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Aims The antimicrobial peptide cathelicidin (Camp) has multifunctional immunomodulatory activities. However, its roles in inflammation-related myocardial ischemia/reperfusion (MI/R) injury remain unclear. Methods and results In this study, adult male C57BL/6 wild-type (WT) mice were subjected to MI/R injury by left anterior descending coronary artery ligation for 45 min followed by 3 or 24 h of reperfusion. An abundant cardiac expression of cathelicidin was observed during ischemia and reperfusion, which was mainly derived from heart-infiltrating neutrophils. Knockout of Camp in mice reduced MI/R-induced myocardial inflammation, infarct size, and circulating cTnI levels (an indicator of heart damage). CRAMP (the mature form of murine cathelicidin) administration of WT mice immediately before MI/R exerted detrimental effects on the reperfused heart. CRAMP exacerbates MI/R injury via a TLR4 and P2X7R/NLRP3 inflammasome-dependent mechanism, since I/R-induced myocardial infarction was reserved by inhibition of TLR4, P2X7R, or NLRP3 inflammasome in CRAMP-treated WT mice. Depletion of neutrophils before MI/R abrogated the amplification of infarct size in CRAMP-treated WT mice. Heart-infiltrating neutrophils were found to be one of major cellular sources of myocardial IL-1β (a “first line” pro-inflammatory cytokine) at the early stage of MI/R. At this stage, CRAMP administration just before MI/R induced pro-IL-1β protein expression in heart-infiltrating neutrophils, but not in non-neutrophils. In vitro experiments showed that LL-37 (the mature form of human cathelicidin) treatment promotes the processing and secretion of IL-1β from human neutrophils via stimulating TLR4 signaling and P2X7R/NLRP3 inflammasome. Conclusions Our findings reveal that, at the early stage of MI/R, neutrophil-derived cathelicidin plays an injurious role in the heart. Cathelicidin aggravates MI/R injury by over-activating TLR4 signaling and P2X7R/NLRP3 inflammasome in heart-infiltrating neutrophils, which leads to the excessive secretion of IL-1β and subsequent inflammatory injury.

Solving high-resolution structures of membrane proteins has been an important challenge for decades, still lagging far behind that of soluble proteins even with the recent remarkable technological advances in X-ray crystallography and electron microscopy. Central to this challenge is the necessity to isolate and solubilize membrane proteins in a stable, natively folded and functional state, a process influenced by not only the proteins but also their surrounding chemical environment. This review highlights recent community efforts in the development and characterization of novel membrane agents and ligand tools to stabilize individual proteins and protein complexes, which together have accelerated progress in membrane protein structural biology.

Biochar (BC) addition is widely used in agriculture to condition soils. However, the effects of BC addition on soil microbial community diversity and composition in karstic regions are unclear, especially after long-term application. To address this knowledge-gap, a field experiment was established to examine changes in soil physicochemical properties and microbial communities following six years of BC amendment. BC was applied to calcareous soils in a karstic region of southwestern China at four levels (w/w): 0%, 1.0%, 5.0%, and 10%. Bacterial community composition was then investigated in both the rhizosphere and bulk soils by 16S rRNA gene sequencing on the Illumina MiSeq Platform. BC addition increased soil pH, total carbon (TC), total nitrogen (TN), and total hydrogen (TH) contents in the rhizosphere and bulk soils. In addition, BC amendment was associated with changes in soil bacterial community compositions and diversities, especially at higher BC application levels. The relative abundances of Gemmatimonadetes increased in rhizosphere soils with increasing BC amendment, while those of the Bacteroidetes, Firmicutes, and Cyanobacteria decreased. The relative abundances of Proteobacteria and Chloroflexi increased in bulk soils with increasing BC application levels, while those of the Bacteroidetes and Verrucomicrobia decreased. Canonical correspondence analysis indicated that bacterial community composition was related to soil characteristics including pH, TC, TN, and TH contents in both rhizosphere and bulk soils. Importantly, variations in these soil parameters were closely associated with BC application rates. These results indicate that long-term BC application significantly impacts soil bacterial community characteristics in karstic regions via modulation of soil physiochemical properties.

