Seawater operating bio-photovoltaic cells coupling semiconductor photoanodes and enzymatic biocathodes

Access to fresh water and energy is ranked as one of the most severe challenges to humankind. The restricted availability of fossil fuels and clean water does not match the increasing energy demands and growing population needs, which, desirably, should be satisfied in the most sustainable, clean and inexpensive way. Here, we report clean and sustainable conversion of solar energy into electricity by photo- and bio-electrocatalytic recycling of the H2O/O2 redox couple in a hybrid bio-photovoltaic (BPV) membraneless cell comprising a sunlight-illuminated water-oxidizing semiconductor anode (either Zn-doped hematite or TiO2) and an oxygen-reducing enzymatic biocathode, in such environmental media as seawater. Upon simulated solar light illumination (AM 1.5G, 100 mW cm−2), the maximum power density (Pmax) generated by the cell was 236 and 21.4 μW cm−2 in 1 M Tris–HCl and seawater, both at pH 8, respectively. In seawater its ionic content inhibited mostly the activity of the photoanode, but not that of the biocathode. The obtained Pmax values were orders of magnitude higher than those of a photo-electrochemical cell with a Pt mesh cathode (0.32 μW cm−2 in seawater). The demonstrated thermodynamically feasible coupling of cost-effective photoactive materials such as TiO2 or hematite semiconductors and enzymatic counterparts in seawater media opens a prospective clean and sustainable way of transformation of the most abundant, clean and renewable source of energy – solar light – and the Earth's most massive water resource – seawater – into electricity, which can also be used for fresh water production

ПАТОКОМПЛЕКС ГИБРИДОВ ЛУКА РЕПЧАТОГО Allium cepa l. В ПОСЕВНОЙ КУЛЬТУРЕ ПРИ КАПЕЛЬНОМ ОРОШЕНИИ

The phytopathogenic complex is studied and yield of nine hybrids of bulb onion under growing in annual crops using drip irrigation. The same diseases that afflicted bulb onions in Siberia in the biennial crop of onions are revealed. The highest yield for this technology was shown by F1 hybrid Bonus - 65,5 tones per hectare, average yield - Sherman F1, fopra F1, Solushn F1, Hilton F1.Изучен фитопатогенный комплекс и урожайность 9 гибридов лука репчатого при выращивании в однолетней культуре с использованием капельного орошения. Выявлены те же заболевания, что поражают лук-репку в Сибири при выращивании из севка. Наибольшую урожайность при такой технологии показал Bonus F1 - 65,5 т/га, среднюю - Sherman F1, Корга F1, Solushn F1, Hilton F1

Horseradish and soybean peroxidases: comparable tools for alternative niches?

Horseradish and soybean peroxidases (HRP and SBP, respectively) are useful biotechnological tools. HRP is often termed the classical plant heme peroxidase and although it has been studied for decades, our understanding has deepened since its cloning and subsequent expression, enabling numerous mutational and protein engineering studies. SBP, however, has been neglected until recently, despite offering a real alternative to HRP: SBP actually outperforms HRP in terms of stability and is now used in numerous biotechnological applications, including biosensors. Review of both is timely. This article summarizes and discusses the main insights into the structure and mechanism of HRP, with special emphasis on HRP mutagenesis, and outlines its use in a variety of applications. It also reviews the current knowledge and applications to date of SBP, particularly biosensors. The final paragraphs speculate on the future of plant heme-based peroxidases, with probable trends outlined and explored

