Publications

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2015
The Quest for Anticancer Vaccines: Deciphering the Fine-Epitope Specificity of Cancer-Related Monoclonal Antibodies by Combining Microarray Screening and Saturation Transfer Difference NMR, Coelho, Helena, Matsushita T., Artigas G., Hinou H., Cañada FJ, Lo-Man R., Leclerc C., Cabrita E. J., Jiménez-Barbero J., Nishimura S. - I., Garcia-Martín F., and Marcelo F. , J. Am. Chem. Soc., Volume 137, p.12438-12441, (2015)
Rationalizing the role of the anion in CO2 capture and conversion using imidazolium-based ionic liquid modified mesoporous sílica, Aquino, Aline S., Bernard FL, Borges JV, Mafra Luis, Dalla Vecchia Felipe, Vieira MO, Ligabue R., Chaban VV, Cabrita E. J., and Einloft S. , RSC Advances, Volume 5, p.64220-64227, (2015)
2014
Assessing diffusion in enzyme loaded sol–gel matrices, Barreira, Gustavo, Ferreira Ana S. D., Vidinha Pedro, Cabral Joaquim M. S., Martinho José M. G., Lima João Carlos, Cabrita Eurico J., and Barreiros Susana , RSC Advances, Volume 4, p.25099-25105, (2014) AbstractWebsite

Pulsed field gradient spin echo high resolution magic angle spinning nuclear magnetic resonance spectroscopy is a powerful technique to characterize confined biosystems. We used this approach to assess the diffusion of solvent and reaction species within sol–gel matrices differing in enzyme loading.

Biochemical, Stabilization and Crystallization Studies on a Molecular Chaperone (PaoD) Involved in the Maturation of Molybdoenzymes., Otelo-Cardoso, AR, Schwuchow V., Rodrigues D., Cabrita E. J., Leimkühler S., Romão MJ, and Santos-Silva T. , PLoS One, Volume 9, p.e87295 , (2014) AbstractWebsite

Molybdenum and tungsten enzymes require specific chaperones for folding and cofactor insertion. PaoD is the chaperone of the periplasmic aldehyde oxidoreductase PaoABC. It is the last gene in the paoABCD operon in Escherichia coli and its presence is crucial for obtaining mature enzyme. PaoD is an unstable, 35 kDa, protein. Our biochemical studies showed that it is a dimer in solution with a tendency to form large aggregates, especially after freezing/thawing cycles. In order to improve stability, PaoD was thawed in the presence of two ionic liquids [C4mim]Cl and [C2OHmim]PF6 and no protein precipitation was observed. This allowed protein concentration and crystallization using polyethylene glycol or ammonium sulfate as precipitating agents. Saturation transfer difference – nuclear magnetic resonance (STD-NMR) experiments have also been performed in order to investigate the effect of the ionic liquids in the stabilization process, showing a clear interaction between the acidic ring protons of the cation and, most likely, negatively charged residues at the protein surface. DLS assays also show a reduction of the overall size of the protein aggregates in presence of ionic liquids. Furthermore, cofactor binding studies on PaoD showed that the protein is able to discriminate between molybdenum and tungsten bound to the molybdenum cofactor, since only a Mo-MPT form of the cofactor remained bound to PaoD.

Ion Jelly Conductive Properties Using Dicyanamide-Based Ionic Liquids, Carvalho, T., Augusto V., Rocha A., Lourenco N. M. T., Correia N. T., Barreiros S., Vidinha P., Cabrita E. J., and Dionisio M. , Journal of Physical Chemistry B, Volume 118, Issue 31, p.9445-59, (2014) AbstractWebsite

The thermal behavior and transport properties of several ion jellys (IJs), a composite that results from the combination of gelatin with an ionic liquid (IL), were investigated by dielectric relaxation spectroscopy (DRS), differential scanning calorimetry (DSC), and pulsed field gradient nuclear magnetic resonance spectroscopy (PFG NMR). Four different ILs containing the dicyanamide anion were used: 1-butyl-3-methylimidazolium dicyanamide (BMIMDCA), 1-ethyl-3-methylimidazolium dicyanamide (EMIMDCA), 1-butyl-1-methylpyrrolidinium dicyanamide (BMPyrDCA), and 1-butylpyridinium dicyanamide (BPyDCA); the bulk ILs were also investigated for comparison. A glass transition was detected by DSC for all materials, ILs and IJs, allowing them to be classified as glass formers. Additionally, an increase in the glass transition temperature upon dehydration was observed with a greater extent for IJs, attributed to a greater hindrance imposed by the gelatin matrix after water removal, rendering the IL less mobile. While crystallization is observed for some ILs with negligible water content, it was never detected for any IJ upon thermal cycling, which persist always as fully amorphous materials. From DRS measurements, conductivity and diffusion coefficients for both cations (D+) and anions (D–) were extracted. D+ values obtained by DRS reveal excellent agreement with those obtained from PFG NMR direct measurements, obeying the same VFTH equation over a large temperature range (ΔT ≈ 150 K) within which D+ varies around 10 decades. At temperatures close to room temperature, the IJs exhibit D values comparable to the most hydrated (9%) ILs. The IJ derived from EMIMDCA possesses the highest conductivity and diffusion coefficient, respectively, 10–2 S·cm–1 and 10–10 m2·s–1. For BMPyrDCA the relaxational behavior was analyzed through the complex permittivity and modulus formalism allowing the assignment of the detected secondary relaxation to a Johari–Goldstein process. Besides the relevant information on the more fundamental nature providing physicochemical details on ILs behavior, new doorways are opened for practical applications by using IJ as a strategy to produce novel and stable electrolytes for different electrochemical devices.