To investigated the effects of thermosonication (TS) on blueberry juice quality. The raw juice (RJ), pasteurized juice (60 °C, 30 min, PJ), and TS treated juice (20 kHz, 200 W, 400 W, and 600 W at 60 °C for 15 min, TJ) were analysed for colour characteristics, total antioxidant contents, antioxidant capacity, and composition of anthocyanins. Results showed that TS treated juice had higher colour density (CD), L*, and ΔE values and lower values of chroma (C), hue angle (h), yellow index (YI). The content of total phenolics, flavonoids, and anthocyanins, were increased by 139.32%, 251.72%, and 94.12%, respectively, in TJ600 sample compared to the RJ samples. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical (▪OH) scavenging capacity were increased to 65.22%, 51.13%, significantly higher than PJ sample. The content of delphinidin-3-O-glucoside (Dp-G) and cyanidin-3-O-glucoside (Cy-G), were 54.40 mg/L, 28.75 mg/L in juice. Correlation analysis indicated that the antioxidant contents play an important role in CD, and Cy-G determines the brightness or darkness of the juice. Collectively, the findings suggested that TS could be a feasible alternative to pasteurization for improving the quality and antioxidant activity of blueberry juice.

We propose high-order finite-volume schemes for numerically solving the steady-state advection–diffusion equation with nonlinear Robin boundary conditions. Although the original motivation comes from a mathematical model of blood clotting, the nonlinear boundary conditions may also apply to other scientific problems. The main contribution of this work is a generic algorithm for generating third-order, fourth-order, and even higher-order explicit ghost-filling formulas to enforce nonlinear Robin boundary conditions in multiple dimensions. Under the framework of finite volume methods, this appears to be the first algorithm of its kind. Numerical experiments on boundary value problems show that the proposed fourth-order formula can be much more accurate and efficient than a simple second-order formula. Furthermore, the proposed ghost-filling formulas may also be useful for solving other partial differential equations.

The Paleocene-Eocene Thermal Maximum (PETM) was a geologically rapid and transient warming event that occurred ca. 56 million years ago (Ma). It was associated with a pronounced negative carbon isotope excursion (CIE) and with profound changes in the atmosphere, hydrosphere and biosphere. This event reflects injections of large amounts of carbon into the atmosphere-ocean system, but, whether single or multiple episodes of carbon release caused this event is uncertain. Here, we present carbon isotope data of bulk carbonate from two parallel limestone sections at Tingri (south Tibet), where the limestone was deposited on a tropical carbonate ramp during the PETM. Carbon isotope data of bulk carbonate from both sections are almost identical, displaying an expanded stepped CIE profile with large magnitude. The stepped CIE profile consists of three discrete intervals of decreasing carbon isotope values, which can be correlated on an inter-regional scale between sections from different depositional environments (lake, carbonate ramp, continental slope, and open ocean). The consistency of these correlations implies occurrence of at least three carbon releases within the CIE and indicates complex processes of carbon injection during the PETM. Moreover, the CIE magnitude of ~ 7‰ recorded at Tingri is tentatively interpreted to reflect carbon isotope changes in the atmosphere and the surface ocean, which is larger than the generally accepted value of ~ 4‰ but is still within the range of some previous records.

In this study, the profile of etoxazole in whole citrus, peel and pulp samples collected from Chongqing, Guangdong and Anhui provinces was monitored and their dietary risk to human had also been assessed. The final residual levels and distributions of etoxazole in citrus samples were detected by using an ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). The results showed that final concentrations of etoxazole in whole citrus, peel, and pulp were ranged at 0.012–0.174, 0.010–0.637, and 0.010–0.011 mg kg−1, respectively. The assessment of dietary risk suggested that chronic dietary risk of etoxazole in whole fruit and peel were 0.010–0.197% and 0.035–0.951%, respectively. Our findings indicated that the chronic risk of daily consumption of citrus fruit is acceptable at recommended dosage.

Knowledge about the influence of tobacco biochar (BC) on soil carbon dioxide (CO2) emissions and carbon (C) budget in a karst region of southwest China is limited. The karst field experiment was conducted in randomly arranged plots and evaluated five treatments: a plot without BC addition (B0), with 1.0 t BC ha−1 (B1C1), 10 t BC ha−1 (B10C10), 25 t BC ha−1 (B25C25) and 50 t BC ha−1 (B50C50). Soil CO2 emissions were assessed using closed chambers at 10-day intervals during a tobacco-growing season. Soil temperature and moisture were simultaneously measured at 5-, 10-, and 20-cm depths. BC amendment increased tobacco productivity, soil organic matter, total nitrogen, available phosphorus, and available potassium contents but decreased total sulfur content. Compared with the control (B0), daily average soil CO2 fluxes significantly increased by 20.0%, 26.3%, 39.4% and 50.2% in the B1, B10, B25, and B50 treatments, respectively. The cumulative soil CO2 emissions for the entire tobacco-growing season were significantly higher in BC amendments than in the control. Furthermore, soil CO2 fluxes were observed to be positively correlated with soil temperature but negatively correlated with soil moisture. Soil respiration sensitivity to temperature (Q10) significantly increased at greater soil depths, whereas decreased in BC-amended soils. Moreover, the BC amendments significantly increased C gain from −1.17 t ha−1 in the B0 treatment to 19.48 t ha−1 in the B50 treatment. Based on C budget, the increase in CO2 emissions in the BC-treated soil was compensated by the higher tobacco biomass and soil C storages. These results suggest that the application of tobacco BC to karst farmland enhances the soil C sequestration.

