Proton Semiconductor Research Articles

Detailed-balance limits for sunlight-to-protonic energy conversion from aqueous photoacids and photobases based on reversible mass-action kinetics

(Photo)chemical and photophysical detailed balance analyses are used to predict optimal properties and efficiency limits for sunlight-to-protonic energy conversion from aqueous photoacids or photobases.

Making and Breaking Bipolar Membrane Protonic Diodes

Historically, bipolar membranes have been used for application in electrodialysis at moderate current densities (<100 mA/cm2). In the past decade bipolar membranes have experienced a renaissance due to interest in driving higher current density processes with intentional pH gradients between the anode and cathode, such as CO2/H2O electrolysis and electrochemical generation of acid and base for direct oceanic carbon capture, two applications that my group actively studies. My group’s main contribution to this field is that we recently showed that bipolar membranes are in fact high-quality protonic diodes, where water serves as a (protonic) semiconductor. Given this fact, we leveraged techniques from the semiconductor physics and electrocatalysis communities, i.e. Mott–Schottky analysis and Butler–Volmer analysis, to further characterize bipolar membrane performance. Using this platform, we have also demonstrated photovoltaic action from photoacid-dye-sensitized bipolar membranes. More recently, we have studied how intentional placement of proton-donating and proton-accepting groups in the bipolar membrane space–charge region forms a recombination/generation junction, which are the non-tunneling variants of tunnel junctions that are important in tandem solar cells. This allows for rapid protonic conduction across originally rather insulating junctions, as desired for ionic conductors in most electrochemical devices. Collectively, our efforts form the foundational framework for new functions and resulting applications that benefit from protonic transfer and transport.

(Keynote) Making and Breaking Bipolar Membrane Protonic Diodes

Bipolar membranes have been studied for >50 years for application in electrodialysis at moderate current densities (<100 mA/cm2). In the past decade bipolar membranes have experienced a renaissance due to interest in driving higher current density processes with intentional pH gradients between the anode and cathode, such as CO2/H2O electrolysis and electrochemical generation of acid and base for direct oceanic carbon capture, two applications that my group actively studies. My group’s main contribution to this field is that we recently showed that bipolar membranes are in fact high-quality protonic diodes, where water serves as a (protonic) semiconductor. Using Mott–Schottky analysis and Butler–Volmer analysis, we reported on the performance of said materials. Using this platform, we have demonstrated photovoltaic action from photoacid-dye-sensitized bipolar membranes. More recently, we have studied how intentional placement of proton-donating and proton-accepting groups in the space–charge region forms a recombination/generation junction, which are the non-tunneling variants of tunnel junctions that are important in tandem solar cells. This allows for rapid protonic conduction across originally rather insulating junctions, as desired for ionic conductors in most electrochemical devices. Collectively, our efforts form the foundational framework for new functions and resulting applications that benefit from protonic transfer and transport.

(Invited) High-Quality Protonic Diodes and Their Transformation into Solar Cells and Conductors

Ionically conductive materials and diodes have been actively studied since the pioneering work of John Bockris in 1959. The subset of purely protonic diodes based on liquid water are far less common, yet are more analogous to electronic semiconductors in that generation, recombination, and transport each occur and junctions fully equilibrate.In my presentation, I will explain how water is a protonic semiconductor and show that it can be doped through addition of salts of H+ and/or OH– that when fixed in place using polymeric bipolar membrane scaffolds enable purely protonic diodes. Electrochemical evaluation is achieved using membrane–electrode–assemblies that drive reversible H2 redox chemistry to transduce changes in electronic electrochemical potential into protonic electrochemical potential, and vice versa. Characterization of the semiconducting properties of these protonic diodes allowed for determination of flatband potentials using Mott–Schottky analysis, and mobilities via analysis of space-charge-limited conduction.Further, via covalent modification of polymers with photoacid dye sensitizers we were able to demonstrate solar cell function, and modification with generation/recombination buffering groups we were able to demonstrate ohmic conduction. The latter is relevant for application of bipolar membranes in CO2 electrolyzers. Collectively, these efforts form the foundational framework for new devices and functions that benefit from purely protonic transport.

Nuclear Quantum Effects Largely Influence Molecular Dissociation and Proton Transfer in Liquid Water under an Electric Field.

