Guillermo Orellana
Universidad Complutense de Madrid, Química Orgánica I, Faculty Member
We have investigated the changes of Na-23 NMR spin-lattice and spin-spin relaxation rates of Na-DNA in dilute aqueous solutions, induced by the intercalating drugs ethidium, propidium,... more
We have investigated the changes of Na-23 NMR spin-lattice and spin-spin relaxation rates of Na-DNA in dilute aqueous solutions, induced by the intercalating drugs ethidium, propidium, 6,7-dihydro-pyrido[2',1':3,4]pyrazino[1,2-f]-phenanthridinediium dihydrate (dq2pyp) and by the electrostatic binder Mg2+. It has been found that the Na-23 spin-lattice relaxation is monoexponential, while the spin-spin relaxation follows a biexponential law. From the linear trends of the relaxation rates observed in the titration experiments of Na-DNA with the drugs we inferred the validity of a two-site model in the fast exchange limit. The relaxation rates of sodium in the bound state have been estimated by using the fraction of bound sodium ions per phosphate charge, predicted by the counterion condensation theory, and the number of sodium ions released per bound drug, calculated from salt dependent equilibrium binding studies. The results show that the addition of the competitors slow down the broad component of the spin-spin relaxation rate of bound sodium in the order dq2pyp approximately propidium < ethidium < Mg2+. This reduction is shown to be due mainly to the decrease of the quadrupolar coupling constant for the slow motions, thus indicating a decrease of the average electric field gradient at the sodium ions close to the DNA surface. We also show that the broad component of the spin-spin relaxation rate linearly correlates with the relative non-polyelectrolyte free energy. This result is discussed in terms of the non-polyelectrolyte interactions affecting R2bB, which can be partitioned into stacking interaction and interactions involving the molecular moieties of the intercalators exposed to the solvent in the minor groove.
Research Interests:
A new type of DNA-interacting violgens derived from the N,N'-dialkyl 6-(2-pyridinium)-phenanthridinium structure (in which dialkyl is -CH2CH2-,-CH2CH2CH2-, or (-CH3)2) have been synthesized. Electronic spectroscopy, steady-state... more
A new type of DNA-interacting violgens derived from the N,N'-dialkyl 6-(2-pyridinium)-phenanthridinium structure (in which dialkyl is -CH2CH2-,-CH2CH2CH2-, or (-CH3)2) have been synthesized. Electronic spectroscopy, steady-state and time-resolved fluorescence, cyclic voltammetry, binding isotherms, viscosity titrations, and molecular modeling techniques were employed to characterize the structural, photophysical and redox properties of the novel drugs as well as the corresponding drug-DNA complexes. The viologens display significant visible absorption (up to ca. 490 nm), and a rather intense luminescence (phi cm from 0.06 to 0.20 at 491-565 nm wavelength maxima) which is efficiently quenched by DNA. The calculated redox potentials of these drugs in their singlet excited state (+2.1 V vs. SHE) predict a large driving force for a photoelectron transfer reaction from the nucleobases to the drugs. Photochemical measurements of the viologens in the presence of mononucleotides, nucleosides, and deoxyribose indicate that the observed fluorescence quenching occurs indeed by electron transfer from the DNA bases rather than the sugar phosphate backbone. Large association constants to double helical DNA (in the order of 10(5) M-1) have been evaluated from the absorbance-based binding isotherms. Viscosimetry supports intercalation of the drugs into the DNA helix. Computer simulations (molecular mechanics of d(CGCGCG)2-drug complexes) confirm the intercalative nature of the binding and provide finer details about the geometry of the different viologen-DNA complexes. Molecular modeling has also revealed a stereoselective interaction of the enantiomeric drug conformers with the chiral DNA helix. A DNA-targeted drug design of future generations of these ligands in order to improve and/or modulate their photochemical, redox, and nucleic acid binding properties appears to be possible by a careful selection of the N,N'-dialkylating chain and/or the substituents on the azaheterocyclic moieties.
