Nuevas herramientas genéticas para el estudio de la vasculatura linfática y de la linfangiogénesis in vivo

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 06-11-200

Subphthalocyaninato boron(III) hydride: synthesis, structure and reactivity

Subphthalocyanine (SubPc) chemistry has been limited so far by their high sensitivity toward strong nucleophiles. In particular, the substitution of the axial chlorine atom by a nucleophilic group in the case of less-reactive SubPcs, such as those bearing electron-withdrawing peripheral substituents, presents some limitations and requires harsh conditions. By taking advantage of the electrophilic character of DIBAL-H, it has been possible to prepare for the first time SubPc-hydride derivatives that exhibit high reactivity as hydroboration reagents of aldehydes. This hydride transfer requires using a typical carbonyl activator (trimethylsilyl triflate) and only one equivalent of aldehyde, affording SubPcs with an axial benzyloxy group in good yield. This transformation has proven to be a useful alternative method for the axial functionalisation of dodecafluoroSubPc, a paradigmatic SubPc derivative, by using electrophiles for the first time. Considering the increasing interest in SubPcs as electron-acceptor semiconductors with remarkable absorption in the visible range to replace fullerene in organic photovoltaic (OPV) devices, it is of the utmost importance to develop new synthetic methodologies for their axial functionalisationFinancial support from Spanish MINECO and MICINN (CTQ2017- 85393-P, PGC2018-094644-B-C21, PDI2019-110091GB-I00) is acknowledged. IMDEA Nanociencia acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, grant SEV2016-0686). J.L. and L.T. acknowledge MECD, Spain, for a F.P.U. fellowship. I.C. and L.M

Molecular identification of the transient species mediating the deactivation dynamics of solvated guanosine and deazaguanosine

Small structural alterations of the purine/pyrimidine core have been related to important photophysical changes, such as the loss of photostability. Similarly to canonical nucleobases, solute-solvent interactions can lead to a change in the excited state lifetimes and/or to the interplay of different states in the photophysics of these modified nucleobases. To shed light on both effects, we here report a complete picture of the absorption spectra and excited state deactivation of deoxyguanosine and its closely related derivative, deoxydeazaguanosine, in water and methanol through the mapping of the excited state potential energy surfaces and molecular dynamics simulations at the TD-DFT level of theory. We show that the N by CH exchange in the imidazole ring of deoxyguanosine translates into a small red-shift of the bright states and slightly faster dynamics. In contrast, changing solvent from water to methanol implies the opposite, i.e., that the deactivation of both systems to the ground state is significantly hindered

Direct Access to Axially Substituted Subphthalocyanines from Trimethylsilyl-Protected Nucleophiles

A new synthetic one-step approach to perform the axial ligand exchange reaction in subphthalocyanines that employs trimethylsilyl-protected nucleophiles as starting materials is reported. Theoretical calculations indicate that the exchange reaction proceeds through a similar 4-centered σ-bond metathesis transition state as the substitution with phenols. This direct method allowed us to synthesize new axial derivatives of singular importance within the chemistry of subphthalocyanines, for which the reactivity and X-ray crystalline structure were studiedFinancial support from the MINECO, Spain (CTQ-2014-52869-P, T.T.; CTQ2014-57729-P, D.G.-R.), and the Comunidad de Madrid (S2013/MIT-2841 FOTOCARBON, T.T.) is acknowledged. M.Y. thank the MICINN (Spain) for the Project No.CTQ2012-35513-C02-0

