Energy transduction and signal averaging of fluctuating electric fields by a single protein ion channel

[EN] We demonstrate the electrical rectification and signal averaging of fluctuating signals using a biological nanostructure in aqueous solution: a single protein ion channel inserted in the lipid bilayer characteristic of cell membranes. The conversion of oscillating, zero time-average potentials into directional currents permits charging of a load capacitor to significant steady-state voltages within a few minutes in the case of the outer membrane porin F (OmpF) protein, a bacterial channel of Escherichia coli. The experiments and simulations show signal averaging effects at a more fundamental level than the traditional cell and tissue scales, which are characterized by ensembles of many ion channels operating simultaneously. The results also suggest signal transduction schemes with bio-electronic interfaces and ionic circuits where soft matter nanodiodes can be coupled to conventional electronic elements.We acknowledge the support from the Ministry of Economic Affairs and Competitiveness and FEDER (project MAT2015-65011-P) and the Generalitat Valenciana (project Prometeo/GV/0069). We thank Profs. A. Alcaraz and V. M. Aguilella for fruitful suggestions. This paper is devoted to the memory of Professor Kyosti Kontturi, Aalto University, Finland.Verdia-Baguena, C.; Gómez Lozano, V.; Cervera, J.; Ramirez Hoyos, P.; Mafe, S. (2017). Energy transduction and signal averaging of fluctuating electric fields by a single protein ion channel. Physical Chemistry Chemical Physics. 19(1):292-296. https://doi.org/10.1039/c6cp06035hS29229619

Voltage-controlled current loops with nanofluidic diodes electrically coupled to solid state capacitors

