Browsing by master's degree program "Kemian ja molekyylitieteiden maisteriohjelma"

In terms of nuclear waste management, the behavior of radionuclides with long half-lives, such as I-129, is of special concern especially for the final depository of nuclear waste. In addition, generally speaking, iodine is highly mobile and easily transferable to the natural environment. Furthermore, because iodine is an essential element for the synthesis of thyroid hormones, it accumulates in the human thyroid. Thus, radioactive iodine can also be the greatest potential danger of dose uptake for humans. Among many kinds of iodine species, it is rather challenging to separate iodate selectively from other anions and thus it is necessary to investigate new materials which can adsorb iodate efficiently for the removal of radioactive iodine. In this study, the iodate adsorption ability of hydrous zirconia has been investigated. Hydrous zirconia has been reported as an anion-exchanger, and because of its stability, this material is a promising candidate for selective iodate removal from radioactive waste solutions. White solid of hydrous zirconia was successfully synthesized with an amorphous structure. Its surface showed a character in between amphoteric and basic. The isotherm indicated that the material has a preference to adsorb iodate and the saturation value of adsorption was estimated to 1.8 mmol/g. The material showed lower uptakes as pH got higher. Among several competing anions tested, divalent sulphate ions suppressed the iodate adsorption to some extent due to higher affinity to the material surface. In a basic environment, boric acid also suppressed strongly the adsorption probably because of the formation of tetrahydroxyborate with hydroxide sites on the material surface. These suppressions of iodate adsorption became stronger as the concentration got higher. Post-heating at 400 °C resulted in the transformation of the material structure to tetragonal and a slight improvement of iodate adsorption rate. As the temperature of post-heating got higher, the structure became more monoclinic and showed the lower uptakes, which may be due to the loss of hydroxide sites. A column setup of the material with simulant of wastewater from Fukushima Daiichi Nuclear Power Plant has been operating and approximately 11,000 bed-volume of the solution has been gone through, but still, the column is yet to reach a 100% breakthrough. Based on the results presented in this study, it can be concluded that synthesized hydrous zirconia showed clear iodate preference and a possible high performance for the waste treatment from nuclear power plants.

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.

Nowadays one main objective in chemistry is to find environmentally benign alternatives to non-biodegradable materials, like common plastics. Further, as fossil resources are decreasing, novel approaches to utilize renewable materials (like biomass), are becoming increasingly important for the mankind. There is a long-standing interest for utilization of cellulose; it is the most abundant polymer on earth and can be found in many organisms such as plant, algae, and bacteria but also in some animal species. Cellulose is the most abundant biogenic polymer used in the world; its largest source is from wood, which contains up to 50% of cellulose but also other compounds such as lignin (up to 30%), hemicellulose (up to 30%), inorganic salts and proteins. The main challenge is to dissolve cellulose, because of is strong intra- and intermolecular hydrogen bonding, it is not soluble in common molecular organic solvents and does not melt. According to these problems of cellulose dissolution, a novel class of solvents has been designed and called: Ionic liquids (ILs). ILs are made of an organic cation and an organic or inorganic anion, their major difference from classic salts is their lower melting point (under 100°C) They are able to do covalent and ionic bonds as normal organic solvent do, but their special character comes from the fact that ILs are able to do also strong H-bonding and columbic interactions. The mechanism of the dissolution itself has been studied using molecular dynamics and it has been shown that the anion and cellulose build a strong hydrogen-bonding network between them; the cation has a different stabilizing effect on dissolution as it is dominated by Van der Walls and electrostatic interactions. The structure of the IL plays a big role. A non-hindered cation will be more effective and, an anion with high basicity will be the most effective. Many of the ILs studied to dissolve cellulose contain phosphonium cations or halogen anions, such combination leads to toxicity and corrosive action against reaction vessels. To diminish the negative effects, other combinations have to be designed. Chemist started to use superbases as a cation and weak acid such as acetic acid as an anion to form superbase-based ILs. ILs-based on guanidine are known to be chemically and thermally stable, this comes from the high proton delocalisation between the three nitrogen atoms. Even if they are able to dissolve cellulose, their characteristics related to their structure such as high melting point and high viscosity are a problem for lab experiments using a classic magnetic stirring. Also they are limited to 10 wt% cellulose dissolution. A lot of superbase ILs such as immidazolium-based ILs were investigated for cellulose dissolution but they require temperature higher than 90°C enhancing cellulose degradation. So bicyclic guanidine were investigated as a potential class of ILs. Because of their rigid bicyclic structure, they are less affected by steric effect than their acyclic analogue. This explains why chemists started to be interested in bicyclic guanidine species in ILs such as TBD and its methylated version mTBD.

