Can aromaticity enhance the electron transport in molecular wires?

An interesting debate has been recently raised around the role played by aromaticity in the electron transport ability of molecular wires. Normally, it is associated to destructive interference effects, so that the more aromatic the wire the less conductor. This rule was observed experimentally in a series of homologous wires containing ring units of different aromaticity, but theoretical calculations and other recent experiments demonstrate the rule cannot be generalized and depends, for instance, in the type of molecule-electrode contact. However, neither chemical explanation nor qualitative rules were given yet to allow predicting the specific behavior of different molecular junctions. In this work, using series of polymeric molecular wires of different length and formed by different aromatic units, it is proven how it is possible to change from an expected destructive to a constructive interference effect of the aromaticity in the electron transport. Thus, aromaticity may be also employed to enhance the electron transport in a molecular wire. A chemical explanation to the experimental and theoretical observations is given and a simple way of tuning the response of a molecular wire to an external electric voltage by increasing/decreasing its aromaticity and changing its type of molecule-electrode contact is provided.Xunta de Galicia | Ref. GRC2015/01

The effect of spin polarization on the electron transport of molecular wires with diradical character

Some of the most promising materials for application in molecular electronics and spintronics are based on diradical chains. Herein, the proposed relation between increasing conductance with length and diradical character is revisited using ab initio methods that account for the static electron correlation effects. Electron transmission was previously obtained from restricted single determinant wavefuntions or tight-binding approximations, which are unable to account for static correlation. Broken Symmetry Unrestricted Kohn-Sham Density Functional Theory (BS-UKS-DFT) in combination with electron transport analysis based on electron deformation orbitals (EDOs) reflects an exponential decay of the electrical conductance with length. Also, other important effects such as quantum interference are correctly accounted for, leading to a decrease of the conductance as the diradical character increases. As a proof-of-concept, the electrical conductance obtained from BS-UKS-DFT and CASSCF(2,2) wavefunctions were compared in diradical graphene strips in the frame of the pseudo-π approach, obtaining very similar resultsXunta de Galicia | Ref. GRC2019/2

Assessing the reversed exponential decay of the electrical conductance in molecular wires: the undeniable effect of static electron correlation

An extraordinary new family of molecular junctions, inaccurately referred to as "anti-Ohmic" wires in the recent literature, has been proposed based on theoretical predictions. The unusual electron transport observed for these systems, characterized by a reversed exponential decay of their electrical conductance, might revolutionize the design of molecular electronic devices. This behavior, which has been associated with intrinsic diradical nature, is reexamined in this work. Since the diradical character arises from a near-degeneracy of the frontier orbitals, the employment of a multireference approach is mandatory. CASSCF calculations on a set of nanowires based on polycyclic aromatic hydrocarbons (PAHs) demonstrate that, in the frame of an appropriate multireference treatment, the ground state of these systems shows the expected exponential decay of the conductance. Interestingly, these calculations do evidence a reversed exponential decay of the conductance, although now in several excited states. Similar results have been obtained for other recently proposed candidates to "anti-Ohmic" wires. These findings open new horizons for possible applications in molecular electronics of these promising systems.Xunta de Galicia | Ref. GRC2019/24Agencia Estatal de Investigación | Ref. PGC2018-095953-B-I0

Remanente de la obturación endodóntica en dientes restaurados con retenedor Intra-radicular y su relación con la condición periapical post-tratamiento