[EN] We describe experimentally and theoretically voltage-controlled current loops obtained with nanofluidic diodes immersed in aqueous salt solutions. The coupling of these soft matter diodes with conventional electronic elements such as capacitors permits simple equivalent circuits which show electrical properties reminiscent of a resistor with memory. Different conductance levels can be reproducibly achieved under a wide range of experimental conditions (input voltage amplitudes and frequencies, load capacitances, electrolyte concentrations, and single pore and multipore membranes) by electrically coupling two types of passive components: the nanopores (ionics) and the capacitors (electronics). Remarkably, these electrical characteristics do not result from slow ionic redistributions within the nanopores, which should be difficult to control and would give only small conductance changes, but arise from the robust collective response of equivalent circuits. Coupling nanoscale diodes with conventional electronic elements allows interconverting ionic and electronic currents, which should be useful for electrochemical signal processing and energy conversion based on charge transport.Support from the Ministry of Economic Affairs and Competitiveness and FEDER (project MAT2015-65011-P), the Generalitat Valenciana (project Prometeo/GV/0069 for Groups of Excellence). M. A, S. N. and W. E acknowledge the funding from the Hessen State Ministry of Higher Education, Research and the Arts, Germany, in the frame of LOEWE project iNAPO. Z. S. acknowledges the funding from the National Science Foundation (CHE 1306058).Ramirez Hoyos, P.; Gómez Lozano, V.; Cervera, J.; Nasir, S.; Ali, M.; Ensinger, W.; Siwy, Z.... (2016). Voltage-controlled current loops with nanofluidic diodes electrically coupled to solid state capacitors. RSC Advances. 6(60):54742-54746. https://doi.org/10.1039/c6ra08277gS5474254746660Fologea, D., Krueger, E., Mazur, Y. I., Stith, C., Okuyama, Y., Henry, R., & Salamo, G. J. (2011). Bi-stability, hysteresis, and memory of voltage-gated lysenin channels. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1808(12), 2933-2939. doi:10.1016/j.bbamem.2011.09.005Pustovoit, M. A., Berezhkovskii, A. M., & Bezrukov, S. M. (2006). Analytical theory of hysteresis in ion channels: Two-state model. The Journal of Chemical Physics, 125(19), 194907. doi:10.1063/1.2364898Ramirez, P., Cervera, J., Ali, M., Ensinger, W., & Mafe, S. (2014). Logic Functions with Stimuli-Responsive Single Nanopores. ChemElectroChem, 1(4), 698-705. doi:10.1002/celc.201300255Martin, C. R., & Siwy, Z. S. (2007). CHEMISTRY: Learning Nature’s Way: Biosensing with Synthetic Nanopores. Science, 317(5836), 331-332. doi:10.1126/science.1146126Hou, X., & Jiang, L. (2009). Learning from Nature: Building Bio-Inspired Smart Nanochannels. ACS Nano, 3(11), 3339-3342. doi:10.1021/nn901402bZhang, H., Tian, Y., & Jiang, L. (2016). Fundamental studies and practical applications of bio-inspired smart solid-state nanopores and nanochannels. Nano Today, 11(1), 61-81. doi:10.1016/j.nantod.2015.11.001Chun, H., & Chung, T. D. (2015). Iontronics. Annual Review of Analytical Chemistry, 8(1), 441-462. doi:10.1146/annurev-anchem-071114-040202Tagliazucchi, M., & Szleifer, I. (2015). Transport mechanisms in nanopores and nanochannels: can we mimic nature? Materials Today, 18(3), 131-142. doi:10.1016/j.mattod.2014.10.020Misra, N., Martinez, J. A., Huang, S.-C. J., Wang, Y., Stroeve, P., Grigoropoulos, C. P., & Noy, A. (2009). Bioelectronic silicon nanowire devices using functional membrane proteins. Proceedings of the National Academy of Sciences, 106(33), 13780-13784. doi:10.1073/pnas.0904850106Senapati, S., Basuray, S., Slouka, Z., Cheng, L.-J., & Chang, H.-C. (2011). A Nanomembrane-Based Nucleic Acid Sensing Platform for Portable Diagnostics. Topics in Current Chemistry, 153-169. doi:10.1007/128_2011_142Haywood, D. G., Saha-Shah, A., Baker, L. A., & Jacobson, S. C. (2014). Fundamental Studies of Nanofluidics: Nanopores, Nanochannels, and Nanopipets. Analytical Chemistry, 87(1), 172-187. doi:10.1021/ac504180hPérez-Mitta, G., Tuninetti, J. S., Knoll, W., Trautmann, C., Toimil-Molares, M. E., & Azzaroni, O. (2015). Polydopamine Meets Solid-State Nanopores: A Bioinspired Integrative Surface Chemistry Approach To Tailor the Functional Properties of Nanofluidic Diodes. Journal of the American Chemical Society, 137(18), 6011-6017. doi:10.1021/jacs.5b01638Ali, M., Nasir, S., Ramirez, P., Ahmed, I., Nguyen, Q. H., Fruk, L., … Ensinger, W. (2011). Optical Gating of Photosensitive Synthetic Ion Channels. Advanced Functional Materials, 22(2), 390-396. doi:10.1002/adfm.201102146Ali, M., Nasir, S., Ramirez, P., Cervera, J., Mafe, S., & Ensinger, W. (2013). Carbohydrate-Mediated Biomolecular Recognition and Gating of Synthetic Ion Channels. The Journal of Physical Chemistry C, 117(35), 18234-18242. doi:10.1021/jp4054555Ali, M., Ahmed, I., Nasir, S., Ramirez, P., Niemeyer, C. M., Mafe, S., & Ensinger, W. (2015). Ionic Transport through Chemically Functionalized Hydrogen Peroxide-Sensitive Asymmetric Nanopores. ACS Applied Materials & Interfaces, 7(35), 19541-19545. doi:10.1021/acsami.5b06015Albrecht, T. (2011). How to Understand and Interpret Current Flow in Nanopore/Electrode Devices. ACS Nano, 5(8), 6714-6725. doi:10.1021/nn202253zLemay, S. G. (2009). Nanopore-Based Biosensors: The Interface between Ionics and Electronics. ACS Nano, 3(4), 775-779. doi:10.1021/nn900336jGomez, V., Ramirez, P., Cervera, J., Nasir, S., Ali, M., Ensinger, W., & Mafe, S. (2015). Charging a Capacitor from an External Fluctuating Potential using a Single Conical Nanopore. Scientific Reports, 5(1). doi:10.1038/srep09501Ramirez, P., Gomez, V., Cervera, J., Nasir, S., Ali, M., Ensinger, W., & Mafe, S. (2015). Energy conversion from external fluctuating signals based on asymmetric nanopores. Nano Energy, 16, 375-382. doi:10.1016/j.nanoen.2015.07.013Tybrandt, K., Forchheimer, R., & Berggren, M. (2012). Logic gates based on ion transistors. Nature Communications, 3(1). doi:10.1038/ncomms1869Apel, P. (2001). Track etching technique in membrane technology. Radiation Measurements, 34(1-6), 559-566. doi:10.1016/s1350-4487(01)00228-1Cervera, J., Schiedt, B., Neumann, R., Mafé, S., & Ramírez, P. (2006). Ionic conduction, rectification, and selectivity in single conical nanopores. The Journal of Chemical Physics, 124(10), 104706. doi:10.1063/1.2179797Ali, M., Ramirez, P., Mafé, S., Neumann, R., & Ensinger, W. (2009). A pH-Tunable Nanofluidic Diode with a Broad Range of Rectifying Properties. ACS Nano, 3(3), 603-608. doi:10.1021/nn900039fRamirez, P., Gomez, V., Verdia-Baguena, C., Nasir, S., Ali, M., Ensinger, W., & Mafe, S. (2016). Designing voltage multipliers with nanofluidic diodes immersed in aqueous salt solutions. Physical Chemistry Chemical Physics, 18(5), 3995-3999. doi:10.1039/c5cp07203dWang, D., Kvetny, M., Liu, J., Brown, W., Li, Y., & Wang, G. (2012). Transmembrane Potential across Single Conical Nanopores and Resulting Memristive and Memcapacitive Ion Transport. Journal of the American Chemical Society, 134(8), 3651-3654. doi:10.1021/ja211142eMomotenko, D., & Girault, H. H. (2011). Scan-Rate-Dependent Ion Current Rectification and Rectification Inversion in Charged Conical Nanopores. Journal of the American Chemical Society, 133(37), 14496-14499. doi:10.1021/ja2048368Zhang, A., & Lieber, C. M. (2015). Nano-Bioelectronics. Chemical Reviews, 116(1), 215-257. doi:10.1021/acs.chemrev.5b0060

