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Browsing by Author "Freitas, Sara"

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  • Bartolosides E–K from a Marine Coccoid Cyanobacterium
    Publication . Afonso, Tiago B.; Costa, M. Sofia; Rezende de Castro, Roberta; Freitas, Sara; Silva, Artur; Schneider, Maria Paula Cruz; Martins, Rosario; Leão, Pedro N.
    The glycosylated and halogenated dialkylresorcinol (DAR) compounds bartolosides A-D (1-4) were recently discovered from marine cyanobacteria and represent a novel family of glycolipids, encoded by the brt biosynthetic gene cluster. Here, we report the isolation and NMR- and MS-based structure elucidation of monoglycosylated bartolosides E-K (5-11), obtained from Synechocystis salina LEGE 06099, a strain closely related to the cyanobacterium that produces the diglycosylated 2-4. In addition, a genome region containing orthologues of brt genes was identified in this cyanobacterium. Interestingly, the major bartoloside in S. salina LEGE 06099 was 1 (above 0.5% dry wt), originally isolated from the phylogenetically distant filamentous cyanobacterium Nodosilinea sp. LEGE 06102. Compounds 5-11 are analogues of 1, with different alkyl chain lengths or halogenation patterns. Their structures and the organization of the brt genes suggest that the DAR-forming ketosynthase BrtD can generate structural diversity by accepting fatty acyl-derived substrates of varying length. Compound 9 features a rare midchain gem-dichloro moiety, indicating that the putative halogenase BrtJ is able to act twice on the same midchain carbon.
    2016Journal article Restricted access Show more
  • Hierridin B Isolated from a Marine Cyanobacterium Alters VDAC1, Mitochondrial Activity, and Cell Cycle Genes on HT-29 Colon Adenocarcinoma Cells
    Publication . Freitas, Sara; Martins, Rosario; Costa, Margarida; Leão, Pedro; Vitorino, Rui; Vasconcelos, Vitor; Urbatzka, Ralph
    Hierridin B was isolated from a marine cyanobacterium Cyanobium sp. strain and induced cytotoxicity selectively in HT-29 adenocarcinoma cells. The underlying molecular mechanism was not yet elucidated.
    2016Journal article Open access Show more
  • Insights into the potential of picoplanktonic marine cyanobacteria strains for cancer therapies – Cytotoxic mechanisms against the RKO colon cancer cell line
    Publication . Freitas, Sara; Martins, Rosario; Campos, Alexandre; Azevedo, Joana; Osório, Hugo; Costa, Margarida; Barros, Piedade; Vasconcelos, Vitor; Urbatzka, Ralph
    In this work, we analysed the potential of picoplanktonic marine cyanobacteria strains as a source of anticancer compounds by elucidating the cytotoxic mechanisms of an ethyl acetate fraction of Cyanobium sp. (LEGE06113) and the Synechocystis salina (LEGE06155) on the RKO colon adenocarcinoma cell line.
    2016Journal article Restricted access Show more
  • UAV Trials for Multi-Spectral Imaging Target Detection and Recognition in Maritime Environment
    Publication . Silva, Hugo; Soares Almeida, José Miguel; Lopes, Flávio; Ribeiro, J.P.; Freitas, Sara; Amaral, Guilherme; Almeida, Carlos; Martins, Alfredo; Silva, Eduardo
    This paper addresses the use of heterogeneous sensors for target detection and recognition in maritime environment. An Unmanned Aerial Vehicle payload was assembled using hyperspectral, infrared, electro-optical, AIS and INS information to collect synchronized sensor data with vessel ground-truth position for conducting air and sea trials. The data collected is used to develop automated robust methods for detect and recognize vessels based on their exogenous physical characteristics and their behaviour across time. Data Processing preliminary results are also presented.
    2016Journal article Restricted access Show more