Thiostrepton (TS: TS; C72H85N19O18S5) is a thiazoline antibiotic that is effective against Gram-positive bacteria and the malarial parasite, Plasmodium falciparum. Tight binding of TS to the bacterial L11-23S ribosomal RNA (rRNA) complex of the large 50S ribosomal unit inhibits protein biosynthesis. The TS producing organism, Streptomyces azureus, biosynthesizes thiostrepton-resistance methyltransferase (TSR), an enzyme that uses S-adenosyl-L-methionine (AdoMet) as a methyl donor, to modify the TS target site. Methylation of A1067 (Escherichia coli ribosome numbering) by TSR circumvents TS binding. The S. azureus tsr gene was overexpressed in E. coli and the protein purified for biochemical characterization. Although the recombinant protein was produced in a soluble form, its tendency to aggregate made handling a challenge during the initial stages of establishing a purification protocol. Different purification conditions were screened to generate an isolation protocol that yields milligram quantities of protein with little aggregation and sufficient purity for crystallographic studies. Enzymological characterization of TSR was carried out using an assay to monitor AdoMet-dependent ([methyl-3H]-AdoMet) methylation of the rRNA substrate by liquid scintillation counting. During the optimization of assay, it was found that, although this method is frequently employed, it is very time and labour intensive. A scintillation proximity assay was investigated to evaluate whether it could be a method for collecting kinetic data, and was found that further optimization is required. Comparative sequence analysis of TSR has shown it to be a member of the novel Class IV SpoUT family of AdoMet-dependent MTases. Members of this class possess a non-canonical AdoMet binding site containing a deep trefoil knot. Selected SpoUT family proteins were used as templates to develop a TSR homology model for monomeric and dimeric forms. Validation of the homology models was performed with structural validation servers and the model was then used as the basis of ongoing mutagenesis experiments. The X-ray crystal structure of TSR bound with AdoMet (2.45 Å) was elucidated by our collaborators, Drs. Mark Dunstan and Graeme Conn (University of Manchester). This structure confirms TSR MTase’s membership in the SpoUT MTase family with a deep trefoil knot in the catalytic domain. The AdoMet bound in the crystal structure is in an extended conformation not previously observed in SpoUT MTases. RNA docking simulations revealed some features that may be relevant to binding and recognition of TSR to the L11 binding domain of the RNA substrate. Two structure-activity studies were conducted to investigate the TS-rRNA interaction and TS solubility. Computational analyses of TS conformations, molecular orbitals and dynamics provided insight into the possible modes of TS binding to rRNA. Single-site modification of TS was attempted, targeting the dehydroalanine and dehydrobutyrine residues of the antibiotic. These moieties were modified using the polar thiol, 2-mercaptoethanesulfonic acid (2-MESNA). Similar modifications had been previously used to improve solubility and bioavailability of antibiotics. The resulting analogue was structurally characterized (NMR and mass spectrometry) and showed antimicrobial activity against Bacillus subtilis and Staphylococcus aureus.

Mokslinio tyrimo įstaigose atliekami platūs ir išsamūs naujų augalų bei augalinės kilmės vaistinių preparatų paieškų tyrimai, nes augalinės kilmės vaistai efektyviai terapiškai veikia žmogaus organizmą, nesukelia komplikacijų, turi mažiau šalutinių poveikių. Naujausios epidemiologinės studijos parodė, jog flavonoidų vartojimas susijęs su mažesne koronarinių širdies ligų, insultų, diabeto rizika, taip pat mažesne vėžinių susirgimų rizika. Sergantiesiems minėtomis ligomis aktualu vartoti natūralios prigimties antioksidantus – medžiagas, saugančias nuo žalingo antioksidantų poveikio. Turtingi flavonoidais yra plačiai pasaulyje išplitę Fabaceae šeimos Desmodium genties augalai. Dėl plataus biologinio veikimo spektro Desmodium genties augalai gali būti vartojami šiuolaikinių vaistinių augalinių preparatų kūrimui ir gamybai. Desmodium canadense (L.) DC. preparatai pasižymi antieksudaciniu, priešuždegiminiu, hipoazoteminiu, antivirusiniu, antimikrobiniu, antihistamininiu ir imunostimuliuojančiu poveikiu. Darbo tikslas – ištirti šeštųjų – septintųjų auginimo metų kanadinės jakšūnės (Desmodium canadense (L.) DC.) biologinius savumus Lietuvos klimatinėmis sąlygomis, apibendrinti augimo ypatumus antraisiais – septintaisiais vegetacijos metais ir nustatyti ryšį tarp vegetacijos laikotarpio, meteorologinių sąlygų bei įvairių vegetacijos tarpsnių pradžios ar trukmės. Buvo nustatyti kanadinės jakšūnės antžeminės dalies augimo ypatumai šeštaisiais ir septintaisiais auginimo metais. Ištirta... [toliau žr. visą tekstą] / Wide and comprehensive researches of new plants and herbal preparations are effected in the institutions of scientifical researching. It’s because the reason that herbal drugs have a therapeutical effect on human body, these preparations don’t have complications and have less adverse effects. Recent epidemiological studies indicated that the intake of flavonoids is associated with a reduce risk if coronary heart disease, stroke, diabetes, and cancer. So it is useful to use these natural antioxidants – substances that protect cells from damaging action of oxidation – for those, who have such problems. Plants of Desmodium genus of Fabaceae family, that are spread in all the world, are plentiful of flavonoids. Because of their wide biological effect plants of Desmodium genus can be used to create and make modern herbal preparations. Preparations of Desmodium canadense (L.) DC. have antiexudative, anti-inflammatory, hypoazotemical, antiviral, antimicrobical, antihistaminic and also immunostimulating effects. The aim of work – to determine biological features of showy tick trefoil of sixth and seventh vegetation year in Lithuanian climate conditions, to generalize the peculiarity of growing of second – seventh vegetation year and to measure the relation between the meteorological factors of vegetation period and the beginning and length in different vegetations periods. In result it was determined biological features of Showy tick trefoil of sixth and seventh vegetation year. It... [to full text]