Performance of discrete heat engines and heat pumps in finite time

The performance in finite time of a discrete heat engine with internal friction is analyzed. The working fluid of the engine is composed of an ensemble of noninteracting two level systems. External work is applied by changing the external field and thus the internal energy levels. The friction induces a minimal cycle time. The power output of the engine is optimized with respect to time allocation between the contact time with the hot and cold baths as well as the adiabats. The engine's performance is also optimized with respect to the external fields. By reversing the cycle of operation a heat pump is constructed. The performance of the engine as a heat pump is also optimized. By varying the time allocation between the adiabats and the contact time with the reservoir a universal behavior can be identified. The optimal performance of the engine when the cold bath is approaching absolute zero is studied. It is found that the optimal cooling rate converges linearly to zero when the temperature approaches absolute zero.Comment: 45 pages LaTeX, 25 eps figure

Possible Impact of Co-infections of Tuberculosis and Malaria on the CD4+ Cell Counts of HIV Patients in Nigeria

Background: This study focused on evaluating the possible impact of co-infections of tuberculosis and malaria on the CD4+ cell counts in HIV infected subjects. Methods: This is a cross sectional study. The subjects were drawn from three hospitals and a blood bank in LagosState. After due consent, blood samples were obtained from 69 subjects with single infections (HIV, TB, and Malaria), 34 subjects with multiple infections (HIV/Malaria, HIV/TB, Malaria/TB, HIV/TB/Malaria) and 24 blood donors (controls). The CD4+ cell counts of all the 127 blood samples were estimated using a FACS count. Results: Data obtained were analysed and a comparison of the results showed that the median CD4+ counts in all groups of subjects with HIV infections (whether single or co-infection) were similar and significantly lower than the median counts for the healthy control group as well as groups without HIV infection (malaria, TB and malaria/TB). Conclusion: Overall data further confirmed the progressive depletion of CD4+ cells in HIV infection while co-infections with TB and malaria did not have any impact on the CD4+ cells of HIV infected subjects. A larger prospective study is needed.Fond: Cette \ue9tude a \ue9t\ue9 consacr\ue9e \ue1 l'\ue9valuation de l'impact possible de co-infections de tuberculose et le paludisme sur les comptes de cellule CD4+ des sujets infect\ue9s du VIH. M\ue9thode: Ceci est une \ue9tude transversale. Les sujets ont \ue9t\ue9 choisis de trois diff\ue9rents h\uf4pitaux et une banque du sang dans l'Etat de Lagos. Apr\ue8s le consentement n\ue9cessaire, les \ue9chantillons de sang ont \ue9t\ue9 obtenus de 69 sujets avec les mono-infections (VIH, TB, et le Paludisme), 34 sujets avec les infections multiples (le VIH/PALUDISME, LE VIH/TB, LE Paludisme/TB, VIH/TB/le Paludisme) et 24 donneurs de sang (les contr\uf4les). les comptes de cellule CD4+ de tous les 127 \ue9chantillons de sang ont \ue9t\ue9 estim\ue9s utilisant une compte FACS. R\ue9sultats: les donn\ue9es obtenues ont \ue9t\ue9 analys\ue9es et une comparaison des r\ue9sultats a d\ue9montr\ue9 que le m\ue9dian des comptes CD4+ dans tous les groupes de sujets avec les infections de VIH (soit mono ou co-infection) \ue9taient similaires et significativement plus bas que les comptes m\ue9dianes pour le groupe de contr\uf4le sain de m\ueame que les groupes sans l'infection de VIH (le paludisme, TB et le paludisme/TB). Conclusion: les donn\ue9es g\ue9n\ue9rales ont confirm\ue9 le plus l'\ue9puisement progressif des cellules CD4+ dans l'infection de VIH pendant que les co-infections avec TB et le paludisme n'ont pas eu aucun impact sur les cellules CD4+ des sujets infect\ue9s de VIH. Une plus profonde \ue9tude sera n\ue9cessaire

