Percorrer por autor "Quintas, Alexandre"
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- 2-Phenoxyethanol derivatization in ink dating determinationPublication . Leal, Teresa Argente; Ferreira, Carla; Quintas, Alexandre; Bernardo, Alexandra
- An ancestral HIV-2/simian immunodeficiency virus peptide with potent HIV-1 and HIV-2 fusion inhibitor activityPublication . Borrego, Pedro; Calado, Rita; Marcelino, José M.; Pereira, Patrícia; Quintas, Alexandre; Barroso, Helena; Taveira, Nuno"Objectives: To produce new fusion inhibitor peptides for HIV-1 and HIV-2 based on ancestral envelope sequences. Methods: HIV-2/simian immunodeficiency virus (SIV) ancestral transmembrane protein sequences were reconstructed and ancestral peptides were derived from the helical region 2 (HR2). The activity of one ancestral peptide (named P3) was examined against a panel of HIV-1 and HIV-2 primary isolates in TZM-bl cells and peripheral blood mononuclear cells and compared to T-20. Peptide secondary structure was analyzed by circular dichroism. Resistant viruses were selected and resistance mutations were identified by sequencing the env gene. Results: P3 has 34 residues and overlaps the N-terminal pocket-binding region and heptad repeat core of HR2. In contrast to T-20, P3 forms a typical a-helical structure in solution, binds strongly to the transmembrane protein, and potently inhibits both HIV-2 (mean IC50, 63.8 nmol/l) and HIV-1 (11 nmol/l) infection, including T-20-resistant isolates. The N43K mutation in the HR1 region of HIV-1 leads to 120-fold resistance to P3 indicating that the HR1 region in transmembrane glycoprotein is the target of P3. No HIV-2-resistant mutations could be selected by P3 suggesting that the genetic barrier to resistance is higher in HIV-2 than in HIV-1. HIV-1-infected patients presented significantly lower P3-specific antibody reactivity compared to T-20. Conclusion: P3 is an HIV-2/SIV ancestral peptide with low antigenicity, high stability, and potent activity against both HIV-1, including variants resistant to T-20, and HIV-2. Similar evolutionary biology strategies should be explored to enhance the production of antiviral peptide drugs, microbicides, and vaccines."
- Analysis of questioned documents on Egas Moniz Forensic and Psychological Sciences LaboratoryPublication . Leal, Teresa Argente; Mourato, Manuel; Cunha, José Abrantes da; Quintas, Alexandre
- Assessing the content of a package of SGT-151 sold onlinePublication . Luzio, Ana; Couceiro, Joana; Ferreira, Carla; Quintas, Alexandre
- A biophysical perspective on the unexplored mechanisms driving Parkinson’s disease by amphetamine-like stimulantsPublication . Ferreira, Carla; Couceiro, Joana; Tenreiro, Sandra; Quintas, Alexandre
- Chemical analysis of gunpowder and gunshot residuesPublication . Serol, Miguel; Ahmad, Samir Marcos; Quintas, Alexandre; Família, CarlosThe identification of firearms is of paramount importance for investigating crimes involving firearms, as it establishes the link between a particular firearm and firearm-related elements found at a crime scene, such as projectiles and cartridge cases. This identification relies on the visual comparison of such elements against reference samples from suspect firearms or those existing in databases. Whenever this approach is not possible, the chemical analysis of the gunpowder and gunshot residue can provide additional information that may assist in establishing a link between samples retrieved at a crime scene and those from a suspect or in the identification of the corresponding model and manufacturer of the ammunition used. The most commonly used method for the chemical analysis of gunshot residue is scanning electron microscopy with energy dispersive X-ray, which focuses on the inorganic elements present in ammunition formulation, particularly heavy metals. However, a change in the legal paradigm is pushing changes in these formulations to remove heavy metals due to their potential for environmental contamination and the health hazards they represent. For this reason, the importance of the analysis of organic compounds is leading to the adoption of a different set of analytical methodologies, mostly based on spectroscopy and chromatography. This manuscript reviews the constitution of primer and gunpowder formulations and the analytical methods currently used for detecting, characterising, and identifying their compounds. In addition, this contribution also explores how the information provided by these methodologies can be used in ammunition identification and how it is driving the development of novel applications within forensic ballistics.