Research Interests: Computer Graphics, Photochemistry, Cyclic Voltammetry, Molecular modeling, Molecular Mechanics, and 15 moreDNA, Computer Simulation, Electron Transfer, Drug Design, Excited states, Base Sequence, Cations, Drug Stability, Nucleotides, Biochemistry and cell biology, Nucleic Acid, Fluorescence quenching, Redox Potential, Driving force, and Molecular Sequence Data
Research Interests:
Fluorescence immunoassays are popular for achieving high sensitivity, but they display limitations in biological samples due to strong absorption of light, background fluorescence from matrix components, or light scattering by the... more
Fluorescence immunoassays are popular for achieving high sensitivity, but they display limitations in biological samples due to strong absorption of light, background fluorescence from matrix components, or light scattering by the biomacromolecules. A powerful strategy to overcome these problems is introduced here by using fluorescent magnetic nanobeads doped with two boron-dipyrromethane dyes displaying intense emission in the visible and near-infrared regions, respectively. Careful matching of the emission and absorption features of the dopants leads to a virtual Stokes shift larger than 150 nm achieved by an intraparticle Förster resonance energy transfer (FRET) process between the donor and the acceptor dyes. Additionally, the magnetic properties of the fluorescent beads allow preconcentration of the sample. To illustrate the usefulness of this approach to increase the sensitivity of fluorescence immunoassays, the novel nanoparticles are employed as labels for quantification of ...
Research Interests:
A 2,3-diaminophenazine bis-urea fluorescent probe monomer (1) was developed. 1 responds to phenylphosphate and phosphorylated amino acids in a ratiometric fashion with en-hanced fluorescence accompanied by the development of a red-shifted... more
A 2,3-diaminophenazine bis-urea fluorescent probe monomer (1) was developed. 1 responds to phenylphosphate and phosphorylated amino acids in a ratiometric fashion with en-hanced fluorescence accompanied by the development of a red-shifted emission band arising from an excited-state proton transfer (ESPT) process in the hydrogen bonded probe-analyte complex. The two urea groups of 1 form a cleft-like binding pocket (Kb >1010 L2 mol-2 for 1:2 complex). Imprinting of 1 in presence of ethyl ester- and fluorenylmethyloxycarbon-yl- (Fmoc) protected phosphorylated tyrosine (Fmoc-pTyr-OEt) as the template, methacrylamide as comonomer and eth-yleneglycol dimethacrylate as crosslinker yields few-nanometer-thick molecularly imprinted polymer (MIP) shells on silica core microparticles with excellent selectivity for the tem-plate in a buffered biphasic assay. The supramolecular recog-nition features were established by spectroscopic and NMR studies. Rational screening of comonomers and crossl...
Research Interests:
Covalent tethering of a Ru(II) dye to gallium nitride surfaces has been accomplished as a key step in the development of innovative sensing devices in which the indicator support (semiconductor) plays the role of both support and... more
Covalent tethering of a Ru(II) dye to gallium nitride surfaces has been accomplished as a key step in the development of innovative sensing devices in which the indicator support (semiconductor) plays the role of both support and excitation source. Luminescence emission decays and time-resolved emission spectra confirm the presence of the dye on the semiconductor surfaces, while X-ray photoelectron spectroscopy proves its covalent bonding. The O(2) sensitivity of the new device is comparable to those of other ruthenium-based sensor systems. This achievement paves the way to a new generation of integrable ultracompact microsensors that combine semiconductor emitter-probe assemblies.
Research Interests:
Research Interests:
We have investigated the changes of Na-23 NMR spin-lattice and spin-spin relaxation rates of Na-DNA in dilute aqueous solutions, induced by the intercalating drugs ethidium, propidium,... more
We have investigated the changes of Na-23 NMR spin-lattice and spin-spin relaxation rates of Na-DNA in dilute aqueous solutions, induced by the intercalating drugs ethidium, propidium, 6,7-dihydro-pyrido[2',1':3,4]pyrazino[1,2-f]-phenanthridinediium dihydrate (dq2pyp) and by the electrostatic binder Mg2+. It has been found that the Na-23 spin-lattice relaxation is monoexponential, while the spin-spin relaxation follows a biexponential law. From the linear trends of the relaxation rates observed in the titration experiments of Na-DNA with the drugs we inferred the validity of a two-site model in the fast exchange limit. The relaxation rates of sodium in the bound state have been estimated by using the fraction of bound sodium ions per phosphate charge, predicted by the counterion condensation theory, and the number of sodium ions released per bound drug, calculated from salt dependent equilibrium binding studies. The results show that the addition of the competitors slow down the broad component of the spin-spin relaxation rate of bound sodium in the order dq2pyp approximately propidium < ethidium < Mg2+. This reduction is shown to be due mainly to the decrease of the quadrupolar coupling constant for the slow motions, thus indicating a decrease of the average electric field gradient at the sodium ions close to the DNA surface. We also show that the broad component of the spin-spin relaxation rate linearly correlates with the relative non-polyelectrolyte free energy. This result is discussed in terms of the non-polyelectrolyte interactions affecting R2bB, which can be partitioned into stacking interaction and interactions involving the molecular moieties of the intercalators exposed to the solvent in the minor groove.
