Export 112 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
Moreira, IP, Esteves C, Palma SICJ, Ramou E, Carvalho ALM, Roque ACA.  2022.  Synergy between silk fibroin and ionic liquids for active gas-sensing materials, jun. Materials Today Bio. 15:100290.: Elsevier AbstractPDFWebsite

Silk fibroin is a biobased material with excellent biocompatibility and mechanical properties, but its use in bioelectronics is hampered by the difficult dissolution and low intrinsic conductivity. Some ionic liquids are known to dissolve fibroin but removed after fibroin processing. However, ionic liquids and fibroin can cooperatively give rise to functional materials, and there are untapped opportunities in this combination. The dissolution of fibroin, followed by gelation, in designer ionic liquids from the imidazolium chloride family with varied alkyl chain lengths (2–10 carbons) is shown here. The alkyl chain length of the anion has a large impact on fibroin secondary structure which adopts unconventional arrangements, yielding robust gels with distinct hierarchical organization. Furthermore, and due to their remarkable air-stability and ionic conductivity, fibroin ionogels are exploited as active electrical gas sensors in an electronic nose revealing the unravelled possibilities of fibroin in soft and flexible electronics.

Esteves, C, Palma SICJ, Costa HMA, Alves C, Santos GMC, Ramou E, Carvalho AL, Alves V, Roque ACA.  2022.  Tackling Humidity with Designer Ionic Liquid-Based Gas Sensing Soft Materials, dec. Advanced Materials. 34:2107205., Number 8: John Wiley & Sons, Ltd AbstractPDFWebsite

Relative humidity is simultaneously a sensing target and a contaminant in gas and volatile organic compound (VOC) sensing systems, where strategies to control humidity interference are required. An unmet challenge is the creation of gas-sensitive materials where the response to humidity is controlled by the material itself. Here, humidity effects are controlled through the design of gelatin formulations in ionic liquids without and with liquid crystals as electrical and optical sensors, respectively. In this design, the anions [DCA]− and [Cl]− of room temperature ionic liquids from the 1-butyl-3-methylimidazolium family tailor the response to humidity and, subsequently, sensing of VOCs in dry and humid conditions. Due to the combined effect of the materials formulations and sensing mechanisms, changing the anion from [DCA]− to the much more hygroscopic [Cl]−, leads to stronger electrical responses and much weaker optical responses to humidity. Thus, either humidity sensors or humidity-tolerant VOC sensors that do not require sample preconditioning or signal processing to correct humidity impact are obtained. With the wide spread of 3D- and 4D-printing and intelligent devices, the monitoring and tuning of humidity in sustainable biobased materials offers excellent opportunities in e-nose sensing arrays and wearable devices compatible with operation at room conditions.

Pina, AS, Guilherme M, Pereira AS, Fernandes CSM, Branco RJF, Lowe CR, Roque ACA.  2014.  A tailor made affinity pair “tag-receptor” for the purification of fusion proteins. ChemBioChem. 15(10):1423-35. AbstractWebsite

A novel affinity “tag–receptor” pair was developed as a generic platform for the purification of fusion proteins. The hexapeptide RKRKRK was selected as the affinity tag and fused to green fluorescent protein (GFP). The DNA fragments were designed, cloned in Pet-21c expression vector and expressed in E. coli host as soluble protein. A solid-phase combinatorial library based on the Ugi reaction was synthesized: 64 affinity ligands displaying complementary functionalities towards the designed tag. The library was screened by affinity chromatography in a 96-well format for binding to the RKRKRK-tagged GFP protein. Lead ligand A7C1 was selected for the purification of RKRKRK fusion proteins. The affinity pair RKRKRK-tagged GFP with A7C1 emerged as a promising solution (Ka of 2.45×105 M−1). The specificity of the ligand towards the tag was observed experimentally and theoretically through automated docking and molecular dynamics simulations.

Fernandes, CSM, Pina AS, Dias AMGC, Branco RJF, Roque ACA.  2014.  A theoretical and experimental approach toward the development of affinity adsorbents for GFP and GFP-fusion proteins purification. Journal of Biotechnology. 186:13-20. AbstractWebsite

The green fluorescent protein (GFP) is widely employed to report on a variety of molecular phenomena, but its selective recovery is hampered by the lack of a low-cost and robust purification alternative. This work reports an integrated approach combining rational design and experimental validation toward the optimization of a small fully-synthetic ligand for GFP purification. A total of 56 affinity ligands based on a first-generation lead structure were rationally designed through molecular modeling protocols. The library of ligands was further synthesized by solid-phase combinatorial methods based on the Ugi reaction and screened against Escherichia coli extracts containing GFP. Ligands A4C2, A5C5 and A5C6 emerged as the new lead structures based on the high estimated theoretical affinity constants and the high GFP binding percentages and enrichment factors. The elution of GFP from these adsorbents was further characterized, where the best compromise between mild elution conditions, yield and purity was found for ligands A5C5 and A5C6. These were tested for purifying a model GFP-fusion protein, where ligand A5C5 yielded higher protein recovery and purity. The molecular interactions between the lead ligands and GFP were further assessed by molecular dynamics simulations, showing a wide range of potential hydrophobic and hydrogen-bond interactions.

