Effective pore size and radius of capture for K+ ions in K-channels

Indexación: Web of Science; Scopus.Reconciling protein functional data with crystal structure is arduous because rare conformations or crystallization artifacts occur. Here we present a tool to validate the dimensions of open pore structures of potassium-selective ion channels. We used freely available algorithms to calculate the molecular contour of the pore to determine the effective internal pore radius (r(E)) in several K-channel crystal structurss. r(E) was operationally defined as the radius of the biggest sphere able to enter the pore from the cytosolic side. We obtained consistent r(E) estimates for MthK and Kv1.2/2.1 structures, with r(E) = 5.3-5.9 angstrom and r(E) = 4.5-5.2 angstrom, respectively. We compared these structural estimates with functional assessments of the internal mouth radii of capture (r(C)) for two electrophysiological counterparts, the large conductance calcium activated K-channel (r(C) = 2.2 angstrom) and the Shaker K-v-channel (r(C) = 0.8 angstrom), for MthK and Kv1.2/2.1 structures, respectively. Calculating the difference between r(E) and r(C), produced consistent size radii of 3.1-3.7 angstrom and 3.6-4.4 angstrom for hydrated K+ ions. These hydrated K+ estimates harmonize with others obtained with diverse experimental and theoretical methods. Thus, these findings validate MthK and the Kv1.2/2.1 structures as templates for open BK and Kv-channels, respectively.http://recursosbiblioteca.unab.cl:2226/articles/srep1989

Gating-induced large aqueous volumetric remodeling and aspartate tolerance in the voltage sensor domain of Shaker K+ channels

Indexación: Scopus.ACKNOWLEDGMENTS. We thank Chris Lingle and Yu Zhou (Washington University) for critical reading of the manuscript and Victoria Prado for Xenopus care and oocyte preparation. We also thank Millennium Scientific Initiative P029-022-F. This work was supported by Fondecyt Postdoctoral Grants 3170599 (to I.D.-F.) and 3160321 (to H.M.).Neurons encode electrical signals with critically tuned voltage-gated ion channels and enzymes. Dedicated voltage sensor domains (VSDs) in these membrane proteins activate coordinately with an unresolved structural change. Such change conveys the transmembrane translocation of four positively charged arginine side chains, the voltage-sensing residues (VSRs; R1–R4). Countercharges and lipid phosphohead groups likely stabilize these VSRs within the low-dielectric core of the protein. However, the role of hydration, a sign-independent charge stabilizer, remains unclear. We replaced all VSRs and their neighboring residues with negatively charged aspartates in a voltage-gated potassium channel. The ensuing mild functional effects indicate that hydration is also important in VSR stabilization. The voltage dependency of the VSR aspartate variants approached the expected arithmetic summation of charges at VSR positions, as if negative and positive side chains faced similar pathways. In contrast, aspartates introduced between R2 and R3 did not affect voltage dependence as if the side chains moved outside the electric field or together with it, undergoing a large displacement and volumetric remodeling. Accordingly, VSR performed osmotic work at both internal and external aqueous interfaces. Individual VSR contributions to volumetric works approached arithmetical additivity but were largely dissimilar. While R1 and R4 displaced small volumes, R2 and R3 volumetric works were massive and vectorially opposed, favoring large aqueous remodeling during VSD activation. These diverse volumetric works are, at least for R2 and R3, not compatible with VSR translocation across a unique stationary charge transfer center. Instead, VSRs may follow separated pathways across a fluctuating low-dielectric septum. © National Academy of Sciences. All rights reserved.https://www.pnas.org/content/115/32/820

Field desorption ion source development for neutron generators

A new approach to deuterium ion sources for deuterium-tritium neutron generators is being developed. The source is based upon the field desorption of deuterium from the surfaces of metal tips. Field desorption studies of microfabricated field emitter tip arrays have been conducted for the first time. Maximum fields of 30 V/nm have been applied to the array tip surfaces to date, although achieving fields of 20 V/nm to possibly 25 V/nm is more typical. Both the desorption of atomic deuterium ions and the gas phase field ionization of molecular deuterium has been observed at fields of roughly 20 V/nm and 20-30 V/nm, respectively, at room temperature. The desorption of common surface adsorbates, such as hydrogen, carbon, water, and carbon monoxide is observed at fields exceeding ~10 V/nm. In vacuo heating of the arrays to temperatures of the order of 800 C can be effective in removing many of the surface contaminants observed

