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Publications 2018


D-A-D-2H-benzo[d][1,2,3]triazole Derivatives as p-type Semiconductors in Organic Field-effect Transistors.

I. Torres-Moya, I. Arrechea-Marcos, C. Tardío, J. R. Carrillo, A. Díaz-Ortiz, J. Teodomiro López-Navarrete, M. C. Ruiz Delgado, P. Prieto, R. Ponce.

RSC Adv. 2018, 8, 21879-21888.

DOI: 10.1039/c8ra03246g

A series of Donor–π–Acceptor–π–Donor compounds based on a 2H-benzo[d][1,2,3]triazole core branched with different alkynyl donor groups has been characterized and tested in organic field-effect transistors (OFETs). The electronic and molecular structures were elucidated through optical and vibrational spectroscopy in conjunction with DFT calculations. The results indicate that the planarity of the structure and the good intramolecular charge transfer from the electron-donating to the electron-withdrawing fragments play a critical role in the application of the compounds as semiconductors in OFET devices. The compounds were tested in a top-contact/bottom-gate thin film transistor architecture, and they behave as p-type semiconductors.


Self-Assembled Alkynyl Azoles and Benzoazoles as Colored Optical Waveguides.

I. Torres, R. Martín, A. Díaz-Ortiz, P. Prieto, J. R. Carrillo.

Isr. J. Chem. 2018, 58, 827-836.

DOI: 10.1002/ijch.201800030

Different alkynyl azoles and benzoazoles have been synthesized in good yields by carbon‐carbon coupling reactions. The self‐assembly of some of these compounds by the slow diffusion technique led to well‐defined ribbons and needle‐like aggregates. The X‐ray study of some materials showed that the CH‐π interactions involving the C≡C triple bond and the heteroatoms induce aggregation along with H‐bonds due to the methoxy groups. A fluorescence and confocal optical microscopy study of most of the aggregates indicated optical waveguide behavior with different colors.


Photoinduced Palladium‐Catalyzed Negishi Cross‐Couplings Enabled by the Visible‐Light Absorption of Palladium–Zinc Complexes

I. Abdiaj, L. Huck, J. M. Mateo, M. V. Gomez, A. de la Hoz, A. Díaz-Ortiz, J. Alcázar

Angew. Chem. Int. Ed. 201857, 13231 –13236

A visible-light-induced Negishi cross-coupling is enabled by the activation of a Pd0–Zn complex. With this photocatalytic method, the scope of deactivated aryl halides that can be employed in the Negishi coupling was significantly expanded. NMR experiments conducted in the presence and absence of light confirmed that the formation of the palladium–zinc complex is key for accelerating the oxidative addition step.


Visible‐Light‐Induced Nickel‐Catalyzed Negishi Cross‐Couplings by Exogenous‐Photosensitizer‐Free Photocatalysis

 I. Abdiaj, A. Fontana, M. V. Gómez-Almagro, A. de la Hoz, J. Alcázar

Angew. Chem. Int. Ed., 201847, 8473-8477

The merging of photoredox and transition‐metal catalysis has become one of the most attractive approaches for carbon–carbon bond formation. Such reactions require the use of two organo‐transition‐metal species, one of which acts as a photosensitizer and the other one as a cross‐coupling catalyst. We report herein an exogenous‐photosensitizer‐free photocatalytic process for the formation of carbon–carbon bonds by direct acceleration of the well‐known nickel‐catalyzed Negishi cross‐coupling that is based on the use of two naturally abundant metals. This finding will open new avenues in cross‐coupling chemistry that involve the direct visible‐light absorption of organometallic catalytic complexes.


Pushing nuclear magnetic resonance sensitivity limits with microfluidics and photo-chemically induced dynamic nuclear polarization

Among the methods to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy, small-diameter NMR coils (microcoils) are promising tools to tackle the study of mass-limited samples. Alternatively, hyperpolarization schemes based on dynamic nuclear polarization techniques provide strong signal enhancements of the NMR target samples. Here we present a method to effortlessly perform photo-chemically induced dynamic nuclear polarization in microcoil setups to boost NMR signal detection down to sub-picomole detection limits in a 9.4T system (400 MHz 1H Larmor frequency). This setup is unaffected by current major drawbacks such as the use of high-power light sources to attempt uniform irradiation of the sample, and accumulation of degraded photosensitizer in the detection region. The latter is overcome with flow conditions, which in turn open avenues for complex applications requiring rapid and efficient mixing that are not easily achievable on an NMR tube without resorting to complex hardware.