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Research Interests:
An optical sensing system, alternative to current electrochemical techniques, has been developed for determining the oxygen permeability (Dk) of rigid gas-permeable contact lenses. The novel sensor is based on kinetic measurements of the... more
An optical sensing system, alternative to current electrochemical techniques, has been developed for determining the oxygen permeability (Dk) of rigid gas-permeable contact lenses. The novel sensor is based on kinetic measurements of the oxygen partial pressure inside a chamber sealed by the sample contact lens, where a thin luminescent O2-sensitive film is placed. The standard equation for calculating the Dk
Research Interests:
Résumé/Abstract Design, synthesis and spectroscopic characterization of the novel luminescent indicator (4-acetoxy-1, 10-phenanthroline) bis (1, 10-phenanthroline) ruthenium (ll) dichloride (abbreviated [Ru (phen) 2 (4AOp)] 2+, 2 Cl-) has... more
Résumé/Abstract Design, synthesis and spectroscopic characterization of the novel luminescent indicator (4-acetoxy-1, 10-phenanthroline) bis (1, 10-phenanthroline) ruthenium (ll) dichloride (abbreviated [Ru (phen) 2 (4AOp)] 2+, 2 Cl-) has led to the development of a ...
Research Interests:
A new type of DNA-interacting violgens derived from the N,N'-dialkyl 6-(2-pyridinium)-phenanthridinium structure (in which dialkyl is -CH2CH2-,-CH2CH2CH2-, or (-CH3)2) have been synthesized. Electronic spectroscopy, steady-state... more
A new type of DNA-interacting violgens derived from the N,N'-dialkyl 6-(2-pyridinium)-phenanthridinium structure (in which dialkyl is -CH2CH2-,-CH2CH2CH2-, or (-CH3)2) have been synthesized. Electronic spectroscopy, steady-state and time-resolved fluorescence, cyclic voltammetry, binding isotherms, viscosity titrations, and molecular modeling techniques were employed to characterize the structural, photophysical and redox properties of the novel drugs as well as the corresponding drug-DNA complexes. The viologens display significant visible absorption (up to ca. 490 nm), and a rather intense luminescence (phi cm from 0.06 to 0.20 at 491-565 nm wavelength maxima) which is efficiently quenched by DNA. The calculated redox potentials of these drugs in their singlet excited state (+2.1 V vs. SHE) predict a large driving force for a photoelectron transfer reaction from the nucleobases to the drugs. Photochemical measurements of the viologens in the presence of mononucleotides, nucleosides, and deoxyribose indicate that the observed fluorescence quenching occurs indeed by electron transfer from the DNA bases rather than the sugar phosphate backbone. Large association constants to double helical DNA (in the order of 10(5) M-1) have been evaluated from the absorbance-based binding isotherms. Viscosimetry supports intercalation of the drugs into the DNA helix. Computer simulations (molecular mechanics of d(CGCGCG)2-drug complexes) confirm the intercalative nature of the binding and provide finer details about the geometry of the different viologen-DNA complexes. Molecular modeling has also revealed a stereoselective interaction of the enantiomeric drug conformers with the chiral DNA helix. A DNA-targeted drug design of future generations of these ligands in order to improve and/or modulate their photochemical, redox, and nucleic acid binding properties appears to be possible by a careful selection of the N,N'-dialkylating chain and/or the substituents on the azaheterocyclic moieties.
