Browsing by Author "Oliveira, Raquel"
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- Common mechanistic pathways in rare congenital syndromes with primary microcephalyPublication . Jorge, Xavier; Milagre, Inês; Ferreira, Anita; Calado, Sofia; Oliveira, Raquel; Carvalhal, SaraPrimary microcephaly is an often-seen phenotype in several rare congenital syndromes. It is characterised by a smaller brain size at birth compared to the norm. The causes of this malformation are not fully understood, but genetic testing suggests a connection with defective genes involved in mitotic regulation and proteins related to DNA repair and replication pathways. Cohesinopathies represent a group of rare syndromes, where several subtypes exhibit spontaneous railroad chromosomes and primary microcephaly. This includes Roberts Syndrome, Warsaw Breakage Syndrome and a recently characterised syndrome caused by mutations in the BUB1 gene. Currently, we are examining fibroblast cells from patients with these syndromes to identify common mechanistic pathways. In this context, we have identified a new promising candidate: Topoisomerase II alpha, a protein responsible for resolving of the DNA catenation both in the DNA replication and mitosis. Defective localisation of Topoisomerase II alpha may contribute to the observed mitotic defects in these cells. We are currently exploring the impact of these defects on brain development using reprogramming techniques to assess proper neuronal differentiation.
- Oxidation management of white wines using cyclic voltammetry and multivariate process monitoringPublication . Martins, Rui C.; Oliveira, Raquel; Bento, Fatima; Geraldo, Dulce; Lopes, Vitor V.; Pinho, Paula Guedes de; Oliveira, Carla M.; Ferreira, António C. SilvaThe development of a fingerprinting strategy capable to evaluate the “oxidation status” of white wines based on cyclic voltammetry is proposed here. It is known that the levels of specific antioxidants and redox mechanisms may be evaluated by cyclic voltammetry. This electrochemical technique was applied on two sets of samples. One group was composed of normal aged white wines and a second group obtained from a white wine forced aging protocol with different oxygen, SO2, pH, and temperature regimens. A study of antioxidant additions, namely ascorbic acid, was also made in order to establish a statistical link between voltammogram fingerprints and chemical antioxidant substances. It was observed that the oxidation curve presented typical features, which enables sample discrimination according to age, oxygen consumption, and antioxidant additions. In fact, it was possible to place the results into four significant orthogonal directions, compressing 99.8% of nonrandom features. Attempts were made to make voltammogram fingerprinting a tool for monitoring oxidation management. For this purpose, a supervised multivariate control chart was developed using a control sample as reference. When white wines are plotted onto the chart, it is possible to monitor the oxidation status and to diagnose the effects of oxygen regimes and antioxidant activity. Finally, quantification of substances implicated in the oxidation process as reagents (antioxidants) and products (off-flavors)was tried using a supervised algorithmic the partial least square regression analysis. Good correlations (r > 0.93) were observed for ascorbic acid, Folin-Ciocalteu index, total SO2, methional, and phenylacetaldehyde. These results show that cyclic voltammetry fingerprinting can be used to monitor and diagnose the effects of wine oxidation.