Gas Phase Structure and Reactivity of Doubly Charged Microhydrated Calcium(II)-Catechol Complexes Probed by Infrared Spectroscopy

Doubly charged microhydrated adducts formed from catechol and calcium(II) were produced in the gas phase using electrospray ionization (ESI) appearing as the most important ions in the mass spectra recorded. The gas phase structures of [Ca(catechol)2(H2O)]2+ and [Ca(catechol)2(H2O)2]2+ have been assayed by IR multiphoton dissociation (IRMPD) spectroscopy, recording their vibrational spectra in the 3450–3750 cm–1 range (OH stretching region) and in the 900–1700 cm–1 fingerprint spectral region. The agreement between experimental and calculated IR spectra of the selected cluster ions confirmed the suitability of the proposed geometries. In addition, quantum chemical calculations at the B3LYP/6-311+G(d,p) level of theory were performed for [Ca(catechol)2(H2O)]2+ to gain insight into the major routes of dissociation. The results suggest that loss of the water molecule is the lowest energy fragmentation channel followed by charge separation products and neutral loss of one catechol molecule, in agreement with the product ions observed upon collision-induced dissociation (CID).Fil: Butler, Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Arroyo Mañez, Pau. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Cabrera, Gabriela Myriam. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Phillipe Maître. Universite Paris Sud; Franci

Lipase-catalyzed synthesis of new substituted phenylacetamides. Hammett analysis and computational study of the enzymatic aminolysis

A series of hydroxy‐, methoxy‐, and nitrophenylacetamides was synthesized by enzyme catalysis. The 28 new products were obtained through a lipase‐catalyzed two‐step reaction in very good to excellent yield. In the case of nitro derivatives, a one‐pot, two‐step methodology allowed the desired products to be obtained in high yields. The influence of various reaction parameters in the lipase‐catalyzed reactions, such as enzyme source, nucleophile (alcohol or amine)/substrate ratio, enzyme/substrate ratio, solvent and temperature were studied. It was observed that nitro‐substituted phenylacetates were more reactive in the aminolysis reaction than phenylacetates substituted with a hydroxyl group. To study this substituent effect, a Hammett analysis and the determination of the ρ parameter were carried out. Moreover, a computational study was applied to the most representative systems, performing an exploration of the potential energy surface for the catalyzed and noncatalyzed aminolysis reaction for nitro‐ and hydroxyphenylacetates. Both analysis showed that the presence of a strongly electron‐attracting group favors the activity of the enzyme, in complete agreement with the experimental results of the enzymatic catalysis

Differentiation of isomeric hydroxypyridine N-Oxides using metal complexation and electrospray ionization mass spectrometry

Differentiation between two isomers of hydroxypyridine N-oxide according to the metal cation adducts generated by electrospray ionization (ESI) was investigated for different metal cations, namely Mg (II), Al (III), Ca (II), Sc (III), Fe (III), Co (II), Ni (II), Cu (II), Zn (II), Ga (III), besides the diatomic cation VO(IV). Protonated molecules of the isomeric hydroxypyridine N-oxides as well as the singly/doubly charged adducts formed from neutral or deprotonated ligands and a doubly/ triply charged cation were produced in the gas phase using ESI, recording mass spectra with different metal ions for each isomer. While complex formation was successful for 2- hydroxypyridine N-oxide with trivalent ions, in the case of 3-hydroxypyridine N-oxide, only peaks related to the protonated molecule were present. On the other hand, divalent cations formed specific species for each isomer, giving characteristic spectra in every case. Hence, differentiation was possible irrespective of the metal cation utilized. In addition, quantum chemical calculations at the B3LYP/6-31+G(d,p) level of theory were performed in order to gain insight into the different complexation of calcium(II) with the isomers of hydroxypyridine N-oxide. The relative stability in the gas phase of the neutral complexes of calcium made up of two ligands, as well as the singly charged and doubly charged complexes, was investigated. The results of these calculations improved the understanding of the differences observed in the mass spectra obtained for each isomer.Fil: Butler, Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Arroyo Mañez, Pau. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Cabrera, Gabriela Myriam. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentin

Gas phase structure and reactivity of doubly charged microhydrated calcium(II)-catechol complexesprobed by infrared spectroscopy

Doubly charged microhydrated adducts formed from catechol and calcium(II) were produced in the gas phase using electrospray ionization (ESI) appearing as the most important ions in the mass spectra recorded. The gas phase structures of [Ca(catechol)2(H2O)]2+ and [Ca(catechol)2(H2O)2]2+ have been assayed by IR multiphoton dissociation (IRMPD) spectroscopy, recording their vibrational spectra in the 3450-3750 cm-1 range (OH stretching region) and in the 900-1700 cm-1 fingerprint spectral region. The agreement between experimental and calculated IR spectra of the selected cluster ions confirmed the suitability of the proposed geometries. In addition, quantum chemical calculations at the B3LYP/6-311+G(d,p) level of theory were performed for [Ca(catechol)2(H2O)]2+ to gain insight into the major routes of dissociation. The results suggest that loss of the water molecule is the lowest energy fragmentation channel followed by charge separation products and neutral loss of one catechol molecule, in agreement with the product ions observed upon collision-induced dissociation (CID)