Utility of Repeated Praziquantel Dosing in the Treatment of Schistosomiasis in High-Risk Communities in Africa: A Systematic Review

Infection by Schistosoma worms causes serious disease among people who live in areas of Africa, South America, and Asia where these parasites are regularly transmitted. Although yearly treatment with the drug praziquantel is fairly effective in reducing or eliminating active infection, it does not cure everyone, and reinfection remains a continuing problem in high-risk communities. Studies have suggested that a repeat dose of praziquantel, given 2 to 8 weeks after the first dose, can improve cure rates and reduce remaining intensity of infections in population-based programs. Our systematic review of published research found that, on average, in Africa, such repeated dosing appears to offer particular advantages in the treatment of S. mansoni, the cause of intestinal schistosomiasis, but there was less consistent improvement after double-dosing for S. haematobium, the cause of urogenital schistosomiasis. Based on this evidence, we used a calibrated life-path model to predict the costs and benefits of a single-dose vs. a double-dose strategy in a typical high-risk community. Our projections suggest cost-effective incremental benefits from double dosing in terms of i) limiting a person's total years spent infected and ii) limiting the number of years they spend with heavy infection, with consequent improvements in quality of life

Prevalence Distribution and Risk Factors for Schistosoma hematobium Infection among School Children in Blantyre, Malawi

Schistosoma hematobium infection is a parasitic infection endemic in Malawi. Schistosomiasis usually shows a focal distribution of infection and it is important to identify communities at high risk of infection and assess effectiveness of control programs. We conducted a survey in one district in Malawi to determine prevalence and factors associated with S. hematobium infection among primary school pupils. Using a questionnaire, information on history of passing bloody urine and known risk factors associated with infection was collected. Urine samples were collected and examined for S. hematobium eggs. One thousand one hundred and fifty (1,150) pupils were interviewed, and out of 1,139 pupils who submitted urine samples, 10.4% were infected. Our data showed that male gender, child's knowledge of an existing open water source (includes river, dam, springs, lake, etc.) in the area, history of urinary schistosomiasis in the past month, distance of less than 1 km from school to nearest open water source and age 8–10 years compared to those 14 years and older were independently associated with infection. These findings suggest that children attending schools in close proximity to open water sources are at increased risk of infection

Noise Properties of Rectifying Nanopores

Ion currents through three types of rectifying nanoporous structures are studied and compared for the first time: conically shaped polymer nanopores, glass nanopipettes, and silicon nitride nanopores. Time signals of ion currents are analyzed by power spectrum. We focus on the low-frequency range where the power spectrum magnitude scales with frequency, f, as 1/f. Glass nanopipettes and polymer nanopores exhibit non-equilibrium 1/f noise, thus the normalized power spectrum depends on the voltage polarity and magnitude. In contrast, 1/f noise in rectifying silicon nitride nanopores is of equilibrium character. Various mechanisms underlying the voltage-dependent 1/f noise are explored and discussed, including intrinsic pore wall dynamics, and formation of vortices and non-linear flow patterns in the pore. Experimental data are supported by modeling of ion currents based on the coupled Poisson-Nernst-Planck and Navier Stokes equations. We conclude that the voltage-dependent 1/f noise observed in polymer and glass asymmetric nanopores might result from high and asymmetric electric fields inducing secondary effects in the pore such as enhanced water dissociation

Emergent Matters: Reflections on Collaborative Practice-led Research

This paper will show how collaborative practice-led research can lead to the generation of new knowledge and new artistic work. In it we will address two aspects, firstly how separate creative practices can positively combine when connected by a research focus and, secondly, how a digital technology can be a catalyst for collaborative practice-led research. We begin by outlining some central concerns pertaining to collaborative and practice-led research and describe how these approaches can come together in a creative arts context. As an example of effective collaborative practice-led we present a case study description of our computational art project that generates animated image and sound. We point out interesting parallels between emergent properties of the generative techniques of practice and the collaborative research relationship, and conclude that it is the emergent nature of the collaborative and creative processes that produce research and artistic outcomes that are more than the sum of the parts. \ud \ud The structure of this article begins by outlining the two board themes of this paper, practice-led research and collaborative practice, then moves to a description of our Pixels project which illustrates how these two streams can be successfully combined within a the one activity