Browsing by study line "Kemi"

Haihtuvia yhdisteitä, mukaan lukien haihtuvia orgaanisia yhdisteitä, tuottavat sekä ihmiset että mikrobit osana niiden normaalia aineenvaihduntaa. Ihmiskehossa joko normaalisti tai esimerkiksi bakteeri-infektion johdosta syntyneet haihtuvat yhdisteet pystyvät kulkeutumaan veren mukana läpi ihmiskehon, ja päätyä esimerkiksi verestä keuhkorakkuloiden kautta uloshengitettävään ilmaan tai munuaisten kautta virtsaan, jolloin niiden läsnäolo on mahdollista havaita näistä näytematriiseista. Myös bakteerit voivat päätyä esimerkiksi verenkiertoon tai virtsateihin, jolloin niiden muodostamia haihtuvia yhdisteitä voidaan mahdollisesti havaita näistä näytematriiseista ja yhdisteitä voitaisiin käyttää indikaattorina esimerkiksi tietyn taudinaiheuttajan läsnäolosta. Tämän tutkielman kirjallisuusosuudessa tutustutaan mikrobiperäisten haihtuvien yhdisteiden potentiaaliin ja haasteisiin diagnostiikassa. Bakteerien tuottamia yhdisteitä voidaan tutkia erilaisilla in vitro-malleilla, jolla tarkoitetaan bakteerien kasvattamista ihmiskehon ulkopuolella esimerkiksi kasvatusliuoksessa tai kliinisissä matriiseissa. Tämän avulla bakteerien tuottamia yhdisteitä voidaan tutkia ilman mahdollisia ihmiskehon aikaansaamia isäntävasteita bakteereille ja näin tutkia tietyn taudinaiheuttajan eli patogeenin tuottamia merkkiaineyhdisteitä. Toinen lähestymistapa on tutkia esimerkiksi tiettyä sairautta potevan ihmisen uloshengitysilmaa ja pyrkiä erottamaan tiettyä sairautta potevat terveistä henkilöistä. Kirjallisuusosassa käydään läpi haihtuvien yhdisteiden analytiikassa käytettyjä analyysimenetelmiä sekä niiden etuja ja rajoituksia verrattuna kaasukromatografia-massaspektrometriaan (GC-MS). Tässä tutkielmassa käydään myös läpi suun patogeenisten bakteerien, tarkemmin sanottuna hampaiden kiinnityskudoksia tuhoavaan parodontiittiin liitettyjen bakteerien roolia taudinaiheuttajina, bakteerien tuottamia haihtuvia yhdisteitä sekä yhdisteiden mahdollista biologista alkuperää. Suun patogeeniset bakteerit ja parodontiitti voivat aiheuttaa myös lukuisia muita sairauksia, joten suun patogeenien tunnistaminen on yksi haihtuvien yhdisteiden analytiikan potentiaalinen sovellutusalue. Sen lisäksi, että näillä haihtuvilla yhdisteillä on potentiaali diagnostiikassa olla tiettyä patogeenia indikoivia merkkiaineyhdisteitä, ne ovat myös osallisena parodontiitin syntymisessä sekä etenemisessä. Tutkielman kokeellisessa osassa identifioitiin suun patogeenisten anaerobisten bakteerien tuottamia haihtuvia yhdisteitä in vitro käyttämällä kiinteäfaasimikrouutto-kaasukromatografi-massaspektrometriä (SPME-GC-MS). Mittauksia varten rakennettiin näytteenottosysteemi, jonka avulla yhdistettiin bakteeriviljely, SPME-näytteenotto sekä yhdisteiden reaaliaikainen analyysi protonisiirtoreaktio-massaspektrometrillä (PTR-MS). Työn tarkoituksena oli tutkia, millaisia haihtuvia yhdisteitä suun bakteerit tuottavat ja tuottavatko bakteerit sellaisia yhdisteitä, joita voidaan mahdollisesti käyttää kyseisiä bakteereja indikoivina merkkiaineyhdisteinä tulevaisuudessa. Tutkimuksessa identifioitiin kahden patogeenin, jotka olivat Porphyromonas gingivalis ja Prevotella nigrescens, tuottamat haihtuvat yhdisteet ja molemmille bakteereille löydettiin kaksi potentiaalista merkkiaineyhdistettä, joiden avulla bakteerit voidaan erottaa toisistaan sekä mahdollisesti muista suun patogeeneista. P.gingivalis tuotti kaksi spesifistä esteriä, isoamyyli asetaattia ja isoamyyli propionaattia, ja P.nigrescens 3-(metyylitioli)propionaalia sekä 2-metyylibutaanihappoa. Tutkimuksen perusteella ei voida kuitenkaan tehdä laajoja johtopäätöksiä, koska kyseisissä analyysi- ja bakteeriviljelyolosuhteissa on analysoitu vain kahden patogeenisen bakteerin tuottamat yhdisteet, sillä kahden muun tutkimukseen valitun bakteerin viljely ei onnistunut.