No hay evidencia clínica para afirmar que 4-5mm es la longitud aceptada del remanente de obturación endodóntica en dientes restaurados con retenedor intraradicular (RI). Objetivo: Estimar la relación entre el remanente del material de obturación endodóntica en dientes restaurados con RI y la condición periapical post-tratamiento bajo observación en imágenes tomográficas (CBCT). Métodos: Estudio observacional, descriptivo y de corte transversal. Se incluyen dientes permanentes, con obturación endodóntica óptima y restaurados con RI observados en periodos 1año. Se excluyen raíces con espacio visible entre el retenedor y el material obturador. Dos observadores entrenados clasificaron la variable dependiente: condición periapical en normalidad o en enfermedad. Para la variable explicativa se realizaron mediciones continuas del remanente. Análisis estadístico: Una Prueba-F, significativa al 5%, determinó la variabilidad inter-examinador. Se realizó un análisis en Componentes Principales (ACP) para promediar mediciones del remanente de obturación. Un Modelo de Regresión Logística (MRL), con 95% confianza (IC), estimó la relación entre el remanente y el resultado del tratamiento. Resultados: 103 raíces, de 68 pacientes, conformaron la muestra. La Prueba-F no registró diferencias significativas inter-examinador al cuantificar la variable explicativa, (Vp-Coronal=0,767; Vp-Sagital=0,483; Vp-Axial=0,623) y la dependiente (Vp=0,487). Un MRL determinó la no asociación entre la longitud del remanente de obturación y la condición periapical post-tratamiento (OR=0.69, IC95%; 0.244-2.33, P=0.126). En el Corte sagital oblicuo se observó, al 10% de significancia, una relación inversamente proporcional por cada unidad de aumento en la longitud del remanente y la probabilidad de fracasar disminuye en 17.6% (OR=0.36, IC95%; 0.009-13.254, P=0.61). Conclusión: No existe relación entre la longitud del remanente y la condición periapical post-tratamiento

Las creencias en el noviazgo universitario: infidelidad, mentira y engaño

Este ejercicio de investigación se llevó a cabo bajo un diseño metodológico cualitativo. Con este diseño se lograron identificar, desde los lenguajes juveniles y sus experiencias, las creencias que son factores importantes para la generación de violencia en los noviazgos. Algunas de estas creencias entre universitarios son: la intolerancia, la inseguridad, la infidelidad, la falta de diálogo, el irrespeto, los celos, la incidencia del ambiente, la baja autoestima, entre otras. Estas categorías emergentes dan cuenta de las creencias sociales existentes en estos sujetos, con respecto al cómo o al por qué se generan actos de violencia en las relaciones de noviazgo en las parejas heterosexuales de jóvenes universitarios

Corrección del prolapso de cúpula vaginal mediante colpopexia vía abdominal

Introducción: Las disfunciones del suelo pélvico se considera­n un problema de salud en el mundo y constituyen una de las indicaciones de operaciones ginecológicas más comunes. Entre sus variantes está el prolapso de la cúpula vaginal. Objetivos: Evaluar los resultados de la corrección del prolapso de cúpula vaginal por la técnica de colpopexia, mediante fijación con tiras aponeuróticas a la pared abdominal anterior. Métodos: Se realizó un estudio observacional, descriptivo. Las variables utilizadas fueron la edad, presencia de comorbilidades, el número de cirugías previas y el grado de satisfacción subjetivo de las pacientes, luego del procedimiento. Resultados: Hubo predominio de edades avanzadas en la muestra estudiada con 89,5 % de pacientes mayores de 55 años. En la mayoría de las pacientes se encontró una o más comorbilidades que favorecieron la presencia de esta afección. Un total de 8 pacientes habían sido sometidas a una cirugía correctora previa para el prolapso (30,7 %). Al mes de la cirugía el 80,7 % tenía una puntuación de 1-3 de la escala de evaluación PGI-I, valor que fue en ascenso y alcanzó el 96,1 % a los 3 meses, el 100 % a los 6 meses y al año. Conclusiones: La corrección del prolapso de la cúpula vaginal, mediante colpopexia por vía abdominal es una alternativa de tratamiento para las pacientes, fundamentalmente jóvenes o que quieren conservar la funcionalidad vaginal y la vida sexual activa

Human prefoldin modulates co-transcriptional pre-mRNA splicing.

