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- Sjödin, Marcus O.D. 1978-
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Advances for Biomarker Discovery in Neuroproteomics using Mass Spectrometry : From Method Development to Clinical Application
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Proteins offer a prominent group of compounds which may be ubiquitously affected in disease and used as biomarkers for early diagnosis, assessing treatment or drug development. Clinical proteomics aim to screen for protein biomarkers by a comprehensive analysis of all proteins expressed in a biological matrix during a certain pathology. Characterization of thousands of proteins in a complex biological matrix is from an analytical point of view a challenging task. Hence, sophisticated methods that are sensitive, specific and robust in a high-throughput manner are required. Mass spectrometry (MS) is able to perform this to a wide extent is.A prominent source for finding protein biomarkers related to neurological diseases is the central nervous system (CNS) due to close proximity of the pathogenesis. Neuroproteomic analysis of CNS tissue samples is thus likely to reveal novel biomarkers. Cerebrospinal fluid (CSF) bathes the entire CNS and offers a good balance between clinical implementation and usefulness. Both matrices put further requirements on the methodology due to a high dynamic range, low protein concentration and limited sample amount.The central objective of this thesis was to develop, assess and utilize analytical methods to be used in combination with MS to enable protein biomarker discovery in the CNS. The use of hexapeptide ligand libraries was exemplified on CSF from patients with traumatic brain injury and demonstrated the ability to compress the dynamic range to enable protein profiling in the order of mg/mL to pg/mL. Further, a method based on cloud-point extraction was developed for simultaneous enrichment and fractionation of hydrophobic/hydrophilic proteins in brain tissue. Comparison between label and label-free MS based strategies were carried out, mimicking the true conditions with a few differentially expressed proteins and a bulk of proteins occurring in unchanged ratio. Finally, a clinical application was carried out to explore the molecular mechanism underlying the analgesic effect of spinal cord stimulation (SCS) in patients with neuropathic pain. The CSF concentration of Lynx1 was found to increase upon SCS. Lynx1, acting as a specific modulator of the cholinergic system in the CNS, may act as a potential important molecular explanation of SCS-induced analgesia.
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- Wetterhall, Magnus, 1973-
(author)
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Electrifying the Molecules of Life : Peptide and Protein Analysis by Capillary Electrophoresis Coupled to Electrospray Ionization Mass Spectrometry
- 2004
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Doctoral thesis (other academic/artistic)abstract
- This thesis describes the current status and novel aspects of the analysis of the molecules of life, i.e. peptides and proteins, using capillary electrophoresis (CE) coupled to mass spectrometry (MS) via (sheathless) electrospray ionization (ESI). Early reports of sheathless CE-ESI-MS were plagued by limited lifetimes of the electrospray emitter. In this thesis, two new approaches, the Black Dust and the Black Jack methods, utilizing polymer-embedded graphite instead of noble metals are presented. These emitters have shown improved long-term stability and proven excellent for sheathless electrospray operation. Failure of an emitter is often caused by electrochemical reactions occurring at the emitter-liquid interface. The electrochemical properties of the graphite coated emitters were therefore evaluated by classical electrochemical methods, such as cyclic voltammetry and chronoamperometry. The graphite coated emitters showed excellent electrochemical stability and properties compared to noble metal and polymer configurations. Analyte-wall interactions have long been known to cause problems in the CE analysis of biomolecules. This can be circumvented by internal modification of the capillary walls. Additionally, it is of outermost importance to have a stable and sufficiently high electroosmotic flow (EOF) to sustain the electrospray, when using a sheathless approach. New monomer and polymer coatings are presented for rapid and high-efficient CE-ESI-MS separations of peptides and proteins. Furthermore, the use of CE-ESI coupled to Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) shows great potential for rapid proteomic probing of human cerebrospinal fluid. The results are comparable with more established techniques, such as liquid chromatography and two-dimensional gel electrophoresis coupled to MS. However, the CE-ESI-FTICRMS analysis has significantly lower sample consumption and faster analysis time compared to the other techniques. The applications and use of CE-ESI-MS is expected to have a bright future with continued growth as current trends of multidimensional hyphenation and microfabricated devices are further developed and explored.
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