Semeano, ATS, Maffei DF, Palma S, Li RWC, Franco BDGM, Roque ACA, Gruber J.  2018.  Tilapia fish microbial spoilage monitored by a single optical gas sensor. Food Control. 89:72-76. AbstractPDFWebsite

As consumption of fish and fish-based foods increases, non-destructive monitoring of fish freshness also becomes more prominent. Fish products are very perishable and prone to microbiological growth, not always easily detected by organoleptic evaluation. The analysis of the headspace of fish specimens through gas sensing is an interesting approach to monitor fish freshness. Here we report a gas sensing method for monitoring Tilapia fish spoilage based on the application of a single gas sensitive gel material coupled to an optical electronic nose. The optical signals of the sensor and the extent of bacterial growth were followed over time, and results indicated good correlation between the two determinations, which suggests the potential application of this simple and low cost system for Tilapia fish freshness monitoring.

Pina, AS, Carvalho S, Dias AMGC, Guilherme M, Pereira AS, Caraça LT, Coroadinha AS, Lowe CR, Roque ACA.  2016.  Tryptophan tags and de novo designed complementary affinity ligands for the expression and purification of recombinant proteins. Journal of Chromatography A. 1472:55–65. AbstractWebsite

A common strategy for the production and purification of recombinant proteins is to fuse a tag to the protein terminal residues and employ a “tag-specific” ligand for fusion protein capture and purification. In this work, we explored the effect of two tryptophan-based tags, NWNWNW and WFWFWF, on the expression and purification of Green Fluorescence Protein (GFP) used as a model fusion protein. The titers obtained with the expression of these fusion proteins in soluble form were 0.11 mg ml−1 and 0.48 mg ml−1 for WFWFWF and NWNWNW, respectively. A combinatorial library comprising 64 ligands based on the Ugi reaction was prepared and screened for binding GFP-tagged and non-tagged proteins. Complementary ligands A2C2 and A3C1 were selected for the effective capture of NWNWNW and WFWFWF tagged proteins, respectively, in soluble forms. These affinity pairs displayed 106 M−1 affinity constants and Qmax values of 19.11 ± 2.60 ug g−1 and 79.39 ug g−1 for the systems WFWFWF AND NWNWNW, respectively. GFP fused to the WFWFWF affinity tag was also produced as inclusion bodies, and a refolding-on column strategy was explored using the ligand A4C8, selected from the combinatorial library of ligands but in presence of denaturant agents.

Hussain, A, Semeano ATS, Palma SICJ, Pina AS, Almeida J, Medrado BF, Pádua ACCS, Carvalho AL, Dionísio M, Li RWC, Gamboa H, Ulijn RV, Gruber J, Roque ACA.  2017.  Tunable Gas Sensing Gels by Cooperative Assembly. Advanced Functional Materials. 1700803:1–9. AbstractPDFWebsite

The cooperative assembly of biopolymers and small molecules can yield functional materials with precisely tunable properties. Here, the fabrication, characterization, and use of multicomponent hybrid gels as selective gas sensors are reported. The gels are composed of liquid crystal droplets self-assembled in the presence of ionic liquids, which further coassemble with biopolymers to form stable matrices. Each individual component can be varied and acts cooperatively to tune gels' structure and function. The unique molecular environment in hybrid gels is explored for supramolecular recognition of volatile compounds. Gels with distinct compositions are used as optical and electrical gas sensors, yielding a combinatorial response conceptually mimicking olfactory biological systems, and tested to distinguish volatile organic compounds and to quantify ethanol in automotive fuel. The gel response is rapid, reversible, and reproducible. These robust, versatile, modular, pliant electro-optical soft materials possess new possibilities in sensing triggered by chemical and physical stimuli.

Branco, RJF, Dias AMGC, Roque ACA.  2012.  Understanding the molecular recognition between antibody fragments and protein A biomimetic ligand. Journal of Chromatography A. 1244:106-115. AbstractWebsite

Affinity chromatography with protein A from Staphylococcus aureus (SpA) is the most widespread and
accepted methodology for antibody capture during the downstream process of antibody manufacturing.
A triazine based ligand (ligand 22/8) was previously developed as an inexpensive and robust alternative
to SpA chromatography (Li et al. [12] and Teng et al. [11]). Despite the experimental success, there is no
structural information on the binding modes of ligand 22/8 to antibodies, namely to Immunoglobulin G
(IgG) molecules and fragments. In this work, we addressed this issue by a molecular docking approach
allied to molecular dynamics simulations. Theoretical results confirmed the preference of the synthetic
ligand to bind IgG through the binding site found in the crystallographic structure of the natural complex
between SpA and the Fc fragment of IgG. Our studies also suggested other unknown “hot-spots” for
specific binding of the affinity ligand at the hinge between VH and CH1 domains of Fab fragment. The best
docking poses were further analysed by molecular dynamics studies at three different protonation states
(pH 3, 7 and 11). The main interactions between ligand 22/8 and the IgG fragments found at pH 7 were
weaker at pH 3 and pH 11 and in these conditions the ligand start losing tight contact with the binding
site, corroborating the experimental evidence for protein elution from the chromatographic adsorbents
at these pH conditions.

