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Wavelet Denoising of High-Bandwidth Nanopore and Ion-Channel Signals
摘要： Recent work has pushed the noise-limited bandwidths of solid-state nanopore conductance recordings to more than 5 MHz and of ion channel conductance recordings to more than 500 kHz through the use of integrated complementary metal-oxide-semiconductor (CMOS) integrated circuits. Despite the spectral spread of the pulse-like signals that characterize these recordings when a sinusoidal basis is employed, Bessel filters are commonly used to denoise these signals to acceptable signal-to-noise ratios (SNRs) at the cost of losing many of the faster temporal features. Here, we report improvements to the SNR that can be achieved using wavelet denoising instead of Bessel filtering. When combined with state-of-the-art high-bandwidth CMOS recording instrumentation, we can reduce baseline noise levels by over a factor of four compared to a 2.5-MHz Bessel filter while retaining transient properties in the signal comparable to this filter bandwidth. Similarly, for ion channel recordings, we achieve a temporal response better than a 100-kHz Bessel filter with a noise level comparable to that achievable with a 25-kHz Bessel filter. Improvements in SNR can be used to achieve robust statistical analyses of these recordings, which may provide important insights into nanopore translocation dynamics and mechanisms of ion channel function.
关键词： ion channel,Nanopore,CMOS,wavelet,denoise.,SNR
更新于2025-09-23 15:23:52
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Ultrafast Protein Response in Channelrhodopsin-2 Studied by Time-Resolved IR Spectroscopy
摘要： Ultrafast IR transient absorption in the carbonyl vibrational region of protonated aspartate and glutamate residues in Channelrhodopsin-2 from Chlamydomonas reinhardtii shows immediate protein response to retinal excitation. The observed difference bands are formed directly after the excitation on the sub-ps time scale and were assigned to side chains in the retinal vicinity, such as D156 and E90. This finding implies an ultrafast and effective energy transfer from the retinal to its environment via hydrogen-bonded networks and reveals extraordinary strong chromophore-protein coupling and intense interaction within the protein. Relevance on the protein function as optically gated ion channel are discussed.
关键词： Channelrhodopsin-2,protein response,ion channel,Ultrafast IR transient absorption,hydrogen-bonded networks,chromophore-protein coupling,retinal excitation
更新于2025-09-23 15:19:57
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Stability of target waves in excitable media under electromagnetic induction and radiation
摘要： Local periodic stimulus can trigger stable pulse and target wave in the excitable media, the potential mechanism is that each cell is activated by continuous driving to keep pace with the external forcing. Indeed, local diversity in excitability and heterogeneity are induced when external forcing with diversity is applied on the media. When target wave is formed and propagated, the media will be modulated, e.g. it can emit electric signal from sinoatrial node and develops target wave in the cardiac tissue, and then the heartbeat is controlled completely. In fact, the distribution of electromagnetic field in the media is changed when external electric stimulus is applied on the media; therefore, the effect of electromagnetic induction becomes important during the information encoding and signal propagation. In this paper, the Morris-Lecar model is used to describe the local kinetic of the media and an induction current is considered thus the effect of electromagnetic induction can be described. Then the artificial heterogeneity is triggered to investigate the formation and development of target waves in the excitable media with electromagnetic induction and even radiation, which is described by using Gaussian white noise. Diversity in excitability and conductance of ion channels is considered, respectively, thus different kinds of artificial heterogeneity are developed to find the stability of target waves. It is found that the target wave encounters breakup with increasing of the intensity of electromagnetic radiation.
关键词： bifurcation,electromagnetic induction,memristor,target wave,ion channel
更新于2025-09-19 17:15:36
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Excitation modes in a cylindrical plasma waveguide with helical wiggler field and ion channel guiding
摘要： Analysis of high frequency eigen modes of a cylindrical metallic waveguide filled with a helical wiggler and a relativistic electron beam and guiding by an ion-channel is presented. A relativistic nonlinear wave equation is derived in a form including the coupling of EH, HE, HE betatron (HE - Be), and EH betatron (EH - Be) modes due to ion channel guiding and wiggler magnetic field. Six families of eigen modes are found. The cutoff frequencies in TM, TE modes are illustrated for this configuration.
关键词： Ion-channel guiding,waveguide,Eigen modes,Helical wiggler field
更新于2025-09-11 14:15:04
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Microchannel Fabrication Using A Photo-Patternable Adhesive Material for Recording Conformational Changes of KcsA Channel with the Diffracted X-ray Tracking Method
摘要： Diffracted X-ray tracking (DXT) method can trace conformational changes of KcsA potassium ion channel during gating by recording position of diffraction spot from a gold nanocrystal attached to the channel as a movie. For high-resolution imaging under controlled microenvironments for KcsA channels, we report a microfluidic device consisting of two SiN membrane windows bonded with a photo patternable adhesive material. The reduced signal-to-background ratio as well as suitable adhesive material thickness for the microchannel are discussed in the experiment at the synchrotron radiation facility.
关键词： diffracted X-ray tracking method,adhesive bonding,microfluidics,KcsA ion channel
更新于2025-09-04 15:30:14