on the surface roughness and the surface chemistry. Super water repellent surfaces have numerous applications in our daily life such as drag …

Use Of Esi-Fticr-Ms To Characterize Dissolved Organic Matter In Headwater Streams Draining Forest-Dominated And Pasture-Dominated Watersheds, Yuehan Lu, Xiaping Li, Rajaa Mesfioui, James E. Bauer, R. M. Chambers, Elizabeth A. Canuel, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) has proven to be a powerful technique revealing complexity and diversity of natural DOM molecules, but its application to DOM analysis in grazing-impacted agricultural systems remains scarce. In the present study, we presented a case study of using ESI-FTICR-MS in analyzing DOM from four headwater streams draining forest-or pasture-dominated watersheds in Virginia, USA. In all samples, most formulas were CHO compounds (71.8-87.9%), with other molecular series (CHOS, CHON, CHONS, and CHOP (N, S)) accounting for only minor fractions. All samples were dominated by molecules falling in the lignin-like region (H/C …

Investigations Into Ambient Ionization Mechanisms: Electrospray Ionization And Direct Analysis In Real Time Mass Spectrometry, Stephen Colin Gibson

Doctoral Dissertations

Mass spectrometry (MS) is an important tool for chemical analyses. Despite the MS requirement for generation of analyte gas-phase ions, many ion source designs afford little-to-no fragmentation, allowing characterization of intact molecules. However, this does not assure that detected ions are representative of the analytes’ natural state. Ionization mechanisms are generally complex and rarely fully understood. Fundamental research into these mechanisms provides greater insight into the relationship between solution chemistry and mass spectra. Work herein addresses aspects of two ambient ionization mechanisms: electrospray ionization (ESI) and Direct Analysis in Real Time (DART).

Ions produced by ESI are dispersed into a …

Tandem Mass Spectrometry Of Multiply Charged Polymers: Using Ms3 Strategies For Full Structural Characterization Of Polyacrylamides, Paul M. Krauss

Williams Honors College, Honors Research Projects

In mass spectrometry, a compound is taken and converted into a gas-phase ion by an electrical charge (Balogh, 2009). From these ions, a chart is then created that displays the mass to charge ratio, which is able to then be analyzed to find out the charge of the ions, as well as the mass of the compound (Balogh, 2009). One specific type of mass spectrometry there is available is known as a fragmentation spectrometry. In fragmentation spectrometry, the molecule is not only ionized and analyzed, but fragmented parts that are formed into ions are also ionized and analyzed. This is …

The Utilization Of Chiral Ion Mobility Spectrometry For The Detection Of Enantiomeric Mixtures And Thermally Labile Compounds, Howard K. Holness

FIU Electronic Theses and Dissertations

This dissertation utilized electrospray ion mobility mass spectrometry (ESI-IMS-MS) to develop methods necessary for the separation of chiral compounds of forensic interest. The compounds separated included ephedrines and pseudoephedrines, that occur as impurities in confiscated amphetamine type substances (ATS) in an effort to determine the origin of these substances. The ESI-IMS-MS technique proved to be faster and more cost effective than traditional chromatographic methods currently used to conduct chiral separations such as gas and liquid chromatography. Both mass spectrometric and computational analysis revealed the separation mechanism of these chiral interactions allowing for further development to separate other chiral compounds by …

Bacterial Spores Remain Viable After Electrospray Charging And Desolvation, Sara Nielson Pratt

Theses and Dissertations

The electrospray survivability of B. subtilis spores and E. coli was tested in atmospheric mobility experiments. E. coli did not survive electrospray charging and desolvation, but B. subtilis did. Experimental conditions ensured that any surviving bacteria were charged, desolvated, and de-agglomerated. B. subtilis was also found to survive both positive and negative electrospray and subsequent introduction into vacuum conditions. Attempts were made to measure the charge distribution of viable B. subtilis spores using electrostatic deflection. From those experiments, it was found that either the spores do not become highly charged under the electrospray conditions used or only spores in a …

Electronic Structure Characterization Of Nanocrystalline Surfaces And Interfaces With Photoemission Spectroscopy, Sebastian Gutmann

USF Tampa Graduate Theses and Dissertations

In this study, photoemission spectroscopy (PES) was used to investigate the electronic properties of nanocrystalline titanium dioxide (TiO₂), zinc oxide (ZnO), and cadmium selenide (CdSe). Electrospray deposition technique enabled the preparation of thin films in vacuum from a dispersion prepared outside the vacuum chamber. This method also allowed the step-wise formation of interfaces and the monitoring of the evolution of the electronic structure with intermittent PES characterization.

The work function of nanocrystalline TiO₂ and ZnO was measured with ultraviolet photoemission spectroscopy (UPS) and low-intensity x-ray photoemission spectroscopy (LIXPS). Measurements on environmentally contaminated surfaces revealed an instantaneous and …

Microfluidic Devices Interfaced To Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry For Proteomics, Jeonghoon Lee

LSU Doctoral Dissertations

Microfluidic interfaces were developed for off-line matrix-assisted laser desorption/ionization mass spectrometry (MALDI). Microfluidic interfaces allow samples to be manipulated on-chip and deposited onto a MALDI target plate for analysis. For this research, microfluidic culturing devices and automated digestion and deposition microfluidic chip platforms were developed for the identification of proteins. The microfluidic chip components were fabricated on a poly(methyl methacrylate), PMMA, wafer using the hot embossing method and a molding tool with structures prepared via micromilling. One of the most important components of the chip system was a trypsin microreactor. An open channel microreactor was constructed in a 100 µm …

Ammonia Elimination From Protonated Nucleobases And Related Synthetic Substrates, Ming Qian, Shuo Yang, Hong Wu, Papiya S. Majumdar, Nathan D. Leigh, Rainer Glaser

Chemistry Faculty Research & Creative Works

The results are reported of mass-spectrometric studies of the nucleobases adenine 1h (1, R = H), guanine 2h, and cytosine 3h. The protonated nucleobases are generated by electrospray ionization of adenosine 1r (1, R = ribose), guanosine 2r, and deoxycytidine 3d (3, R = deoxyribose) and their fragmentations were studied with tandem mass spectrometry. In contrast to previous EI-MS studies of the nucleobases, NH₃ elimination does present a major path for the fragmentations of the ions [1h + H]⁺, [2h + H]⁺, and …

Hydration Studies Of Electrospray Ions From Amino Acids And Small Peptides, Chuong Quoc Nguyen

Theses and Dissertations

This project was undertaken to gain a better understanding of the hydration behaviors of gas phase ions from solutions containing amino acids and peptides. In order to characterize their hydration behavior, the molecules of interest in solutions were first converted into gas phase ions by electrospray ionization (ESI). The completely desolvated ions were then deliberately dispersed into an inert bath gas, usually nitrogen, containing accurately known concentrations of solvent vapor. The resulting mixtures of ions and bath gas were subsequently passed into a vacuum chamber by way of an adiabatic supersonic free jet expansion. The cooling during that expansion caused …