Proton transfer in liquid water controls acid-base chemistry, crucial enzyme reactions, and the functioning of fuel cells. Externally applied static electric fields in water are capable of dissociating molecules and transferring protons across the H-bond network. However, the impact of nuclear quantum effects (NQEs) on these fundamental field-induced phenomena has not yet been reported. By comparing state-of-the-art ab initio molecular dynamics (AIMD) and path integral AIMD simulations of water under electric fields, I show that quantum delocalization of the proton lowers the molecular ionization threshold to approximately one-third. Moreover, also the water behavior as a protonic semiconductor is considerably modified by the inclusion of NQEs. In fact, when the quantum nature of the nuclei is taken into account, the proton conductivity is ∼50% larger. This work proves that NQEs sizably affect the protolysis phenomenon and proton transfer in room-temperature liquid water.

Purely Protonic Solar Cells Fabricated from Photoacid-Modified Ion-Exchange Membranes

Analogies have been drawn between electronic semiconductors and water since 1956 when Fuller explained the similarity between silicon ionization, which generates an electron and a hole as mobile charge carriers, and water ionization, which yields a hydroxide and a proton as mobile charge carriers.1 Since then our group has taken steps to produce a water-based pn-junction solar cell that uses water as a protonic semiconductor. Toward this, we have demonstrated photovoltaic action using photoacid-modified Nafion membranes alone2 and when laminated to an anion-exchange membrane,3 yet each demonstration required the membrane to be wetted by an aqueous acid–base gradient. In this report, a liquid-electrolyte-free photoacid-modified ion-exchange membrane–electrode–assembly (MEA) driving reversible H2 redox chemistry is described. The cell architecture consists of a three-layer membrane (cation-selective Nafion membrane, aminopyrene-functionalized polyphenylene oxide, anion-selective X37 membrane) that was characterized using direct membrane contacts consisting of platinized platinum mesh. The MEA achieved V oc = 10 mV and J sc = 7.5 μA/cm2 under low-intensity 405 nm illumination, resulting in an internal quantum efficiency of ~0.2%. The reported composite MEA overcomes the problem of co-ion crossover by eliminating co-ions altogether while still exhibiting photovoltaic action due to the charge-separating potential across the membrane interfaces. Because photovoltaic performance persists in the absence of electrolyte gradients and because the potentiometric measurements conducted here are only sensitive to the electrochemical potential of protons, we can conclude that the light-induced voltage and current originate from protons and/or hydroxides, and no other ionic species. This MEA thus serves as a robust proof-of-concept of water’s role as a protonic semiconductor. It also offers a promising format for fundamental studies on the origin of photovoltaic action in photoacid–polymer-electrolyte membranes in the absence of the convoluting effects of liquid electrolyte. Acknowledgments: This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Research Award under award number DE-SC0019162 from the Solar Photochemistry Program. Fuller, C. S. Chem. Prog. 1956, 17, 75-93.White, W.; Sanborn, C. D.; Reiter, R. S.; Fabian, D. M.; Ardo, S. J. Am. Chem. Soc. 2017, 139, 11726–11733.White, W.; Sanborn, C. D.; Fabian, D. M.; Ardo, S. Joule 2018, 2, 94-109.

P1.09-31 Preliminary Experience with Liquid Biopsies in a Resource Constrained Setting and Its Impact on Treatment Decision Making

Liquid biopsies are potentially useful for molecular testing in the presence of inadequate tissue and for detection of resistance mechanisms in EGFR mutated NSCLC patients. Initial experience with liquid biopsies for advanced/metastatic NSCLC patients in a resource constrained setting is described herein. Retrospective audit of liquid biopsies performed over a 21-month period for NSCLC patients at a tertiary referral centre in North India. Testing methods included digital-droplet-PCR (ddPCR), Next-Generation-Sequencing (NGS) and Real-Time-PCR (RT-PCR). ddPCR was used to detect specific EGFR mutations (L858R exon21, E746_A750 exon19 deletions and T790M exon20) in ctDNA (detection limit based upon amplifiable DNA ranging from 0.5%-<0.01% of mutant allele). For NGS, cfDNA extracted from plasma was subjected to target enrichment by high multiplex PCR amplification and analyzed for mutations using gene panel (BRAF, EGFR, ERBB2/HER2, KRAS, MET) on the Ion Proton semiconductor sequencer (Life Technology, USA). RT-PCR assay using EGFR-RT52 kit (EntroGen USA) detects known somatic mutations in exons 18-21 of EGFR by amplifying mutant-specific sequences and relies on fluorescent probes for detection (detection limit of 1%). 42 patients [61.9% (n=26) males] underwent liquid biopsies. ddPCR, NGS and RT-PCR were performed in 31(73.8%), 7(16.7%) and 4(9.5%) patients respectively. Timing was prior to/during first-line treatment in 23(54.8%) and at progression on first-line treatment in 19(45.2%) patients. In the former, indication was inadequate tissue for molecular analysis (n=15), detection of other targetable mutation (after EGFR wild type status on tissue; n=3) and checking ctDNA status of T790M exon 20 detected in tissue (n=5). Among 19 patients with progression on first-line treatment, 17 were those with a sensitizing EGFR mutation at baseline who had progressed on EGFR-TKI of which 47.1% (n=8) were found to have T790M exon 20 mutation. The primary EGFR sensitizing mutation detected in tissue at baseline was also detected in ctDNA in 9 of 20 patients with a sensitivity of 45.0%. Agreement between results of tissue testing and liquid biopsy testing for EGFR mutations was 48.0% (12/25). Potential change in management with use of liquid biopsies was observed in 12 patients (28.6% overall and 52.6% if done at progression). Preliminary experience in our resource constrained setting indicates that greatest utility of liquid biopsies is for EGFR mutated patients with progression on EGFR-TKI wherein T790M detection rates are comparable to those reported in literature. However, the overall sensitivity and agreement is lower than that reported in literature and perhaps may be related to small number of patients.

