High Resolution Mass Spectrometry of Polyfluorinated Polyether-Based Formulation

High resolution mass spectrometry (HRMS) was successfully applied to elucidate the structure of a polyfluorinated polyether (PFPE)-based formulation. The mass spectrum generated from direct injection into the MS was examined by identifying the different repeating units manually and with the aid of an instrument data processor. Highly accurate mass spectral data enabled the calculation of higher-order mass defects. The different plots of MW and the nth-order mass defects (up to n = 3) could aid in assessing the structure of the different repeating units and estimating their absolute and relative number per molecule. The three major repeating units were -C2H4O-, -C2F4O-, and -CF2O-. Tandem MS was used to identify the end groups that appeared to be phosphates, as well as the possible distribution of the repeating units. Reversed-phase HPLC separated of the polymer molecules on the basis of number of nonpolar repeating units. The elucidated structure resembles the structure in the published manufacturer technical data. This analytical approach to the characterization of a PFPE-based formulation can serve as a guide in analyzing not just other PFPE-based formulations but also other fluorinated and non-fluorinated polymers. The information from MS is essential in studying the physico-chemical properties of PFPEs and can help in assessing the risks they pose to the environment and to human health

Refining molecular stratigraphy through mass spectrometry imaging of sediments at sub-millimeter resolution

This dissertation focused on the implementation of a new, extraction-free approach to molecular stratigraphy by mass spectrometry imaging (MSI) that allows to increase the spatial and temporal resolution to the micrometer and subannual scale. With this novel technique, detailed insights into the drivers of lipid biomarker-derived proxies were gained by addressing the small-scale differences of the signal archived in the sedimentary record. Together with the improved understanding of the proxy signal, application of MSI to varved sediments from the Santa Barbara Basin, off Southern California revealed insights into the dynamics and interdependencies of ocean surface temperatures, upwelling strength, and bottom water oxygen content during the 20th century

Technological developments in mass spectrometry towards molecular structural elucidation of macromolecular assemblies

Retrieving higher-order structural features of macromolecular assemblies (MMAs), such as protein complexes and viruses, is of great interest. These characteristics are crucial for understanding the functions and interactions of MMAs with other molecular species or receptors. While various techniques such as cryogenic-electron microscopy, nuclear magnetic resonance, and x-ray crystallography are capable of providing high-resolution structures of MMAs, they come with some limitations. This thesis primarily focuses on the technological developments in mass spectrometry (MS) in retrieving molecular features of MMAs at different levels of their organization. For that, aspects of soft-ionizing techniques (nano-electrospray ionization and matrix-assisted laser desorption/ionization), axial/orthogonal reflectron time-of-flight and high-resolution Orbitrap MS, top-down proteomics (ultraviolet photodissociation and higher-energy collisional dissociation), and mass-to-charge ratio/time-resolved imaging using pixelated Timepix and Timepix3 application-specific integrated circuit based detection assemblies were brought together

Photochemical modification of polyethylene terephthalate surface

The prospect of obtaining desired surface-mediated characteristics while retaining bulk-mediated physical properties and avoiding potential environmental issues with wet chemical technology lends considerable appeal to photochemical approaches to surface modification.;We undertook a combined experimental and computational approach to investigate the effect of deep UV irradiation on the polyethylene terephthalate (PET) surface. its response to 172 nm UV from a xenon examiner lamp in the absence of oxygen was characterized with X-ray Photoelectron Spectroscopy (XPS), Time of Flight/Secondary Ion Mass Spectrometry (ToF/SIMS), transmission infrared spectroscopy (IR), and Atomic Force Microscopy (AFM). The surface chemistry details suggested that the primary photochemical reactions involved a Norrish type I based decarbonylation and a Norrish type II process yielding terminal carboxylic acid groups, consistent with the possible photochemistry from n-pi* type lowest singlet excited states of PET according to the computational modeling results. By directly populating n-pi* type excited states, 172 nm UV promoted effective surface photochemistry of PET with further helps from the high UV absorptivity and the high surface mobility of the molecules.;Utilizing this active surface radical chemistry, a new grafting strategy was developed to impart desirable functional properties to the surface. A broad range of grafting chemicals can be employed in their vapor forms, demonstrated with an alkene or an alkane. Surface analysis with XPS, ToF/SIMS, AFM, and water contact angle measurements confirmed the effectiveness of the approach, supporting the notion of the surface radical initiated processes.;A potentially useful anti-stain/soil coating was developed by grafting with a fluorocarbon species. Surface analysis suggested that the grafted fluorocarbon formed a nano-scale self-assembled monolayer. The coating had a similar water contact angle as that of a pure fluoropolymer but a better oil repellency due to the special molecular orientation in the graft layer.;A potential antimicrobial application was demonstrated with amine chemicals. Structure characterization and computational modeling results suggested that the photochemistry of the UV active grafting chemicals also played an important role in the grafting process. A double bond structure in the amine species protected the amine functional groups and the resulting coating demonstrated antimicrobial activity against E. coli

An evaporite sequence from ancient brine recorded in Bennu samples.