Illumination of Nanoliter-NMR Spectroscopy Chips for Real-Time Photochemical Reaction Monitoring

M. V. Gómez, A. Juan, F. Jiménez-Márquez, A. de la Hoz, A. Velders

Anal. Chem.201890 (3), pp 1542–1546

We report the use of a small-volume nuclear-magnetic-resonance (NMR)-spectroscopy device with integrated fiber-optics for the real-time detection of UV–vis-light-assisted chemical reactions. An optical fiber is used to guide the light from LEDs or a laser diode positioned safely outside the magnet toward the 25 nL detection volume and placed right above the microfluidic channel, irradiating the transparent back of the NMR chip. The setup presented here overcomes the limitations of conventional NMR systems for in situ UV–vis illumination, with the microchannel permitting efficient light penetration even in highly concentrated solutions, requiring lower-power light intensities, and enabling high photon flux. The efficacy of the setup is illustrated with two model reactions activated at different wavelengths.


Colored optical waveguides in self-assembled thiadiazole-based materials

R. Martín, P. Prieto, J. R. Carrillo, I. Torres, C. A. Strassert. K. Soloviova, A. M. Rodríguez, L. Sánchez, A. Díaz-Ortiz.

Dyes Pygments, 2018, 151, 327-334

DOI: 10.1016/j.dyepig.2018.01.001

The photophysical features and waveguiding behavior of two series of thiadiazoles are reported. The different substitution patterns on the thiadiazole moiety (1,3,4- or 1,2,5-system) result in bent and linear molecular geometries in which the peripheral substitution plays a prominent role in their aggregation ability. Thus, only the presence of the 3,4,5-trimethoxyaryl moiety favors the aggregation of thiadiazoles 5 and 8 into crystalline supramolecular structures. The linear geometry and the aggregation of the methoxy-substituted benzo[c][1,2,5]thiadiazole 8 have been corroborated by X-diffraction analysis. The photoluminescence (PL) quantum yields of the aggregated heterocycles 5 and 8 decreases with respect to the PL quantum yield in solution due to an aggregation-caused quenching (ACQ) effect. Despite this ACQ, the crystalline aggregates of both bent and linear thiadiazoles 5 and 8 exhibit waveguiding behavior with different emission colors (red, green and blue).


The Singular NMR Fingerprint of a Polyproline II Helical Bundle

M. Á. Treviño, D. Pantoja-Uceda, M. Menéndez, M. V. Gomez, M. Mompeán, D. V. Laurents.

J. Am. Chem. Soc. 2018, 140, 16988-17000.

DOI: 10.1021/jacs.8b05261

Polyproline II (PPII) helices play vital roles in biochemical recognition events and structures like collagen and form part of the conformational landscapes of intrinsically disordered proteins (IDPs). Nevertheless, this structure is generally hard to detect and quantify. Here, we report the first thorough NMR characterization of a PPII helical bundle protein, the Hypogastrura harveyi “snow flea” antifreeze protein (sfAFP). J-couplings and nuclear Overhauser enhancement spectroscopy confirm a natively folded structure consisting of six PPII helices. NMR spectral analyses reveal quite distinct Hα2 versus Hα3 chemical shifts for 28 Gly residues as well as 13Cα, 15N, and 1HN conformational chemical shifts (Δδ) unique to PPII helical bundles. The 15N Δδ and 1HN Δδ values and small negative 1HN temperature coefficients evince hydrogen-bond formation. 1H–15N relaxation measurements reveal that the backbone structure is generally highly rigid on ps–ns time scales. NMR relaxation parameters and biophysical characterization reveal that sfAFP is chiefly a dimer. For it, a structural model featuring the packing of long, flat hydrophobic faces at the dimer interface is advanced. The conformational stability, measured by amide H/D exchange to be 6.24 ± 0.2 kcal·mol–1, is elevated. These are extraordinary findings considering the great entropic cost of fixing Gly residues and, together with the remarkable upfield chemical shifts of 28 Gly 1Hα, evidence significant stabilizing contributions from CαHα ||| O═C hydrogen bonds. These stabilizing interactions are corroborated by density functional theory calculations and natural bonding orbital analysis. The singular conformational chemical shifts, J-couplings, high hNOE ratios, small negative temperature coefficients, and slowed H/D exchange constitute a unique set of fingerprints to identify PPII helical bundles, which may be formed by hundreds of Gly-rich motifs detected in sequence databases. These results should aid the quantification of PPII helices in IDPs, the development of improved antifreeze proteins, and the incorporation of PPII helices into novel designed proteins.


Differential effects of graphene materials on the metabolism and function of human skin cells

J. Frontiñán-Rubio, M. V. Gómez, C. Martín, J. M. González-Domínguez, M. Durán-Prado, E. Vázquez.

Nanoscale, 2018, 10, 11604-11615.