ЭКОЛОГИЧЕСКОЕ ПОСЛЕДЕЙСТВИЕ ДЛЯ МИКРОФЛОРЫ ПОЧВЫ ИНТЕНСИВНОГО ВЫРАЩИВАНИЯ ЛУКА В ОДНОЛЕТНЕЙ КУЛЬТУРЕ

Abstract. The paper investigates long-term influence of intensive rearing of non-perennial onion on microflora and phytotoxicity of leached chernozem in a year after harvesting. Early season and middle season hybrids were experimentally cultivated in 2010–2011 supported by drop irrigation, fertigation and plant protection agents. The researchers arranged two control grounds where zero tillage was restricted; they selected soil samples from the control sample plots and other land in the end of vegetation and incubate them during a year in growth chamber by means of modelling seasons. After a year, the researchers analyzed the number of bacterium consuming organic and mineral nitrogen, oligonitrophils, actonomyces and fungi and phytoxicity of tested radish. The revealed lack of long-term phytotoxic effects of intensive technology on soil microflora, which destructs easily decomposed organic remnants and further nitrogen immobilization. Negative effects were observed under early season onion hybrids after 17–20 % suppressing actonomyces and fungi and longterm soil oligotrophic ability; middle season hybrids are characterized by long-term oligotrophic ability and suppressing actonomyces in 1.6 times. This technology affects the environment as a breach in microbial community revealed in changing number of hydrolitics, copyotrophs and oligotrophs. It certifies about longer than 12 months period of soil microflora remediation after pesticide stress in the Ob area.Изучено пролонгированное влияние интенсивного выращивания однолетней культуры лука репчатого на состояние микрофлоры и фитотоксичность выщелоченного чернозема через год после уборки лука. Раннеспелый и среднеспелый гибриды лука выращивали в 2010–2011 гг. в двух производственных опытах на фоне капельного орошения, фертигации и применения средств защиты растений. В посевах выделяли контрольные площадки, где ограничивали гербицидные обработки. В конце вегетации с контрольных делянок и остальной площади отбирали почвенные образцы, которые инкубировали в течение года в климакамере, моделируя смену сезонов. По истечении года в почве анализировали численность бактерий, усваивающих органический и минеральный азот, олигонитрофилов, актиномицетов и грибов и фитотоксичность на тест-объекте редисе. Выявили отсутствие длительных фитотоксических эффектов и последействия интенсивной технологии для почвенной микрофлоры, осуществляющей деструкцию легкоразлагаемых органических остатков и дальнейшую иммобилизацию азота. Негативные последствия проявились под раннеспелыми гибридами лука подавлением на 17–20 % численности актиномицетов и грибов и пролонгирован ной олиготрофностью почвы, под среднеспелыми гибридами – пролонгированной олиготрофностью и подавлением в 1,6 раза обилия актиномицетов. Экологическим последствием изученной технологии стало нарушение структуры микробного сообщества, выразившееся в изменении соотношений гидролитиков, копиотрофов и олиготрофов. Это свидетельствует о более длительном, чем 12 месяцев, сроке восстановления в Приобье микрофлоры почвы после пестицидного стресса.

A DNA nanoswitch incorporating the fluorescent base analogue 2-aminopurine detects single nucleotide mismatches in unlabelled targets

DNA nanoswitches can be designed to detect unlabelled nucleic acid targets and have been shown to discriminate between targets which differ in the identity of only one base. This paper demonstrates that the fluorescent base analogue 2-aminopurine (AP) can be used to discriminate between nanoswitches with and without targets and to discriminate between matched and mismatched targets. In particular, we have used both steady-state and time-resolved fluorescence spectroscopy to determine differences in AP environment at the branchpoint of nanoswitches assembled using complementary targets and targets which incorporate single base mismatches

Direct electrochemistry of Heme Proteins on Electrodes Modified with Didodecyldimethyl Ammonium Bromide and Carbon Black

A novel matrix based on commercially available carbon black (CB) N220 and didodecyldimethyl ammonium bromide (DDAB) was shown to be a reliable support for direct electron transfer reactions between screen printed electrode (SPE) and Fe(III)-heme proteins. Cytochrome c(cytc), myoglobin (Mb), horseradish peroxidase (HRP) and cytochromes P450 (CYP 51A1, CYP 3A4, CYP 2B4) generated well-shaped cyclic voltammograms on SPE/CB/ DDAB electrodes (both in solution and in immobilized state). The attractive performance characteristics of CB modified electrodes are advantageous over single-walled carbon nanotubes (SW CNT) based ones. The achieved direct electrochemistry of heme proteins on CB/DDAB-modified electrodes provided successful elaboration of the immunosensor for cardiac Mb. The immunosensor showed applicability for diagnostics of myocardial infarction displaying significant difference in cardiac Mb content of human blood plasma samples taken from the corresponding patients

