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- Activity coefficients of aqueous Hydrochloric acid solutions up to a Molality of 6.0 mol kg-1 at temperatures from (5 to 45) °CPublication . Juusola, Pekka M.; Partanen, Jaakko; Vahteristo, Kari P.; Mendonça, António; Minkkinen, Pentti O.Simple three parameter activity coefficient equation originating from the DebyeHückel theory was used for the calculation of activity coefficients of aqueous hydrochloric acid at temperatures 5-45 °C up to a molality of 6 moI kg-I. N ew data from galvanic ce1ls without a liquid junction were used in the parameter estimations of this equation. These data consist of sets of measurements in the molality range 0.3-6.5 moI kg-I at temperatures 5, 15, 25, 35, and 45°C. It was observed that alI estimated parameters folIow very simple equations with respect to temperature. They are either constant or depend linearly on the temperature. The activity coefficient equation was tested with the celI potential difference data of Hamed and Ehlers (1933), ElIis (1916), Ákerlõf and Teare (1938), and Faita and Mussini (1964). It was observed that the most important data in these sets can be predicted welI by means of the activity coefficient equation. The activity coefficients obtained using the new equation were also compared to those obtained by means of the two-parameter Hückel and Pitzer equations presented by Partanen and Covington (2002) up to molality 2.0 moI kg-t, to those obtained by means of the Pitzer equations presented by Saluja et ai. (1986) and Holmes et ai. (1987), and to those obtained by means of the equation presented by Hamer and Wu (1972) for the temperature of 25°C.
- Electroepoxidation of natural and synthetic alkenes mediated by sodium bromidePublication . Inês, Massuquinini; Mendonça, António; Esteves, Ana P.; Mendonça, Dina; Medeiros, Maria J.Electroepoxidation of synthetic alkenes (styrene, trans-stilbene and trans-b-methylstyrene) and of some natural terpenes (limonene, terpinolene, geraniol, a-terpinene, g-terpinene and a-terpineol) mediated by sodium bromide was performed in MeCN:H2O (4:1) at platinum electrodes. The indirect electrochemical oxidation of the olefins led to the corresponding epoxides in yields ranging from 23% to 79%.
- Phenolic compounds: a novel approach to reduce egg allergenicity?Publication . Vapor, Alcides; Tomaz, Cândida T.; Mendonça, AntónioHen's egg allergy has been climbing in all countries due to eggs ubiquity in foodstuffs. This allergy is an IgE mediated reaction that affects mainly infants and young children. So far, the processes used to decrease the allergenicity of egg proteins, such as cooking, thermal processing, storage and enzymatic digestion have not been totally effective. Previous studies demonstrated that proteins form complexes with phenolic compounds, so the aim of this work was to analyze the effect of these compounds in ovalbumin (OVA) conformation and its possible application to reduce eggs allergenicity. OVA was incubated at different temperatures with phenolic compounds (caffeic, chlorogenic, ferulic, gallic and tannic acids; resveratrol and quercetin) and was analyzed by circular dichroism (CD), Attenuated Total Reflection–Fourier Transform Infra-Red (ATRFTIR) spectroscopy and fluorescence. Changes in the secondary structure of OVA were evidenced by CD and ATR-FTIR. Also, protein fluorescence decreased with increasing concentrations of phenolic compounds. The thermodynamic analysis suggested that electrostatic interactions are important in the binding process, and the quenching mechanism occur by contact. This was confirmed by docking where the phenolic compounds bind specifically to some regions of the protein, including those with the allergenic epitopes.
- Kolbe Electrosynthesis of 1,2-Di(bicyclo[2.2.1]heptan-2-yl)ethane and 1,2-DiphenylethanePublication . Mendonça, António; Inês, Massuquinini; Esteves, Ana P.; Mendonça, Dina; Medeiros, Maria J.Kolbe electrosynthesis, at low current densities, of 1,2-diphenylethane and 1,2-di(bicyclo[2.2.1]heptan-2-yl)ethane with 77 and 72% yields, respectively, is described.
