Analytical strategies for the screening of microcontaminants and transformation products in aquatic environment

The characterization of anthropogenic contamination and understanding of the associated risks for humans and the environment is a challenge, since tens of thousands of compounds are constantly discharged into different environmental compartments. The hydrosphere has a very powerful potential to disseminate contaminants of emerging concern (CECs), which can then reach other compartments such as soil, plants, and sediments, so evaluation of its contamination is essential. The identification of CECs in aquatic systems is analytically difficult, since there is a need to achieve increasingly low detection limits (µg L-1 and ng L-1) and cover the widest possible range of compounds. Expanding knowledge about aquatic contamination requires the use of sensitive methods that allow unequivocal identification of CECs, which may be achieved by methods using liquid or gas chromatography coupled with high resolution mass spectrometry. In addition, sensitive analytical methods should be associated with in silico prediction by (quantitative) structure-activity relationship ((Q)SAR) tools and multi-criteria decision analysis ranking methods, in order to not only obtain conclusions about contaminants present in the environment, but also to identify those of most concern. Considering these issues, the present thesis is divided into three chapters. Chapter 1 describes an adapted analytical method for the identification of pharmaceuticals and metabolites in raw hospital wastewater, using three different identification strategies: i) for confirmed compounds (when analytical standards are available); ii) for suspect compounds (when analytical standards are not available); and iii) for metabolites by common fragmentation profile. The method employed a custom database containing up to 1380 compounds. Six samples collected monthly were analyzed by liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC- QTOF MS). A total of 35 metabolites and 43 pharmaceuticals were identified. Risk assessment of the identified compounds was performed using in silico (Q)SAR prediction methods. Chapter 2 presents a study of the degradation of diazepam (DZP), a pharmaceutical identified in all the samples analyzed, as described in Chapter 1, by solar photo-Fenton treatment, which is an advanced oxidation process (AOP). The identification of previously reported and new transformation products (TPs) formed during DZP degradation was performed by LC-QTOF MS analysis. In addition, a methodfor the preconcentration of DZP and its TPs was developed, based on dispersive liquid- liquid microextraction (DLLME). The extraction method was fast, cheap, easy, and efficient. In the absence of this preconcentration step, it was not possible to identify one of the TPs formed during the solar photo-Fenton process. In this study, (Q)SAR tools were also used to predict some of the toxicological parameters of DZP and its TPs. These predictions showed mutagenicity alerts for two TPs, reflecting their higher toxicity, compared to DZP itself. Chapter 3 describes a more embracing approach. Surface water analysis was carried out by LC-QTOF MS, with application of a screening methodology using a database containing information about 3250 compounds belonging to different CEC classes. After LC-QTOF MS screening analyses of 27 river samples, it was possible to identify 150 compounds (133 compounds as suspects, and 17 compounds as confirmed). In silico predictions for the identified compounds were performed using (Q)SAR tools, providing information about eight different selected endpoints. The great number of compounds and predicted endpoints hindered the general evaluation of toxicity. Therefore, in order to obtain a better understanding of the risk of each identified compound, two different multi-criteria decision analysis ranking methods (toxicological priority index (ToxPi) and technique for order of preference by similarity to ideal solution (TOPSIS)) were used, considering a different weight for each endpoint. After ranking, the ToxPi and TOPSIS results were evaluated and showed similarity for the first 20 priority compounds. TOPSIS showed high robustness in sensitivity tests, indicating its suitability as an appropriate tool for use in association with screening results, which could support quantitative analytical methods performed subsequently. Throughout the different studies, it was possible to propose strategies for identification, degradation, extraction, toxicity evaluation, and ranking of microcontaminants present in aquatic environments. It was possible to obtain new results never previously reported, highlighting the contribution and importance of the study for research concerning contamination of the aquatic environment