Photophysical Characterization of Isoguanine in a Prebiotic-Like Environment

It is intriguing how a mixture of organic molecules survived the prebiotic UV fluxes and evolved into the actual genetic building blocks. Scientists are trying to shed light on this issue by synthesizing nucleic acid monomers and their analogues under prebiotic Era-like conditions and by exploring their excited state dynamics. To further add to this important body of knowledge, this study discloses new insights into the photophysical properties of protonated isoguanine, an isomorph of guanine, using steady-state and femtosecond broadband transient absorption spectroscopies, and quantum mechanical calculations. Protonated isoguanine decays in ultrafast time scales following 292 nm excitation, consistently with the barrierless paths connecting the bright S1 (ππ*) state with different internal conversion funnels. Complementary calculations for neutral isoguanine predict similar photophysical properties. These results demonstrate that protonated isoguanine can be considered photostable in contrast to protonated guanine, which exhibits 40-fold longer excited state lifetimesThe authors acknowledge funding from the National Science Foundation (Grant No. CHE-1800052), the Ramón y Cajal Program (Grant: RYC-2016-20489) and the Ministerio de Ciencia, Innovación y Universidades (PGC2018-094644-B-C21, PID2021- 125207NB-C31 and PRE2019-090448 projects). L. M. F. thanks the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with Universidad Autónoma de Madrid in the line Support to Young Researchers, in the context of the V PRICIT (Regional Programme of Research and Technological Innovation) (SI3/PJI/2021-00331

The origin of efficient triplet state population in sulfur-substituted nucleobases

Elucidating the photophysical mechanisms in sulfur-substituted nucleobases (thiobases) is essential for designing prospective drugs for photo-and chemotherapeutic applications. Although it has long been established that the phototherapeutic activity of thiobases is intimately linked to efficient intersystem crossing into reactive triplet states, the molecular factors underlying this efficiency are poorly understood. Herein we combine femtosecond transient absorption experiments with quantum chemistry and nonadiabatic dynamics simulations to investigate 2-thiocytosine as a necessary step to unravel the electronic and structural elements that lead to ultrafast and near-unity triplet-state population in thiobases in general. We show that different parts of the potential energy surfaces are stabilized to different extents via thionation, quenching the intrinsic photostability of canonical DNA and RNA nucleobases. These findings satisfactorily explain why thiobases exhibit the fastest intersystem crossing lifetimes measured to date among bio-organic molecules and have near-unity triplet yields, whereas the triplet yields of canonical nucleobases are nearly zeroS.M., P.M. and L.G. thank the Austrian Science Fund (FWF) through project P25827, the COST action CM1204 (XLIC) and the Vienna Scientific Cluster (VSC) for the allocation of computational time. We also thank F. Plasser for assistance with the TheoDORE program. I.C. and L.M.-F. thank the Comunidad Autónoma de Madrid, the Ministerio de Economía y Competitividad (Spain) for an FPU (L.M.-F.) grant, the Projects FOTOCARBON-CM S2013/MIT-2841 and No. CTQ2015-63997-C2, and the ERA-Chemistry Project PIM2010EEC-00751 for financial support, as well as the Centro de Computación Científica UAM for generous allocation of computational time. M.P., N.D. and C.E.C.-H. acknowledge the CAREER program of the National Science Foundation (Grant No. CHE-1255084) for financial suppor

Sub-laser-cycle control of coupled electron–nuclear dynamics at a conical intersection

Nonadiabatic processes play a fundamental role in the understanding of photochemical processes in excited polyatomic molecules. A particularly important example is that of radiationless electronic relaxation at conical intersections (CIs). We discuss new opportunities for controlling coupled electron–nuclear dynamics at CIs, offered by the advent of nearly single-cycle, phase-stable, mid-infrared laser pulses. To illustrate the control mechanism, a two-dimensional model of the NO2 molecule is considered. The key idea of the control scheme is to match the time scale of the laser field oscillations to the characteristic time scale of the wave packet transit through the CI. The instantaneous laser field changes the shape and position of the CI as the wave packet passes through. As the CI moves in the laser field, it ‘slices’ through the wave packet, sculpting it in the coordinate and momentum space in a way that is sensitive to the carrier-envelope phase of the control pulse. We find that the electronic coherence imparted on the sub-laser-cycle time scale manifests during much longer nuclear dynamics that follow on the many tens of femtosecond time scale. Control efficiency as a function of molecular orientation is analyzed, showing that modest alignment is sufficient for showing the described effects.ERA-ChemistryDFG SMEU FP7 Marie Curie ITN CORINFMINECO:European Research Council: http://dx.doi.org/10.13039/501100000781Engineering and Physical Sciences Research Council: http://dx.doi.org/10.13039/501100000266CAM NANOFRONTMAGMINECO FPU (LMF)European Cooperation in Science and Technology: http://dx.doi.org/10.13039/501100000921Peer Reviewe