2012
Thymus mastichina: Chemical Constituents and their Anti-cancer Activity , Gordo, Joana, Máximo Patrícia, Cabrita Eurico, Lourenço Ana, Oliva Abel, Almeida Joana, Filipe Mariana, Cruz Pedro, Barcia Rita, Santos Miguel, and Cruz Helder , Natural Product Communications, Volume 7, Issue 11, p.1491-1494, (2012)
Understanding the Ion Jelly Conductivity Mechanism, Carvalho, T., Augusto V., Brás A. R., Lourenço N. M. T., Afonso CAM, Barreiros S., Correia N. T., Vidinha P., Cabrita E. J., Dionísio M., and Roling B. , Journal of Physical Chemistry B, Volume 116, p.2664-2676, (2012) Abstract

The properties of the light flexible device, ion jelly, which combines gelatin with an ionic liquid (IL) were recently reported being promising to develop safe and highly conductive electrolytes. This article aims for the understanding of the ion jelly conductive mechanism using dielectric relaxation spectroscopy (DRS) in the frequency range 10−1−106 Hz; the study was complemented with differential scanning calorimetry (DSC) and pulse field gradient nuclear magnetic resonance (PFG NMR) spectroscopy. The room temperature ionic liquid 1-butyl-3-methylimmidazolium dicyanamide (BMIMDCA) used as received (1.9% w/w water content) and with 6.6% (w/w) of water content and two ion jellies with two different ratios BMIMDCA/gelatin/water % (w/w), IJ1 (41.1/46.7/12.2) and IJ3 (67.8/25.6/6.6), have been characterized. A glass transition was detected by DSC for all materials allowing for classifying them as glass formers. For the ionic liquid, it was observed that the glass transition temperature decreases with the increase of water content. While in subsequent calorimetric runs crystallization was observed for BMIMDCA with negligible water content, no crystallization was detected for any of the ion jelly materials upon themal cycling. To the dielectric spectra of all tested materials, both dipolar relaxation and conductivity contribute; at the lowest frequencies, electrode and interfacial polarization highly dominate. Conductivity, which manifests much more intensity relative to dipolar reorientations, strongly evidences subdiffusive ion dynamics at high frequencies. From dielectric measures, transport properties as mobility and diffusion coefficients were extracted. Data treatment was carried out in order to deconvolute the average diffusion coefficients estimated from dielectric data in its individual contributions of cations (D+) and anions (D−). The D+ values thus obtained for IJ3, the ion jelly with the highest IL/gelatin ratio, cover a large temperature range up to room temperature and revealed excellent agreement with direct measurements from PFG NMR, obeying to the same VFT equation. For BMIMDCA6.6%water, which has the same water amount as IJ3, the diffusion coefficients were only estimated from DRS measurements over a limited temperature range; however, a single VFT equation describes both DRS and PFG NMR data. Moreover, it was found that the diffusion coefficients and mobility are similar for the ionic liquid and IJ3, which points to a role of both water and gelatin weakening the contact ion pair, facilitating the translational motion of ions and promoting its dissociation; nevertheless, it is conceivable that a critical composition of gelatin that leads to those properties. The VFT temperature dependence observed for the conductivity was found to be determined by a similar dependence of the mobility. Both conductivity and segmental motion revealed to be correlated as inferred by the relatively low values of the decoupling indexes. The obtained results show that ion jelly could be in fact a very promising material to design novel electrolytes for different electrochemical devices, having a performance close to the IL but presenting an additional stability regarding electrical measurements and resistance against crystallization relative to the bulk ionic liquid.

2009
Influence of feeding strategies of mixed microbial cultures on the chemical composition and microstructure of copolyesters P(3HB-co-3HV) analyzed by NMR and statistical analysis, Ivanova, G., Serafim L. S., Lemos P. C., Ramos A. M., Reis M. A. M., and Cabrita E. J. , Magnetic Resonance in Chemistry, JUN 2009, Volume 47, Number 6, p.497-504, (2009) Abstract
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2007
A new lupene triterpenetriol and anticholinesterase activity of Salvia sclareoides, Rauter, Amelia P., Branco Isabel, Lopes Rui G., Justino Jorge, Silva Filipa V. M., Noronha Joao P., Cabrita Eurico J., Brouard Ignacio, and Bermejo Jaime , Fitoterapia, DEC 2007, Volume 78, Number 7-8, p.474-481, (2007) Abstract
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