- Activity coefficients in the evaluation of food preservativesPublication . Mendonça, António; Vaz, Margarida I. P. M.; Mendonça, DinaFood preservatives are used in very low concentrations. However, usually they are used in aqueous high ionic strength solutions. The Pitzer model allows activity coefficient determination in these cases. Without the knowledge of activity coefficients, activity or ‘correct concentration’ cannot be known. In this work, the activity coefficients of sodium chloride, potassium chloride and calcium chloride in pure solutions were calculated by the Debye H¨uckel theory and the Pitzer theory. The calculated values were compared with experimental values. Activity coefficients of pure sodium benzoate in aqueous mixed solutions with potassium chloride or calcium chloride were evaluated using the Pitzer model. The same evaluation can be done to more complex systems once all Pitzer parameters values for the ionic species are known.
- Breast cancer targeted photothermal therapy mediated by hyaluronic acid functionalized reduced graphene oxidePublication . Sousa, Ana Rita Lima; Diogo, Duarte de Melo; Alves, Cátia Gomes; Costa, Elisabete; Louro, Ricardo; Mendonça, António G.; Correia, I.J.The use of graphene-based nanomaterials in cancer photothermal therapy (PTT) is an emerging alternative to the currently available cancer treatments. In this regard, reduced graphene oxide (rGO) has been widely explored for cancer PTT due to its excellent photothermal capacity. However, rGO has some limitations, such as low colloidal stability and water insolubility, as well as absence of targeting capacity towards cancer cells. Herein, rGO produced by an environmentally- friendly method was functionalized with an amphiphilic polymer based on hyaluronic acid (HA-rGO) through hydrophobic-hydrophobic interactions for application in targeted breast cancer PTT. The functionalization improved rGO colloidal stability and cytocompatibility towards normal and breast cancer cells, as well as conferred targeting capacity towards CD44 overexpressing breast cancer cells. In addition, the photothermal effect mediated by HA-rGO upon laser irradiation reduced breast cancer cells’ viability. Overall, HA-rGO demonstrated a great potential for being used on-demand and selective treatment of breast cancer cells.
- Combining Photothermal‐Photodynamic Therapy Mediated by Nanomaterials with Immune Checkpoint Blockade for Metastatic Cancer Treatment and Creation of Immune MemoryPublication . Sousa, Rita Lima; Melo, Bruna L.; Alves, Cátia; Moreira, André; Mendonça, António; Correia, I.J.; Diogo, Duarte de MeloThe pursuit of effective treatments for metastatic cancer is still one of the most intensive areas of research in the biomedical field. In a not-so-distant past, the scientific community has witnessed the rise of immunotherapy based on immune checkpoint inhibitors (ICIs). This therapeutic modality intends to abolish immunosuppressive interactions, re-establishing T cell responses against metastasized cancer cells. Despite the initial enthusiasm, the ICIs were later found to be associated with low clinical therapeutic outcomes and immune-related side effects. To address these limitations, researchers are exploring the combination of ICIs with nanomaterial-mediated phototherapies. These nanomaterials can accumulate within the tumor and produce, upon interaction with light, a temperature increase (photothermal therapy) and/or reactive oxygen species (photodynamic therapy), causing damage to cancer cells. Importantly, these photothermal-photodynamic effects can pave the way for an enhanced ICI-based immunotherapy by inducing the release of tumor-associated antigens and danger-associated molecular patterns, as well as by relieving tumor hypoxia and triggering a pro-inflammatory response. This progress report analyses the potential of nanomaterial-mediated photothermal-photodynamic therapy in combination with ICIs, focusing on their ability to modulate T cell populations leading to an anti-metastatic abscopal effect and on their capacity to generate immune memory that prevents tumor recurrence.
- A Introdução à Qualidade no Currículo de Química Analítica: Necessidades e MotivaçãoPublication . Mendonça, AntónioA Qualidade na sociedade moderna é uma exigência, não só às empresas mas também aos profissionais. Deste modo, as exigências colocadas aos novos licenciados vão para além dos seus conhecimentos de Qualidade adquiridos nos currículos clássicos de Química Analítica. Existem excelentes manuais de Química Analítica, como o de Valcárcel [l] ou o de Kellner et ai. [2], que colocam o tema da Qualidade numa posição importante. Infelizmente, nem sempre é possível efectuar o estudo aprofundado da Qualidade no currículo de Química Analítica, sobretudo quando os alunos não pertencem a licenciaturas em Química ou em variantes desta, dado que existem outras matérias a ser leccionadas e que não podem ser menosprezadas. Valcárcel [l] sugere diferentes conteúdos a leccionar de acordo com o nível de compreensão desejado, que ocuparão pelo menos, 20 a 30 horas, o que corresponderia na prática à ocupação quase que exclusiva de uma disciplina semestral. Neste trabalho, apresenta-se uma proposta para a inclusão no currículo de Química Analítica de , licenciaturas, não nucleares em Química, de uma Introdução à Qualidade. Partindo de casos práticos justifica-se a necessidade de normalização e daí progride-se no sentido da Qualidade em Química, figura l. Espera-se deste modo motivar os alunos para a importância da Química Analítica no âmbito da Qualidade.
