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We studied the association of mitochondrial DNA (mtDNA) haplogroups with weight and body mass index (BMI) gain at 96 weeks in 1019 treatment-naive persons with HIV (PWH) who initiated first-line antiretroviral therapy (ART) since 2014. The mean increase in weight and BMI over the study period was 2.90â kg and 0.98â kg/m2, respectively. We found a significant adjusted association between the major UK mtDNA haplogroup and lower weight and BMI increase at 96 weeks after ART initiation. Our findings reveal a potential role for mitochondrial genetics in the complex phenomenon of weight gain after initial ART in PWH.
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Índice de Masa Corporal , ADN Mitocondrial , Infecciones por VIH , Haplotipos , Aumento de Peso , Humanos , Infecciones por VIH/tratamiento farmacológico , Infecciones por VIH/genética , Aumento de Peso/efectos de los fármacos , Aumento de Peso/genética , Masculino , Femenino , Adulto , ADN Mitocondrial/genética , Persona de Mediana Edad , Fármacos Anti-VIH/uso terapéutico , Fármacos Anti-VIH/efectos adversos , Mitocondrias/genética , Mitocondrias/efectos de los fármacos , Reino Unido/epidemiologíaRESUMEN
Quantum tunneling is a fundamental phenomenon that plays a pivotal role in the motion and interaction of atoms and molecules. In particular, its influence in the interaction between water molecules and carbon surfaces can have significant implications for a multitude of fields ranging from atmospheric chemistry to separation technologies. Here, we unveil at the molecular level the complex motion dynamics of a single water molecule on the planar surface of the polycyclic aromatic hydrocarbon phenanthrene, which was used as a small-scale carbon surface-like model. In this system, the water molecule interacts with the substrate through weak O-H···π hydrogen bonds, in which phenanthrene acts as the hydrogen-bond acceptor via the high electron density of its aromatic cloud. The rotational spectrum, which was recorded using chirped-pulse Fourier transform microwave spectroscopy, exhibits characteristic line splittings as dynamical features. The nature of the internal dynamics was elucidated in great detail with the investigation of the isotope-substitution effect on the line splittings in the rotational spectra of the H218O, D2O, and HDO isotopologues of the phenanthrene-H2O complex. The spectral analysis revealed a complex internal dynamic showing a concerted tunneling motion of water involving its internal rotation and its translation between the two equivalent peripheral rings of phenanthrene. This high-resolution spectroscopy study presents the observation of a tunneling motion exhibited by the water monomer when interacting with a planar carbon surface with an unprecedented level of detail. This can serve as a small-scale analogue for water motions on large aromatic surfaces, i.e., large polycyclic aromatic hydrocarbons and graphene.
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The remedy of memory deficits has been inadequate, as all potential candidates studied thus far have shown limited to no effects and a search for an effective strategy is ongoing. Here, we show that an expression of RGS14414 in rat perirhinal cortex (PRh) produced long-lasting object recognition memory (ORM) enhancement and that this effect was mediated through the upregulation of 14-3-3ζ, which caused a boost in BDNF protein levels and increase in pyramidal neuron dendritic arborization and dendritic spine number. A knockdown of the 14-3-3ζ gene in rat or the deletion of the BDNF gene in mice caused complete loss in ORM enhancement and increase in BDNF protein levels and neuronal plasticity, indicating that 14-3-3ζ-BDNF pathway-mediated structural plasticity is an essential step in RGS14414-induced memory enhancement. We further observed that RGS14414 treatment was able to prevent deficits in recognition, spatial, and temporal memory, which are types of memory that are particularly affected in patients with memory dysfunctions, in rodent models of aging and Alzheimer's disease. These results suggest that 14-3-3ζ-BDNF pathway might play an important role in the maintenance of the synaptic structures in PRh that support memory functions and that RGS14414-mediated activation of this pathway could serve as a remedy to treat memory deficits.