The literature section of this thesis provides an overview of modern ion-mobility spectrometry techniques in context with recent applications in analytical chemistry. While ion-mobility spectrometry is an “old” separation technique, it has received in recent years increasing attention for its unique ability to achieve separation of isomeric molecular species. Ion-mobility spectrometry can be readily hyphenated with chromatographic and mass spectrometric techniques, introducing an additional separation dimension with the unique capability of differentiating isobaric analyte ions based on their collision cross sections. After a brief introduction into the theory of ion-mobility spectrometry, most recent applications in the field are presented with the focus being on the discrimination of small isomeric molecules. The research project section of the thesis reports the synthesis of isomerically pure standard materials of the commercially unavailable pepper alkaloids piperettine and piperettyline, and the qualitative and quantitative analysis of piperettine in selected pepper fruit samples. Strategies for the synthesis of piperettine reported in the literature are reviewed, and critically evaluated in terms of practicability and overall yields. A new, expedient, and operationally convenient synthetic approach to isomerically pure piperettine and piperettyline from inexpensive starting materials is described. In course of stability studies, both alkaloids were found to be stable in the crystalline states and as solutions in a range of organic solvents under exclusion of ambient light. However, diluted solutions of both compounds proved extremely photosensitive, with extensive double bond isomerization occurring within seconds upon sunlight exposure. An analytical method for the quantification of piperettine in pepper fruit samples was developed, involving liquid extraction, extract clean-up by solid-phase extraction, and HPLC-UV analysis. The use of a chiral stationary phase (Chiralpak IB) under optimized reversed phase condition allowed for the first time clean separation of piperettine from its naturally co-occurring isomers, and thus for its unambiguous quantification. Subsequently, this method was employed to quantify piperettine in black, green, white, and red long pepper samples. The observed piperettine content were 1.4 – 3.7 mg/g in the pepper fruit samples, representing 46 – 69% of the total sum of isomers.

The tear film is a thin liquid layer enveloping the cornea and conjunctiva. It serves as a crucial protective barrier safeguarding the ocular surface from environmental factors. Its functions also include ensuring optimal hydration and maintaining a consistently smooth optical surface. The tear film consists of three discernible layers. The outermost layer is the remarkably thin tear film lipid layer, measured on the nanometer scale, yet crucial for impeding evaporation and maintaining ocular surface homeostasis. The tear film lipid layer forms from meibum: a complex mixture of lipids secreted by Meibomian glands. Meibum mainly consists of lipids from five different classes, with wax esters constituting about 50 % of meibum’s composition. The majority of tear film lipids are branched. Branched lipids are methyl-branched either from the penultimate or antepenultimate carbon, with the former being more common. Due to challenges in obtaining sufficient and uncontaminated meibum samples, there is a high demand for synthetically produced lipids. Pure samples of lipids of varying structures are needed as standards in studies regarding meibum composition. Additionally, lipids and lipid mixtures are required for biophysical studies concerning tear film models and researching the molecular mechanisms associated with ocular surface diseases. Given the demand for various tear film lipids, it is surprising that there have been no prior attempts to synthesize branched lipid species or study their effect on lipid assembly, despite their prevalence in meibum. To meet the demand for various tear film lipids, especially branched species, we aimed to design a synthetic approach capable of producing a wide range of such tear film lipid analogs. This method proved successful in synthesizing the most abundant tear film lipid, the iso-branched wax ester C18:1/26:0. The results of this synthesis are presented in this thesis.

