Miniaturised technologies for the development of artificial lipid bilayer systems

Artificially reproducing cellular environments is a key aim of synthetic biology, which has the potential to greatly enhance our understanding of cellular mechanisms. Microfluidic and lab-on-a-chip (LOC) techniques, which enable the controlled handling of sub-microlitre volumes of fluids in an automated and high-throughput manner, can play a major role in achieving this by offering alternative and powerful methodologies in an on-chip format. Such techniques have been successfully employed over the last twenty years to provide innovative solutions for chemical analysis and cell-, molecular- and synthetic- biology. In the context of the latter, the formation of artificial cell membranes (or artificial lipid bilayers) that incorporate membrane proteins within miniaturised LOC architectures offers huge potential for the development of highly sensitive molecular sensors and drug screening applications. The aim of this review is to give a comprehensive and critical overview of the field of microsystems for creating and exploiting artificial lipid bilayers. Advantages and limitations of three of the most popular approaches, namely suspended, supported and droplet-based lipid bilayers, are discussed. Examples are reported that show how artificial cell membrane microsystems, by combining together biological procedures and engineering techniques, can provide novel methodologies for basic biological and biophysical research and for the development of biotechnology tools.     

Determination of perfluorinated alkyl acid concentrations in biological standard reference materials

Standard reference materials (SRMs) are homogeneous, well-characterized materials used to validate measurements and improve the quality of analytical data. The National Institute of Standards and Technology (NIST) has a wide range of SRMs that have mass fraction values assigned for legacy pollutants. These SRMs can also serve as test materials for method development, method validation, and measurement for contaminants of emerging concern. Because inter-laboratory comparison studies have revealed substantial variability of measurements of perfluoroalkyl acids (PFAAs), future analytical measurements will benefit from determination of consensus values for PFAAs in SRMs to provide a means to demonstrate method-specific performance. To that end, NIST, in collaboration with other groups, has been measuring concentrations of PFAAs in a variety of SRMs. Here we report levels of PFAAs and perfluorooctane sulfonamide (PFOSA) determined in four biological SRMs: fish tissue (SRM 1946 Lake Superior Fish Tissue, SRM 1947 Lake Michigan Fish Tissue), bovine liver (SRM 1577c), and mussel tissue (SRM 2974a). We also report concentrations for three in-house quality-control materials: beluga whale liver, pygmy sperm whale liver, and white-sided dolphin liver. Measurements in SRMs show an array of PFAAs, with perfluorooctane sulfonate (PFOS) being the most frequently detected. Reference and information values are reported for PFAAs measured in these biological SRMs.

Chemical analysis of surgical smoke by infrared laser spectroscopy

The chemical composition of surgical smoke, a gaseous by-product of some surgical devices??lasers, drills, vessel sealing devices??is of great interest due to the many toxic components that have been found to date. For the first time, surgical smoke samples collected during routine keyhole surgery were analyzed with infrared laser spectroscopy. Traces (ppm range) of methane, ethane, ethylene, carbon monoxide and sevoflurane were detected in the samples which consisted mostly of carbon dioxide and water vapor. Except for the anaesthetic sevoflurane, none of the compounds were present at dangerous concentrations. Negative effects on the health of operation room personnel can be excluded for many toxic compounds found in earlier studies, since their concentrations are below recommended exposure limits.     

Highly stable gel electrolytes for dye solar cells based on chemically engineered polymethacrylic hosts

Four different species of ionically conductive polymers were synthesized and successfully implemented to formulate novel quasi-solid electrolytes for dye solar cells. A power conversion efficiency superior to 85% of the correspondent liquid electrolyte as well as an excellent cell's stability was demonstrated after 500 days of storage.     

Precision measurements and computations of transition energies in rotationally cold triatomic hydrogen ions up to the midvisible spectral range

First-principles computations and experimental measurements of transition energies are carried out for vibrational overtone lines of the triatomic hydrogen ion H(3)(+) corresponding to floppy vibrations high above the barrier to linearity. Action spectroscopy is improved to detect extremely weak visible-light spectral lines on cold trapped H(3)(+) ions. A highly accurate potential surface is obtained from variational calculations using explicitly correlated Gaussian wave function expansions. After nonadiabatic corrections, the floppy H(3)(+) vibrational spectrum is reproduced at the 0.1 cm(-1) level up to 16600 cm(-1).     