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Corteza Perirrinal , Proteínas 14-3-3/genética , Proteínas 14-3-3/metabolismo , Proteínas 14-3-3/farmacología , Animales , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Hipocampo/metabolismo , Humanos , Trastornos de la Memoria/metabolismo , Trastornos de la Memoria/prevención & control , Ratones , Plasticidad Neuronal/fisiología , Ratas , Roedores/metabolismoRESUMEN
OBJECTIVES: We compared the characteristics and clinical outcomes of hospitalized individuals with COVID-19 with [people with HIV (PWH)] and without (non-PWH) HIV co-infection in Spain during the first wave of the pandemic. METHODS: This was a retrospective matched cohort study. People with HIV were identified by reviewing clinical records and laboratory registries of 10 922 patients in active-follow-up within the Spanish HIV Research Network (CoRIS) up to 30 June 2020. Each hospitalized PWH was matched with five non-PWH of the same age and sex randomly selected from COVID-19@Spain, a multicentre cohort of 4035 patients hospitalized with confirmed COVID-19. The main outcome was all-cause in-hospital mortality. RESULTS: Forty-five PWH with PCR-confirmed COVID-19 were identified in CoRIS, 21 of whom were hospitalized. A total of 105 age/sex-matched controls were selected from the COVID-19@Spain cohort. The median age in both groups was 53 (Q1-Q3, 46-56) years, and 90.5% were men. In PWH, 19.1% were injecting drug users, 95.2% were on antiretroviral therapy, 94.4% had HIV-RNA < 50 copies/mL, and the median (Q1-Q3) CD4 count was 595 (349-798) cells/µL. No statistically significant differences were found between PWH and non-PWH in number of comorbidities, presenting signs and symptoms, laboratory parameters, radiology findings and severity scores on admission. Corticosteroids were administered to 33.3% and 27.4% of PWH and non-PWH, respectively (P = 0.580). Deaths during admission were documented in two (9.5%) PWH and 12 (11.4%) non-PWH (P = 0.800). CONCLUSIONS: Our findings suggest that well-controlled HIV infection does not modify the clinical presentation or worsen clinical outcomes of COVID-19 hospitalization.
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COVID-19/epidemiología , Consumidores de Drogas/estadística & datos numéricos , Infecciones por VIH/epidemiología , Hospitalización/estadística & datos numéricos , Adolescente , Corticoesteroides/uso terapéutico , Adulto , Anciano , Anciano de 80 o más Años , Fármacos Anti-VIH/uso terapéutico , Recuento de Linfocito CD4 , COVID-19/mortalidad , Niño , Preescolar , Femenino , Infecciones por VIH/tratamiento farmacológico , Infecciones por VIH/mortalidad , Humanos , Lactante , Recién Nacido , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , España/epidemiología , Adulto Joven , Tratamiento Farmacológico de COVID-19RESUMEN
The benefits that technology can provide in terms of health and support for independent living are in many cases not enough to break the barriers that prevent older adults from accepting and embracing technology. This work proposes a hardware and software platform based on a smart mirror, which is equipped with a set of digital solutions whose main focus is to overcome older adults' reluctance to use technology at home and wearable devices on the move. The system has been developed in the context of two use cases: the support of independent living for older individuals with neurodegenerative diseases and the promotion of physical rehabilitation activities at home. Aspects such as reliability, usability, consumption of computational resources, performance and accuracy of the proposed platform and digital solutions have been evaluated in the initial stages of the pilots within the SHAPES project, an EU-funded innovation action. It can be concluded that the SHAPES smart mirror has the potential to contribute as a technological breakthrough to overcome the barriers that prevent older adults from engaging in the use of assistive technologies.