P1.09-15 Preliminary Experience with Liquid Biopsies in a Resource Constrained Setting and its Impact on Treatment Decision Making

Liquid biopsies are potentially useful for molecular testing in the presence of inadequate tissue and for detection of resistance mechanisms in EGFR mutated NSCLC patients. Initial experience with liquid biopsies for advanced/metastatic NSCLC patients in a resource constrained setting is described herein. Retrospective audit of liquid biopsies performed over a 21-month period for NSCLC patients at a tertiary referral centre in North India. Testing methods included digital-droplet-PCR (ddPCR), Next-Generation-Sequencing (NGS) and Real-Time-PCR (RT-PCR). ddPCR was used to detect specific EGFR mutations (L858R exon21, E746_A750 exon19 deletions and T790M exon20) in ctDNA (detection limit based upon amplifiable DNA ranging from 0.5%-<0.01% of mutant allele). For NGS, cfDNA extracted from plasma was subjected to target enrichment by high multiplex PCR amplification and analyzed for mutations using gene panel (BRAF, EGFR, ERBB2/HER2, KRAS, MET) on the Ion Proton semiconductor sequencer (Life Technology, USA). RT-PCR assay using EGFR-RT52 kit (EntroGen USA) detects known somatic mutations in exons 18-21 of EGFR by amplifying mutant-specific sequences and relies on fluorescent probes for detection (detection limit of 1%). 42 patients [61.9% (n=26) males] underwent liquid biopsies. ddPCR, NGS and RT-PCR were performed in 31(73.8%), 7(16.7%) and 4(9.5%) patients respectively. Timing was prior to/during first-line treatment in 23(54.8%) and at progression on first-line treatment in 19(45.2%) patients. In the former, indication was inadequate tissue for molecular analysis (n=15), detection of other targetable mutation (after EGFR wild type status on tissue; n=3) and checking ctDNA status of T790M exon 20 detected in tissue (n=5). Among 19 patients with progression on first-line treatment, 17 were those with a sensitizing EGFR mutation at baseline who had progressed on EGFR-TKI of which 47.1% (n=8) were found to have T790M exon 20 mutation. The primary EGFR sensitizing mutation detected in tissue at baseline was also detected in ctDNA in 9 of 20 patients with a sensitivity of 45.0%. Agreement between results of tissue testing and liquid biopsy testing for EGFR mutations was 48.0% (12/25). Potential change in management with use of liquid biopsies was observed in 12 patients (28.6% overall and 52.6% if done at progression). Preliminary experience in our resource constrained setting indicates that greatest utility of liquid biopsies is for EGFR mutated patients with progression on EGFR-TKI wherein T790M detection rates are comparable to those reported in literature. However, the overall sensitivity and agreement is lower than that reported in literature and perhaps may be related to small number of patients.

New polymorphic microsatellite loci revealed for the dusky shark Carcharhinus obscurus through Ion Proton double-digest RAD sequencing.