and possible treatment methods.A caracterização e compreensão da contaminação antropogênica e dos seus riscos para o homem e o meio ambiente é um desafio, uma vez que dezenas de milhares de compostos são constantemente despejados em diferentes compartimentos ambientais. A hidrosfera tem potencial muito poderoso para disseminar contaminantes de preocupação emergente (CECs), os quais podem atingir outros compartimentos como solo, plantas e sedimentos. Portanto, a avaliação de sua contaminação é essencial. A identificação de CECs em sistemas aquáticos é analiticamente complexa, sendo necessário atingir limites de detecção cada vez mais baixos (μg L-1 e ng L-1) e abranger a maior gama possível de compostos. Tal necessidade requer o uso de métodos sensíveis que permitem a identificação inequívoca de CECs e, para isso, uma possibilidade é o uso da cromatografia líquida ou a gás associada a espectrometria de massa de alta resolução. Além disso, os métodos analíticos podem ser associados a predições in silico por métodos de relações quantitativas entre a estrutura e atividade ((Q)SAR) e métodos de tomada de decisão multicritério, a fim de não apenas obter conclusões sobre os contaminantes presentes no ambiente, mas também para identificar aqueles que merecem maior atenção. Considerando essas questões, a presente tese está dividida em três capítulos. O Capítulo 1 descreve um método analítico para a identificação de fármacos e metabólitos em efluente hospitalar bruto, usando três estratégias de identificação: i) compostos confirmados (quando padrões analíticos estão disponíveis); ii) para compostos suspeitos (quando padrões analíticos não estão disponíveis); e iii) para metabólitos com perfil de fragmentação comum. O método empregou uma base de dados personalizada contendo 1380 compostos. Seis amostras coletadas mensalmente foram analisadas por cromatografia líquida acoplada à espectrometria de massa por tempo de vôo (LC-QTOF MS). Um total de 35 metabólitos e 43 fármacos foram identificados. A avaliação de risco dos compostos identificados foi realizada usando métodos de predição in silico (Q)SAR. O Capítulo 2 apresenta um estudo da degradação do diazepam (DZP), fármaco identificado em todas as amostras analisadas no Capítulo 1, através do processo de foto- Fenton solar, que é um processo avançado de oxidação (AOP). A identificação de produtos de transformação (TPs) formados durante a degradação do DZP foi realizada pela análise em um sistema LC-QTOF MS. Além disso, um método para a pré-concentração de DZP e seus TPs foi desenvolvido, baseado em microextração líquido- líquido dispersiva (DLLME). O método de extração proposto é rápido, barato, fácil e eficiente. Na ausência desta etapa de pré-concentração, não foi possível identificar um dos TPs formados durante o processo de foto-Fenton solar. Neste estudo, métodos (Q)SAR também foram usados para predizer alguns dos parâmetros toxicológicos do DZP e seus TPs. Essas predições mostraram alertas de mutagenicidade para dois TPs, refletindo sua maior toxicidade, em comparação com o próprio DZP. O Capítulo 3 descreve uma abordagem mais abrangente. Análise de águas superficiais, realizada por LC-QTOF MS, com aplicação de uma metodologia de screening utilizando bases de dados contendo informações sobre 3250 compostos pertencentes a diferentes classes de CEC. Após análise screening de 27 amostras de rios, foi possível identificar 150 compostos (133 compostos suspeitos e 17 compostos confirmados). As predições in silico dos compostos identificados foram realizadas usando métodos (Q)SAR, para oito variáveis selecionadas. O grande número de compostos e as diferentes variáreis preditas dificultaram a avaliação geral da toxicidade. Portanto, a fim de obter uma melhor compreensão do risco de cada composto identificado, foram utilizados dois métodos de tomada de decisão multicritério (toxicological priority index (ToxPi) e technique for order of preference by similarity to ideal solution (TOPSIS)), considerando diferentes pesos para cada uma das variáveis. Após a classificação, os resultados de ToxPi e TOPSIS foram avaliados e mostraram similaridade para os 20 compostos mais preocupantes. O TOPSIS mostrou alta robustez em testes de sensibilidade, indicando ser uma ferramenta apropriada para uso em associação com resultados de análise screening, o que pode apoiar e direcionar o desenvolvimento de métodos analíticos quantitativos como segunda etapa. Ao longo dos diferentes estudos, foi possível propor estratégias de identificação, degradação, extração, avaliação de toxicidade e classificação de microcontaminantes presentes em ambientes aquáticos. Foi possível obter novos resultados nunca antes reportados, evidenciando a contribuição e importância do estudo para a pesquisa sobre contaminação do meio aquático e possíveis métodos de tratamento