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Vida Independiente , Dispositivos de Autoayuda , Anciano , Envejecimiento , Estado de Salud , Humanos , Reproducibilidad de los ResultadosRESUMEN
Melanopsin, an atypical vertebrate visual pigment, mediates non-image-forming light responses including circadian photoentrainment and pupillary light reflexes and contrast detection for image formation. Melanopsin-expressing intrinsically photosensitive retinal ganglion cells are characterized by sluggish activation and deactivation of their light responses. The molecular determinants of mouse melanopsin's deactivation have been characterized (i.e., C-terminal phosphorylation and ß-arrestin binding), but a detailed analysis of melanopsin's activation is lacking. We propose that an extended third cytoplasmic loop is adjacent to the proximal C-terminal region of mouse melanopsin in the inactive conformation, which is stabilized by the ionic interaction of these two regions. This model is supported by site-directed spin labeling and electron paramagnetic resonance spectroscopy of melanopsin, the results of which suggests a high degree of steric freedom at the third cytoplasmic loop, which is increased upon C-terminus truncation, supporting the idea that these two regions are close in three-dimensional space in wild-type melanopsin. To test for a functionally critical C-terminal conformation, calcium imaging of melanopsin mutants including a proximal C-terminus truncation (at residue 365) and proline mutation of this proximal region (H377P, L380P, Y382P) delayed melanopsin's activation rate. Mutation of all potential phosphorylation sites, including a highly conserved tyrosine residue (Y382), into alanines also delayed the activation rate. A comparison of mouse melanopsin with armadillo melanopsin-which has substitutions of various potential phosphorylation sites and a substitution of the conserved tyrosine-indicates that substitution of these potential phosphorylation sites and the tyrosine residue result in dramatically slower activation kinetics, a finding that also supports the role of phosphorylation in signaling activation. We therefore propose that melanopsin's C-terminus is proximal to intracellular loop 3, and C-terminal phosphorylation permits the ionic interaction between these two regions, thus forming a stable structural conformation that is critical for initiating G-protein signaling.
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Fototransducción , Opsinas de Bastones , Animales , Luz , Ratones , Fosforilación , Células Ganglionares de la Retina/metabolismo , Opsinas de Bastones/genética , Opsinas de Bastones/metabolismoRESUMEN
Memory deficits affect a large proportion of the human population and are associated with aging and many neurologic, neurodegenerative, and psychiatric diseases. Treatment of this mental disorder has been disappointing because all potential candidates studied thus far have failed to produce consistent effects across various types of memory and have shown limited to no effects on memory deficits. Here, we show that the promotion of neuronal arborization through the expression of the regulator of G-protein signaling 14 of 414 amino acids (RGS14414) not only induced robust enhancement of multiple types of memory but was also sufficient for the recovery of recognition, spatial, and temporal memory, which are kinds of episodic memory that are primarily affected in patients or individuals with memory dysfunction. We observed that a surge in neuronal arborization was mediated by up-regulation of brain-derived neurotrophic factor (BDNF) signaling and that the deletion of BDNF abrogated both neuronal arborization activation and memory enhancement. The activation of BDNF-dependent neuronal arborization generated almost 2-fold increases in synapse numbers in dendrites of pyramidal neurons and in neurites of nonpyramidal neurons. This increase in synaptic connections might have evoked reorganization within neuronal circuits and eventually supported an increase in the activity of such circuits. Thus, in addition to showing the potential of RGS14414 for rescuing memory deficits, our results suggest that a boost in circuit activity could facilitate memory enhancement and the reversal of memory deficits.-Masmudi-Martín, M., Navarro-Lobato, I., López-Aranda, M. F., Delgado, G., Martín-Montañez, E., Quiros-Ortega, M. E., Carretero-Rey, M., Narváez, L., Garcia-Garrido, M. F., Posadas, S., López-Téllez, J. F., Blanco, E., Jiménez-Recuerda, I., Granados-Durán, P., Paez-Rueda, J., López, J. C., Khan, Z. U. RGS14414 treatment induces memory enhancement and rescues episodic memory deficits.