The Paleocene-Eocene thermal maximum (PETM) was an extraordinary pulse of global warming that left an indelible mark on the Earth approximately 56 Ma ago. This warming event is associated with an addition of large amounts of 13C-depleted carbon into the atmosphere-ocean system, but the magnitude of the negative carbon isotope excursion (CIE) signaling the PETM onset and often used to estimate mass of the released carbon is still debated. Here we gauge the CIE magnitude through the use of secondary ion mass spectrometry (SIMS) to perform in situ δ13C measurements within individual larger benthic foraminifera preserved in a tropical shallow-marine limestone section at Tingri, south Tibet. This SIMS-based δ13C record yields a CIE (Δ~7‰) comparable in magnitude to that registered by some terrestrial PETM records but larger than the ~4‰ CIE returned by surface-dwelling planktonic foraminifera in deep-sea records. We posit that the CIE magnitude in the surface ocean and atmosphere was ~7‰, and that previous ~4‰ estimates are attenuated by incomplete preservation and/or diagenetic overprinting. Mass balance calculations indicate that the released carbon mass during the CIE would not exceed 28,000 petagrams, given that the carbon was sourced from organic matter, permafrost, thermogenic methane, methane hydrate, or any of their combinations. Our study demonstrates that δ13C records from some shallow-marine carbonate sections can avoid strong diagenetic alteration, preserving primary signals of deep-time carbon perturbations.

In this follow-up of our previous work [30], the author proposes a high-order semi-implicit method for numerically solving the incompressible Navier-Stokes equations on locally-refined periodic domains. Fourth-order finite-volume stencils are employed for spatially discretizing various operators in the context of structured adaptive mesh refinement (AMR). Time integration adopts a fourth-order, semi-implicit, additive Runge-Kutta method to treat the non-stiff convection term explicitly and the stiff diffusion term implicitly. The divergence-free condition is fulfilled by an approximate projection operator. Altogether, these components yield a simple algorithm for simulating incompressible viscous flows on periodic domains with fourth-order accuracies both in time and in space. Results of numerical tests show that the proposed method is superior to previous second-order methods in terms of accuracy and efficiency. A major contribution of this work is the analysis of a fourth-order approximate projection operator.

Summary MsbA is an essential ATP-binding cassette transporter in Gram-negative bacteria that transports lipid A and lipopolysaccharide from the cytoplasmic leaflet to the periplasmic leaflet of the inner membrane. Here we report the X-ray structure of MsbA from Salmonella typhimurium at 2.8-A resolution in an inward-facing conformation after cocrystallization with lipid A and using a stabilizing facial amphiphile. The structure displays a large amplitude opening in the transmembrane portal, which is likely required for lipid A to pass from its site of synthesis into the protein-enclosed transport pathway. Putative lipid A density is observed further inside the transmembrane cavity, consistent with a trap and flip model. Additional electron density attributed to lipid A is observed near an outer surface cleft at the periplasmic ends of the transmembrane helices. These findings provide new structural insights into the lipid A transport pathway through comparative analysis with existing MsbA structures.

Lagrangian flux through a fixed curve segment within a time interval ( t n , t n + k ) can be formulated as an integral at the initial time t n over a compact point set called donating region, in which each particle will pass through the curve during the time interval and contribute to the flux. Based an explicit, constructive, and analytical solution of the donating region, the author proposes algorithms of Lagrangian flux calculation (LFC) as algebraic quadratures over the spline-approximated donating regions. This generic formulation yields high accuracies up to the 8th-order both in time and space. As another benefit, LFC leads to a conservative semi-Lagrangian method whose time step size is free of the Eulerian stability constraint C r ⩽ 1 . The high accuracy and robustness of the proposed LFC algorithms are demonstrated by various numerical tests with Courant numbers ranging from 1 to 10,000 and with accuracies from the 2nd order to the 8th order. LFC might also be useful in designing hybrid Eulerian methods for complex geometries.