The Caenorhabditis elegans DAF-12 nuclear receptor: Structure, dynamics, and interaction with ligands

A structure for the ligand binding domain (LBD) of the DAF-12 receptor from Caenorhabditis elegans was obtained from the X-ray crystal structure of the receptor LBD from Strongyloides stercoralis bound to (25R)-Δ7-dafachronic acid (DA) (pdb:3GYU). The model was constructed in the presence of the ligand using a combination of Modeller, Autodock, and molecular dynamics (MD) programs, and then its dynamical behavior was studied by MD. A strong ligand binding mode (LBM) was found, with the three arginines in the ligand binding pocket (LBP) contacting the C-26 carboxylate group of the DA. The quality of the ceDAF-12 model was then evaluated by constructing several ligand systems for which the experimental activity is known. Thus, the dynamical behavior of the ceDAF-12 complex with the more active (25S)-Δ7-DA showed two distinct binding modes, one of them being energetically more favorable compared with the 25R isomer. Then the effect of the Arg564Cys and Arg598Met mutations on the (25R)-Δ7-DA binding was analyzed. The MD simulations showed that in the first case the complex was unstable, consistent with the lack of transactivation activity of (25R)-Δ7-DA in this mutant. Instead, in the case of the Arg598Met mutant, known to produce a partial loss of activity, our model predicted smaller effects on the LBM with a more stable MD trajectory. The model also showed that removal of the C-25 methyl does not impede the simultaneous strong interaction of the carboxylate with the three arginines, predicting that 27-nor-DAs are putative ceDAF-12 ligands. © 2012 Wiley Periodicals, Inc.Fil: Alvarez, Lautaro Damian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Arroyo Mañez, Pau. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; ArgentinaFil: Estrin, Dario Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; ArgentinaFil: Burton, Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; Argentin

Combined experimental and computational investigation of the absorption spectra of E- and Z-cinnamic acids in solution: the peculiarity of Z-cinnamics

Cinnamic acids are present in all kinds of plant tissues and hence in herbs and derived medicines, cosmetics and foods. The interest in their role in plants and their therapeutic applications has grown exponentially. Because of their molecular structure they can exist in E- and Z-forms, which are both found in plants. However, since only the E-forms are commercially available, very few in vitro and in vivo studies of the Z-form have been reported. In this work the physico-chemical properties of Z-cinnamic acids in solution have been examined by means of UV-absorption spectroscopy and high-level quantum mechanical computations. For each isomer similar absorption spectra were obtained in methanol and acetonitrile. However, distinct trends were found for Z- and E forms of cinnamic acids in water, where a higher hypsochromic shift of the Z-isomer relative to the E-form was observed. In general the wavelength of maximal absorption of the Z-form is dramatically blue shifted (−30 to −40 nm) to λ < 280 nm, while a slightly blue shift of the absorption maxima for the corresponding E-form (+3 to −4 nm) was observed. This difference is associated with the non-planar, largely distorted, Z-structure and to the almost complete flat structure of the E-form. The results provide a basis for the study of functional and biotechnological roles of cinnamic acids and for the analysis of samples containing mixture of both geometric isomers.Fil: Salum, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Arroyo Mañez, Pau. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Luque, F. Javier. Universidad de Barcelona; EspañaFil: Erra Balsells, Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentin

Combined experimental and computational investigation of the absorption spectra of E- and Z-cinnamic acids in solution: The peculiarity of Z-cinnamics

Cinnamic acids are present in all kinds of plant tissues and hence in herbs and derived medicines, cosmetics and foods. The interest in their role in plants and their therapeutic applications has grown exponentially. Because of their molecular structure they can exist in E- and Z-forms, which are both found in plants. However, since only the E-forms are commercially available, very few in vitro and in vivo studies of the Z-form have been reported. In this work the physico-chemical properties of Z-cinnamic acids in solution have been examined by means of UV-absorption spectroscopy and high-level quantum mechanical computations. For each isomer similar absorption spectra were obtained in methanol and acetonitrile. However, distinct trends were found for Z- and E forms of cinnamic acids in water, where a higher hypsochromic shift of the Z-isomer relative to the E-form was observed. In general the wavelength of maximal absorption of the Z-form is dramatically blue shifted (−30 to −40 nm) to λ < 280 nm, while a slightly blue shift of the absorption maxima for the corresponding E-form (+3 to −4 nm) was observed. This difference is associated with the non-planar, largely distorted, Z-structure and to the almost complete flat structure of the E-form. The results provide a basis for the study of functional and biotechnological roles of cinnamic acids and for the analysis of samples containing mixture of both geometric isomers