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Encéfalo/efectos de los fármacos , Trastornos de la Memoria/tratamiento farmacológico , Plasticidad Neuronal/efectos de los fármacos , Fragmentos de Péptidos/farmacología , Proteínas RGS/farmacología , Animales , Encéfalo/fisiopatología , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Trastornos de la Memoria/metabolismo , Memoria Episódica , Ratones , Neuritas/metabolismo , Plasticidad Neuronal/fisiología , Neuronas/metabolismo , Ratas , Transducción de Señal/efectos de los fármacos , Sinapsis/efectos de los fármacos , Sinapsis/metabolismoRESUMEN
BACKGROUND: The aim of the study was to evaluate the performance of "Acute Physiology and Chronic Health Evaluation II" (APACHE-II), "Simplified Acute Physiology Score 3" (SAPS-3), and "APACHE-II Score for Critically Ill Patients with a Solid Tumor" (APACHE-IICCP) models in cancer patients admitted to ICU. METHODS: Prospective cohort study of 414 patients with an active solid tumor. Discrimination was assessed by area under receiver operating characteristic (AROC) curves and calibration by Hosmer-Lemeshow goodness-of-fit C test (H-L). RESULTS: The hospital mortality rate was 32.6%. In the total cohort, discrimination for prognostic models were: APACHE-IICCP (AROC 0.98), APACHE-II (AROC 0.96), SAPS-3 for Central and South American countries (SAPS-3CSA) (AROC 0.95), and SAPS-3 (AROC 0.91). Calibration was good (p value of H-L test > 0.05) using APACHE-IICCP, APACHE-II and SAPS-3CSA models. Estimation of the probability of death was more precise with APACHE-IICCP (standardized mortality ratio, SMR = 1.03) and SAPS-3 (SMR = 1.08) models. Further analysis showed that discrimination was high with all prognostic model whether for patients with planned ICU admission (AROC APACHE-IICCP 0.97, APACHE-II 0.96, SAPS-3 0.95, SAPS-3CSA 0.95) or for patients with unplanned ICU admission (AROC APACHE-IICCP 0.97, APACHE-II 0.94, SAPS-3 0.86, SAPS-3CSA 0.95). Calibration was good for all predictive models in both subgroups (p value of H-L test > 0.05, except for APACHE-II model inpatients with planned ICU admission). CONCLUSIONS: In this prospective study, general predictive models (e.g., APACHE-II, SAPS-3) and cancer-specific models (e.g., APACHE-IICCP) are accurate in predicting hospital mortality. Other studies confirming these results are required.
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APACHE , Modelos Estadísticos , Neoplasias/etiología , Neoplasias/mortalidad , Anciano , Área Bajo la Curva , Enfermedad Crítica/mortalidad , Femenino , Mortalidad Hospitalaria , Humanos , Unidades de Cuidados Intensivos/estadística & datos numéricos , Masculino , Persona de Mediana Edad , Pronóstico , Estudios Prospectivos , Curva ROCRESUMEN
The simplest non-proteinogenic amino acid α-aminoisobutyric acid (Aib), an analogue of glycine and alanine, has been vaporized by laser ablation and probed by high-resolution Fourier transform microwave spectroscopic techniques. Comparison of the experimental rotational and 14 N nuclear quadrupole constants with that predicted ab initio has allowed the identification of three conformers of Aib exhibiting three types of hydrogen-bond interactions I (NHâ â â O=C, cis-COOH), II (OHâ â â N, trans-COOH), and III (N-Hâ â â O-H, cis-COOH) within the amino acid backbone. The observation of conformer III, not detected previously for related proteinogenic amino acids with a nonpolar side chain in a supersonic expansion, indicates that the presence of the methyl groups should restrict the conformational relaxation from conformer Aib-III to Aib-I. For conformer Aib-II, the rotational spectra of the 13 C isotopomers reveal a tunneling motion arising from the two equivalent methyl groups in the molecule. The observation of a single spectrum at the midpoint between those predicted for the two 13 C of the methyl groups has been explained by considering a double-minimum potential function with a low-energy interconversion barrier for a large amplitude internal motion. This singular fact has been corroborated by the anomalous centrifugal distortion effects determined in conformer Aib-II.
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Ácidos Aminoisobutíricos , Alanina/análogos & derivados , Ácidos Aminoisobutíricos/química , Glicina/análogos & derivados , Enlace de Hidrógeno , Conformación MolecularRESUMEN
15-Crown-5 ether (15C5) and its complexes with water have been studied using broadband Fourier transform microwave spectroscopy in a supersonic jet. A new conformer of 15C5 has been observed and established as the new global minimum out of a total of nine isolated structures. In addition, two 15C5-H2O and two 15C5-(H2O)2 clusters have been observed. The cluster structures have been unambiguously identified through the observation of water 18O isotopologue spectra. In all the clusters, at least one water molecule, located close to the axis of the 15C5 ring, interacts through two simultaneous hydrogen bonds to the endocyclic oxygen atoms. This interaction reshapes the 15C5 ring to reduce its rich conformational landscape to only two open structures, related to those found in complexes with Li+ or Na+ ions. In the most abundant 15C5-(H2O)2 form, the two water molecules repeat the same interaction scheme while binding to opposite sides of the ring. In the second most abundant dihydrated form the two water molecules lie on the same side of the ring. This finding is exceptionally rare because water-water interactions typically prevail over the formation of additional solute-water contacts, and it showcases the particular binding features of crown ethers.
