| 1. |
- Mashayekhy Rad, Farshid, 1973-
(författare)
-
Analytical methods for biomolecules involved in atmospheric aerosol formation in the Arctic
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the Arctic, increasing ice-free conditions and nutrients freed from the melting ice must strongly influence the marine life. Aerosol emissions from microbiological marine processes may affect the low clouds and fogs over the summer Arctic, which in turn have effects on the melting of sea ice. The radiative properties of the high Arctic low clouds are strongly dependent on the number concentration of airborne water-soluble particles, known as cloud condensation nuclei (CCN). If the effects of CCN on cloud optical properties is to be fully understood it is important to be able to specify the source and concentrations of the Arctic aerosol particles.Previous studies in the Arctic have indicated that organic material formed in the uppermost ocean surface is transferred to the atmosphere and plays a potentially very important role in the aerosol-fog/cloud cycle. However, many aspects of this process remain unverified and chemical characterisation of targeted groups of biomolecules is still notably fragmentary or non-existing. Investigation of biomolecules, particularly amino acids, peptides and proteins together with mono- and polysaccharides and fatty acids in the airborne aerosol, and their relative contributions to fog/cloud water, requires development of an array of “cutting edge” analytical techniques and methods.In this thesis, electrospray ionization mass spectrometry was used for all applications and target biomolecules. The measurements in the Arctic turned out to be challenging due to the highly complex, salty matrices, combined with very low concentration and high diversity of the target biomolecules, and each step of the analytical chain needed careful consideration. To increase the detectability of the very low levels of polysaccharides and proteins in aerosols, these compounds were hydrolyzed to their subunits, monosaccharides and amino acids. Monosaccharides were separated using hydrophilic interaction chromatography, which was beneficial for their detection in electrospray ionization mass spectrometry. Amino acids were derivatized, yielding improvement in reversed-phase chromatographic separation, ionization efficiency as well as selectivity. For fatty acids in a sea surface sample, a novel fast screening method was developed, utilizing travelling-wave ion mobility separation as an orthogonal technique connected to mass spectrometry. In addition, a method for the detection of wood burning as an anthropogenic source of aerosols was developed, utilizing anhydrous monosaccharides as markers. This method can be used in the upcoming expeditions for source apportionment studies.The results from the analyses of the aerosol and fog water samples, collected over the summer pack ice north of 80 °N, show that both total polysaccharides and total proteinaceous compounds (sum of proteins, peptides and amino acids) occurred at the pmol m-3 to nmol m-3 level. Interestingly, the levels were found higher between different years, suggested to be coupled to less ice coverage and thus to a higher biological activity in the ocean surface. The highest concentrations of polysaccharides, as an indication of marine polymer gels, were found during the summer over the pack ice area. In addition, a pilot source apportionment study was carried out combining the measurement of different molecular tracers, used as source markers. This study indicates the seasonality and abundance of marine polymer gels as an important feature of the Arctic Ocean connected to the melting and freezing of sea ice. It should be further studied how the abundance of these gels, which have a high potential for cloud droplet activation, affect the melting and freezing of the perennial sea ice.Given the successful development of analytical methods for targeted groups of biomolecules, this thesis has supported the importance of biomolecules as CCN and for cloud formation in the Arctic. Less ice coverage may further increase the number of biomolecular CCN which could change the radiative balance, by the formation of more low-level clouds. Overall, more studies are required to further unravel the complex relationship of biogenic sources, atmospheric chemistry and meteorology to assess the impact of climate change on the Arctic.