Research Interests: Computer Graphics, Photochemistry, Cyclic Voltammetry, Molecular modeling, Molecular Mechanics, and 15 moreDNA, Computer Simulation, Electron Transfer, Drug Design, Excited states, Base Sequence, Cations, Drug Stability, Nucleotides, Biochemistry and cell biology, Nucleic Acid, Fluorescence quenching, Redox Potential, Driving force, and Molecular Sequence Data
This work describes the development and application of class-selective molecularly imprinted polymers (MIPs) for the analysis of beta-lactamase-resistant penicillins, namely cloxacillin (CLOXA), oxacillin (OXA), and dicloxacillin... more
This work describes the development and application of class-selective molecularly imprinted polymers (MIPs) for the analysis of beta-lactamase-resistant penicillins, namely cloxacillin (CLOXA), oxacillin (OXA), and dicloxacillin (DICLOXA), in milk samples. Our method is based on molecularly imprinted solid-phase extraction (MISPE) coupled to high-performance liquid chromatography (HPLC) with diode-array detection (DAD). 2-Biphenylylpenicillin (2BPEN), a surrogate with a close resemblance to beta-lactamase-resistant penicillins in terms of size, shape, hydrophobicity, and functionality, was synthesized and used as the template for the polymer synthesis. A MIP library was prepared and screened to select the optimum functional monomer, N-(2-aminoethyl)methacrylamide, and cross-linker, trimethylolpropane trimethacrylate, that provided the best recognition for the target antibiotics. For the MISPE application, the MIPs were prepared in the form of microspheres, using porous silica beads...
Research Interests: Engineering, Molecular Imprinting, Polymers, Biological Sciences, Solid Phase Extraction, and 10 moreAnimals, Milk, High Pressure Liquid Chromatography, CHEMICAL SCIENCES, Anti-Bacterial Agents, Analytical and Bioanalytical Chemistry, Beta Lactamases, Dicloxacillin, Penicillins, and limit of detection
Research Interests:
Molecularly imprinted polymers (MIPs), human-made polymers capable of recognizing a particular molecule in thepresence of others due to the selective cavities of the material, have been successfully applied to the development... more
Molecularly imprinted polymers (MIPs), human-made polymers capable of recognizing a particular molecule in thepresence of others due to the selective cavities of the material, have been successfully applied to the development ofchromatographic and solid phase ...
Research Interests:
Research Interests:
Research Interests:
Background. The development of alternative processes to eliminate pathogenic agents in water is a matter of growing interest. Current drinking water disinfection procedures, such as chlorination and ozonation, can generate disinfection... more
Background. The development of alternative processes to eliminate pathogenic agents in water is a matter of growing interest. Current drinking water disinfection procedures, such as chlorination and ozonation, can generate disinfection by-products with carcinogenic and mutagenic ...
Research Interests:
ABSTRACT
... Study of physical parameters which influence the quality of hollow waveguides. Author(s): Reuben Dahan; Jacob Dror; Alexandra Inberg; Nathan I. Croitoru. The direct or waveguide transmitted beam shape of carbon dioxide laser was... more
... Study of physical parameters which influence the quality of hollow waveguides. Author(s): Reuben Dahan; Jacob Dror; Alexandra Inberg; Nathan I. Croitoru. The direct or waveguide transmitted beam shape of carbon dioxide laser was recorded by irradiating perspex blocks. ...
ABSTRACT
Research Interests:
Frontiers in Chemical Sensors Novel Principles and Techniques Volume Editors: Guillermo Orellana Maria C. Moreno-Bondi With contributions by J. Alonso Y. Amao L. Basabe-Desmonts S. Busche V. Cadarso CM Charlton M. Crego-Calama C. ...
Research Interests:
Method for prepg. thin films for chem. optical sensors. The invention relates to the development of thin films comprising acrylic polymers on a light-transparent material as optical sensors that contain a luminescent indicator, the... more
Method for prepg. thin films for chem. optical sensors. The invention relates to the development of thin films comprising acrylic polymers on a light-transparent material as optical sensors that contain a luminescent indicator, the light-emitting properties of said indicator changing depending on the concn. of a pre-detd. chem. species present in the medium into which the sensor film is inserted. The films are obtained by thermal or photochem. polymn. of acrylic monomers in the presence of a polymn. initiator and of the luminescent indicator that is phys. immobilized in the polymer network formed. The resulting thin films can be used for the detn. of pollutants in water. [on SciFinder(R)]
DESCRIPTION Molecularly imprinted membrane of fluorescent nanofilaments with red emission for sensoring
TuDI (Invited) 3:30pm-4:00pm From Molecular Engineering of Luminescent Indicators to Environmental Analytical Chemistry in the Field with Fiber-optic (Bio)sensors Guillermo Orellana Laboratory of Applied Photochemistry, Dpmt, of Organic... more
TuDI (Invited) 3:30pm-4:00pm From Molecular Engineering of Luminescent Indicators to Environmental Analytical Chemistry in the Field with Fiber-optic (Bio)sensors Guillermo Orellana Laboratory of Applied Photochemistry, Dpmt, of Organic Chemistry, Faculty of Chemistry, ...