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Rapid identification of respiratory pathogens, such as influenza virus A (FluA), influenza virus B (FluB), and respiratory syncytial virus (RSV), reduces unnecessary antimicrobial use and enhances infection control practice. We performed a comparative evaluation of three molecular methods: (i) the Aries Flu A/B & RSV, (ii) the Xpert Xpress Flu/RSV, and (iii) the Cobas Flu A/B & RSV assays. The clinical performances of the three methods were evaluated using 200 remnant nasopharyngeal swab (NPS) specimens against a combined reference standard. The limits of detection (LODs) were determined using FluA, FluB, and RSV control strains with known titers. The 95% LODs were between 1.702 and 0.0003 50% tissue culture infective dose (TCID50), with no significant differences revealed among the three assays. Perfect qualitative detection agreement was obtained in the reproducibility study. The Cobas assay failed at the first run on 13 clinical specimens, resulting in an invalid rate of 6.5%. The sensitivities and specificities for all assays were 96.0 to 100.0% and 99.3 to 100% for all three viruses. For on-demand single-specimen and batched 12-specimen workflows, the test turnaround times were 115.5 and 128.8 min for the Aries assay (12 sample capacity), 34.2 and 44.2 min for the Xpress assay (16 sample capacity), and 21.0 and 254.4 min for the Cobas assay (one instrument), respectively. In summary, the Aries, Xpress, and Cobas Liat assays demonstrated excellent sensitivities and specificities for simultaneous detection and identification of FluA, FluB, and RSV from NPS specimens in cancer patients. Test turnaround time was significantly shorter on the Xpress when instrument scalability is unlimited.
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Virus de la Influenza A/aislamiento & purificación , Virus de la Influenza B/aislamiento & purificación , Técnicas de Diagnóstico Molecular/instrumentación , Virus Sincitial Respiratorio Humano/aislamiento & purificación , Infecciones del Sistema Respiratorio/diagnóstico , Femenino , Humanos , Masculino , Técnicas de Diagnóstico Molecular/normas , Nasofaringe/virología , Reproducibilidad de los Resultados , Infecciones del Sistema Respiratorio/virología , Sensibilidad y Especificidad , Factores de TiempoRESUMEN
Breast carcinoma is the leading cause of cancer-related mortality in women worldwide, with an estimated 1.38 million new cases and 458,000 deaths in 2008 alone. This malignancy represents a heterogeneous group of tumours with characteristic molecular features, prognosis and responses to available therapy. Recurrent somatic alterations in breast cancer have been described, including mutations and copy number alterations, notably ERBB2 amplifications, the first successful therapy target defined by a genomic aberration. Previous DNA sequencing studies of breast cancer genomes have revealed additional candidate mutations and gene rearrangements. Here we report the whole-exome sequences of DNA from 103 human breast cancers of diverse subtypes from patients in Mexico and Vietnam compared to matched-normal DNA, together with whole-genome sequences of 22 breast cancer/normal pairs. Beyond confirming recurrent somatic mutations in PIK3CA, TP53, AKT1, GATA3 and MAP3K1, we discovered recurrent mutations in the CBFB transcription factor gene and deletions of its partner RUNX1. Furthermore, we have identified a recurrent MAGI3-AKT3 fusion enriched in triple-negative breast cancer lacking oestrogen and progesterone receptors and ERBB2 expression. The MAGI3-AKT3 fusion leads to constitutive activation of AKT kinase, which is abolished by treatment with an ATP-competitive AKT small-molecule inhibitor.