Prefoldin is a heterohexameric complex conserved from archaea to humans that plays a cochaperone role during the co-translational folding of actin and tubulin monomers. Additional functions of prefoldin have been described, including a positive contribution to transcription elongation and chromatin dynamics in yeast. Here we show that prefoldin perturbations provoked transcriptional alterations across the human genome. Severe pre-mRNA splicing defects were also detected, particularly after serum stimulation. We found impairment of co-transcriptional splicing during transcription elongation, which explains why the induction of long genes with a high number of introns was affected the most. We detected genome-wide prefoldin binding to transcribed genes and found that it correlated with the negative impact of prefoldin depletion on gene expression. Lack of prefoldin caused global decrease in Ser2 and Ser5 phosphorylation of the RNA polymerase II carboxy-terminal domain. It also reduced the recruitment of the CTD kinase CDK9 to transcribed genes, and the association of splicing factors PRP19 and U2AF65 to chromatin, which is known to depend on CTD phosphorylation. Altogether the reported results indicate that human prefoldin is able to act locally on the genome to modulate gene expression by influencing phosphorylation of elongating RNA polymerase II, and thereby regulating co-transcriptional splicing.Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación [BFU2016-77728-C3-1-P to S.C. and BFU2017-85420-R to J.C.R.] co-financed with European Union funds (FEDER); Andalusian Government [P12-BIO1938MO, BIO271, US-1256285 to S.C., BIO321 to J.C.R.]; Junta de Andalucía (to L.P.-B.). Funding for open access charge: Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación [BFU2016-77728-C3-1-P]

Human prefoldin modulates co-transcriptional pre-mRNA splicing

Trabajo presentado en el IV Meeting RNALife, celebrado en Sevilla (España) del 12 al 13 de julio de 2021.Prefoldin is a heterohexameric complex conserved from archaea to humans that plays a co-chaperone role during the co-translational folding of actin and tubulin monomers. Additional functions of prefoldin have been described, including a positive contribution to transcription elongation and chromatin dynamics in yeast. Here we show that prefoldin perturbations provoked transcriptional alterations across the human genome. Severe pre-mRNA splicing defects were also detected, particularly after serum stimulation. We found impairment of co-transcriptional splicing during transcription elongation, which explains why the induction of long genes with a high number of introns was affected the most. We detected genome-wide prefoldin binding to transcribed genes and found that it correlated with the negative impact of prefoldin depletion on gene expression. Lack of prefoldin caused global decrease in Ser2 and Ser5 phosphorylation of the RNA polymerase II carboxy-terminal domain. It also reduced the recruitment of the CTD kinase CDK9 to transcribed genes, and the association of splicing factors PRP19 and U2AF65 to chromatin, which is known to depend on CTD phosphorylation. Altogether the reported results indicate that human prefoldin is able to act locally on the genome to modulate gene expression by influencing phosphorylation of elongating RNA polymerase II, and thereby regulating co-transcriptional splicing

Early dysfunction of functional connectivity in healthy elderly with subjective memory complaints

It is still an open question whether subjective memory complaints (SMC) can actually be considered to be clinically relevant predictors for the development of an objective memory impairment and even dementia. There is growing evidence that suggests that SMC are associated with an increased risk of dementia and with the presence of biological correlates of early Alzheimer's disease. In this paper, in order to shed some light on this issue, we try to discern whether subjects with SMC showed a different profile of functional connectivity compared with subjects with mild cognitive impairment (MCI) and healthy elderly subjects. In the present study, we compare the degree of synchronization of brain signals recorded with magnetoencephalography between three groups of subjects (56 in total): 19 with MCI, 12 with SMC and 25 healthy controls during a memory task. Synchronization likelihood, an index based on the theory of nonlinear dynamical systems, was used to measure functional connectivity. Briefly, results show that subjects with SMC have a very similar pattern of connectivity to control group, but on average, they present a lower synchronization value. These results could indicate that SMC are representing an initial stage with a hypo-synchronization (in comparison with the control group) where the brain system is still not compensating for the failing memory networks, but behaving as controls when compared with the MCI subjects