Detection of the TCDD binding-fingerprint within the Ah receptor ligand binding domain by structurally driven mutagenesis and functional analysis

The aryl hydrocarbon receptor (AhR) is a ligand-dependent, basic helix-loop-helix Per-Arnt-Sim (PAS)-containing transcription factor that can bind and be activated by structurally diverse chemicals, including the toxic environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Our previous three-dimensional homology model of the mouse AhR (mAhR) PAS B ligand binding domain allowed identification of the binding site and its experimental validation. We have extended this analysis by conducting comparative structural modeling studies of the ligand binding domains of six additional highaffinity mammalian AhRs. These results, coupled with site-directed mutagenesis and AhR functional analysis, have allowed detection of the "TCDD binding-fingerprint" of conserved residues within the ligand binding cavity necessary for high-affinity TCDD binding and TCDD-dependent AhR transformation DNA binding. The essential role of selected residues was further evaluated using molecular docking simulations of TCDD with both wild-type and mutant mAhRs. Taken together, our results dramatically improve our understanding of the molecular determinants of TCDD binding and provide a basis for future studies directed toward rationalizing the observed species differences in AhR sensitivity to TCDD and understanding the mechanistic basis for the dramatic diversity in AhR ligand structure. © 2009 American Chemical Society

Comparative analysis of homology models of the Ah receptor ligand binding domain: Verification of structure-function predictions by site-directed mutagenesis of a nonfunctional receptor

The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor that mediates the biological and toxic effects of a wide variety of structurally diverse chemicals, including the toxic environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). While significant interspecies differences in AHR ligand binding specificity, selectivity, and response have been observed, the structural determinants responsible for those differences have not been determined, and homology models of the AHR ligand-binding domain (LBD) are available for only a few species. Here we describe the development and comparative analysis of homology models of the LBD of 16 AHRs from 12 mammalian and nonmammalian species and identify the specific residues contained within their ligand binding cavities. The ligand-binding cavity of the fish AHR exhibits differences from those of mammalian and avian AHRs, suggesting a slightly different TCDD binding mode. Comparison of the internal cavity in the LBD model of zebrafish (zf) AHR2, which binds TCDD with high affinity, to that of zfAHR1a, which does not bind TCDD, revealed that the latter has a dramatically shortened binding cavity due to the side chains of three residues (Tyr296, Thr386, and His388) that reduce the amount of internal space available to TCDD. Mutagenesis of two of these residues in zfAHR1a to those present in zfAHR2 (Y296H and T386A) restored the ability of zfAHR1a to bind TCDD and to exhibit TCDD-dependent binding to DNA. These results demonstrate the importance of these two amino acids and highlight the predictive potential of comparative analysis of homology models from diverse species. The availability of these AHR LBD homology models will facilitate in-depth comparative studies of AHR ligand binding and ligand-dependent AHR activation and provide a novel avenue for examining species-specific differences in AHR responsiveness. © 2013 American Chemical Society

Bares 2.0 wave buoy and sustainable buoy network

The aim of this article is to show the operation of the Bares 2.0 wave buoy and the Bares network developed by HCTech. In the marine sector it is highly important to know the state of the sea for applications such as the construction of ports, the study of the impact of waves in coastal areas, the development and calibration of forecasting wave models, the knowledge of the state of the maritime navigation channels, etc. Some of the great difficulties that exist in order to obtain the information of ocean waves is the high cost of the buoys, installation and maintenance. The Bares network aims to cover areas of high oceanographic interest, the target is a sustainable network of buoys that facilitate the access to wave data. The features of this network are the optimized cost, high reliability and reduced maintenance.Peer Reviewe

AUV/ASC cooperative survey

In this paper we describe a solution to perform autonomous surveys taking advantage of a cooperative multivehicle setup. In the proposed configuration, an ASC provides –through an USBL- absolute positioning and communications to an AUV. Thus, by following the AUV with the surface vehicle we facilitate the reception of USBL measurements in the AUV regardless of the extent of the mission. This turns into an improved navigation on the AUV’s side, with the drift bounded thanks to the absolute measurements. Experimental results show that the proposed algorithm is able to maintain the ASC at a close distance and improve the navigation of the AUV. Moreover, the bathymetric maps built from the AUV data are consistent enough to enable the automatic detection of present targets and program further localized missions in the area.Peer Reviewe

A pilot study of the relations within which hearing voices participates : towards a functional distinction between voice hearers and controls

The current research used the Implicit Relational Assessment Procedure (IRAP) as a preliminary step toward bringing a broad, functional approach to understanding psychosis, by focusing on the specific phenomenon of auditory hallucinations of voices and sounds (often referred to as hearing voices). On this path, we created a taxonomy of some critical features of voice hearing based on the existing literature (i.e., perceived normality of voices, appraisals of self and other people hearing voices, and fear of voices) as a focus of our experimental manipulations. It was our hope that our findings would add to the broad literature that has used explicit measures to study these phenomena, and that the use of an 'implicit' measure might assist toward a functional analytic understanding. Three pilot studies were conducted to assess the relations within which hearing voices participates in non-clinical voice hearers (i.e., individuals who hear voices but have no clinical diagnosis or distress) and compared to non-voice hearing control participants. The IRAP effects demonstrated both positive and negative relational responses across the three studies, and these effects varied according to explicit levels of delusional ideation. Furthermore, these IRAP effects also predicted explicit aspects of voice hearing and well-being. The current set of pilot studies demonstrate the utility and precision of the IRAP in this domain, and we propose that this type of experimental analysis may hold potential for future bottom-up functional analyses of voice hearing

Development and application of optical fibre strain and pressure sensors for in-flight measurements

Fibre optic based sensors are becoming increasingly viable as replacements for traditional flight test sensors. Here we present laboratory, wind tunnel and flight test results of fibre Bragg gratings (FBG) used to measure surface strain and an extrinsic fibre Fabry–Perot interferometric (EFFPI) sensor used to measure unsteady pressure. The calibrated full scale resolution and bandwidth of the FBG and EFFPI sensors were shown to be 0.29% at 2.5 kHz up to 600 με and 0.15% at up to 10 kHz respectively up to 400 Pa. The wind tunnel tests, completed on a 30% scale model, allowed the EFFPI sensor to be developed before incorporation with the FBG system into a Bulldog aerobatic light aircraft. The aircraft was modified and certified based on Certification Standards 23 (CS-23) and flight tested with steady and dynamic manoeuvres. Aerobatic dynamic manoeuvres were performed in flight including a spin over a g-range −1g to +4g and demonstrated both the FBG and the EFFPI instruments to have sufficient resolution to analyse the wing strain and fuselage unsteady pressure characteristics. The steady manoeuvres from the EFFPI sensor matched the wind tunnel data to within experimental error while comparisons of the flight test and wind tunnel EFFPI results with a Kulite pressure sensor showed significant discrepancies between the two sets of data, greater than experimental error. This issue is discussed further in the paper