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Neoplasias de la Mama/clasificación , Neoplasias de la Mama/genética , Mutación/genética , Translocación Genética/genética , Algoritmos , Neoplasias de la Mama/patología , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Subunidad beta del Factor de Unión al Sitio Principal/genética , Análisis Mutacional de ADN , Exoma/genética , Femenino , Fusión Génica/genética , Humanos , Proteínas de la Membrana/genética , México , Proteínas Proto-Oncogénicas c-akt/antagonistas & inhibidores , Proteínas Proto-Oncogénicas c-akt/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , VietnamRESUMEN
A newborn boy presented with a progressively infiltrating and painful congenital ulcerated plaque on the back of his left foot. A partial excision was performed and histopathologic examination confirmed a diagnosis of a plexiform fibrohistiocytic tumor. This rare tumor usually appears in children and adolescents, with congenital presentations even more uncommon. This case details the exceptional presentation of a congenital ulcerated plexiform fibrohistiocytic tumor with a review of the current literature.
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Histiocitoma Fibroso Benigno/patología , Neoplasias Cutáneas/patología , Neoplasias de los Tejidos Blandos/patología , Pie/patología , Humanos , Recién Nacido , Masculino , Úlcera Cutánea/patologíaRESUMEN
The feasibility of NO3- removal by the synergistic action of a prevailing denitrifying anoxic methane oxidising (DAMO), and nitrate-reducing and sulfide-oxidising bacterial (NR-SOB) consortium, using CH4 and H2 S from biogas as electron donors in a biotrickling filter was investigated. The influence of NO3- concentration on N2 O production during this process was also evaluated. The results showed that NO3- was removed at rates up to 2.8 g mreactor-3 h-1 using CH4 as electron donor. N2 O production rates correlated with NO3- concentration in the liquid phase, with a 10-fold increase in N2 O production as NO3- concentration increased from 50 to 200 g m-3 . The use of H2 S as co-electron donor resulted in a 13-fold increase in NO3- removal rates (â¼18 gNO3- m-3 h-1 ) and complete denitrification under steady-state conditions, which was supported by higher abundances of narG, nirK, and nosZ denitrifying genes. Although the relative abundance of the DAMO population in the consortium was reduced from 60% to 13% after H2 S addition, CH4 removals were not compromised and H2 S removal efficiencies of 100% were achieved. This study confirmed (i) the feasibility of co-oxidising CH4 and H2 S with denitrification, as well as (ii) the critical need to control NO3- concentration to minimize N2 O production by anoxic denitrifiers. Biotechnol. Bioeng. 2017;114: 665-673. © 2016 Wiley Periodicals, Inc.
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Biocombustibles , Reactores Biológicos/microbiología , Sulfuro de Hidrógeno/metabolismo , Nitratos/metabolismo , Archaea/metabolismo , Bacterias/metabolismo , Desnitrificación , Sulfuro de Hidrógeno/análisis , Metano/metabolismo , Nitratos/análisisRESUMEN
Microwave spectroscopy, considered as the most definitive gas phase structural probe, is able to distinguish between different conformational structures of a molecule, because they have unique spectroscopic constants and give rise to distinct individual rotational spectra.Previously, application of this technique was limited to molecular specimens possessing appreciable vapor pressures, thus discarding the possibility of studying many other molecules of biological importance, in particular those with high melting points, which had a tendency to undergo thermal reactions, and ultimately degradation, upon heating.Nowadays, the combination of laser ablation with Fourier transform microwave spectroscopy techniques, in supersonic jets, has enabled the gas-phase study of such systems. In this chapter, these techniques, including broadband spectroscopy, as well as results of their application into the study of the conformational panorama and structure of biomolecular building blocks, such as amino acids, nucleic bases, and monosaccharides, are briefly discussed, and with them, the tools for conformational assignation - rotational constants, nuclear quadrupole coupling interaction, and dipole moment.
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Aminoácidos/química , Carbohidratos/química , Microondas , Análisis Espectral/métodos , Estructura Molecular , Ácidos NucleicosRESUMEN
2-Azetidinone-water clusters can be considered as appropriate models for investigating the interaction of the peptide functional group with water. The rotational spectra of 2-azetidinone-(H2O)n (n = 1, 2) complexes have been studied in the 6-18 GHz frequency range using a molecular beam Fourier transform microwave spectrometer. Two different isomers have been observed for the 1 : 1 adduct. The most stable (1 : 1a) is stabilized by two hydrogen bonds O-H···O=C and N-H···O with water closing a ring with the peptide group. For the other conformer (1 : 1b), water is placed on the other side of the carbonyl group stabilized by O-H···O=C and C-H···O hydrogen bonds. In 2-azetidinone-(H2O)2 the water molecules close a ring with the peptide group forming three different hydrogen bonds: O-H···O=C, O-H···O and N-H···O. The spectra of the parent and several isotopologues of each cluster have been investigated in order to determine their structures. The hydrogen bond geometries show that the dominant interaction is the O-H···O=C hydrogen bond, in good agreement with the observed preference of water to interact with this group in proteins. A comparison between the geometries of the different observed adducts shows clearly how cooperative hydrogen bonding plays an important role in the stabilization of these complexes. No detectable structural changes have been observed for 2-azetidinone upon hydration with one water molecule.