Curved nanographenes: Multiple emission, thermally activated delayed fluorescence, and non-radiative decay

The intriguing and rich photophysical properties of three curved nanographenes (CNG 6, 7, and 8) are investigated by time-resolved and temperature-dependent photoluminescence (PL) spectroscopy. CNG 7 and 8 exhibit dual fluorescence, as well as dual phosphorescence at low temperature in the main PL bands. In addition, hot bands are detected in fluorescence as well as phosphorescence, and, in the narrow temperature range of 100–140 K, thermally activated delayed fluorescence (TADF) with lifetimes on the millisecond time-scale is observed. These findings are rationalized by quantum-chemical simulations, which predict a single minimum of the S1 potential of CNG 6, but two S1 minima for CNG 7 and CNG 8, with considerable geometric reorganization between them, in agreement with the experimental findings. Additionally, a higher-lying S2 minimum close to S1 is optimized for the three CNG, from where emission is also possible due to thermal activation and, hence, non-Kasha behavior. The presence of higher-lying dark triplet states close to the S1 minima provides mechanistic evidence for the TADF phenomena observed. Non-radiative decay of the T1 state appears to be thermally activated with activation energies of roughly 100 meV and leads to disappearance of phosphorescence and TADF at T > 140

The Influence of Nutrition in Alzheimer's Disease: Neuroinflammation and the Microbiome vs. Transmissible Prion

Alzheimer's disease (AD) is a primary, progressive, neurodegenerative disorder. Many risk factors for the development of AD have been investigated, including nutrition. Although it has been proven that nutrition plays a role in AD, the precise mechanisms through which nutrition exerts its influence remain undefined. The object of this study is to address this issue by elucidating some of the mechanisms through which nutrition interacts with AD. This work is a qualitative systematic bibliographic review of the current literature searchable on various available databases, including PubMed, Web of Science, and Google Scholar. Our evidence comprises 31 articles selected after a systematic search process. Patients suffering with AD present a characteristic microbiome that promotes changes in microglia generating a proinflammatory state. Many similarities exist between AD and prion diseases, both in terms of symptoms and in the molecular mechanisms of pathogenesis. Changes in the composition of the gut microbiome due to dietary habits could be one of the environmental factors affecting the development of AD; however, this is probably not the only factor. Similarly, the mechanism for self-propagation of beta-amyloid seen in AD is similar to that seen in prions

Mesityl or imide acridinium photocatalysts: accessible versus inaccessible charge-transfer states in photoredox catalysis

A study on C9-imide acridinium photocatalysts with enhanced photoredox catalytic activity with respect to the well-established C9-mesityl acridinium salt is presented. The differences observed rely on the diverse accessibility of singlet chargetransfer excited states, which have been proven by CASPT2/CASSCF calculations, fluorescence and quenching studiesThe Boehringer Ingelheim Stiftung (Exploration Grant), the Deutsche Forschungsgemeinschaft (DFG), Spanish Government (CTQ2015-64561-R, CTQ2015-63997-C2, ENE2016-79608-C2-1-R) and Community of Madrid (2016-T1/AMB-1275) are acknowledged. The authors wish to thank ’’Comunidad de Madrid’’ for its support to the FotoArt-CM Project (S2018/NMT-4367) through the Program of R&D activities between research groups in Technologies 2013, co-financed by European Structural Fun