Research Interests:
In order to establish the basis for the rational design of a novel family of intercalating chiral photonuclease drugs aimed at photochemotherapy, namely N, N'-dialkylated 6-(2-pyridinium)phenanthridinium (pyp) dications, a detailed... more
In order to establish the basis for the rational design of a novel family of intercalating chiral photonuclease drugs aimed at photochemotherapy, namely N, N'-dialkylated 6-(2-pyridinium)phenanthridinium (pyp) dications, a detailed investigation of the DNA binding of the dq2pyp member (where dq2 stands for -CH2CH2-), was conducted. The study addresses the sequence- and enantiospecificity, as well as polyelectrolyte effects in the drug-DNA interaction. Binding isotherms with synthetic polynucleotides, forcefield calculations, affinity chromatography in a DNA-cellulose stationary phase and salt-dependent equilibrium and kinetic studies with DNA were used. dq2pyp shows a strong preference for alternating GC over AT base pairs; binding to homopolymeric DNA is weak (< 3 x 10(4) M-1). Affinity chromatography shows enantiospecific binding of dq2pyp to DNA. The polyelectrolyte contribution to the binding free energy are shown to be relatively important (-4.8 kcal/nmol out of an overa...
Research Interests:
Frontiers in Chemical Sensors Novel Principles and Techniques Volume Editors: Guillermo Orellana Maria C. Moreno-Bondi With contributions by J. Alonso Y. Amao L. Basabe-Desmonts S. Busche V. Cadarso CM Charlton M. Crego-Calama C. ...
Research Interests:
ABSTRACT This chapter provides a comprehensive guide to the current sensor devices for online monitoring of water-quality parameters and in situ analysis of the most common pollutants. Both physical and chemical sensing devices are... more
ABSTRACT This chapter provides a comprehensive guide to the current sensor devices for online monitoring of water-quality parameters and in situ analysis of the most common pollutants. Both physical and chemical sensing devices are reviewed. When available, biosensors (chemical sensors based on recognition materials of biological origin) are also considered.
Photophysics of Polyazaaromatic Ruthenium(I1) Complexes Interacting with DNA ... Jean-Paul Lecomtet and And&amp;amp;amp;amp;amp; Kirsch-De Mesmaeker.97 Service de Chimie Organique Physique, CP 160108, Universitd Libre de Bruxelles, 50... more
Photophysics of Polyazaaromatic Ruthenium(I1) Complexes Interacting with DNA ... Jean-Paul Lecomtet and And&amp;amp;amp;amp;amp; Kirsch-De Mesmaeker.97 Service de Chimie Organique Physique, CP 160108, Universitd Libre de Bruxelles, 50 Av.FDRoosevelt, B-1050 Bruxelles, Belgium
Research Interests: The()
()
The first demonstration of fabrication of submicron lateral resolution molecularly imprinted polymer (MIP) patterns by photoinduced local polymerization within metal subwavelength apertures is reported. The size of the photopolymerized... more
The first demonstration of fabrication of submicron lateral resolution molecularly imprinted polymer (MIP) patterns by photoinduced local polymerization within metal subwavelength apertures is reported. The size of the photopolymerized MIP features is finely tuned by the dose of 532 nm radiation. Rhodamine 123 (R123) has been selected as a fluorescent model template to prove the recognition capability of the MIP nanostructures, which has been evaluated by fluorescence lifetime imaging microscopy (FLIM) with single photon timing measurements. The binding selectivity provided by the imprinting effect has been confirmed in the presence of compounds structurally related to R123. These results pave the way to the development of nanomaterial architectures with biomimetic artificial recognition properties for environmental, clinical and food testing.