DOI: 10.1039/C8NR00897C

Graphene-related materials (GRMs) such as graphene oxide (GO) and few-layer graphene (FLG) are used in multiple biomedical applications; however, there is still insufficient information available regarding their interactions with the main biological barriers such as skin. In this study, we explored the effects of GO and FLG on HaCaTs human skin keratinocytes, using NMR-based metabolomics and fluorescence microscopy to evaluate the global impact of each GRM on cell fate and damage. GO and FLG at low concentrations (5 μg mL−1) induced a differential remodeling of the metabolome, preceded by an increase in the level of radical oxygen species (ROS) and free cytosolic Ca2+. These changes are linked to a concentration-dependent increase in cell death by triggering apoptosis and necrosis, the latter being predominant at higher concentrations of the nanostructures. In addition, both compounds reduce the ability of HaCaT cells to heal wounds. Our results demonstrate that the GO and FLG used in this study, which mainly differ in their oxidation state, slightly trigger differential effects on HaCaTs cells, but with evident outcomes at the cellular and molecular levels. Their behavior as pro-apoptotic/necrotic substances and their ability to inhibit cell migration, even at low doses, should be considered in the development of future applications.


Oligostilbenoids in Vitis vinifera L. Pinot Noir grape cane extract: Isolation, characterization, in vitro antioxidant capacity and anti-proliferative effect on cancer 

V. Saez, E. Pastene, C. Vergara, C. Mardones, I. Hermosin-Gutierrez, S. Gomez-Alonso, M. V. Gomez, C. Theoduloz, S. Riquelme, D. von Baer

Food Chem., 2018, 265, 101-110

DOI: 10.1016/j.foodchem.2018.05.050

The following oligostilbenoids were isolated from extracts of Vitis vinifera L. Pinot Noir grape canes produced at a pilot-plant scale: (E)-ε-viniferin, (E)-resveratrol, (E)-piceatannol, ampelopsin A, vitisin B, pallidol, (E)-δ-viniferin, (E)-ω-viniferin, (E)-trans-cis-miyabenol C, isorhapontigenin, scirpusin A, and a new isomer named isoscirpusin A. The antioxidant capacity of the isolated stilbenoids was studied by three different assays, and their 50% inhibition concentration (IC50) against cancer cells was determined by MTT reduction assay. Besides (E)-resveratrol, stilbenoids have outstanding antioxidant capacity in the ORAC-FL assay. The strongest antiproliferative effect was observed for (E)-piceatannol and ampelopsin A against the bladder cancer cell line J82. (E)-Piceatannol has inhibitory effect on human lung cancer SK-MES-1 cells. Moreover, the whole extract has antiproliferative effect on all tested cell lines. In conclusion, beside (E)-resveratrol, grape cane extract contains oligostilbenoids with potential health benefits. This underexploited viticultural residue has the potential to produce valuable phytochemicals or ingredients in functional foods.


Regulation of the oxidative balance with coenzyme Q10 sensitizes human glioblastoma cells to radiation and temozolomide

J. Frontiñán-Rubioa, R. María Santiago-Mora, C. M. Nieva-Velasco, G. Ferrín, A. Martínez-González, M. Victoria Gómez, M. Moreno, J. Ariza, E. Lozano, J. Arjona-Gutiérrez, A. Gil-Agudo, M. De la Mata, M. Pesic, J. R. Peinado, J. M. Villalba, L. Pérez-Romasanta, V. M. Pérez-García, F.  J. Alcaín, M. Durán-Prado.

Radiotherapy and Oncology, 2018, 128, 236-244

DOI: 10.1016/j.radonc.2018.04.033


To investigate how the modulation of the oxidative balance affects cytotoxic therapies in glioblastomain vitro.

Material and methods

Human glioblastoma U251 and T98 cells and normal astrocytes C8D1A were loaded with coenzyme Q10 (CoQ). Mitochondrial superoxide ion (O2radical dot) and H2O2 were measured by fluorescence microscopy. OXPHOS performance was assessed in U251 cells with an oxytherm Clark-type electrode. Radio- and chemotherapy cytotoxicity was assessed by immunostaining of γH2AX (24 h), annexin V and nuclei morphology, at short (72 h) and long (15 d) time. Hif-1α, SOD1, SOD2 and NQO1 were determined by immunolabelingCatalase activity was measured by classic enzymatic assayGlutathione levels and total antioxidant capacity were quantified using commercial kits.


CoQ did not affect oxygen consumption but reduced the level of O2radical dot and H2O2 while shifted to a pro-oxidant cell status mainly due to a decrease in catalase activity and SOD2 level. Hif-1α was dampened, echoed by a decrease lactate and several key metabolites involved in glutathione synthesis. CoQ-treated cells were twofold more sensitive than control to radiation-induced DNA damage and apoptosis in short and long-term clonogenic assays, potentiating TMZ-induced cytotoxicity, without affecting non-transformed astrocytes.


CoQ acts as sensitizer for cytotoxic therapies, disarming GBM cells, but not normal astrocytes, against further pro-oxidant injuries, being potentially useful in clinical practice for this fatal pathology.