Non-local signatures of the chiral magnetic effect in Dirac semimetal Bi0.97_{0.97}Sb0.03_{0.03}

The field of topological materials science has recently been focussing on three-dimensional Dirac semimetals, which exhibit robust Dirac phases in the bulk. However, the absence of characteristic surface states in accidental Dirac semimetals (DSM) makes it difficult to experimentally verify claims about the topological nature using commonly used surface-sensitive techniques. The chiral magnetic effect (CME), which originates from the Weyl nodes, causes an $\textbf{E}\cdot\textbf{B}$-dependent chiral charge polarization, which manifests itself as negative magnetoresistance. We exploit the extended lifetime of the chirally polarized charge and study the CME through both local and non-local measurements in Hall bar structures fabricated from single crystalline flakes of the DSM Bi$_{0.97}$Sb$_{0.03}$. From the non-local measurement results we find a chiral charge relaxation time which is over one order of magnitude larger than the Drude transport lifetime, underlining the topological nature of Bi$_{0.97}$Sb$_{0.03}$.Comment: 6 pages, 6 figures + 7 pages of supplemental materia

Adding magnetism to Bi2Te3/Bi2 multilayers

Bi2Te3 is a 3D topological insulator with a single Dirac cone on the surface [1]. This surface state can be gapped by means of magnetic doping, resulting in the quantum anomalous hall state [2]. Recently, there has been an increasing interest in natural superlattices containing Bi2Te3, such as Bi4Te3 [3]. This compound consists of alternating Bi2 and Bi2Te3 layers. The exact topological nature of these compounds is still under debate. Here we fabricated the Bi4Te3 thin films with molecular beam epitaxy and characterized the films with X-ray diffraction, transmission electron microscopy and electrical transport measurements. We show that these films exhibit weak antilocalization, hinting towards the presence of a 2D surface state. Furthermore, we magnetically doped the films with V and observed signatures of magnetism in electrical transport measurements. [1] Y. L. Chen, et al., Science, 325, 5937. (2009). [2] C.-Z. Chang, et al, Science, 340, 6129. (2013)[3] D. Nabok, et al, Phys. Rev. Mat. 6, 034204. (2022)<br/

Vitality club:a proof-of-principle of peer coaching for daily physical activity by older adults

Many age-related diseases can be prevented or delayed by daily physical activity. Unfortunately, many older adults do not perform physical activity at the recommended level. Professional interventions do not reach large numbers of older adults for a long period of time. We studied a peer-coach intervention, in which older adults coach each other, that increased daily physical activity of community dwelling older adults for over 6 years. We studied the format and effects of this peer coach intervention for possible future implementation elsewhere. Through interviews and participatory observation we studied the format of the intervention. We also used a questionnaire (n = 55) and collected 6-min walk test data (n = 261) from 2014 to 2016 to determine the motivations of participants and effects of the intervention on health, well-being and physical capacity. Vitality Club is a self-sustainable group of older adults that gather every weekday to exercise coached by an older adult. Members attend on average 2.5 days per week and retention rate is 77.5% after 6 years. The members perceived improvements in several health measures. In line with this, the 6-min walk test results of members of this Vitality Club improved with 21.7 meters per year, compared with the decline of 2-7 meters per year in the general population. This Vitality Club is successful in durably engaging its members in physical activity. The members perceive improvements in health that are in line with improvements in a physical function test. Because of the self-sustainable character of the intervention, peer coaching has the potential to be scaled up at low cost and increase physical activity in the increasing number of older adults

Vitality club: a proof-of-principle of peer coaching for daily physical activity by older adults

Many age-related diseases can be prevented or delayed by daily physical activity. Unfortunately, many older adults do not per- form physical activity at the recommended level. Professional interventions do not reach large numbers of older adults for a long period of time. We studied a peer-coach intervention, in which older adults coach each other, that increased daily physi- cal activity of community dwelling older adults for over 6 years. We studied the format and e ects of this peer coach interven- tion for possible future implementation elsewhere. Through interviews and participatory observation we studied the format of the intervention. We also used a questionnaire (n = 55) and collected 6-min walk test data (n = 261) from 2014 to 2016 to determine the motivations of participants and effects of the intervention on health, well-being and physical capacity. Vitality Club is a self-sustainable group of older adults that gather every weekday to exercise coached by an older adult. Members attend on average 2.5 days per week and retention rate is 77.5% after 6 years. The members perceived improve- ments in several health measures. In line with this, the 6-min walk test results of members of this Vitality Club improved with 21.7 meters per year, compared with the decline of 2–7 meters per year in the general population. This Vitality Club is successful in durably engaging its members in physical activity. The members perceive improvements in health that are in line with improvements in a physical function test. Because of the self-sustainable character of the intervention, peer coaching has the potential to be scaled up at low cost and increase physical activity in the increasing number of older adults.  Prevention, Population and Disease management (PrePoD

The structure of the bacterial oxidoreductase enzyme DsbA in complex with a peptide reveals a basis for substrate specificity in the catalytic cycle of DsbA enzymes

Oxidative protein folding in Gram-negative bacteria results in the formation of disulfide bonds between pairs of cysteine residues. This is a multistep process in which the dithiol-disulfide oxidoreductase enzyme, DsbA, plays a central role. The structure of DsbA comprises an all helical domain of unknown function and a thioredoxin domain, where active site cysteines shuttle between an oxidized, substrate-bound, reduced form and a DsbB-bound form, where DsbB is a membrane protein that reoxidizes DsbA. Most DsbA enzymes interact with a wide variety of reduced substrates and show little specificity. However, a number of DsbA enzymes have now been identified that have narrow substrate repertoires and appear to interact specifically with a smaller number of substrates. The transient nature of the DsbA-substrate complex has hampered our understanding of the factors that govern the interaction of DsbA enzymes with their substrates. Here we report the crystal structure of a complex between Escherichia coli DsbA and a peptide with a sequence derived from a substrate. The binding site identified in the DsbA-peptide complex was distinct from that observed for DsbB in the DsbA-DsbB complex. The structure revealed details of the DsbA-peptide interaction and suggested a mechanism by which DsbA can simultaneously show broad specificity for substrates yet exhibit specificity for DsbB. This mode of binding was supported by solution nuclear magnetic resonance data as well as functional data, which demonstrated that the substrate specificity of DsbA could be modified via changes at the binding interface identified in the structure of the comple