Studying the Chlorophyll Fluorescence in Cyanobacteria with Membrane Computing Techniques

In this paper, we report a pioneer study of the decrease in chlorophyll uorescence produced by the reduction of MTT (a dimethyl thiazolyl diphenyl tetrazolium salt) monitored using an epi uorescence microscope coupled to automate image analysis in the framework of P systems. Such analysis has been performed by a family of tissue P systems working on the images as data inpuJunta de Andalucía P08-TIC-04200Ministerio de Economía y Competitividad TIN2012-3743

Cytomolecular identification of individual wheat-wheat chromosome arm associations in wheat-rye hybrids

Chromosome pairing in the meiotic metaphase I of wheatrye hybrids has been characterized by sequential genomic and fluorescent in situ hybridization allowing not only the discrimination of wheat and rye chromosomes, but also the identification of the individual wheat and rye chromosome arms involved in the chromosome associations. The majority of associations (93.8%) were observed between the wheat chromosomes. The largest number of wheat-wheat chromosome associations (53%) was detected between the A and D genomes, while the frequency of B-D and A-B associations was significantly lower (32 and 8%, respectively). Among the A-D chromosome associations, pairing between the 3AL and 3DL arms was observed with the highest frequency, while the most frequent of all the chromosome associations (0.113/ cell) was found to be the 3DS-3BS. Differences in the pairing frequency of the individual chromosome arms of wheat-rye hybrids have been discussed in relation to the homoeologous relationships between the constituent genomes of hexaploid wheat

Multiple dens invaginatus, mulberry molar and conical teeth : case report and genetic considerations

Dens in dente, also known as dens invaginatus and dilated compound odontoma, is a malformation that can occur on primary, permanent, or supernumerary teeth that is characterized by a deep invagination of the surface of a crown or root covered with enamel. This abnormality in tooth morphology generally affect the maxillary lateral incisors but several cases of multiple dens invaginatus have been reported in the literature. A 15 year-old female patient is reported here presenting five dens invaginatus: four in the permanent mandibular incisors and one in the permanent, maxillary left central incisor, additionally the following dental findings were observed: a permanent mandibular left mulberry molar, molarization of some premolars, several microdontic conoid teeth, retention of five primary teeth, absence of several permanent teeth germs, a macrodontic molar with abnormal roots and several periapical radiolucencies associated to the dens invaginatus. There was no family history of similar dental findings to those observed in the patient. There are several genes that participate in the development of teeth, of those, the following five genes could be implicated as responsible or co-participators for some of the dental anomalies present in this patient: MSX1 (Muscle segment homeobox 1), DLX1 and DLX2 (Distal-less homeobox 1 and 2 genes), PAX9 (Paired box gene) and PITX2 (Pituitary homeobox transciption factor 2)

Instrumental relacionado con el fuego y el banquete

El artículo da a conocer un pequeño lote de fragmentos de espetones de bronce procedentes de dos tumbas de la necrópolis de La Cerrada de los Santos (Aragoncillo) y de otro enterramiento del cementerio de Chera (Prados Redondos), todos ellos en la provincia de Guadalajara y pertenecientes al Celtibérico Antiguo. Estos hallazgos amplían el mapa de su reparto en la Península. El estudio se completa con un morillo de hierro, muy probablemente procedente de la necrópolis de El Atance, también en la provincia de Guadalajara. El trabajo da pie al estudio metalográfico de los ejemplares y a la reflexión sobre su significado en relación con los ritos de fuego y los banquete

The motion of the 2D hydrodynamic Chaplygin sleigh in the presence of circulation

We consider the motion of a planar rigid body in a potential flow with circulation and subject to a certain nonholonomic constraint. This model is related to the design of underwater vehicles. The equations of motion admit a reduction to a 2-dimensional nonlinear system, which is integrated explicitly. We show that the reduced system comprises both asymptotic and periodic dynamics separated by a critical value of the energy, and give a complete classification of types of the motion. Then we describe the whole variety of the trajectories of the body on the plane.Comment: 25 pages, 7 figures. This article uses some introductory material from arXiv:1109.321