- Characterization of physicochemical parameters of “amarelo da beira baixa”Publication . Santos, Tomás; Resende, M.; Mendonça, António; Estevinho, Letícia M.; Paulo, Luísa; Anjos, Ofélia“Amarelo da Beira Baixa” cheese is a cured cheese, produced with raw milk from sheep’s or sheep’s and goat’s, with a semi-hard or semi-soft paste and characterized by a yellow color. It is produced in the central region of Portugal, namely Castelo Branco, with a Protected Designation of Origin (PDO). These cheeses represent 52.6% of the cheeses from Beira Baixa region, which accounting for 25% of the Portugal cheese production. This work aimed to compare the physicochemical parameters (colour, pH, ashes, salt, moisture content, protein, total lipids, profile of saturated and unsaturated fatty acids, carbohydrates and energetic value) for PDO cheeses (n=34) and cheeses without certification (n=26). The mean values and standard deviations, respectively, that characterize these PDO cheeses for each parameter are: colour (L*: 73,08±10,37; a*: -3,4±1,2; b*: 18,5±4,4), pH: 5.44±0.25; ashes: 4.06±0.56%; salt: 2.34±0.61 g/100 g; moisture content: 42.92±4.34%; protein: 20.98±1.11%; total lipids: 31.23±3.67%; carbohydrates: 0.81±0.74% and energetic value: 368.3±35.4 kcal. The profile of saturated are (SFA) 18.6±1.9 % and unsaturated fatty acids are MUFA: 8.8± 0.5 % and PUFA: 1.4± 0.3 %, also relatively to PDO cheeses. Only the parameters moisture content/dry extract, protein, pH and two fatty acids (C18:2 and C20:0) present significant differences (Scheffe test with α=0.05) for PDO cheeses compared to those without certifications. The results present in this study denoting a good production process of “Amarelo da Beira Baixa” cheeses, in this region, and that more producer could be aggregated to the PDO.
- Interactions of Phenolic Compounds with OvalbuminPublication . Vapor, Alcides; Tomaz, Cândida T.; Mendonça, AntónioOvalbumin (OVA) is the major protein in egg white and can cause allergy mainly in infants and young children [1]. Egg allergy is an IgE mediated reaction and is one the most common food allergies. So far, the avoidance of the egg has been the unique way to prevent this allergy [2]. It is well known that phenolic compounds can bind to proteins promoting structural and functional changes. In this work, the interactions between OVA and the phenolic compounds were studied through spectroscopic techniques (fluorescence, circular dichroism (CD), Fourier transform infrared spectroscopy (FTIR)) and docking. OVA solutions were incubated at different temperatures and times, with different phenolic compounds prepared with the same buffer solution (Gallic, Caffeic, Ferulic, Chlorogenic and Tannic Acids, Resveratrol and Quercetin). Results indicate that OVA's structure was affected by the binding of phenolic compounds. CD and FTIR experiments showed changes in the secondary structure of OVA, originated by the conversion of α-helix into β-sheets [1]. Fluorescence spectra demonstrated that phenolics are quenchers of fluorescent aminoacids (Tyrosine, Phenylalanine and Tryptophan) meaning that interactions occur directly or near these aminoacids. Fluorescence results also suggest that these interactions are electrostatic and thermodynamically favorable (∆G<0). Docking studies showed that the tested phenolic compounds can interact directly with OVA epitopes, or with its neighbors, thus avoiding the IgE binding. Therefore, the phenolic compounds can be used as a strategy for reducing egg allergy in foods.