80 research outputs found
Electrochemical response of biased nanoelectrodes in solution
Novel approaches to DNA sequencing and detection require the measurement of
electrical currents between metal probes immersed in ionic solution. Here, we
experimentally demonstrate that these systems maintain large background
currents with a transient response that decays very slowly in time and noise
that increases with ionic concentration. Using a non-equilibrium stochastic
model, we obtain an analytical expression for the ionic current that shows
these results are due to a fast electrochemical reaction at the electrode
surface followed by the slow formation of a diffusion layer. During the latter,
ions translocate in the weak electric field generated after the initial rapid
screening of the strong fields near the electrode surfaces. Our theoretical
results are in very good agreement with experimental findings
Life-Detection Technologies for the Next Two Decades
Since its inception six decades ago, astrobiology has diversified immensely
to encompass several scientific questions including the origin and evolution of
Terran life, the organic chemical composition of extraterrestrial objects, and
the concept of habitability, among others. The detection of life beyond Earth
forms the main goal of astrobiology, and a significant one for space
exploration in general. This goal has galvanized and connected with other
critical areas of investigation such as the analysis of meteorites and early
Earth geological and biological systems, materials gathered by sample-return
space missions, laboratory and computer simulations of extraterrestrial and
early Earth environmental chemistry, astronomical remote sensing, and in-situ
space exploration missions. Lately, scattered efforts are being undertaken
towards the R&D of the novel and as-yet-space-unproven life-detection
technologies capable of obtaining unambiguous evidence of extraterrestrial
life, even if it is significantly different from Terran life. As the suite of
space-proven payloads improves in breadth and sensitivity, this is an apt time
to examine the progress and future of life-detection technologies.Comment: 6 pages, the white paper was submitted to and cited by the National
Academy of Sciences in support of the Astrobiology Science Strategy for the
Search for Life in the Univers
Infrared spectroscopy on poly(dG)-poly(dC) DNA at low hydration
Infrared absorption measurements have been made on dry samples of poly(dG)-poly(dC) DNA at various relative humidity and temperatures. The water content, controlled by the relative humidity, reduces as temperature increases and reaches a very low value of ~ 0.1 wpn above 120℃. This minimum water content is maintained when the samples are brought back to room temperature as long as they are kept at the relative humidity of ~0 %. The molecular vibrations, which characterize the backbone structure as well as the base stacking and pairing, indicate that our samples maintain an A-form double helical structure at all the values of water content. The disorder in the base stacking is observed as the result of the decrease of the water content. Additionally the denaturation appears at high temperatures above 100℃, which reversibly disappears with decreasing temperature
ユウキ ブンシセイ ドウタイ ノ コウゾウ ト ブッセイ ニ カンスル ケンキュウ
京都大学0048新制・課程博士博士(工学)甲第8927号工博第2018号新制||工||1201(附属図書館)UT51-2001-F257京都大学大学院工学研究科分子工学専攻(主査)教授 田中 一義, 教授 横尾 俊信, 教授 北川 進学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDA
Pore Structures for High-Throughput Nanopore Devices
Nanopore devices are expected to advance the next-generation of nanobiodevices because of their strong sensing and analyzing capabilities for single molecules and bioparticles. However, the device throughputs are not sufficiently high. Although analytes pass through a nanopore by electrophoresis, the electric field gradient is localized inside and around a nanopore structure. Thus, analytes located far from a nanopore cannot be driven by electrophoresis. Here, we report nanopore structures for high-throughput sensing, namely, inverted pyramid (IP)-shaped nanopore structures. Silicon-based IP-shaped nanopore structures create a homogeneous electric field gradient within a nanopore device, indicating that most of the analytes can pass through a nanopore by electrophoresis, even though the analytes are suspended far from the nanopore entrance. In addition, the nanostructures can be fabricated only by photolithography. The present study suggests a high potential for inverted pyramid shapes to serve as nanopore devices for high-throughput sensing
Total variation denoising-based method of identifying the states of single molecules in break junction data
Abstract Break junction (BJ) measurements provide insights into the electrical properties of diverse molecules, enabling the direct assessment of single-molecule conductances. The BJ method displays potential for use in determining the dynamics of individual molecules, single-molecule chemical reactions, and biomolecules, such as deoxyribonucleic acid and ribonucleic acid. However, conductance data obtained via single-molecule measurements may be susceptible to fluctuations due to minute structural changes within the junctions. Consequently, clearly identifying the conduction states of these molecules is challenging. This study aims to develop a method of precisely identifying conduction state traces. We propose a novel single-molecule analysis approach that employs total variation denoising (TVD) in signal processing, focusing on the integration of information technology with measured single-molecule data. We successfully applied this method to simulated conductance traces, effectively denoise the data, and elucidate multiple conduction states. The proposed method facilitates the identification of well-defined plateau lengths and supervised machine learning with enhanced accuracies. The introduced TVD-based analytical method is effective in elucidating the states within the measured single-molecule data. This approach exhibits the potential to offer novel perspectives regarding the formation of molecular junctions, conformational changes, and cleavage
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