Instituto Universitario Mixto Of Tecnologia Quimica

San Sebastián de los Reyes, Spain

Instituto Universitario Mixto Of Tecnologia Quimica

San Sebastián de los Reyes, Spain
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De Lucas N.C.,Federal University of Rio de Janeiro | Correa R.J.,Federal University of Rio de Janeiro | Garden S.J.,Federal University of Rio de Janeiro | Santos G.,Federal University of Rio de Janeiro | And 8 more authors.
Photochemical and Photobiological Sciences | Year: 2012

The influence of ring size on the photobehaviour of condensed 1,4-naphthoquinone systems, such as pyrano- and furano-derivatives (1 and 2, respectively) has been investigated. The absorption spectra for both families of naphthoquinones reveal clear differences; in the case of 2 they extend to longer wavelengths. A solvatochromic red shift in polar solvents is consistent with the π,π* character of the S0 → S1 electronic transition in all cases. Theoretical (B3LYP) analysis of the HOMO and LUMO Kohn-Sham molecular orbitals of the S0 state indicates that they are π and π* in nature, consistent with the experimental observation. A systematic study on the efficiency of singlet oxygen generation by these 1,4-naphthoquinones is presented, and values larger than 0.7 were found in every case. In accordance with these results, laser flash photolysis of deoxygenated acetonitrile solutions led to the formation of detectable triplet transient species with absorptions at 390 and 450 nm (1) and at 370 nm (2), with ISC close to 1. Additionally, the calculated energies for the T 1 states relative to the S0 states at UB3LYP/6- 311++G** are ca. 47 kcal mol-1 for 1 and 43 kcal mol -1 for 2. A comparison of the geometrical parameters for the S 0 and T1 states reveals a marked difference with respect to the arrangement of the exocyclic phenyl ring whilst a comparison of electronic parameters revealed the change from a quinone structure to a di-dehydroquinone diradical structure. This journal is © The Royal Society of Chemistry and Owner Societies.

Bosca F.,Instituto Universitario Mixto Of Tecnologia Quimica | Sastre G.,Instituto Universitario Mixto Of Tecnologia Quimica | Andreu J.M.,CSIC - Biological Research Center | Jornet D.,Instituto Universitario Mixto Of Tecnologia Quimica | And 2 more authors.
RSC Advances | Year: 2015

Colchicine (COL) is a bioactive molecule with antitumor properties. When COL binds to tubulin (TU), it inhibits microtubule assembly dynamics. We have investigated COL-TU interactions using laser flash photolysis (LFP) technique and performing fully flexible molecular dynamics simulations. Excitation of COL at 355 nm in aqueous medium did not lead to any transient absorption spectrum. By contrast, in the presence of TU a transient peaking at λmaxca. 420 nm was registered and assigned as triplet excited COL complexed with TU (3COL∗@TU). In aerated medium, the lifetime was τ ca. 160 μs and the quantum yield was 0.138. Likewise, when the bicyclic COL analog MTC was submitted to LFP in the presence of TU, 3MTC@TU∗ was detected with a lifetime of ca. 62 μs and a quantum yield of 0.296, Aqueous solutions of MTC did not produce any signal in the microsecond timescale. The triplet energy of MTC was obtained by means of emission measurements and found to be ca. 200 kJ mol-1, a value that matches with that previously reported for COL (188 kJ mol-1). Molecular dynamic simulations, both with the ground and triplet excited state, reveal a strong interaction between COL and TU to give stabilized complexes with restricted mobility inside the protein binding site. These results demonstrate that LFP is a useful methodology to study the binding of COL derivatives to TU and open a new way to evaluate the interactions of non-fluorescent anticancer drugs with this protein. © The Royal Society of Chemistry 2015.

Marin M.L.,Instituto Universitario Mixto Of Tecnologia Quimica | Lhiaubet-Vallet V.,Instituto Universitario Mixto Of Tecnologia Quimica | Santos-Juanes L.,Universidad Politécnica de Ingeniería | Soler J.,Universidad Politécnica de Ingeniería | And 4 more authors.
Applied Catalysis B: Environmental | Year: 2011

The role of hydroxyl radical in different solar photocatalytic processes, namely photo-Fenton, titanium dioxide-based oxidation and organic photocatalysis (triphenylpyrylium) has been investigated. Using a methodology based on the flash photolytic generation of OH. from N-hydroxypyridine-2(1H)-thione, followed by t-stilbene trapping, the reaction rate constants of different pesticides (dimethoate, methidathion, alachlor and pyrimethanyl) with this reactive oxygen species in deaerated acetonitrile have been determined. The results obtained under photo-Fenton conditions are in reasonable agreement with the estimated rate constants; hence the assumption that the photo-Fenton reaction mainly involves participation of the hydroxyl radical seems plausible. The oxidation pattern using titanium dioxide was also investigated; however, under these conditions no clear correlation could be found due to participation of an alternative electron transfer mechanism.Finally, pyrimethanil was the most reactive pesticide when photodegradation was carried out in the presence of TPP, in spite of its low reactivity towards hydroxyl radical. Laser flash photolysis experiments evidenced that the reaction occurs via photoinduced electron transfer within a ground state complex; this is in good correlation with the relative amount of pyranyl radical formation. © 2011 Elsevier B.V.