In recent years, the development trend of power grids character shows increased demand for using cables of both current overhead and newly constructed lines. In order to preserve reliable operation and to predict the maintenance requirements, it is crucial to regard not only the parameters certified by manufacturers, but also externalities induced by real environment and incorporate these externalities into cable models in simulation software. The diploma thesis deals with determining of characteristic parameters of single core cables in real environment, which are affected by real grounding methods of metal shielding. The emphasis is put on analysis of current cable models in simulation software PSCAD and its evaluation using two-step experiment 1) measurement of shunt parameters in laboratory using electronic bridge model and 2) on field measurement of cable series parameters in real environment.

Peripheral blood biomarkers can inform clinical care and drug development. Establishing causality between biomarker and disease is often critical for such applications, but epidemiological studies are limited due to biases from confounding and reverse causation. Mendelian randomization analysis leverages random inheritance of genetic variants at conception to mimic properties of randomized studies and estimate unconfounded effects between biomarker and disease, or vice-versa. This thesis demonstrates the utility of Mendelian randomization as a complementary tool to elucidate observational studies, predict drug safety and repurposing opportunities, and improve diagnostic biomarkers for cardiometabolic diseases. First, we characterized the hypothesized relationship between lipoprotein(a) and atrial fibrillation. We demonstrated both observed and genetically predicted lipoprotein(a) levels were associated with higher risk of atrial fibrillation across multiple independent cohorts. Importantly, risk was partly mediated independent of atherosclerotic cardiovascular disease, a known consequence of elevated lipoprotein(a) and itself a risk factor for atrial fibrillation. Next, we explored the lifelong effects of endogenous testosterone across a comprehensive set of 461 health outcomes in 161,268 males from the UK Biobank cohort. Using Mendelian randomization analysis, we found higher testosterone had beneficial effects on body composition and bone mineral density but adverse effects on prostate cancer, androgenic alopecia, spinal stenosis, and hypertension. Finally, we applied Mendelian randomization with the intention of discovering biomarkers caused by disease, which are expected to represent markers of early disease. As a proof-of-concept, we applied this framework to identify biomarkers associated with genetic predisposition to kidney function among 238 biomarkers measured in the ORIGIN trial. We discovered reduced kidney function caused increased trefoil factor 3 and showed its addition to models with known risk factors improved discrimination of incident early-stage chronic kidney disease. Taken together, Mendelian randomization identified biomarkers that warrant further study, with promising implications for screening, prevention, and treatment of different cardiometabolic diseases. / Thesis / Doctor of Philosophy (PhD) / Biological markers associated with disease can inform novel therapeutics or diagnostics but distinguishing causation from correlation is challenging. Mendelian randomization – a technique that leverages random inheritance of genetic variation to infer causality – was used to examine the role of biomarkers in cardiometabolic diseases. First, we implicated lipoprotein(a) as a risk factor for atrial fibrillation that acts independent of atherosclerotic cardiovascular disease. Second, we comprehensively characterized the lifelong effects of testosterone on health outcomes in males, where we found evidence of both beneficial and adverse effects on disease. Finally, we discovered trefoil factor 3 as a diagnostic marker for early-stage chronic kidney disease. Altogether, this thesis demonstrated different applications of Mendelian randomization that showcase its utility as a complementary tool to reveal causal biomarkers, and served to identify biomarkers for cardiometabolic diseases that merit further studies to evaluate their potential benefit on patient care.