Percorrer por autor "Basílio, Nuno"
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- 2-Hydroxychalcone−β-Cyclodextrin Conjugate with pH-Modulated Photoresponsive Binding PropertiesPublication . Paulino, Micael; Pérez-Juste, Ignacio; Cid, María Magdalena; Da Silva, José Paulo; Pereira, M. Manuela A.; Basílio, NunoStimuli-responsive supramolecular receptors are important building blocks for the construction of self-assembled functional materials. We report the design and synthesis of a pH and light-responsive 2-hydroxychalcone-beta-cyclodextrin conjugate (1-Ct) and its characterization by spectroscopic and computational methods. 1-Ct follows the typical reaction network of trans-chalcone-flavylium photoswitches. Upon light irradiation, 1-Ct can be photochemically converted into the cis-chalcone/hemiketal forms (1-Cc/1-B) under neutral pH conditions or to the flavylium cation (1-AH+) at acidic pH values. This stimuli-responsive beta-cyclodextrin host, 1Ct, was found to form stronger intramolecular self-inclusion complexes (Kintra = 14) than 1-AH+ (Kintra = 3) and weaker than 1-Cc/1-B (overall Kintra = 179), allowing control over their stability and binding properties by combinations of pH and light stimuli.
- Cooperative assembly of discrete stacked aggregates driven by supramolecular host-guest complexationPublication . Basílio, Nuno; Piñeiro, Ángel; Silva, José P. da; García-Río, Luísp-Sulfonatocalix[4]arene (SC4) interacts with the aromatic dye crystal violet (CV) to form complexes with stoichiometries ranging from SC4:CV = 1:1 up to 1:5 both in solution and in the gas phase. While the 1:1 complex is of the inclusion type, as frequently observed for other guests, in the higher-order complexes the CV molecules interact with SC4 in a peripheral manner. The formation of such complexes is driven by ionic interactions established between the dye and the calixarene and by CV-CV stacking interactions. The application of an advanced fitting procedure made possible a quantitative analysis of the UV-vis data and allowed the determination of the stepwise binding constants. This unprecedented approach provides evidence that the formation of the highest-order complexes occurs through a cooperative mechanism. Moreover, the development of a quantitative analytical model enables the possibility of using this type of system for water-soluble sensing assays, as is also exemplified in the present work. © 2013 American Chemical Society.
- How reliable is the evaluation of DNA binding constants? insights and best practices based on an inter-laboratory fluorescence titration studyPublication . Dömötör, Orsolya; Binacchi, Francesca; Ribeiro, Nádia; Busto, Natalia; Gonzalez-García, Jorge; Garcia-España, Enrique; Correia, Isabel; Enyedy, Éva A.; Hamacek, Josef; Terenzi, Alessio; Basílio, Nuno; Barone, Giampaolo; PALMA ANTUNES CAVACO, ISABEL MARIA; Biver, TaritaIn all experimental sciences, the precision and reliability of quantitative measurements are paramount. This is particularly true when examining the interactions between small molecules and biomolecules/polyelectrolytes, such as DNAs/RNAs, and yet it is overlooked in most publications of thermodynamic binding parameters. This paper presents findings from COST Action 18202 “Network for Equilibria and Chemical Thermodynamics Advanced Research,” which assessed the consistency of data derived from the interactions of calf-thymus DNA (CT-DNA) with the fluorescent intercalator ethidium bromide (EB) through spectrofluorimetric titrations. We first discuss critical experimental aspects and propose a reference experimental protocol which can be used to calibrate procedures for the determination of nucleic acid binding equilibrium constants. We then fit the experimental points according to different procedures and analyse the results focusing on the statistical dispersion of the data, aiming at enlightening the strong and weak points of different fitting procedures. The implications of this work are significant, demonstrating how the statistical dispersion of experimental data can influence the interpretation of biochemical coordination mechanisms. Our study reveals that, despite rigorous protocol standardization, the determination of binding parameters remains sensitive to the choice of data fitting method, with deviations in the logarithmic stability constant (logK) values not falling below 5 % relative standard deviation (RSD), or ± 0.5 logK units for 95 % confidence. This variability evidences the critical need for standardized best practices in data treatment as well as experimental procedures. Although our study focuses on the EB/CT-DNA system through fluorescence titrations, the broader implications for other methodologies across various biochemical systems highlight the importance of this first-of-its-kind inter-laboratory comparison in advancing our understanding of biochemical coordination processes.