New photochromic azoderivatives with potent acetylcholinesterase inhibition

The design of photochromic cholinesterase inhibitors is a challenge of the photopharmacological approach towards the remote control of acetylcholinesterase (AChE) enzyme and its potential application in Alzheimer's disease therapy. In this work, a series of azoderivatives were designed, synthesized and evaluated as AChE inhibitors. The optimized microwave-assisted synthesis (two steps) showed excellent yields with a total reaction time no longer than 40 min. The results showed that all the synthesized compounds exhibited high AChE inhibitory activity at the micromolar range (IC50, 0.65–8.52 μM). Moreover, compound 19, with double four-hydrocarbon chain connected to piperidine, showed a powerful in vitro enzymatic response for its Z isomer (IC50: 0.43 μM) determined by Ellman's assay. Also, 19 showed a stable photostationary state monitored by UV/Vis absorption spectroscopy and 1H NMR spectra. These results indicate that 19 can act as an efficient photo-responsible probe to remote control AChE activity. Molecular modelling analysis of 19 Z revealed its affinity by the peripheral anionic site of AChE, providing understanding of its higher inhibition power. This study contributes to the development of new promising agents for photopharmacological treatment of Alzheimer's disease.Fil: Biscussi, Brunella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Sequeira, María Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Richmond, Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Arroyo Mañez, Pau. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Murray, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin

New photochromic azoderivatives with potent acetylcholinesterase inhibition

The design of photochromic cholinesterase inhibitors is a challenge of the photopharmacological approach towards the remote control of acetylcholinesterase (AChE) enzyme and its potential application in Alzheimer′s disease therapy. In this work, a series of azoderivatives were designed, synthesized and evaluated as AChE inhibitors. The optimized microwave-assisted synthesis (two steps) showed excellent yields with a total reaction time no longer than 40 min. The results showed that all the synthesized compounds exhibited high AChE inhibitory activity at the micromolar range (IC50, 0.65-8.52 μM). Moreover, compound 19, with double fourhydrocarbon chain connected to piperidine, showed a powerful in vitro enzymatic response for its Z isomer (IC50: 0.43 μM) determined by Ellman′ s assay. Also, 19 showed a stable photostationary state monitored by UV/Vis absorption spectroscopy and 1H NMR spectra. These results indicate that 19 can act as an efficient photoresponsible probe to remote control AChE activity. Molecular modelling analysis of 19 Z revealed its affinity by the peripheral anionic site of AChE, providing understanding of its higher inhibition power. This study contributes to the development of new promising agents for photopharmacological treatment of Alzheimer′s disease

Design and microwave-assisted synthesis of aza-resveratrol analogs with potent cholinesterase inhibition

Background: Currently approved Alzheimer's disease medications mainly comprise acetylcholinesterase inhibitors. Many of these inhibitors are either natural compounds or synthetic molecules inspired in natural compounds. Hybrids molecules that can interact with different target sites of the enzyme could lead to the discovery of effective multitarget drugs. Objective: Design, synthesize and evaluate a series of new aza-resveratrol analogues as in vitro acetyl- and butyrylcholinesterase inhibitors. Method: The synthesis is achieved by a simple and efficient microwave-assisted method, from commercially available starting materials. Compounds are designed as hybrids of an aza-stilbene nucleus (Schiff base) connected to a tertiary amine by a hydrocarbon chain of variable length, designed to interact both with the peripheric anionic site and the catalytic site of the enzyme. Results: All the derivatives inhibit both enzymes in a concentration dependent manner, acting as moderate to potent cholinesterase inhibitors. The most potent inhibitors are compounds 12b (IC50 = 0.43 µM) and 12a (IC50 = 0.31 µM) for acetyland butyrylcholinesterase, respectively. Compounds 12a and 12b also exhibit significant acetylcholinesterase inhibition in SH-SY5Y human neuroblastoma cells without cytotoxic properties. Enzyme kinetic studies and molecular modelling reveal that inhibitor 12b targets both the catalytic active site and the peripheral anionic site of acetylcholinesterase what makes it able to modulate the self-induced β-amyloid aggregation. Furthermore, the molecular modelling analysis helps to assess the impact of the linker length in the inhibitory activity of this family of new cholinesterase inhibitors. Conclusion: These compounds have potential to serve as a dual binding site inhibitor and might provide a useful template for the development of new anti- Alzheimer's disease agents