Osvaldo S Ascenso

Universidade NOVA de Lisboa | NOVA · Institute of Chemical and Biological Technology (ITQB)

Many proteins are usually not stable under different stresses, such as temperature and pH variations, mechanical stresses, high concentrations, and high saline contents, and their transport is always difficult, because they need to be maintained in a cold regime, which is costly and very challenging to achieve in remote areas of the world. For this...

A series of new hydroxylated chalcone derivatives with different substitution patterns on a phenyl ring A and B, were prepared by Claisen–Schmidt condensation in an aqueous alkaline base. The antiproliferative activity of the studied compounds was evaluated against the human leukaemia cell line U-937. The structure-activity relationship of these na...

A new synthetic route for the quorum sensing signal Autoinducer-2 (AI-2) is described and used for the preparation of [4-13C]-AI-2 starting from [1-13C]-bromoacetic acid. The key step in this process was the enantioselective reduction of an intermediate ketone. This synthesis provides, selectively, both enantiomers of the labelled or unlabelled par...

Histone deacetylases are involved in chromatin remodelling and thus play a vital role in the epigenetic regulation of gene expression. HDAC inhibitors alter the acetylation status of histone and non-histone proteins to regulate various cellular events such as transcription. Novel HDAC inhibitors were designed and synthesised to promote higher level...

Determining the stability of downstream process (DSP) intermediates is an extremely important parameter used to maintain product quality attributes within their acceptance ranges. The IgG4 monoclonal antibody studied (mAb1) showed aggregation under acidic conditions, inhibiting the use of low pH treatment to inactivate endogenous retroviruses, and...

Quorum sensing (QS) regulates population-dependent bacterial behaviours, such as toxin production, biofilm formation and virulence. Autoinducer-2 (AI-2) is to date the only signalling molecule known to foster inter-species bacterial communication across distantly related bacterial species. In this work, the synthesis of pure enantiomers of C4-propo...

The plant hormone conjugate 2-O-(indole-3-acetyl)-myo-inositol (IAInos) has been selectively prepared for the first time by two routes from myo-inositol. One of the syntheses depended upon the construction of the 3-indoleacetyl group by a Fischer indole synthesis on an unreactive axial hydroxyl group, while the other via a direct acylation of the e...

Non-volatile S-Alkyl-S-phenyl-2,3,4,5-tetramethylphenylsulfonium triflate or tetrafluoroborate salts have been used to alkylate alcohols in the presence of sodium hydride. This is a simple and efficient method for the synthesis of ethers from complex alcohols and an alternative to the usual O-alkylation methods. This method was especially important...

1′,2,3,3′,4,4′,6-Hepta-O-benzyl-6′-N-methacryloyl-6′-deoxysucrose 1, 6′-deoxy-6′-N-methacryloyloxyethylureido sucrose 2 and 6,6′-dideoxy-6,6′-N-dimethacryloyloxyethylureido sucrose 3 have been homo-polymerized and copolymerized with styrene by a free radical process, yielding polymer materials with pendant sucrose moieties, attached to the polymer...

Molecular Farming - the use of plant based systems for production of recombinant proteins - is an emerging field with a high potential impact in the pharmaceutical sector. Plant production platforms offer significant advantages when compared to traditional expression systems, namely in terms of safety and cost. However, a major challenge remains so...

The aim of this work was to study the application of two biodegradable chelating agents, pyridine-2,6-dicarboxylic acid (PDA) and methylglycinediacetic acid (MGDA), in the treatment of the pulp, prior to hydrogen peroxide bleaching. Such compounds must remove transition metals (Mn, Fe and Cu) from pulp, that catalyze the degradation of hydrogen per...

Autoinducer-2 (AI-2) is a signalling molecule for bacterial inter-species communication. A synthesis of (S)-4,5-dihydroxypentane-2,3-dione (DPD), the precursor of AI-2, is described starting from methyl glycolate. The key step was an asymmetric reduction of a ketone with (S)-Alpine borane. This new method was highly reproducible affording DPD for b...

Values of binary mutual diffusion (interdiffusion) coefficients, obtained by using the Taylor dispersion method, for aqueous solutions of γ-cyclodextrin in the concentration range from (0.002 to 0.010) mol·dm−3 and temperatures (298.15 and 310.15) K are reported. From these experimental results, the hydrodynamic radius values for the γ-cyclodextrin...