Methylene blue not ferrocene: Optimal reporters for electrochemical detection of protease activity

AbstractElectrochemical peptide-based biosensors are attracting significant attention for the detection and analysis of proteins. Here we report the optimisation and evaluation of an electrochemical biosensor for the detection of protease activity using self-assembled monolayers (SAMs) on gold surfaces, using trypsin as a model protease. The principle of detection was the specific proteolytic cleavage of redox-tagged peptides by trypsin, which causes the release of the redox reporter, resulting in a decrease of the peak current as measured by square wave voltammetry. A systematic enhancement of detection was achieved through optimisation of the properties of the redox-tagged peptide; this included for the first time a side-by-side study of the applicability of two of the most commonly applied redox reporters used for developing electrochemical biosensors, ferrocene and methylene blue, along with the effect of changing both the nature of the spacer and the composition of the SAM. Methylene blue-tagged peptides combined with a polyethylene-glycol (PEG) based spacer were shown to be the best platform for trypsin detection, leading to the highest fidelity signals (characterised by the highest sensitivity (signal gain) and a much more stable background than that registered when using ferrocene as a reporter). A ternary SAM (T-SAM) configuration, which included a PEG-based dithiol, minimised the non-specific adsorption of other proteins and was sensitive towards trypsin in the clinically relevant range, with a Limit of Detection (LoD) of 250pM. Kinetic analysis of the electrochemical response with time showed a good fit to a Michaelis–Menten surface cleavage model, enabling the extraction of values for kcat and KM. Fitting to this model enabled quantitative determination of the solution concentration of trypsin across the entire measurement range. Studies using an enzyme inhibitor and a range of real world possible interferents demonstrated a selective response to trypsin cleavage. This indicates that a PEG-based peptide, employing methylene blue as redox reporter, and deposited on an electrode as a ternary SAM configuration, is a suitable platform to develop clinically-relevant and quantitative electrochemical peptide-based protease biosensing

Voltammetric behaviour of hydrogen peroxide at a silver electrode fabricated from a rewritable digital versatile disc (DVD) and its determination in water samples

In this study we investigated the possibility of applying Ag electrodes manufactured from recordable rewritable digital versatile discs (DVD-RW) for the voltammetric determination of hydrogen peroxide. The calibration plot was linear from 0.087 mM to 3.41 mM hydrogen peroxide with a sensitivity of 58.7 μA mM-1 over this range. A corresponding detection limit of 78.35 μM, based on a signal-to-noise-ratio of 3 was recorded. No interferences were observed by 500 mg L-1 chloride, 50 mg L-1 nitrate, 700 mg L-1 sulphate or 700 mg L-1 carbonate which are found in swimming pool water at these concentrations. Using the multiple standard addition method a percentage recovery of 90.67% with a coefficient of variation of 4.69% (n = 5) was found for a representative swimming pool water concentration of 1.2 mM hydrogen peroxide. Therefore, the performance data suggests that the method is reliable at the concentrations examined in this study and that a rapid, simple, economical and precise method of monitoring hydrogen peroxide in swimming pool and aquaculture applications is possible. © 2013 The Royal Society of Chemistry

A Review on Direct Electrochemistry of Catalase for Electrochemical Sensors

Catalase (CAT) is a heme enzyme with a Fe(III/II) prosthetic group at its redox centre. CAT is present in almost all aerobic living organisms, where it catalyzes the disproportionation of H2O2 into oxygen and water without forming free radicals. In order to study this catalytic mechanism in detail, the direct electrochemistry of CAT has been investigated at various modified electrode surfaces with and without nanomaterials. The results show that CAT immobilized on nanomaterial modified electrodes shows excellent catalytic activity, high sensitivity and the lowest detection limit for H2O2 determination. In the presence of nanomaterials, the direct electron transfer between the heme group of the enzyme and the electrode surface improved significantly. Moreover, the immobilized CAT is highly biocompatible and remains extremely stable within the nanomaterial matrices. This review discusses about the versatile approaches carried out in CAT immobilization for direct electrochemistry and electrochemical sensor development aimed as efficient H2O2 determination. The benefits of immobilizing CAT in nanomaterial matrices have also been highlighted