We report paleomagnetic results from the Zhepure Shan Formation and the Youxia Formation of the Tingri section (28°42′N/86°43′E) and the Longjiang section (28°27′N/86°40′E) in southern Tibet. A lower coercive component demagnetized below 30 mT and a higher coercive component demagnetized between 30 mT and 100 mT were separated. Rockmagnetic analyses reveal magnetite as the remanence carrier. The differences in coercivity are probably due to a wider grain size spectrum and therefore different domain states. Remanence directions of the low-coercive component are highly scattered and were not considered for further analysis. Directions of the high coercive component of Members A–C of the Zhepure Shan Fm are fairly well grouped within sites (k > 8 for most sites) whereas those of Member D and the overlying Youxia Fm are highly dispersed. Applied fold tests indicate a postfolding remanence for Members A–C. The latest possible time for remanence acquisition of Members A–C is constrained to a mean of 48 Ma by comparing the determined paleolatitudes to the curve of expected paleolatitudes versus age, calculated from the APWP of India. Deformation of the rocks is likely related to India–Asia collision and therefore the remanence age yields a constraint on the latest possible age of the India–Asia collision. In consideration of an extended pre-collisional northern Indian margin (Greater India) the determined values of 48 Ma (mean) and 37 Ma (youngest possible age within 95% confidence limits) underestimate the age of the continental collision.

The author presents a polynomial-based algorithm for high-order multidimensional interpolation at the coarse–fine interface in the context of adaptive mesh refinement on structured Cartesian grids. The proposed algorithm reduces coarse–fine interpolation to matrix–vector products by exploiting the static mesh geometry and a family of nonsingularity-preserving stencil transformations. As such, no linear system is solved at the runtime and the ill-conditioning of Vandermonde matrix is avoided. The algorithm is also generic in that D , the dimensionality of the computational domain, and p, the degree of the interpolating polynomial, are both arbitrary positive integers. Stability and accuracy are verified by interpolating simple functions, and by applying the proposed method to adaptively solving Poisson’s equation and the convection–diffusion equation. The companion MATLAB® package, AMRCFI, is also freely available for convenience and more implementation details.

Crystal structures of the xenobiotic metabolizing cytochrome P450 2B4 have demonstrated markedly different conformations in the presence of imidazole inhibitors or in the absence of ligand. However, knowledge of the plasticity of the enzyme in solution has remained scant. Thus, hydrogen-deuterium exchange mass spectrometry (DXMS) was utilized to probe the conformations of ligand-free P450 2B4 and the complex with 4-(4-chlorophenyl)imidazole (4-CPI) or 1-biphenyl-4-methyl-1H-imidazole (1-PBI). The results of DXMS indicate that the binding of 4-CPI slowed the hydrogen-deuterium exchange rate over the B′- and C-helices and portions of the F-G-helix cassette compared with P450 2B4 in the absence of ligands. In contrast, there was little difference between the ligand-free and 1-PBI-bound exchange sets. In addition, DXMS suggests that the ligand-free P450 2B4 is predominantly open in solution. Interestingly, a new high resolution structure of ligand-free P450 2B4 was obtained in a closed conformation very similar to the 4-CPI complex. Molecular dynamics simulations performed with the closed ligand-free structure as the starting point were used to probe the energetically accessible conformations of P450 2B4. The simulations were found to equilibrate to a conformation resembling the 1-PBI-bound P450 2B4 crystal structure. The results indicate that conformational changes observed in available crystal structures of the promiscuous xenobiotic metabolizing cytochrome P450 2B4 are consistent with its solution structural behavior.

The ghost cell approaches (GCA) for handling stationary solid boundaries, regular or irregular, are first investigated theoretically and numerically for the diffusion equation with Dirichlet boundary conditions. The main conclusion of this part of investigation is that the approximation for the diffusion term has to be second-order accurate everywhere in order for the numerical solution to be rigorously second-order accurate. Violating this principle, the linear and quadratic GCAs have the following shortcomings: (1) restrictive constraints on grid size when the viscosity is small; (2) susceptibleness to instability of a time-explicit formulation for strongly transient flows; (3) convergence deterioration to zeroth- or first-order for solutions with high-frequency modes. Therefore, the widely-used linear extrapolation for enforcing no-slip boundary conditions should be avoided, even for regular solid boundaries. As a remedy, a simple method based on explicit jump approximation (EJA) is proposed. EJA hinges on the idea that a velocity-derivative jump at the boundary reduces to the value of the velocity-derivative at the fluid side because the velocity of the stationary boundary is zero. Although the time-marching linear system of EJA is not symmetric, it is strictly diagonal dominant with positive diagonal entries. Numerical results show that, over a large range of viscosity and grid sizes, EJA performs much better than GCAs in terms of stability and accuracy. Furthermore, the second-order convergence of EJA does not depend on viscosity and the spectrum of the solution, as those of GCAs do. This paper is written with enough details so that one can reproduce the numerical results.