- Circular dichroism of anthocyanidin 3-glucoside self-aggregatesPublication . Gavara, Raquel; Petrov, Vesselin; Quintas, Alexandre; Pina, Fernando"Self-association constants for the flavylium cations of the six most common anthocyanidin 3-glucosides were determined by circular dichroism (CD) and UV–Vis spectroscopy. Along with previous 1H NMR results, all measurements were consistent with a monomer–dimer model. The CD spectra of the antho-cyanidin 3-glucosides were similar to the analogues 3,5-diglucosides. All dimers of the anthocyanidin 3-glucosides exhibited left-handed CD signals, with petunidin-3-glucoside and myrtillin having the most intense signals. In addition, the magnitude of the molar ellipticity, [h], was generally higher for the 3-glucosides than for the 3,5-diglucosides. For all six anthocyanins studied, the CD absorption spectra of their dimers showed evidence of the splitting of the monomer absorption into lower (J) and higher (H) energy bands. The angle and the distance between the dipolar moments of the two monomers comprising the dimer were obtained from the lower energy absorption band. While the angle was more or less similar in all six dimers, the separation distance between the monomer dipole moments differed dramatically. The intensity of the CD signal displayed a linear dependence with the inverse square of the dipole moment distances."
- Determination of phytocannabinoids in cannabis samples by ultrasound-assisted solid-liquid extraction and high-performance liquid chromatography with diode array detector analysisPublication . Correia, Beatriz; Ahmad, Samir Marcos; Quintas, AlexandreThe characterisation of cannabis plants, especially the determination of specific phytocannabinoids, has gained enormous importance in the last decade, mainly due to the recent changes in cannabis control in several countries or states. This is particularly relevant for the forensic, medical or recreative industry to have a rapid, inexpensive, and reliable methodology to identify and quantify phytocannabinoids. Furthermore, spiking cannabis products with Δ8-tetrahydrocannabinol (THC) is a contemporary trend that demands improving or replacing current methods to include this cannabinoid. The current study presents an ultrasound-assisted solid-liquid extraction followed by high-performance liquid chromatography with diode array detection (HPLC-DAD) methodology to identify and quantify Δ9-THC, Δ8-THC, cannabidiol, cannabinol, Δ9-tetrahydrocannabinolic acid and cannabidiolic acid in cannabis products. The herbal samples were extracted with ethanol:acetonitrile (50:50, v:v) by ultrasonication using only 50 mg of sample. The plant oils were diluted in ethanol. The optimised procedure allowed ≈100% extraction efficiency of the target cannabinoids. The validation assays showed that the method is linear (R2 > 0.997), selective, sensitive, precise and accurate, with suitable limits of detection (0.125–0.250 µg mL−1) and quantification (0.500 µg mL−1). The method was successfully applied to cannabis samples, demonstrating its suitability for routine analyses. This contribution follows the current demand for fast and straightforward analysis services of this plant and its derivatives, using small amounts of sample. The present study compares very favourably against other works, particularly in regards to the extraction efficiency, speed of the overall procedure, method sensitivity, and ability to monitor Δ8-THC spiked samples using a novel solvent mixture.
- Development of green approaches for preconcentration of local anesthetics in biological matricesPublication . Pereira, Joana; Rocha, Daniela C.; Neng, Nuno R.; Torres, M. Edite; Quintas, Alexandre; Ahmad, Samir M.Poster presented at the CQE Days - 5º encontro anual do Centro de Química Estrutural do Instituto Superior Técnico da Universidade de Lisboa. Lisboa, 25-26 may 2023
- Development of green methodologies for pre-concentration of local anaesthetics in biological matricesPublication . Pereira, Joana; Rocha, Daniela C.; Neng, Nuno R.; Torres, M. Edite; Quintas, Alexandre; Ahmad, Samir M.Poster presented at the 6th International Congress of CiiEM—Immediate and Future Challenges to Foster One Health. Monte de Caparica, 5-7 july 2023