|
|
| 2. |
- Riboni, Nicolò, 1989-
(författare)
-
New Materials and Improved Ambient Techniques in Mass Spectrometry
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mass spectrometry (MS) is used in several fields, e.g. biology, environmental monitoring, medicine and forensics due to excellent qualitative and quantitative capabilities. The development of new instrumental setups and ionization sources is crucial to analyze a variety of compounds at trace levels. The synergy between material science and analytical chemistry allowed the development of new materials characterized by specific features of polarity, porosity and functionalization, able to interact with targeted analytes in complex matrices, resulting in high extraction efficiency even in presence of overwhelming amounts of interfering compounds. New methods based on the use of new materials and MS techniques for analytes extraction and detection have been proposed, providing fast analysis times, enhanced selectivity and increased sensitivity.In this thesis, the development of new materials and setups for mass spectrometric applications is discussed.In Paper I-III the design, synthesis, characterization and evaluation of the analytical performances of four new supramolecular receptors for targeted extraction of benzene, toluene, ethylbenzene and xylenes (BTEX) are reported. The synthesized materials were used as solid-phase microextraction coatings (SPME) for the GC-MS determination of BTEX at trace levels in urban air. In addition, a portable device for in-situ and real-time monitoring of BTEX using these receptors in the preconcentration unit is presented.In Paper IV the development of coated ion sources able to improve the performances of an interface coupling liquid chromatography (LC) and electron ionization (EI), called Direct-EI LC-MS, is discussed. The coatings, obtained by sol-gel technique, were deposited onto commercial stainless steel EI sources to increase the inertness of its vaporization surface.In Paper V, a rapid screening method for the detection of new psychoactive substances (NPS) in oral fluids is presented. New slides based on polylactide (PLLA), carbon particles and silica were tested as probe materials to promote the ionization of the analytes in desorption electrospray ionization – high resolution mass spectrometry (DESI-HRMS). Microextraction by packed sorbent (MEPS) of the analytes from the saliva samples was required due to the high signal suppression. The developed MEPS-DESI-HRMS method was validated and applied for the determination of NPS in road-collected samples.In Paper VI the development of a new setup called solvent assisted paper spray ionization (SAPSI) is reported. This integrated solution allowed the increased data acquisition time and a close control over the ionization conditions. It was applied for the analysis of biomolecules, namely proteins, lipids, glycans, and amyloid peptides/aggregates, in aqueous solution as well as in human serum and cerebrospinal fluid. Different oligomeric species of amyloid aggregates were detected and it was possible to perform real-time monitoring of disaggregation processes. Modified protein species of physiological relevance such as oxidation, cysteinylation, glycosylation and glycation, and adduct formation were identified.In conclusion, the new materials and setups discussed in this thesis allowed the development of selective and sensitive MS methods for the determination of different target compounds in complex matrices at trace levels with reduced sample pretreatment.
|
|
| 3. |
- Jiang, Liying, 1977-
(författare)
-
Mass Spectrometry of Non-protein Amino Acids : BMAA and Neurodegenerative Diseases
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Neurodegenerative diseases have been shown to correlate positively with an ageing population. The most common neurodegenerative diseases are amyotrophic lateral sclerosis (ALS), Parkinson’s disease and Alzheimer’s disease. The cause of these diseases is believed to be the interaction between genetic and environmental factors, synergistically acting with ageing. BMAA (β-methylamino-L-alanine) is one kind of toxin present in our environment and might play an important role in the development of those diseases.BMAA was initially isolated from cycad seeds in Guam, where the incidence of ALS/Parkinsonism-dementia complex among the indigenous people was 50 – 100 times higher than the rest of the world in the 1950’s. BMAA can induce toxic effects on rodents and primates. Furthermore, it can potentiate neuronal injury on cell cultures at concentrations as low as 10 µM. BMAA was reported to be produced by cyanobacteria, and could bio-magnify through the food chain.In this thesis, work was initially focused on the improvement of an existing analytical method for BMAA identification and quantification using liquid chromatography coupled with tandem mass spectrometry. Subsequently, the refined method was applied to environmental samples for probing alternative BMAA producer(s) in nature and to seafood samples for estimation of human exposure to this toxin.In Paper I, a systematic screening of the isomers of BMAA in a database was performed and seven potential isomers were suggested. Three of them were detected or suspected in natural samples. In Paper II, a deuterated internal standard was synthesized and used for quantifying BMAA in cyanobacteria. In Paper III, Diatoms were discovered to be a BMAA producer in nature. In Paper IV, ten popular species of seafood sold in Swedish markets were screened for BMAA. Half of them were found to contain BMAA at a level of 0.01 – 0.90 µg/g wet weight. In Future perspectives, the remaining questions important in this field are raised.
|
|
| 4. |
- Maddalo, Gianluca, 1979-
(författare)
-
Strategies to explore the membrane proteome of a cell
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The cell envelope plays key roles in numerous processes such as maintaining cellular integrity, communication with other cells, signal transduction, maintenance of cellular homeostasis, and regulation of the traffic of molecules between the cell and the extracellular milieu. Essential membrane components in many of these processes are proteins. It is estimated that ~20-30% of the predicted open reading frames (ORFs) of all organisms encode membrane proteins. Furthermore, two thirds of drug targets are membrane proteins. However, despite their importance, membrane proteins have so far been mostly neglected in most proteomic studies, due to the inherent challenges in analyzing them. The focus of this thesis is to devise strategies that allow investigation of membrane proteins and their associated complexes. Optimization of sample preparation in the underlying studies has allowed important goals to be reached in membrane protein analyses at various levels such as elucidation of their primary structure by collision-induced dissociation (CID) and electron-capture dissociation (ECD) mass spectrometry (MS), profiling membrane proteins and their complexes, the discovery of novel protein complexes, definition of their topology, and unambiguous identification of protein-bound ligand(s). This thesis paves the way for better characterization of membrane proteins and their assemblies hinting towards the crucial role(s) they play in maintaining normal cell physiology.