The non-model shark species, dusky shark Carcharhinus obscurus, is a bio-economically and recreationally important shark in many areas of its range. Despite of the fishery importance of C. obscurus few genetic resources are currently available for the species. Here, we report on the isolation of eight novel microsatellite loci from C. obscurus using a double-digest restriction site associated DNA (RAD) sequencing approach on the Ion Proton semiconductor platform (ddRADseq-ion). We characterised the loci in 26 individuals and all loci were polymorphic, exhibiting 5-10 alleles (average 6.6), and observed and expected heterozygosities of 0.385-0.962 and 0.479-0.847, respectively. We found that all pairs of loci were in linkage equilibrium and conformed to Hardy-Weinberg expectations. The loci reported in this study are only the second set of microsatellite loci ever characterized for C. obscurus and will be valuable for molecular ecology studies for this vulnerable species.

Analysis of the accuracy of Z-scores of non-invasive prenatal testing for fetal Trisomies 13, 18, and 21 that employs the ion proton semiconductor sequencing platform

BackgroundNon-invasive prenatal testing (NIPT) is frequently being used to screen for trisomies 13, 18 and 21 for prenatal diagnosis. However, NIPT performs poorly when compared with invasive testing and thus should not be used to diagnose trisomies. The result of NIPT for an individual woman in most genome-wide methods is calculated as a Z-score. The aim of this study was to assess the correlation between Z-scores of NIPT results and the accuracy of non-invasive prenatal testing.ResultsWe evaluated 108 pregnant women with positive NIPT results, which were validated through karyotype analysis of amniotic fluid puncture by means of sequencing, bioinformatics analysis, and follow-up. Utilizing the ion proton semiconductor sequencing platform, we report a performance evaluation of NIPT-positive results at Third Affiliated Hospital of Zhengzhou University of Henan Province, China, by classifying Z-scores as 3 ≤ Z<5, 5 ≤ Z < 9 and Z ≥ 9. The findings indicate that positive NIPT results at Z ≥ 9 have a higher accuracy compared with positive NIPT results at 5 ≤ Z < 9 and 3 ≤ Z<5.ConclusionsThe findings show that Z-scores of NIPT results are closely related to the accuracy of non-invasive prenatal testing. However, false-positive NIPT results at 3 ≤ Z<5 may occur due to confined placental mosaicism (CPM).

Target amplicon exome-sequencing identifies promising diagnosis and prognostic markers involved in RTK-RAS and PI3K-AKT signaling as central oncopathways in primary central nervous system lymphoma.

Exome-sequencing for somatic mutation detection and copy number variation analysis are effective and valid methods for evaluating human cancers in current molecular medicine. We conducted target amplicon exome-sequencing analyses using PCR target enrichment and next-generation sequencing on Ion Proton semiconductor sequencers. Twenty-seven primary central nervous system lymphoma (PCNSL) specimens and their corresponding noncancerous tissues were used for multiplex PCR amplification to obtain targeted coverages of the entire coding regions of 409 cancer-related genes. The average of the total numbers of somatic mutations including single-nucleotide variations and insertion/deletion mutations in each specimen was 13.3. Of these, the average of the ratios of nonsynonymous substitutions in each specimen was 74.8%. The most frequent mutations in 27 specimens were in PIM1, MYD88, CD79B, DST, IRF4, ERBB3, MYH11, DCC, and KMT2D. Furthermore, somatic mutations of MYH11 were related to poor prognoses in PCNSL patients. Copy number variations were also duplicated and/or deleted from deep-sequencing in segmental genomic islands. In addition to these prognostic marker candidates, analysis of RTK-RAS-MAPK signaling and the PTEN-PI3K-AKT proapoptotic pathway showed that somatic activations and aberrations, respectively, may be involved in a promising central oncopathway harboring mTOR, c-Myc, FOXO1, and p53. This study provides a foundation for molecular targeted therapies based on genome diagnostics and prognosis in PCNSL.

Profiling cancer-related gene mutations in oral squamous cell carcinoma from Japanese patients by targeted amplicon sequencing.

Somatic mutation analysis is a standard practice in the study of human cancers to identify mutations that cause therapeutic sensitization and resistance. We performed comprehensive genomic analyses that used PCR target enrichment and next-generation sequencing on Ion Proton semiconductor sequencers. Forty-seven oral squamous cell carcinoma (OSCC) samples and their corresponding noncancerous tissues were used for multiplex PCR amplification to obtain targeted coverage of the entire coding regions of 409 cancer-related genes (covered regions: 95.4% of total, 1.69 megabases of target sequence). The number of somatic mutations in 47 patients with OSCC ranged from 1 to 20 with a mean of 7.60. The most frequent mutations were in TP53 (61.7%), NOTCH1 (25.5%), CDKN2A (19.1%), SYNE1 (14.9%), PIK3CA (10.6%), ROS1 (10.6%), and TAF1L (10.6%). We also detected copy number variations (CNVs) in the segments of the genome that could be duplicated or deleted from deep sequencing data. Pathway assessment showed that the somatic aberrations within OSCC genomes are mainly involved in several important pathways, including cell cycle regulation and RTK–MAPK-PI3K. This study may enable better selection of therapies and deliver improved outcomes for OSCC patients when combined with clinical diagnostics.