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Azetidinas/química , Modelos Biológicos , Péptidos/química , Agua/química , Complejos de Coordinación , Estructura Molecular , Teoría CuánticaRESUMEN
In this work neutral tyrosine has been generated in the gas phase by laser ablation of solid samples, and its most abundant conformers characterized through their rotational spectra. Their identification has been made by comparison between the experimental and ab initio values of the rotational and quadrupole coupling constants. Both conformers are stabilized by an O-Hâ¢â¢â¢N hydrogen bond established within the amino acid skeleton chain and an additional weak N-Hâ¢â¢â¢π hydrogen bond. The observed conformers differ in the orientation of the phenolic -OH group.
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Rayos Láser , Microondas , Tirosina/química , Análisis de Fourier , Enlace de HidrógenoRESUMEN
A structural study of microsolvated clusters of ß-propiolactone (BPL) formed in a pulsed molecular jet expansion is presented. The rotational spectra of BPL-(H2O)n (n=1-5) adducts have been analyzed by broadband microwave spectroscopy. Unambiguous identification of the structures has been achieved using isotopic substitution and experimental measurements of the cluster dipole moment. The observed structures are discussed in terms of the different intermolecular interactions between water molecules and between water and BPL, which include n-π* interactions involving the lone pairs of electrons on waterâ oxygen atoms and the antibonding orbital of the BPL carbonyl group. The changes induced in the structures of the water hydrogen-bonding network by complexation to BPL indicate that water clusters adopt specific configurations to maximize their links to solute molecules.
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Propiolactona/química , Soluciones/química , Agua/química , Enlace de Hidrógeno , Isomerismo , Marcaje Isotópico , Espectrofotometría InfrarrojaRESUMEN
The rotational spectra of laser ablated picolinic and isonicotinic acids have been studied using broadband chirped pulse (CP-FTMW) and narrowband molecular beam (MB-FTMW) Fourier transform microwave spectroscopies. Two conformers of picolinic acid, s-cis-I and s-cis-II, and one conformer of isonicotinic acid have been identified through the analysis of their rotational spectra. The values of the inertial defect and the quadrupole coupling constants obtained for the most stable s-cis-I conformer of picolinic acid, evidence the formation of an O-H···N hydrogen bond between the acid group and the endocyclic N atom. The stabilization provided by this hydrogen bond compensates the destabilization energy due to the adoption of a -COOH trans configuration in this conformer. Its rs structure has been derived from the rotational spectra of several (13)C, (15)N, and (18)O species observed in their natural abundances. Mesomeric effects have been revealed by comparing the experimental values of the (14)N nuclear quadrupole coupling constants in the isomeric series of picolinic, isonicotinic, and nicotinic acids.
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Análisis de Fourier , Ácidos Isonicotínicos/química , Microondas , Ácidos PicolínicosRESUMEN
Two complexes of alanine with water, alanine-(H2O)n (n = 1,2), have been generated by laser ablation of the amino acid in a supersonic jet containing water vapor and characterized using Fourier transform microwave spectroscopy. In the observed complexes, water molecules bind to the carboxylic group of alanine acting as both proton donors and acceptors. In alanine-H2O, the water molecule establishes two intermolecular hydrogen bonds forming a six-membered cycle, while in alanine-(H2O)2 the two water molecules establish three hydrogen bonds forming an eight-membered ring. In both complexes, the amino acid moiety is in its neutral form and shows the conformation observed to be the most stable for the bare molecule. The microsolvation study of alanine-(H2O)n (n = 1,2) can be taken as a first step toward understanding bulk properties at a microscopic level.