Characterization of Quorum-Quenching Lactonases and Plp-Dependent Aminotransferases: Structure, Mechanism and Alternative Turnover

Cell-to-cell communication by bacteria is essential for the regulation of gene expression important in colonization, biofilm formation, virulence and other processes. This communication is called quorum-sensing and is mediated by small molecules called autoinducers. One major class of autoinducers used by gram-negative bacteria is N-acyl homoserine lactones (AHL\u27s). Enzymes capable of disrupting this communication are called quorum-quenching catalysts and have proven to be invaluable biochemical tools for understanding quorum-sensing pathways. Quorum-quenching enzymes hold promise for application in anti-biofouling, agriculture, aquaculture, bioremediation and other synthetic biology settings. However, the mechanisms that these enzymes use to recognize and process their substrates are not well characterized. A better understanding of selectivity and catalysis would enable the production of variant enzymes to recognize specific quorum-sensing signals to serve as catalysts for various applications. Aminotransferases are a class of pyridoxal-5\u27-phosphate (PLP)-dependent enzymes that catalyze a myriad of biochemical reactions involved in several metabolic processes. The importance of these enzymes is further underscored because some of them have been identified as drug targets. For example, inhibition of γ-aminobutyric acid aminotransferase (GABA-AT) was proven effective in the treatment of many neurological disorders, and inhibition of ornithine aminotransferase (OAT) was shown to suppress the growth of hepatocellular carcinoma (HCC). Potent mechanism-based inactivators can be rationally designed against these PLP-dependent drug targets, but one of the remaining challenges is the lack of selectivity against other PLP-dependent off-target enzymes such as aspartate aminotransferase. A better understanding of enzyme selectivity and mechanism would enable the design of molecules capable of displaying desirable specificity of inactivation discerning drug-targets and off-targets. The goal of this dissertation is to provide better understanding of selectivity and catalysis in quorum-quenching enzymes, and selectivity and mechanisms of PLP-dependent aminotransferases. The structural and biochemical characterization of AidC, an N-acyl homoserine lactone lactonase, was carried out using X-ray crystallography and other biochemical techniques. The selectivity of a mechanism-based inactivator was tested in a PLP-dependent aminotransferase drug-target (OAT) and off-target (Asp-AT) using X-ray crystallography and enzyme assays. The proposed mechanism was confirmed by high-resolution mass spectrometry

Collaborative governance in regional climate resilience planning : a case study of the Resilient Mystic Collaborative

Thesis: M.C.P., Massachusetts Institute of Technology, Department of Urban Studies and Planning, September, 2020Cataloged from student-submitted PDF of thesis.Includes bibliographical references (pages 51-53).by Nina Mascarenhas.M.C.P.M.C.P. Massachusetts Institute of Technology, Department of Urban Studies and Plannin

Physical activity in motherhood: intervention, trajectory, and mixed methods analyses

The benefits of physical activity are wide ranging and substantial. Yet the majority of US adults do not meet the recommended minimum guidelines of activity. Mothers, in particular, experience a decline in physical activity after having children. In the transition to having children, the facilitators and barriers to being active change. Though inactivity after having children poses a significant risk, there is insufficient research on the patterns, barriers and facilitators, and potential pathways for intervention. The first chapter of my dissertation explores patterns of physical activity and the association with having a child. The literature suggests that women experience a decline after birth but no studies examined more than 2 time points and thus we do not have sufficient insight into longtime patterns. We used a mixed model to estimate the percent change in physical activity with the event of birth, and for pre-specified times since birth. We found that there was a significant decrease in leisure time physical activity at birth and it persists through 5 years, however, by 10 years, women experience a rebound. The second chapter of my dissertation examines more closely the experience of pregnancy and postpartum and how that affects women’s’ abilities to stay active. We examined data from low-income Latina pregnant and postpartum women affected by gestational diabetes in San Francisco and Sonoma counties. Using a mixed methods design, we collected quantitative survey data and qualitative data from 3 focus groups. We used descriptive statistics to analyze the quantitative survey data, and grounded theory and the Capability, Opportunity, Motivation Behavior (COM-B) framework to code and identify themes from the focus groups. Our samples of pregnant and postpartum Latina women affected by GDM were predominately Spanish speaking, low-income, and born outside the US. In the transition from pregnancy to postpartum, women noted a shift from a focus on self-care in order to maintain a healthy GDM pregnancy to caring primarily for their children. Two strategies that helped postpartum women stay active were setting proximal and family-centered goals and engaging their families in providing instrumental support. Family-centered goals included modeling healthy behaviors for their children and staying healthy in order to support their families. The last chapter of my dissertation was an 8-week arm, randomized trial comparing the effectiveness of a virtual exercise and mobile apps intervention to a waitlist control. Using Google Hangouts, mothers in the intervention exercised together in real time guided by a mobile exercise app of their choosing. We found that a web and mobile app group exercise intervention was a feasible and acceptable way to deliver a physical activity intervention to mothers with young children. The intervention significantly increased physical activity in inactive mothers.As a body of work, my three dissertation papers add a significant contribution to our understanding of the impact of becoming a mother on physical activity level patterns and associated barriers and facilitators. My work also suggests a potential path forward to increasing activity levels for women with children

A Systematic Review of the Inclusion of Non-Inflammatory Ultrasonographic Enthesopathy Findings in Enthesitis Scoring Indices

Ultrasound has advanced the diagnosis and management of patients with inflammatory rheumatic conditions. It can be used to identify and monitor enthesitis, a cardinal feature of spondyloarthropthies. Several enthesitis scoring systems utilizing ultrasound to determine entheseal involvement have been developed. These scoring systems generally rely on determining the presence or absence of erosions, tendon enlargement, power Doppler signal, or enthesophytes. This systematic review identified ultrasound scoring systems that have been utilized for evaluating enthesitis and what key components derive the score. Review of these scoring systems, however, demonstrated confounding as some of the score components including enthesophytes may be seen in non-inflammatory conditions and some components including erosions can be seen from chronic damage, but not necessarily indicate active inflammatory disease. What is furthermore limiting is that currently there is not an agreed upon term to describe non-inflammatory enthesopathies, further complicating these scoring systems. This review highlights the need for a more comprehensive ultrasound enthesopathy scoring index

Capacities and Impacts of Community Arts and Culture Initiatives in Singapore

Social Theory, Politics and the Arts 201

Impacts of Community Arts and Culture Initiatives: A Study of Five Singaporean Neighbourhoods

Great Asian Streets Symposium 2018: Emerging Civic Urbanisms / Designing for Social Impac

Capacities and Impacts of Community Arts and Culture Initiatives in Singapore

10.1080/10632921.2020.1720877STPA (Social Theory, Politics and the Arts) 2018: Culture, Democracy, and the Arts: Rights Here, Right Now1-3

Bringing Arts into the Neighbourhoods: Choosing the Right Space and Strategy

Singapor

Arts and Culture Strategies for Activating Neighbourhood Public Spaces: Bringing Arts to the Heartlands of Singapore

AESOP Annual Congress 2017744-756Lisbon, Portuga

Assessing the Impact of Bringing Arts into Neighbourhoods

Singapor