HCN channels and heart rate

Hyperpolarization and Cyclic Nucleotide (HCN) -gated channels represent the molecular correlates of the "funny" pacemaker current (I(f)), a current activated by hyperpolarization and considered able to influence the sinus node function in generating cardiac impulses. HCN channels are a family of six transmembrane domain, single pore-loop, hyperpolarization activated, non-selective cation channels. This channel family comprises four members: HCN1-4, but there is a general agreement to consider HCN4 as the main isoform able to control heart rate. This review aims to summarize advanced insights into the structure, function and cellular regulation of HCN channels in order to better understand the role of such channels in regulating heart rate and heart function in normal and pathological conditions. Therefore, we evaluated the possible therapeutic application of the selective HCN channels blockers in heart rate control.     

Protective effects of extracts and flavonoids isolated from Scutia buxifolia Reissek against chromosome damage in human lymphocytes exposed to hydrogen peroxide

Flavonoids are claimed to protect against cardiovascular disease, certain forms of cancer and ageing, possibly by preventing initial DNA damage. Therefore, we investigated the protective effects of crude extract, ethyl acetate fraction and flavonoids (quercetin, quercitrin, isoquercitrin and rutin) isolated from the leaves from Scutia buxifolia against chromosome damage induced by H?O? in human lymphocytes by analyzing cellular growth rate, cell viability, mitotic index and chromosomal instability. We found a differential response among the compounds tested, with the ethyl acetate fraction being more effective than the crude extract, a difference perhaps related to the presence of the antioxidants identified and quantified by HPLC/DAD. In general, quercetin, isoquercitrin and rutin recovered the mitotic index and chromosomal instability more than quercitrin after treatment with hydrogen peroxide.     

On the redox behaviour of glycerol at TiO2 electrodes

An experimental work is presented in which alkaline solutions of glycerol are electrochemically treated at TiO₂ electrodes obtained by electrochemical oxidation of Ti foils annealed a 400 °C and 600 °C. The semiconductor properties of the material, strictly correlated to the presence of structural defects, and their different concentration and distribution originated by the different annealing temperature are investigated. In order to derive useful indications for possible application on reduction or photo-oxidation of glycerol, particular attention is paid on the working mechanism of the electrodes in a wide range of potential at which the semiconductor may be under accumulation or depletion regime.     

Investigation of scaling properties in monthly streamflow and Standardized Streamflow Index (SSI) time series in the Ebro basin (Spain)

Scaling behaviors in monthly streamflow and Standardized Streamflow Index (SSI) of 11 gauging stations in Ebro basin (Spain) were analyzed: four located in the mainstream and seven in tributaries. The time span is from 1950 to 2005. The methods used are the power spectrum and the detrended fluctuation analysis. All the streamflows are signaled by the presence of the yearly oscillation, which also plays the role of crossover between two regions: for frequencies smaller than the yearly cycle (or timescales higher than 1 year) the dynamics is approximately random, while for frequencies higher than the yearly frequency (or timescales smaller than 1 year) the dynamics is persistently correlated. The SSI shows approximately similar characteristics, although the annual oscillation is not evidenced. Except for a few peculiar features, the power spectrum and the detrended fluctuation analysis (DFA) have shown similar results for all the streamflow and SSI time series, indicating a universal scaling behavior over the Ebro basin.     

Visibility graph analysis of wind speed records measured in central Argentina

Hourly means of wind speed time series recorded at two wind stations in central Argentina (one inland and the other coastal) are analyzed by means of the visibility graph method. The degree distribution of both series was calculated along with that of their shuffled, Gaussian- and uniform-distributed surrogates. The original series as well as their surrogates show an apparent exponential degree distribution. The v$v$–k$k$ (value–degree) plot of the original wind series indicates that the higher values of the series are not necessarily “hubs” for the series, while that of the surrogates are characterized by a reduced connectivity degree of the higher hubs.