Three major issues associated with numerical simulations of complex free-surface flows, viz. interface tracking, fragmentation and large physical jumps, are addressed by a new hybrid continuum-particle model (HyPAM). The new model consists of three parts: (1) the Polygonal Area Mapping method [Q. Zhang, P.L.-F. Liu, A new interface tracking method: the polygonal area mapping method, J. Comput. Phys. 227(8) (2008) 4063-4088]; (2) a new algorithm that decomposes the interested (water) phase into a continuum zone, a buffer zone and a particle zone, based on material topology and graph theory; (3) a 'passive-response' assumption, in which the air phase is assumed to respond passively to the continuum part of the water phase. The incompressible inviscid Euler equations and the equations describing the free fall of rigid bodies are used as the governing equations for the continuum-buffer zone and the particle zone, respectively, and separately. A number of examples, including water droplet impact, solitary wave propagation, and dam-break problems, are simulated for the illustration and validation of HyPAM. It is shown that HyPAM is more accurate and versatile than a continuum-based Volume-of-Fluid model. One major contribution of this work is the single-phase decomposition algorithm, useful for many other hybrid formulations. Neglecting surface tension, viscosity and particle interactions, HyPAM is currently limited to mildly-fragmented free-surface flows with high Reynolds and Weber numbers.

Article history:Received 10 October 2007Received in revised form 15 March 2008Accepted 4 April 2008Available online 4 June 2008Keywords:Swash zoneTsunami runupDam-breakBoreNon-linear shallow water equationsReynolds averaged Navier–Stokes equationNon-linear k− model The dynamic processes of bore propagation over a uniform slope are studied numerically using a 2-DReynolds Averaged Navier–Stokes (RANS) solver, coupled to a non-linear k− turbulence closure and avolume of fluid (VOF) method. The dam-break mechanism is used to generate bores in a constant depthregion. Present numerical results for the ensemble-averaged flow field are compared with existingexperimental data as well as theoretical and numerical results based on non-linear shallow water (NSW)equations. Reasonable agreement between the present numerical solutions and experimental data isobserved. Using the numerical results, small-scale bore behaviors and flow features, such as the bore collapseprocess near the still-water shoreline, the ‘mini-collapse’ during the runup phase and the ‘back-wash bore’ inthe down-rush phase, are described. In the case of a strong bore, the evolution of the averaged turbulencekinetic energy (TKE) over the swash zone consists of two phases: in the region near the still-water shoreline,the production and the dissipation of TKE are roughly in balance; in the region farther landwards of the still-water shoreline, the TKE decay rate is very close to that of homogeneous grid turbulence. On the other hand,in the case of a weak bore, the bore collapse generated turbulence is confined near the bottom boundarylayer and the TKE decays at a much slower rate.© 2008 Elsevier B.V. All rights reserved.

We present a new method, the polygonal area mapping (PAM) method, for tracking a non-diffusive, immiscible material interface between two materials in two-dimensional incompressible flows. This method represents material areas explicitly as piecewise polygons, traces characteristic points on polygon boundaries along pathlines and calculates new material areas inside interface cells via polygon-clippings in a discrete manner. The new method has very little spatial numerical diffusion and tracks the interface singularities naturally and accurately. In addition to high accuracy, the PAM method can be directly used on either a structured rectangular mesh or an unstructured mesh without any modifications. The mass conservation is enforced by heuristic algorithms adjusting the volume of material polygons. The results from a set of widely used benchmark tests show that the PAM method is superior to existing volume-of-fluid (VOF) methods.