Members of the genus Flavivirus are enveloped single strand positive sense RNA viruses, that include many human pathogens. An emerging flavivirus threat in Finland and elsewhere in Europe is tick-borne encephalitis virus (TBEV), which can cause severe, often debilitating and even lethal neurological infections. There are no specific antivirals against TBEV, and only symptomatic treatment is available for affected individuals. The search for specific antivirals backed up by detailed understanding the virus structure, function and interactions with the host is therefore an unmet need. TBEV work requires biosafety level (BSL) containment facilities of level 3 or higher. This poses significant limitations on experimentation approaches for studying TBEV, and especially its highly virulent subtypes and variants. BSL2 models for TBEV can facilitate research, and such a model has been generated by our collaborator Anna Överby (MIMS, Sweden) based on a non-pathogenic Langat virus expressing surface glycoproteins from a highly virulent TBEV isolate. This model virus, rLGTVch, shows greatly reduced virulence in mice and is genetically tractable. In this thesis project, I have performed the initial structural characterization of this virus. I have optimized the production of rLGTVch, now routinely obtaining virus stocks of titers as high as 109 plaque forming units/ml. I have also established a simple and rapid purification protocol for rLGTVch. Using size exclusion chromatography resin, I obtained a highly concentrated, purified rLGTVch preparations. The purified sample was imaged using cryogenic electron microscopy (cryo-EM), and the three-dimensional structure was determined to a resolution of 4.77 Å. The 3D electron density map allowed me to analyse the structural features of the virion and confirm the similarity to a wild type TBEV strain Kuutsalo-14 structure, thus, confirming the usefulness of this model for antigen presentation. This work paves the way for further studies of TBEV using the significantly safer BSL2 model.

The aim of this work is to synthetize a series of thermoresponsive microgels that have never been reported before, based on strong polycations, and study their properties such as the change in volume in response to a temperature stimulus. Polymer microgels are interesting materials for practical applications as drug delivery systems, in separation techniques and catalysis. The interest on these materials arises from their physical properties of colloids combined with gel properties. The microgels presented in this work can undergo phase transitions not only in water but also in DMF/water mixtures. A crosslinked polymer that displays cloud point behaviour when heated forms a temperature-sensitive gel network. Cloud point is the temperature above which an aqueous solution of a water-soluble polymer becomes turbid in the case of polymer with LCST (Lower Critical Solution Temperature) behaviour. Upon heating such a gel, the gel shrinkage is observed by expelling water over a temperature range. The transition is largely driven by the entropy gain associated with the release of water from the network, and the concomitant collapse of the polymer chains. In addition, the size of the microgels is tuneable by adding NaCl at different concentration. The synthesis is carried out as a normal radical polymerization always in the same conditions except for the solvent mixture. The homopolymer, synthetized for comparison, is polymerized with RAFT (Reversible Addition-Fragmentation chain-Transfer) method. Nuclear Magnetic Resonance (NMR) confirmed the structure of the microgels validating the synthetic method. The hydrodynamic radius of the microgels after the addition of salty solutions at different concentration is determined by Dynamic Light Scattering (DLS). The thermo-responsive properties are investigated in terms of polarity using fluorescence and turbidity measurements and in terms of changes in volume calculated from the hydrodynamic radius with DLS at different temperature. The microgels show a thermo-responsive behaviour in the temperature range between 10 °C and 90 °C. In fact, the raise in temperature causes an increase in volume and hydrophobicity. Finally, it is reported a trend that follows the NaCl concentration of salt solutions added to the microgels. These microgels can be used for a wide range of applications, amongst them, they are useful support for metal nanoparticles for catalytic purposes. Here, AuNPs are formed directly on the microgel and the formation is ascertained by DLS and TGA (Thermogravimetric Analysis). Then, they are tested to effectively work during a catalysis experiment.

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.

Positroniemissiotomografia (PET) on yksi suosituimmista kuvantamistekniikoista kehon metabolian ja kemiallisten muutosten kuvantamiseen nykypäivänä. PET-kuvantaminen edellyttää radiomerkkiainetta, ja fluori-18 on nykyään käytetyin radioisotooppi. Bio ortogonaaliset ja click-reaktiot ovat saaneet paljon huomiota uusien radiomerkkiaineiden valmistuksessa. Bio-ortogonaalisia reaktioita käytetään reaktioiden kohdentamiseen, jotta reaktiot tapahtuisivat nopeasti biologisissa olosuhteissa, esimerkiksi, tetrasiini-trans syklookteeni-reaktiot. Click-reaktiot ovat hyödyllisiä radioleimaamisessa, sillä lyhyet puoliintumisajat edellyttävät nopeita reaktiota. Esimerkiksi, rikki(VI)-fluoridi vaihto (SuFEx) reaktiot olisivat tehokkaita tähän tarkoitukseen. Tämän työn tavoitteena oli luoda uusi tetrasiini SuFEx-ryhmällä, jota voidaan radioleimata fluori-18:lla. Alifaattinen osuus halutusta molekyylistä tuotettiin korkealla saannolla. Tetrasiinin saanto oli alhainen, mutta odotettavissa kirjallisuuden perusteella. Suunniteltu bromi-linkkeri yhdistettiin tetrasiinin amiiniryhmään onnistuneesti. Kuitenkaan saatu yhdiste ei reagoinut hyvin alifaattisen osan kanssa. Tehtiin useita koereaktioita, kuten erilaisten linkkerien käyttö tetrasiinin ja alifaattisen osan välillä, pienemmän kaupallisesti saatavilla olleen alifaattisen osan käyttö ja SuFEx-ryhmän lisääminen suoraan tetrasiiniin. Jotkut näistä kokeista onnistuivat, mutta viimeistä synteesin tuotetta ei voitu analysoida, joten sitä ei voitu radioleimata.