Rodriguez-Muniz G.M.,Instituto Universitario Mixto Of Tecnologia Quimica | Gomis J.,Universidad Politécnica de Ingeniería | Arques A.,Universidad Politécnica de Ingeniería | Amat A.M.,Universidad Politécnica de Ingeniería | And 2 more authors.
Photochemistry and Photobiology | Year: 2014

In this work, a kinetic model, in combination with timeresolved experiments, is applied to assess the involvement of OH in the photodegradation of emerging pollutants (EPs) by means of advanced oxidation processes. In contrast with the general assumption, quenching of the short-lived OH in the real waters by the (highly diluted) EPs must be very inefficient, so removal of EPs cannot purely rely on the generation and reaction of OH. This suggests that more complex pathways have to be considered to explain the photodegradation of EPs actually achieved under the employed oxidative conditions, possibly involving other reactive species with longer lifetimes or chain degradation processes. © 2014 The American Society of Photobiology.

Miro P.,Instituto Universitario Mixto Of Tecnologia Quimica | Arques A.,Universidad Politécnica de Ingeniería | Amat A.M.,Universidad Politécnica de Ingeniería | Marin M.L.,Instituto Universitario Mixto Of Tecnologia Quimica | Miranda M.A.,Instituto Universitario Mixto Of Tecnologia Quimica
Applied Catalysis B: Environmental | Year: 2013

Emerging pollutants, such as drugs, are considered a potential hazard to the environment, and therefore advanced oxidation processes are being considered candidate tools for their elimination. Here, different oxidation processes have been investigated for the degradation of the non-steroidal antiinflammatories diclofenac and meclofenamic acid, derived from the model compound 2,6-dichlorodiphenylamine. They include oxidation under photo-Fenton conditions and treatment with organic photocatalysts such as rose Bengal (RB) and triphenylpyrylium (TPP+) salts. The role of the transient species involved in these processes (hydroxyl radical, singlet oxygen and radical cations, respectively) has been investigated by means of photophysical experiments. Based on the obtained results, participation of hydroxyl radical in photo-Fenton degradation appears feasible whereas singlet oxygen has been demonstrated to be unreactive for the degradation of the selected drugs. Finally the photocatalytic activity of triphenylpyrilium salts has been ascribed to electron transfer from the drugs to the triplet excited state of TPP+; ground state complexes have also been observed in this case, although their contribution to the photodegradation process is only marginal. © 2013 Elsevier B.V.

Rohacova J.,Instituto Universitario Mixto Of Tecnologia Quimica | Marin M.L.,Instituto Universitario Mixto Of Tecnologia Quimica | Miranda M.A.,Instituto Universitario Mixto Of Tecnologia Quimica
Journal of Physical Chemistry B | Year: 2010

Interaction between bile acids and plasma proteins has attracted considerable attention over past decades. In fact, binding of bile acids to human serum albumin (HSA) determines their level in plasma, a value that can be used as a test for liver function. However, very little is known about the role that bile acids-HSA complexes play in hepatic uptake. In the present paper, we report on the utility of the singlet excited state properties of 4-nitrobenzo-2-oxa-1,3-diazole (NBD) fluorescent derivatives of cholic acid (ChA); namely, 3α-NBD-ChA, 3β-NBD-ChA, 3β-NBD-ChTau, 7α-NBD-ChA, and 7β-NBD-ChA to clarify key aspects of bile acids-HSA interactions that remain poorly understood. On the basis of either absorption or emission measurements, formation of NBD-ChA@HSA complexes with 1:1 stoichiometry has been proven. Enhancement of the fluorescence emission upon addition of HSA has been used for determination of the binding constants, which are in the range of 104 M-1. Energy transfer from tryptophan to NBD-ChA occurs by a FRET mechanism; the donor-acceptor distances have been determined according to Förster's theory. The estimated values (27-30 Å) are compatible with both site I and site II occupancy and do not provide sufficient information for a safe assignment; however, fluorescence titration using warfarin (site I probe) and ibuprofen (site II probe) for displacement clearly indicates that the employed cholic acid derivatives bind to HSA at site I. © 2010 American Chemical Society.

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