Investigations on the electrical current-voltage response in protein light receptors

We report a theoretical/computational approach for modeling the current-voltage characteristics of sensing proteins. The modeling is applied to a couple of transmembrane proteins, bacteriorhodopsin and proteorhodopsin, sensitive to visible light and promising biomaterials for the development of a new generation of photo-transducers. The agreement between theory and experiments sheds new light on the microscopic interpretation of charge transfer in proteins and biological materials in general.Comment: 4 pages, 3 figures To be published in J Phys. C: Conf Ser. Proceeding of the Conference IC-MCSQUARE, PRAGUE 201

Photoreceptors for a light biotransducer: a comparative study of the electrical responses of two (type-1)-opsins

The increasing interest in photoactivated proteins as natural replacement of standard inorganic materials in photocells drives to the compared analysis of bacteriorhodopsin and proteorhodopsin, two widely diffused proteins belonging to the family of \textit{type-1} opsins. These proteins share similar behaviours but exhibit relevant differences in the sequential chain of the amino acids constituting their tertiary structure. The use of an impedance network analogue to model the protein main features provides a microscopic interpretation of a set of experiments on their photoconductance properties. In particular, this model links the protein electrical responses to the tertiary structure and to the interactions among neighbouring amino acids. The same model is also used to predict the small-signal response in terms of the Nyquist plot. Interesting enough, these rhodopsins are found to behave like a wide gap semiconductor with intrinsic conductivities of the order of $10^{-7}$ S/cm.Comment: 19 pages, 15 figure

Current voltage characteristics and excess noise at the trap filling transition in polyacenes

Experiments in organic semiconductors (polyacenes) evidence a strong super quadratic increase of the current-voltage (I-V) characteristic at voltages in the transition region between linear (Ohmic) and quadratic (trap free space-charge-limited-current) behaviours. Similarly, excess noise measurements at a given frequency and increasing voltages evidence a sharp peak of the relative spectral density of the current noise in concomitance with the strong super-quadratic I-V characteristics. Here we discuss the physical interpretation of these experiments in terms of an essential contribution from field assisted trapping-detrapping processes of injected carriers. To this purpose, the fraction of filled traps determined by the I-V characteristics is used to evaluate the excess noise in the trap filled transition (TFT) regime. We have found an excellent agreement between the predictions of our model and existing experimental results in tetracene and pentacene thin films of different length in the range $0.65 \div 35 \ \mu m$.Comment: 20 pg, 13 figures, in pres

Proteotronics: Electronic devices based on proteins

The convergent interests of different scientific disciplines, from biochemistry to electronics, toward the investigation of protein electrical properties, has promoted the development of a novel bailiwick, the so called proteotronics. The main aim of proteotronics is to propose and achieve innovative electronic devices, based on the selective action of specific proteins. This paper gives a sketch of the fields of applications of proteotronics, by using as significant example the detection of a specific odorant molecule carried out by an olfactory receptor. The experiment is briefly reviewed and its theoretical interpretation given. Further experiments are envisioned and expected results discussed in the perspective of an experimental validation.Comment: 4 pages, 3 figures; Proceedings of the II national meeting on sensors, Rome (Iatly), February 19-21, 201

The application of the Hough transform to the detection of parallel straight lines

In this paper we study the principal problems posed by the application of the Hough Transform to small scale images . We show that the discretization of image space makes the distribution of parameters in the Hough space non-homogeneous and non-equiprobable . One solution to this defect, which is accentuated by picture limitations, is presented in the case of the detection of straight lines . This method of correction allows the rapid detection of parallel straight lines on a square scan window . We also present an application in the framework of a project for finding the road network on a map .Nous présentons dans cette communication les principaux problèmes posés par l'application de la Transformée de Hough (TH) sur une image de dimensions réduites . Nous abordons le problème de la discrétisation de l'espace image qui rend la distribution des paramètres dans l'espace de Hough non homogène et non équiprobable. Une solution est alors présentée, dans le cas de la détection de droites, afin de corriger cet effet, accentué lorsque les dimensions de l'image sont réduites . Cette méthode de correction permet la détection de droites parallèles sur une fenêtre de balayage carrée . Enfin, nous montrons une application dans le cadre d'un projet de recherche du réseau routier sur une carte géographique

Ultrasonographic renal volume measurements in early autosomal dominant polycystic disease: Comparison with CT-scan renal volume calculations