Summary The nicotinamide nucleotide transhydrogenase (TH) is an integral membrane enzyme that uses the proton-motive force to drive hydride transfer from NADH to NADP + in bacteria and eukaryotes. Here we solved a 2.2-A crystal structure of the TH transmembrane domain ( Thermus thermophilus ) at pH 6.5. This structure exhibits conformational changes of helix positions from a previous structure solved at pH 8.5, and reveals internal water molecules interacting with residues implicated in proton translocation. Together with molecular dynamics simulations, we show that transient water flows across a narrow pore and a hydrophobic "dry" region in the middle of the membrane channel, with key residues His42 α2 (chain A) being protonated and Thr214 β (chain B) displaying a conformational change, respectively, to gate the channel access to both cytoplasmic and periplasmic chambers. Mutation of Thr214 β to Ala deactivated the enzyme. These data provide new insights into the gating mechanism of proton translocation in TH.

Charcot-Marie-Tooth disease type 2D (CMT2D) is a peripheral nerve disorder caused by dominant, toxic, gain-of-function mutations in the widely expressed, housekeeping gene, GARS The mechanisms underlying selective nerve pathology in CMT2D remain unresolved, as does the cause of the mild-to-moderate sensory involvement that distinguishes CMT2D from the allelic disorder distal spinal muscular atrophy type V. To elucidate the mechanism responsible for the underlying afferent nerve pathology, we examined the sensory nervous system of CMT2D mice. We show that the equilibrium between functional subtypes of sensory neuron in dorsal root ganglia is distorted by Gars mutations, leading to sensory defects in peripheral tissues and correlating with overall disease severity. CMT2D mice display changes in sensory behavior concordant with the afferent imbalance, which is present at birth and nonprogressive, indicating that sensory neuron identity is prenatally perturbed and that a critical developmental insult is key to the afferent pathology. Through in vitro experiments, mutant, but not wild-type, GlyRS was shown to aberrantly interact with the Trk receptors and cause misactivation of Trk signaling, which is essential for sensory neuron differentiation and development. Together, this work suggests that both neurodevelopmental and neurodegenerative mechanisms contribute to CMT2D pathogenesis, and thus has profound implications for the timing of future therapeutic treatments.

There have been quite a few approaches developed over the last two decades towards the creation of structurally novel amphiphiles. Some of these reagents have found broad applications in membrane protein biochemistry, being used for the solubilization and stabilization of membrane proteins for functional studies. However, success has been very limited in using these novel amphiphiles to crystallize IMPs. The lack of success exemplifies the significant degree of challenge and makes it clear that other types of amphiphiles are needed. We have contributed hundreds of new detergents through our previous efforts in this area. These detergents have been tested for various purposes (e.g. solubilization, stabilization, NMR, crystallization), and several were found to perform as well or better than the most popular commercial detergents. In particular, the use of our newly designed cholesterol-like facial amphiphiles has facilitated the 3D crystallization and structural determination of several membrane proteins. Interestingly, we have found evidence that facial amphiphiles mediated protein crystal contact. These results open up the possibility for future investigations of using intelligently designed stabilization reagents to mediate membrane protein surface interactions so as to increase crystallization propensity and improve crystal diffraction.

Intercellular gap junction channels are formed by the end-to-end docking of connexin (Cx) hexamers that traverse apposing cell membranes. Each Cx subunit has four transmembrane (TM) α-helices and two extracellular loops (E1 and E2). Three-dimensional crystals of recombinant, purified Cx26 were grown using a new class of detergents designated facial amphiphiles (FAs), which have a cholate backbone with polar groups extending from one face and a short alkyl chain extending from the opposite face. FA-solubilized Cx26 crystallized into the H32 space group with two monomers in the asymmetric unit, and the crystals diffracted isotropically to 3.3-A resolution. Using a molecular replacement search model based on a cryoEM map of Cx43 at 5.7-A resolution [Fleishman et al., Mol. Cell 15: 879-888 (2004)], we solved the structure independently from a previously reported 3.5-A resolution X-ray structure [2ZW3, Maeda et al., Nature 458: 597-602 (2009)]. The overall R/Rfree values and completeness were 0.311/0.328 and 98.9%, respectively, and the Molprobity score was 2.07 (100th percentile). The RMS differences between 2ZW3 and our structure were 0.9 and 1.7-A for the main-chain and side-chain atoms in the TM helices and 1.3 and 1.9-A for the main-chain and side-chain atoms in E1 and E2. Although the topology and fold recapitulated 2ZW3, the maximum differences were significant: 2.7 and 5.9-A for the main chain and side chain atoms in the TM helices and 3.9 and 7.6-A for the main-chain and side-chain atoms in E1 and E2. We generated an electron density map at a resolution comparable to the cryoEM structure of the authentic Cx43 channel. The similarity of the maps suggests that detergent-solubilized Cx26 that crystallized as a dodecamer represents the authentic gap junction channel.