Evaporation or freezing of water-rich fluids with dilute concentrations of dissolved salts can produce brines, as observed in closed basins on Earth1 and detected by remote sensing on icy bodies in the outer Solar System2,3. The mineralogical evolution of these brines is well understood in regard to terrestrial environments4, but poorly constrained for extraterrestrial systems owing to a lack of direct sampling. Here we report the occurrence of salt minerals in samples of the asteroid (101955) Bennu returned by the OSIRIS-REx mission5. These include sodium-bearing phosphates and sodium-rich carbonates, sulfates, chlorides and fluorides formed during evaporation of a late-stage brine that existed early in the history of Bennus parent body. Discovery of diverse salts would not be possible without mission sample return and careful curation and storage, because these decompose with prolonged exposure to Earths atmosphere. Similar brines probably still occur in the interior of icy bodies Ceres and Enceladus, as indicated by spectra or measurement of sodium carbonate on the surface or in plumes2,3

Application of mass spectrometry to the analysis of mixtures

The work presented in this thesis involves the application of mass spectrometry to the analysis of a number of both commercial products and model organic compounds. Use of soft ionisation techniques for thermally labile and ionic compounds (mainly fast atom bombardment, field desorption and thermospray) has been extensively explored for the provision of both qualitative and quantitative information. More established ionisation techniques (electron impact and chemical ionisation) have also been utilized in order to obtain qualitative data. In many cases comparisons have been made between different ionisation modes, and some discussion of the processes occuring is given. Ion structures and decomposition pathways have been elucidated by both tandem mass spectrometry and high mass resolution measurements. Analysis of both complex mixtures and pure compounds has been performed. The systems studied were: surfactants (anionic - sodium alcohol ether sulphates, nonionic - alcohol ethoxylates, cationics - mainly quaternary ammonium salts), organotin PVC heat stabilisers and organic heterocyclic compounds (some chromans, chromenes and corresponding oximes)

Development and optimization of analytical methods for identifying and quantifying organic compounds in biological and paleontological specimens

Preservation of soft tissues is a rare phenomenon which leads to the formation of fossils that survive for millions of years and are then subject to investigations by paleontologists. Several classes of chemical compounds have been reported to be preserved in fossils, including lipids, fatty acids, and porphyrins. However, the process of fossilization is not fully understood, which prompted investigations into the molecular aspects of decay, known as molecular taphonomy studies. The advancements of analytical techniques in recent decades have enabled progress in the field of molecular paleontology dedicated to the search for organic compounds in fossils and to understanding the changes that occur after death. Here, analytical methods are developed for the identification and quantification of organic compounds from biological, taphonomic, and fossil samples, applying various analytical techniques, including high performance liquid chromatography coupled to mass spectrometry and diode array ultraviolet/visible light detection, infrared spectroscopy, nuclear magnetic resonance spectroscopy, and atomic absorption spectrophotometry. First, since this dissertation deals largely with the chemical class of porphyrins, a review article is presented that provides a detailed overview on the chemistry of porphyrins in fossils (Chapter 3). This is followed by a review on the chemistry of the major classes of organic compounds detected in dinosaurs and the analytical techniques used for their identification (Chapter 4). A major part of the studies described in this dissertation aimed to establish and optimize an extraction protocol for heme, the prosthetic group of hemoglobin, from bone, with a high recovery rate, in order to be applied to analyses on fossil dinosaur bone (Chapter 6). Moreover, a molecular taphonomy study on heme was performed, elucidating the chemical degradation products of heme formed under conditions favorable to fossilization (Chapter 5). Furthermore, analytical methods were established for the quantification of two naturally occurring depsipeptides, FR900959 and YM-254890, from mouse organs after intratracheal and intraperitoneal administration, as well as the determination of their chemical stability in simulated gastrointestinal fluids (Chapter 7). Additionally, an analytical method was developed to detect fatty acid constituents of the plant polymer suberin, which is unique to bark, and the results were used to identify preserved bark in a 45-million-year-old fossil tree known as “monkey hair” collected in the Geiseltal Lagerstätte near Halle (Saale), East Germany (Chapter 8). Finally, several collaborative projects were completed, in which different analytical techniques were used to determine calcium concentrations, identify degradation products of fats in samples of the decaying crayfish Cambarellus diminitus, and to identify components of lignin in a fossil wood sample (Chapters 9-11). In summary, the findings of this dissertation demonstrate the power of analytical chemistry for analyzing a variety of compounds originating from diverse matrices, and contributes to the growing field of molecular paleontology. It provides novel findings and contributions to the fossil record, and presents analytical methods that may be applied in the future to study further specimens