Centro de Química Estrutural

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Publications

Contamination analysis of Arctic ice samples as planetary field analogs and implications for future life-detection missions to Europa and Enceladus

Publication . Coelho, Lígia F.; Blais, Marie-Amélie; Matveev, Alex; Keller-Costa, Tina; Vincent, Warwick F.; Da Silva Costa, Rodrigo; Martins, Zita; Canário, João

Missions to detect extraterrestrial life are being designed to visit Europa and Enceladus in the next decades. The contact between the mission payload and the habitable subsurface of these satellites involves significant risk of forward contamination. The standardization of protocols to decontaminate ice cores from planetary field analogs of icy moons, and monitor the contamination in downstream analysis, has a direct application for developing clean approaches crucial to life detection missions in these satellites. Here we developed a comprehensive protocol that can be used to monitor and minimize the contamination of Arctic ice cores in processing and downstream analysis. We physically removed the exterior layers of ice cores to minimize bioburden from sampling. To monitor contamination, we constructed artificial controls and applied culture-dependent and culture-independent techniques such as 16S rRNA amplicon sequencing. We identified 13 bacterial contaminants, including a radioresistant species. This protocol decreases the contamination risk, provides quantitative and qualitative information about contamination agents, and allows validation of the results obtained. This study highlights the importance of decreasing and evaluating prokaryotic contamination in the processing of polar ice cores, including in their use as analogs of Europa and Enceladus.

2022Journal article

Open access

NaCl elicitation enhances metabolite accumulation and stress resilience in Inula crithmoides L. shoot cultures: implications for its nutritional and medicinal value

Publication . Rodrigues, Maria João; Neng, Nuno; Custódio, Luísa

This study explored the impact of sodium chloride (NaCl) elicitation on the accumulation of primary and secondary metabolites and the oxidative stress responses of Inula crithmoides L. (golden samphire) in vitro shoot cultures. Elicitation involved applying different concentrations of NaCl (0, 50, 100, and 200 mM) for 4 weeks. This was followed by assessing its impact on plant growth, physiological parameters (pigments, hydrogen peroxide content, total soluble sugars and proteins, and proline), and secondary metabolism (phenylalanine ammonia-lyase activity, shikimic acid, phenolics, flavonoids, and hydroxycinnamic acids) in the shoots. The extracts were also analysed using high-performance liquid chromatography (HPLC). The NaCl elicitation did not affect shoot growth but increased physiological functions such as photosynthesis and oxidative stress management under moderate salinity levels. In addition, NaCl treatments increased the synthesis of soluble sugars and proteins, particularly proline, as well as bioactive phenolics such as gentisic acid, chlorogenic acid, 4-hydroxybenzoic acid, luteolin-7-O-glucoside, and naringenin-7-O-glucoside. The NaCl elicitation in golden samphire shoot cultures offers a significant method for enhancing the production of important nutritional and bioactive compounds. This underscores the species' potential for cultivation in saline environments and provides valuable prospects for its utilization in the health and nutrition sectors.

2024-04Journal article

Open access

The role of undecenoic acid on the preparation of cecorated MCM-41/Polyethylene hybrids by In situ polymerization: Catalytic aspects and properties of the resultant materials

Publication . Cerrada, María L.; Bento, Artur; Pérez, Ernesto; Lourenço, João P.; Ribeiro, M. Rosário

Functionalized polyethylene-based nanocomposites were prepared by in situ polymerization of ethylene with modified or neat MCM-41 nanoparticles (NMCM-41). Two different synthetic approaches were investigated to improve the compatibility between the hydrophobic HDPE matrix and the hydrophilic NMCM-41: (i) incorporation of UA into the polymeric matrix by copolymerization with ethylene, promoted by the zirconocene catalyst under homogeneous conditions, in the presence of pristine NMCM-41; (ii) use of undecenoic acid (UA) as an interfacial agent to obtain decorated NMCM-41 to be used as nanofiller for the in situ ethylene polymerization, catalyzed by Cp2ZrCl2/MAO under supported conditions. The strong polar character of the carboxylic group is expected to either increase the hydrophilicity of the HDPE chains (strategy i) or interact with the NMCM-41 surface and provide an additional link to the polymeric chains via copolymerization of the vinyl group under supported conditions (strategy ii). Although metallocene catalysts have been shown to copolymerize olefins with functional monomers, the presence of oxygen-containing compounds in the reaction media strongly affects the polymerization activity as a result of the interaction of functional groups with the electrophilic active center of the catalyst. Thus, UA was pre-contacted with tri(isobutyl)aluminum (TIBA) prior to its use in the polymerization to reduce the deactivating character of the carboxylic acid groups towards the zirconocene catalyst. The influence of the UA presence on the polymerization behavior of the protection step is discussed, and the polymerization activities observed for the different approaches are compared. In addition, the thermal behavior and structural details of the resulting materials have been characterized. The impact of using neat or functionalized NMCM-41 on the final dispersion within the polymeric matrix is also analyzed, which is correlated with the mechanical performance exhibited by these HDPE_UA_NMCM-41 nanocomposites.

2023-08-02

Open access

Ethylene removal with metals-based zeolites for climacteric fruits preservation

Publication . Ferreira, R.; Lopes, H.; Fernandes, A.; Lourenço, João P.; Silva, J. M.; João, I. M.; Ribeiro, Filipa

Nowadays, there is a high importance of consuming fresh fruits and vegetables (F&V) in a well-balanced diet. One main issue concerning fruit preservation is ethylene molecule, a natural plant hormone that is responsible for fruits ripening and senescence. Thus, its removal from transportation and cold storage chambers is essential for industrial companies to prevent deterioration or spoilage of F&V and extend their post-harvest life [1].

2022-07-03Conference object

Open access

A novel approach for preparation of nanocomposites with an excellent rigidity/deformability balance based on reinforced HDPE with halloysite

Publication . Cecílio, Duarte M.; Cerrada, Maria L.; Pérez, Ernesto; Fernandes, Auguste; Lourenço, João P.; McKenna, Timothy F. L.; Ribeiro, M. Rosário

An innovative approach, designated as supported activator (SA), allows preparation of high density polyethylene (HDPE)-based highly performant hybrid materials. This procedure makes use of a nano-sized supported methylaluminoxane (MAO)-activator, based on halloysite natural nanotubes (HNT), combined with an in situ supporting concept. The new protocol when compared with a more conventional approach gives rise to higher polymerization activities as well as ultimate materials with better morphological features, greater crystallinity, thicker crystals, and highly increased stiffness. Moreover, a remarkable synergy between rigidity and toughness is attained. The Young’s modulus of a film obtained from the nanocomposite with the highest HNT content increases more than 70 % relatively to a pristine HDPE film, while retaining the limit stretching ability of pristine HDPE (more than 800%). A beneficial impact of using a high aspect ratio support such as HNT in the mechanical properties is also observed, when compared to similar HDPE hybrid materials derived from dendrimer-like silica (DS) nanospheres. Interestingly, polymerization activity, polymer features and derived properties found in the ultimate materials are less impacted by support/filler nature than by preparation method. This fact highlights the crucial role of the synthetic methodology used and corroborates the high potential of the SA route for the preparation of high-performance polyethylene-based nanocomposites with an excellent balance between stiffness and deformability.

2023-02Journal article

Open access