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
- Bar adsorptive microextraction approach for trace determination of local anesthetics in urine matricesPublication . Pereira, Joana R. P.; Rocha, Daniela C.; Neng, Nuno R.; Maurício, Paulo; Torres, M. Edite; Ahmad, Samir M.; Quintas, AlexandreThe present work reports the development, optimization, and validation, of a methodology to determine lidocaine, procaine, tetracaine, and benzocaine in urine matrices. Two extractive preconcentration techniques, solid-phase microextraction (SPME) LC Tips and bar adsorptive microextraction (BAμE), were studied and applied to the four target anesthetics, followed by gas chromatography-mass spectrometry (GC-MS) analysis. Several parameters that could affect microextraction and back-extraction were optimized using two different designs of experiments (Box–Behnken and full-factorial) to maximize extraction efficiency from aqueous media. Under optimized experimental conditions, the BAμE technique showed better performance than SPME LC Tips and was chosen for validation assays and urine sample analysis. In blank urine, the BAµE/GC-MS methodology revealed suitable sensitivity (LOD between 2 and 18 ng/mL), good linearity (r2 ≥ 0.9945) between 0.5 and 30.0 µg/mL and recovery yields of 30.3–97.9%. Good precision (%RSD ≤ 8.8%) and accuracy (bias % between −15.9 and 15.0%) values were achieved. The developed methodology was successfully applied to the target anesthetics analysis of volunteers’ urine matrices and proved to be an environmentally friendly alternative to monitor trace levels of local anesthetics in complex matrices compared to other extraction techniques.
- Bar adsorptive microextraction for trace determination of natural and semi-synthetic cannabinoids in salivaPublication . Pereira, Maria Beatriz; Sá, Joana M. N.; Justino, Gonçalo C.; Quintas, Alexandre; Neng, Nuno R.Cannabis is the most widely consumed illicit substance worldwide, and the rise of synthetic and semi-synthetic cannabinoids poses growing public health concerns due to their high potency and unpredictable effects. This study presents a new analytical methodology for the simultaneous determination of natural and semi-synthetic cannabinoids (cannabidiol (CDB), Δ8-tetrahydrocannabinol (∆8-THC), Δ9-tetrahydrocannabinol (∆9-THC), and hexahydrocannabinol (HHC)) in saliva using gas chromatography coupled with mass spectrometry (GC-MS) in combination with bar adsorptive microextraction (BAμE) as a green sample preparation. The optimized method showed satisfactory recoveries (57.3–80.6%), low detection and quantification limits (1.25 and 4.13 ng/mL, respectively), excellent linearity (r2 ≥ 0.9963), and robust precision and accuracy. Application to authentic saliva samples demonstrated cannabinoid levels consistent with literature values. Overall, the proposed methodology offers a cost-effective, miniaturized, and environmentally sustainable platform for routine oral fluid cannabinoid analysis, highlighting its potential for forensic, clinical, and toxicological applications.
- 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."
- Collaborative harm reduction efforts lead to the first detection of 5-cyano isotodesnitazene in illicit street drugsPublication . Barra, Bárbara F. C.; Pereira, Joana R. P.; Ferreira, Daniela R.; Oeri, Hans; Martins, Daniel; Almeida, Rui M.; Oatley, Giles; Neng, Nuno R.; Gaspar, Helena; Quintas, AlexandreIn the ongoing opioid crisis, regulatory restrictions on fentanyl and its derivatives have led to the emergence of nitazenes, a class of highly potent synthetic opioids synthesised during the 1950s but never approved for medical use. Structurally distinct from traditional opioids, nitazenes have gained increasing presence in illicit drug markets since 2019, contributing to a growing number of drug-related deaths across Europe, North America, and Australia. The rapid proliferation of novel nitazene analogues presents a significant challenge to law enforcement and public health systems. Drug-checking services (DCS) are currently one of the most effective tool for early detection and response, enabling real-time surveillance and consequently reducing the impact of overdoses due to Novel Synthetic Opioids. As a complement, universities can provide the scientific expertise and infrastructure necessary to confirm molecules detected by DCS. This study is the first report identifying and confirming 5-cyano isotodesnitazene in a street-sold drug, through an international collaboration involving two DCSs and three academic institutions. The structural elucidation was achieved through complementary analytical techniques comprising gas chromatography, mass spectrometry, and nuclear magnetic resonance spectroscopy. The present work highlights the essential role that cross-sector cooperation and analytical innovation play in tackling the rapidly evolving threat of novel synthetic opioids.