QB-Artigos
http://hdl.handle.net/10347/17064
2024-03-28T16:52:03ZFirefly luciferin precursor 2-cyano-6-hydroxybenzothiazole: Fluorescence à la carte controlled by solvent and acidity
http://hdl.handle.net/10347/28829
Firefly luciferin precursor 2-cyano-6-hydroxybenzothiazole: Fluorescence à la carte controlled by solvent and acidity
Jadhav, Ankita S.; Carreira Blanco, Carlos; Fernández Rodríguez, Berta; González Fernández, Sonia; Malkhede, Dipalee D.; Mosquera González, Manuel; Ríos Rodríguez, María del Carmen; Rodríguez-Prieto, Flor
2-Cyano-6-hydroxybenzothiazole (CBTOH) is a key intermediate in the biosynthesis of D-luciferin, also used for its chemical synthesis and as luciferin bioluminescence precursor for chemical analysis. We characterized CBTOH and its O-methylated derivative by UV–vis absorption, by steady-state and time-resolved fluorescence spectroscopy, and by density functional theory (DFT) quantum mechanical calculations. Both the acidity of the hydroxyl group and the basicity of the thiazole nitrogen strongly increase upon electronic excitation, triggering solvent- and acidity-dependent deprotonation and protonation processes, with concomitant changes in the fluorescence properties. DFT and time-dependent DFT calculations revealed the existence of a charge displacement that takes place in the excited state from the phenol moiety to the cyanothiazole group for the neutral and the cationic forms of CBTOH. This study reveals CBTOH as the first member of a new class of small dyes with strong photoacid and photobase character, its rich excited-state behavior allowing modulation of its fluorescence properties through solvent and acidity changes. These features make CBTOH a potentially useful fluorescent probe
2020-01-01T00:00:00ZA surfactant concentration model for the systematic determination of the critical micellar concentration and the transition width
http://hdl.handle.net/10347/27376
A surfactant concentration model for the systematic determination of the critical micellar concentration and the transition width
Al-Soufi, Wajih; Novo Rodríguez, Mercedes
The critical micellar concentration (cmc) is a fundamental property of surfactant solutions. Many proposed methods for the definition and determination of the cmc from property-concentration plots yield values, which depend on the studied property, on the specific technique used for its analysis and in many cases on the subjective choice of the chosen type of plot and concentration interval. In this focus review, we revise the application of a surfactant concentration model we proposed earlier that defines the cmc directly based on the surfactant concentration. Known equations for the concentration-dependence of different surfactant properties can then be combined with this concentration model and fitted to experimental data. This modular concept makes it possible to determine the cmc and the transition width in a systematic and unambiguous way. We revise its use in the literature in different contexts: the determination of the cmc of surfactants and their mixtures from different properties (electrical conductivity, NMR chemical shift, self-diffusion, surface tension, UV-Vis absorption, fluorescence intensity and fluorescence correlation). We also revise the dependence of the width of the transition region on composition, detailed studies of the properties of fluorescent probes and the aggregation of non-surfactant systems, namely amyloid peptides
2021-01-01T00:00:00ZSpectroscopic characterization of mitochondrial G-quadruplexes
http://hdl.handle.net/10347/27375
Spectroscopic characterization of mitochondrial G-quadruplexes
Illodo, Sara; Pérez González, Cibrán; Barcia, Ramiro; Rodriguez-Prieto, Flor ; Al-Soufi, Wajih; Novo Rodríguez, Mercedes
Guanine quadruplexes (G4s) are highly polymorphic four-stranded structures formed within guanine-rich DNA and RNA sequences that play a crucial role in biological processes. The recent discovery of the first G4 structures within mitochondrial DNA has led to a small revolution in the field. In particular, the G-rich conserved sequence block II (CSB II) can form different types of G4s that are thought to play a crucial role in replication. In this study, we decipher the most relevant G4 structures that can be formed within CSB II: RNA G4 at the RNA transcript, DNA G4 within the non-transcribed strand and DNA:RNA hybrid between the RNA transcript and the non-transcribed strand. We show that the more abundant, but unexplored, G6AG7 (37%) and G6AG8 (35%) sequences in CSB II yield more stable G4s than the less profuse G5AG7 sequence. Moreover, the existence of a guanine located 1 bp upstream promotes G4 formation. In all cases, parallel G4s are formed, but their topology changes from a less ordered to a highly ordered G4 when adding small amounts of potassium or sodium cations. Circular dichroism was used due to discriminate different conformations and topologies of nucleic acids and was complemented with gel electrophoresis and fluorescence spectroscopy studies
2022-01-01T00:00:00ZUnveiling the multi-step solubilization mechanism of sub-micron size vesicles by detergents
http://hdl.handle.net/10347/20224
Unveiling the multi-step solubilization mechanism of sub-micron size vesicles by detergents
Dalgarno, Paul A.; Juan-Colás, José; Hedley, Gordon J.; Piñeiro Maseda, Lucas; Novo Rodríguez, María de la Merced; Pérez González, Cibrán; Samuel, Ifor D. W.; Leake, Mark C.; Johnson, Steven; Al-Soufi, Wajih; Penedo, J. Carlos; Quinn, Steven D.
The solubilization of membranes by detergents is critical for many technological applications and has become widely used in biochemistry research to induce cell rupture, extract cell constituents, and to purify, reconstitute and crystallize membrane proteins. The thermodynamic details of solubilization have been extensively investigated, but the kinetic aspects remain poorly understood. Here we used a combination of single-vesicle Förster resonance energy transfer (svFRET), fluorescence correlation spectroscopy and quartz-crystal microbalance with dissipation monitoring to access the real-time kinetics and elementary solubilization steps of sub-micron sized vesicles, which are inaccessible by conventional diffraction-limited optical methods. Real-time injection of a non-ionic detergent, Triton X, induced biphasic solubilization kinetics of surface-immobilized vesicles labelled with the Dil/DiD FRET pair. The nanoscale sensitivity accessible by svFRET allowed us to unambiguously assign each kinetic step to distortions of the vesicle structure comprising an initial fast vesicle-swelling event followed by slow lipid loss and micellization. We expect the svFRET platform to be applicable beyond the sub-micron sizes studied here and become a unique tool to unravel the complex kinetics of detergent-lipid interactions
2019-01-01T00:00:00Z