AbstractPurposeTo investigate the correlation and concordance between the ellipsoid volume calculated by ultrasonography measurements (Vol3DUS) and the reference kidney volume measured by CT (VolTDM) in early autosomal dominant polycystic kidney disease (ADPKD).Materials and methodsProspective study of the correlation and concordance of renal volumes in 24 patients with early ADPKD (48 kidneys analysed separately), with calculation of Vol3DUS using the formula for an ellipsoid in three different manners and VolTDM measurement by manual contouring. Calculations of correlation coefficients (r) and coefficients of intra-class correlation (ICC) with confidence intervals at 95%.ResultsThe US volume was strongly correlated with the CT volume by using the maximum width in a transverse section (r=0.83) with a mean Vol3DUS=692±348ml [180; 2069]. The most reproducible ultrasonography measurement was the height. When the kidney volume exceeded 800ml, US underestimated the volume. However, the median error was −57.5ml [−1090; 183] and 85% of the Vol3DUS calculated differed by more than 5% from the reference measurement.ConclusionThe correlation between the US calculated volumes and the CT volumes was strong. However, the median error with ellipsoid US volume was too high to detect a small renal variation in early ADPKD

A post-mortem survey on end-of-life decisions using a representative sample of death certificates in Flanders, Belgium: research protocol

Background: Reliable studies of the incidence and characteristics of medical end-of-life decisions with a certain or possible life shortening effect (ELDs) are indispensable for an evidence-based medical and societal debate on this issue. This article presents the protocol drafted for the 2007 ELD Study in Flanders, Belgium, and outlines how the main aims and challenges of the study (i.e. making reliable incidence estimates of end-of-life decisions, even rare ones, and describing their characteristics; allowing comparability with past ELD studies; guaranteeing strict anonymity given the sensitive nature of the research topic; and attaining a sufficient response rate) are addressed in a post-mortem survey using a representative sample of death certificates. Study design: Reliable incidence estimates are achievable by using large at random samples of death certificates of deceased persons in Flanders (aged one year or older). This entails the cooperation of the appropriate administrative authorities. To further ensure the reliability of the estimates and descriptions, especially of less prevalent end-of-life decisions (e.g. euthanasia), a stratified sample is drawn. A questionnaire is sent out to the certifying physician of each death sampled. The questionnaire, tested thoroughly and avoiding emotionally charged terms is based largely on questions that have been validated in previous national and European ELD studies. Anonymity of both patient and physician is guaranteed through a rigorous procedure, involving a lawyer as intermediary between responding physicians and researchers. To increase response we follow the Total Design Method (TDM) with a maximum of three follow-up mailings. Also, a non-response survey is conducted to gain insight into the reasons for lack of response. Discussion: The protocol of the 2007 ELD Study in Flanders, Belgium, is appropriate for achieving the objectives of the study; as past studies in Belgium, the Netherlands, and other European countries have shown, strictly anonymous and thorough surveys among physicians using a large, stratified, and representative death certificate sample are most suitable in nationwide studies of incidence and characteristics of end-of-life decisions. There are however also some limitations to the study design

Removal of Hepatitis B virus surface HBsAg and core HBcAg antigens using microbial fuel cells producing electricity from human urine

© 2019, The Author(s). Microbial electrochemical technology is emerging as an alternative way of treating waste and converting this directly to electricity. Intensive research on these systems is ongoing but it currently lacks the evaluation of possible environmental transmission of enteric viruses originating from the waste stream. In this study, for the first time we investigated this aspect by assessing the removal efficiency of hepatitis B core and surface antigens in cascades of continuous flow microbial fuel cells. The log-reduction (LR) of surface antigen (HBsAg) reached a maximum value of 1.86 ± 0.20 (98.6% reduction), which was similar to the open circuit control and degraded regardless of the recorded current. Core antigen (HBcAg) was much more resistant to treatment and the maximal LR was equal to 0.229 ± 0.028 (41.0% reduction). The highest LR rate observed for HBsAg was 4.66 ± 0.19 h−1 and for HBcAg 0.10 ± 0.01 h−1. Regression analysis revealed correlation between hydraulic retention time, power and redox potential on inactivation efficiency, also indicating electroactive behaviour of biofilm in open circuit control through the snorkel-effect. The results indicate that microbial electrochemical technologies may be successfully applied to reduce the risk of environmental transmission of hepatitis B virus but also open up the possibility of testing other viruses for wider implementation

Evidence of a causal and modifiable relationship between kidney function and circulating trimethylamine N-oxide

The host-microbiota co-metabolite trimethylamine N-oxide (TMAO) is linked to increased cardiovascular risk but how its circulating levels are regulated remains unclear. We applied "explainable" machine learning, univariate, multivariate and mediation analyses of fasting plasma TMAO concentration and a multitude of phenotypes in 1,741 adult Europeans of the MetaCardis study. Here we show that next to age, kidney function is the primary variable predicting circulating TMAO, with microbiota composition and diet playing minor, albeit significant, roles. Mediation analysis suggests a causal relationship between TMAO and kidney function that we corroborate in preclinical models where TMAO exposure increases kidney scarring. Consistent with our findings, patients receiving glucose-lowering drugs with reno-protective properties have significantly lower circulating TMAO when compared to propensity-score matched control individuals. Our analyses uncover a bidirectional relationship between kidney function and TMAO that can potentially be modified by reno-protective anti-diabetic drugs and suggest a clinically actionable intervention for decreasing TMAO-associated excess cardiovascular risk