Proton transport through hydrated chitosan‐based polymer membranes under electric fields

ABSTRACTProton transport is essential in many areas of chemistry and biology and is especially important in the fields of proton exchange membrane fuel cells and biocompatible, protonic semiconductors. These devices make use of membranes to control the flow of protons for either the generation of energy or to more closely couple electronics and biology. In the present study, we make use of ab initio molecular dynamics simulations, including the effect of applied electric fields, to gain atomistic insight into the intrinsic conductivity of chitosan‐based polymers and demonstrate that chitosan does not act as a significant source of friction for the transport of protons while increasing the number of free ions. Published 2017.† J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1103–1109

The IONA® Test: Development of an Automated Cell-Free DNA-Based Screening Test for Fetal Trisomies 13, 18, and 21 That Employs the Ion Proton Semiconductor Sequencing Platform

Objective: To develop a screening test for fetal trisomy 13, 18, and 21 using cell-free DNA from maternal blood with an automated workflow using the Ion Proton sequencing platform. Methods: An automated next-generation sequencing workflow was developed using the Ion Proton sequencing platform and software developed for straightforward bioinformatic analysis. An algorithm was developed using 239 samples to determine the likelihood of trisomy, using DNA fragment counts and a fetal fraction validity check; the results were compared with those from invasive diagnostic procedures. A further 111 samples were used to assess the tests' sensitivity (detection rate) and specificity (1 minus false-positive rate). Results: The 110 of a possible 111 valid samples used to verify the IONA® test gave 100% sensitivity and specificity, compared with invasive diagnostic procedures; one failed the fetal fraction validity check giving a sample failure rate of 0.29% across all 350 analysed samples. Conclusion: The data indicate that the IONA test provides a robust, accurate automated workflow suitable for use on maternal blood samples to screen for trisomies 13, 18, and 21. The test has the potential to reduce the number of unnecessary invasive procedures performed and facilitate testing by screening laboratories.

Orthogonal NGS for High Throughput Clinical Diagnostics.

Next generation sequencing is a transformative technology for discovering and diagnosing genetic disorders. However, high-throughput sequencing remains error-prone, necessitating variant confirmation in order to meet the exacting demands of clinical diagnostic sequencing. To address this, we devised an orthogonal, dual platform approach employing complementary target capture and sequencing chemistries to improve speed and accuracy of variant calls at a genomic scale. We combined DNA selection by bait-based hybridization followed by Illumina NextSeq reversible terminator sequencing with DNA selection by amplification followed by Ion Proton semiconductor sequencing. This approach yields genomic scale orthogonal confirmation of ~95% of exome variants. Overall variant sensitivity improves as each method covers thousands of coding exons missed by the other. We conclude that orthogonal NGS offers improvements in variant calling sensitivity when two platforms are used, better specificity for variants identified on both platforms, and greatly reduces the time and expense of Sanger follow-up, thus enabling physicians to act on genomic results more quickly.

The feasibility study of Ion Proton semiconductor sequencing platform in the non-invasive prenatal genetic diagnosis