The Fukushima-Daiichi Nuclear Power Plant (FNDPP) accident on March 11, 2011, resulted in the release of radioactive cesium-rich microparticles (CsMPs), which can travel long distances thanks to their small size and light weight. Since the long-term radiobiological health-effects and accumulated radiation dose of inhaled CsMPs remain unknown, this thesis proposes a model for tracking synthetic 44-μm and 2.2-μm borosilicate microparticles, which resemble the SiO2 composition and spherical morphology of CsMPs, under Positron Emission Tomography (PET) by radiolabeling them with positron-emitting radionuclides. The use of 44-μm microparticles was discontinued early on as the size of the 2.2-μm particles was more representative of the more common type A CsMPs (0.1-10 μm). Three different radiolabeling approaches were pursued along this project, two directed at 68Ga-labeling, and a third one at 18Ffluorination. The first and main approach was based on the surface functionalization of the particles with (3-aminopropyl)triethoxysilane (APTES) and a suitable chelator for the coordination of [68Ga]Ga3+ ions, like 2,2′-(7-(1-carboxy-4-((4-isothiocyanatobenzyl)-amino)-4-oxobutyl)-1,4,7-triazonane-1,4-diyl)diacetic acid (p-NCS-Bn-NODAGA) or desferrioxamine (DFO). The second approach involved surface functionalization with ethanolamine, polyethylene glycol (PEG) and DFO. The third approach was based on the natural ability of [18F]F- to substitute silanol groups present on the surface of the borosilicates. Surface functionalization with APTES was confirmed using X-ray photoelectron spectroscopy (XPS), zeta potential and elemental analysis, as opposed to functionalization with PEG-ethanolamine. Scanning electron microscopy (SEM) images showed no significant morphological alterations upon functionalization. 68Ga-labeling of the NODAGA-APTES functionalized 2.2-μm borosilicates was achieved with a mean radiochemical yield (RCY) and radiochemical purity (RCP) of 65 ± 5% and 94 ± 2%, respectively. 68Ga-labeling of DFO-APTES and DFO-PEG-ethanolamine functionalized 2.2-μm borosilicates was not successful (RCY below 15% and RCP of about 50%). 18F-fluorination was not successful due to the high tendency of [18F]F-Si bonds to undergo hydrolysis in aqueous media. The stability of the final [68Ga]Ga-NODAGA-APTES product over a 0-3 hour time period was higher than 90% in five different simulated physiological conditions. The results of this project serve as a promising prospect for the design of radiotracers resembling CsMPs for PET tracking upon in vivo administration.

Catechol is widely produced platform chemical, and many fine chemicals, including pharmaceuticals and pesticides, contain catechol moieties. Catechols are nucleophilic, but their polarity can be reversed by oxidizing them into electrophilic o-benzoquinones (OBQs). OBQs are highly reactive and react readily with nucleophiles but also with dienes, dienophiles and ylides. However, OBQs have many reactive sites, which often leads to lack of selectivity in reactions. In the literature review of this thesis, the methods to control selectivity in nucleophilic additions, cycloadditions and Wittig reactions of OBQs are reviewed. Selectivity is often increased by blocking undesired reactive sites by substituents. If substituents can’t be altered, it is possible to control selectivity by choice of catalysts and substrates as well as stoichiometric ratios of substrates. In addition, the literature review will also focus on how the use of o-benzoquinones have been utilized in organic synthesis. In the experimental part, nucleophilic additions of amino acids and silyl enol ethers to o-benzoquinones are studied in practice. Reactions of amino acids with OBQs resulted only in polymerization despite the efforts to control the selectivity. However, ZnCl2 catalysed addition of silyl enol ethers into OBQs yielded only 1,4-addition products. The method was then optimized with two model reactions after which 30 different 1,4-addition products were successfully synthesized. For most of these products this method is the only proven synthesis route.