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.

Concerns about the state of the environment and the global climate change has created a need for more efficient and greener ways to produce chemicals and fuels. One solution to these challenges is to find improved ways of utilizing biomass. This thesis deals with the valorization of pectin rich biomasses. Bioengineering yeast to express the alternative galacturonic acid catabolism pathway opens up an opportunity to use these underutilized biomasses in a more efficient way. In order to bioengineer yeast, understanding of the metabolic pathways and the enzymes functioning on these pathways is required. In order to map out certain degradation steps, access to non-commercial compounds and structural analogues is a necessity. The aim of this thesis was to develop a synthetic route to D-tagaturonate, and its structural analogues, which are intermediates on the galacturonic acid catabolism pathway. The chosen multistep synthetic route to D-tagaturonate proved to be challenging. The end product was not obtained, however, the laboratory work showed that the synthetic route is feasible after some minor adjustments. On a general level, new information on the limitations of widely utilized protective groups could be uncovered. These findings will help to optimize the synthetic route to D-tagaturonate. In addition, these findings show that there is still room for improvement in orthogonal protective group strategies applicable to the synthesis of complex organic molecules such as carbohydrates.

Triglyseridimatriisit sisältävät käsitteenä kaikki lipidimatriisit, kuten eläinrasvat ja kasviöljyt. Triglyseridien lisäksi nämä lipidimatriisit voivat sisältää myös muita heteroatomeja sisältäviä yhdisteitä kuten esimerkiksi typpi- tai happiyhdisteitä. Rasvoja ja öljyjä voidaan käyttää elintarviketeollisuuden lisäksi myös polttoaineteollisuudessa esimerkiksi rasvahappojen metyyliestereistä koostuvan biodieselin tai hiilivedyistä koostuvan uusiutuvan dieselin tuotantoon. Tässä kirjallisuuskatsauksessa esitellään erilaisia uusiutuvien polttoaineiden valmistukseen yleisesti käytettyjä triglyseridimatriiseja sekä niiden sisältämiä yhdisteluokkia, ja perehdytään näiden analysointiin käytettäviin kvalitatiivisiin ja kvantitatiivisiin eristys- ja analyysimenetelmiin. Työssä esitellään useita eläinrasva- ja kasviöljymatriiseja sekä niissä yleisimmin esiintyviä heteroatomeja sisältäviä yhdisteryhmiä. Yhdisteiden eristykseen käytettävistä menetelmistä esitellään neste-nesteuutto, kiinteäfaasiuutto ja saippuointi, ja vastaavasti analyysimenetelmistä käsitellään nestekromatografia (LC), kaasukromatografia (GC) ja massaspektrometria (MS). Triglyseridimatriisien sisältämien heteroatomeja sisältävien epäpuhtauksien ja niiden pitoisuuksien analysointi on tärkeää, sillä näillä epäpuhtauksilla on ympäristöpäästöjen muodostumisen lisäksi useita negatiivia vaikutuksia esimerkiksi polttoaineen tuotantoon, säilyvyyteen ja toimintakykyyn polttomoottoreissa. Tutkielman kokeellisessa osuudessa validoitiin "Rasvahappoamidien, sterolien ja muiden raskaiden yhdisteiden analysointi öljyistä ja rasvoista kaasukromatografisesti" -menetelmä amideille. Validointi koostui kuudesta osuudesta: lineaarisuudesta, määritysrajan ja toteamisrajan määrityksestä, toistettavuudesta, uusittavuudesta, vaihtelevuudesta sekä takaisinsaantokokeesta. Validointi onnistui pääpiirteittäin hyvin, tulokset olivat luotettavia ja vastasivat odotuksia. Validoidun menetelmän rinnalle kehitettiin myös uuttoon perustuvaa menetelmää saippuoitumattomalle osuudelle rasvoista. Menetelmää testattiin eri uuttoliuottimilla ja menetelmän toistettavuutta kokeiltiin. Menetelmällä saatiin näytteistä eristettyä validoituun menetelmään verrattuna huomattavan paljon enemmän erilaisia yhdisteitä. Menetelmän kehitys jäi kuitenkin kesken, sillä esimerkiksi reaktio-olosuhteiden optimointi ja saantojen kvantitointiin vaadittavan malliyhdisteen löytäminen ovat vielä työn alla.