Objective To evaluate the feasibility of apply Ion Proton semiconductor sequencing platform in non-invasive prenatal genetic diagnosis. Methods Totally 1 000 pregnant women with a singleton pregnancy of 12-32 weeks gestation were selected from the Third affiliated Hospital of Zhengzhou University from Jan to Dec 2013. Using noninvasive prenatal genetic diagnosis based on Ion Proton semiconductor sequencing platform to study their cffDNA. In parallel, 72 pregnant women received invasive prenatal diagnosis by traditional chromosomal analysis with amniocentesis chorionic villus sampling. Results It′s shown that 18 out of 1 000 (1.8%) pregnant women underwent the noninvasive prenatal genetic testing had a high risk for aneuploid chromosomes, including 7 cases of 21-trisomy, 4 cases of 18-trisomy, 2 cases of 13-trisomy, 4 cases of sex chromosomal abnormality, and 1 case of 15-trisomy. It demonstrated that the rate and accuracy of fetal 21-trisomy, 13-trisomy and 18-trisomy by non-invasive prenatal genetic testing were both 100% without misdiagnosis, the rate of detection for sex chromosomal abnormality was 2/2 with a false positive rate of 1/3. However, the 15-trisomy predicted by the non-invasive prenatal diagnosis in a woman was finally proved to be a false positive. Based on the results by karyotyping (55/55) as well as follow-ups (493/493), the specificity of the non-invasive prenatal diagnosis for detection of 21-trisomy, 18-trisomy and 13-trisomy was 100%. One Ion PITM chip could detect 12 to 15 samples in 1.5 h and the whole process of noninvasive detection could be completed in 1 to 1.5 days. Conclusions The non-invasive prenatal diagnosis by Ion Proton semiconductor sequencing platform could provide fast and accurate detection of fetal aneuploidy. The benchtop high-throughput sequencing platform has laid the foundation for the independent application in clinical settings for fetal aneuploidy detection. （Chin J Lab Med，2014,37：861-865） Key words: Prenatal diagnosis; Aneuploidy; Chromosome aberrations; Aneuploidy; Sequence analysis, DNA; High-throughput nucleotide sequencing; Feasibility studies

Creating internal conductivity in dry biological SEM samples by a simple vapour treatment.

Internal sample conductivity in scanning electron microscopy can be a valuable alternative to metal coating. Proton conductivity may be used for this purpose. Many solid materials with active hydrogen atoms, such as hydrogen- and ammonium-salts, organic acids, and even ice, are protonic conductors or semiconductors. Here we present a method to generate proton conductivity in dry biological materials. A simple treatment with hydrogen chloride gas or hydrochloric acid vapour for a few minutes provides sufficient conductivity for many samples. After a removal of excess hydrogen chloride vapour with a vacuum desiccator, the objects may be examined in the SEM without metal coating. The use of internally conductive samples extends the range of easy-to-perform SEM preparation techniques. It is advantageous for material contrast imaging of uncoated samples, and it can be used in combination with metal coating to enhance conductivity on difficult samples with complex overlapping surfaces, where simple metal coating does not reliably eliminate charging problems.

Validation of multiple single nucleotide variation calls by additional exome analysis with a semiconductor sequencer to supplement data of whole-genome sequencing of a human population.

BackgroundValidation of single nucleotide variations in whole-genome sequencing is critical for studying disease-related variations in large populations. A combination of different types of next-generation sequencers for analyzing individual genomes may be an efficient means of validating multiple single nucleotide variations calls simultaneously.ResultsHere, we analyzed 12 independent Japanese genomes using two next-generation sequencing platforms: the Illumina HiSeq 2500 platform for whole-genome sequencing (average depth 32.4×), and the Ion Proton semiconductor sequencer for whole exome sequencing (average depth 109×). Single nucleotide polymorphism (SNP) calls based on the Illumina Human Omni 2.5-8 SNP chip data were used as the reference. We compared the variant calls for the 12 samples, and found that the concordance between the two next-generation sequencing platforms varied between 83% and 97%.ConclusionsOur results show the versatility and usefulness of the combination of exome sequencing with whole-genome sequencing in studies of human population genetics and demonstrate that combining data from multiple sequencing platforms is an efficient approach to validate and supplement SNP calls.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-673) contains supplementary material, which is available to authorized users.

Erratum: H+-type and OH−-type biological protonic semiconductors and complementary devices

Scientific Reports 3, Article number: 2481 (2013); Published: 3 October 2013; Updated: 1 November 2013 The incorrect version of the Supplementary Information file was inadvertently published with this Article. This version contained typographical errors and an additional section ‘Charge carrier concentration estimate’ not relevant to this article.

H+-type and OH- -type biological protonic semiconductors and complementary devices.

Proton conduction is essential in biological systems. Oxidative phosphorylation in mitochondria, proton pumping in bacteriorhodopsin, and uncoupling membrane potentials by the antibiotic Gramicidin are examples. In these systems, H+ hop along chains of hydrogen bonds between water molecules and hydrophilic residues – proton wires. These wires also support the transport of OH− as proton holes. Discriminating between H+ and OH− transport has been elusive. Here, H+ and OH− transport is achieved in polysaccharide- based proton wires and devices. A H+- OH− junction with rectifying behaviour and H+-type and OH−-type complementary field effect transistors are demonstrated. We describe these devices with a model that relates H+ and OH− to electron and hole transport in semiconductors. In turn, the model developed for these devices may provide additional insights into proton conduction in biological systems.