|
|
| 5. |
- Spáčil, Zdeněk, 1982-
(författare)
-
Mass Spectrometry of Biologically Active Small Molecules : Focusing on polyphenols, alkaloids and amino acids
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The foci of this dissertation are on advanced liquid chromatography (LC) separation and mass spectrometry (MS) techniques for the analysis of small bioactive molecules. In addition to discussing general aspects of such techniques the results from analyses of polyphenols (PPs), alkaloids and amino acids published in five appended studies are presented and discussed. High efficiency and well understood principles make LC the method of choice for separating analytes in many kinds of scientific investigations. Moreover, when LC is coupled to an MS instrument, analytes are separated in two stages: firstly they are separated and pre-concentrated in narrow bands using LC and then separated according to their mass-to-charge (m/z) ratios in the MS instrument. Some MS instruments can provide highly accurate molecular weight measurements and mass resolution allowing identification of unknown compounds based purely on MS data, thus making prior separation unnecessary. However, prior separation is essential for analyzing substances in most complex matrices – especially useful is the ultra-high performance LC (UHPLC). The advantages of using UHPLC rather than HPLC for the analysis of PPs in tea and wine were evaluated in one of the studies this thesis is based upon. The phenolic composition of red wine was also examined, using a novel LDI technique, following solid phase extraction (SPE). A class of small aromatic molecules (medicinally important alkaloids) also proved to be amenable to straightforward analysis, by thin layer chromatography (TLC) work-up followed by LDI-MS. Finally, a LC-MS method for monitoring neurotoxins (β-N-methyl-amino-L-alanine and 2,3-diaminobutyric acid) in complex biological matrices was developed and applied. Overall, the studies show that careful attention to the physicochemical properties of analytes can provide insights that can greatly facilitate the development of alternative methods to analyze them, e.g. by LDI.
|
|
| 6. |
- Zguna, Nadezda, 1989-
(författare)
-
Mass-spectrometry based survey of BMAA sources, distribution and transfer
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- β-methylaminoalanine (BMAA) is a neurotoxic non-protein amino acid first isolated from cycad seeds in 1967. It is believed to be connected to neurodegenerative diseases such as Parkinson’s, Alzheimer’s and amyotrophic lateral sclerosis (ALS) and is a ubiquitous compound produced by cyanobacteria, diatoms and dinoflagellates. Consequently, elucidating natural production, distribution and routes for human exposure of BMAA are of particular importance. However, the natural function of BMAA and its mechanisms of toxicity have not been fully established yet. The contradictory results about BMAA presence in cyanobacterial cultures and food webs have been reported by different scientific groups, which required the development of more sensitive and reliable analytical methods. This thesis is focused on the analytical chemistry dimension of BMAA research: covering both new method development and novel applications. New analytical methods for BMAA detection and quantification were developed, focusing on improving sensitivity, since BMAA is normally found in natural samples at low concentrations. In Paper I, a new derivatization technique was implemented, which increased sensitivity and selectivity in the analysis of BMAA and its isomers. Subsequently, this developed method was applied to determine the presence of BMAA in fat and oil matrices in Paper II, which is a step towards discovering BMAA forms other than the documented free and protein-bound BMAA species. In Paper III, a method for separation and quantification of L- and D-BMAA stereoisomers in complex biological matrix was developed and applied to determine the enantiomeric composition of BMAA in cycad seed. Studying environmental distribution of BMAA is important to evaluate potential exposure routes and health risks for humans. Part of the work was devoted to broaden assessment on environmental occurrence of BMAA by applying existing robust methodology to new samples, such as commercial seafood in Paper IV and Baltic Sea biota in Paper V. Some of the “overlooked” aspects in the existing BMAA literature (i.e., BMAA chiral analysis, possible BMAA presence in dietary oil supplements and defined food webs) were successfully addressed. Overall, the thesis presents important analytical developments, which can help to further elucidate sources, distribution and transfer of BMAA.
|
|