Palma, SI, Rodrigues CA, Carvalho A, Morales PM, Freitas F, Fernandes AR, Cabral JS, Roque ACA.  2015.  A value-added exopolysaccharide as a coating agent for MRI nanoprobes. Nanoscale. (7):14272-14283. AbstractWebsite

Fucopol, a fucose-containing exopolysaccharide (EPS) produced by the bacterium Enterobacter A47 DSM 23139 using glycerol as a carbon source, was employed as a new coating material for iron oxide magnetic nanoparticles (MNP). The coated particles were assessed as nanoprobes for cell labeling by Magnetic Resonance Imaging (MRI). The MNP were synthesized by a thermal decomposition method and transferred to aqueous medium by ligand-exchange reaction with meso-2,3-dimercaptosuccinic acid (DMSA). Covalent binding of EPS to DMSA-stabilized nanoparticles (MNP-DMSA) resulted in a hybrid magnetic-biopolymeric nanosystem (MNP-DMSA-EPS) with a hydrodynamic size of 170 nm, negative surface charge at physiological conditions and transverse to longitudinal relaxivities ratio, r2/r1, of 148. In vitro studies with two human cell lines (colorectal carcinoma - HCT116 - and neural stem/progenitor cells - ReNcell VM) showed that EPS promotes internalization of nanoparticles in both cell lines. In vitro MRI cell phantoms also showed superior performance of MNP-DMSA-EPS in ReNcell VM, for which iron dose-dependent MRI signal drop was obtained at relatively low iron concentrations (12 - 20 µg Fe/ml) and short incubation time. Furthermore, ReNcell VM multipotency was not affected by culture in the presence of MNP-DMSA or MNP-DMSA-EPS for 14 days. Our study suggests that Fucopol-coated MNP represent useful cell labeling nanoprobes for MRI.

Padrão, I, Fernandes CSM, Esteves C, Fernandes T, Pina AS, Roque ACA.  2020.  Versatile and Tunable Poly(Ethylene Glycol)‐Based Hydrogels Crosslinked through the Ugi Reaction. ChemPlusChem. 85(12):2737-2741.
Esteves, C, Palma S, Costa H, Alves C, Santos G, Ramou E, Roque AC.  2022.  VOC Sensing in Humid and Dry Environments, may. 2022 IEEE International Symposium on Olfaction and Electronic Nose (ISOEN). :1–3.: IEEE AbstractPDFWebsite

We report the development of gas-sensing multicomponent hybrid materials to be used under humidified and dried environments without the need of sample preconditioning or heavy signal processing. The easy tunability and the unique characteristics presented by the multicomponent hybrid materials suggests their use in nearterm applications in electronic nose systems able to operate in dry or humidified environments.

Batalha, IL, Lychko I, Branco RJF, Iranzo O, Roque ACA.  2019.  β-Hairpins as peptidomimetics of human phosphoprotein-binding domains. Organic & Biomolecular Chemistry. 17:3996-4004. AbstractWebsite

Phosphoprotein-binding domains interact with cognate phosphorylated targets ruling several biological processes. The impairment of such interactions is often associated with disease development, namely cancer. The breast cancer susceptibility gene 1 (BRCA1) C-terminal (BRCT) domain is involved in the control of complex signaling networks of the DNA damage response. The capture and identification of BRCT-binding proteins and peptides may be used for the development of new diagnostic tools for diseases with abnormal phosphorylation profiles. Here we show that designed cyclic β-hairpin structures can be used as peptidomimetics of the BRCT domain, with high selectivity in binding to a target phosphorylated peptide. The amino acid residues and spatial constraints involved in the interaction between a phosphorylated peptide (GK14-P) and the BRCT domain were identified and crafted onto a 14-mer β-hairpin template in silico. Several cyclic peptides models were designed and their binding towards the target peptide and other phosphorylated peptides evaluated through virtual screening. Selected cyclic peptides were then synthesized, purified and characterized. The high affinity and selectivity of the lead cyclic peptide towards the target phosphopeptide was confirmed, and the possibility to capture it using affinity chromatography demonstrated. This work paves the way for the development of cyclic β-hairpin peptidomimetics as a novel class of affinity reagents for the highly selective identification and capture of target molecules.