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International audience; A range of methodologies were herein employed to study the unconventional XBP1 mRNA cleavage mechanism performed by the unfolded protein response (UPR) mediator Inositol Requiring Enzyme 1α (IRE1). Using Protein-RNA molecular docking along with a series of extensive restrained/unrestrained atomistic molecular dynamics (MD) simulations, the dynamical behavior of the system was evaluated and a reliable model of the IRE1/XBP1 mRNA complex was constructed. From a series of well-converged quantum mechanics molecular mechanics well-tempered metadynamics (QM/MM WT-MetaD) simulations using the Grimme dispersion interaction corrected semiempirical parametrization method 6 level of theory (PM6-D3) and the AMBER14SB-OL3 force field, the free energy profile of the cleavage mechanism was determined, along with intermediates and transition state structures. The results show two distinct reaction paths based on general acid-general base type mechanisms, with different activation energies that perfectly match observations from experimental mutagenesis data. The study brings unique atomistic insights into the cleavage mechanism of XBP1 mRNA by IRE1 and clarifies the roles of the catalytic residues H910 and Y892. Increased understanding of the details in UPR signaling can assist in the development of new therapeutic agents for its modulation.

International audience; ER stress is mediated by three sensors and the most evolutionary conserved IRE1α signals through its cytosolic kinase and endoribonuclease (RNase) activities. IRE1α RNase activity can either catalyze the initial step of XBP1 mRNA unconventional splicing or degrade a number of RNAs through regulated IRE1-dependent decay. Until now, the biochemical and biological outputs of IRE1α RNase activity have been well documented; however, the precise mechanisms controlling whether IRE1α signaling is adaptive or pro-death (terminal) remain unclear. We investigated those mechanisms and hypothesized that XBP1 mRNA splicing and regulated IRE1-dependent decay activity could be co-regulated by the IRE1α RNase regulatory network. We identified that RtcB, the tRNA ligase responsible for XBP1 mRNA splicing, is tyrosine-phosphorylated by c-Abl and dephosphorylated by PTP1B. Moreover, we show that the phosphorylation of RtcB at Y306 perturbs RtcB interaction with IRE1α, thereby attenuating XBP1 mRNA splicing. Our results demonstrate that the IRE1α RNase regulatory network is dynamically fine-tuned by tyrosine kinases and phosphatases upon various stresses and that the extent of RtcB tyrosine phosphorylation determines cell adaptive or death outputs.

Secretory trafficking from the endoplasmic reticulum (ER) is subject to regulation by extrinsic and intrinsic factors. While much of the focus has been on biochemical triggers, little is known whether and how the ER is subject to regulation by mechanical signals. Here, we show that COPII-dependent ER-export is regulated by mechanical strain. Mechanotransduction to the ER was mediated via a previously unappreciated ER-localized pool of the small GTPase Rac1. Mechanistically, we show that Rac1 interacts with the small GTPase Sar1 to drive budding of COPII carriers and stimulate ER-to-Golgi transport. Altogether, we establish an unprecedented link between mechanical strain and export from the ER.

The selectivity of the ligand MKC9989, as inhibitor of the Inositol-Requiring Enzyme 1α (IRE1α) transmembrane kinase/ribonuclease protein, towards the residue K907 in the context of Schiff base formation, has been investigated by employing an array of in silico techniques including Multi-Conformation Continuum Electrostatics (MCCE) simulations, Quantum Mechanics/Molecular Mechanics (QM/MM) calculations, covalent docking, and Molecular Dynamics (MD) simulations. According to the MCCE results, K907 displays the lowest pKa value among all 23 lysine residues in IRE1α. The MMCE simulations also indicate a critical interaction between K907 and D885 within the hydrophobic pocket which increases significantly at low protein dielectric constants. The QM/MM calculations reveal a spontaneous proton transfer from K907 to D885, consistent with the low pKa value of K907. A Potential Energy Surface (PES) scan confirms the lack of energy barrier and transition state associated with this proton transfer reaction. Covalent docking and MD simulations verify that the protein pocket containing K907 can effectively stabilize the inhibitor by strong π–π and hydrogen bonding interactions. In addition, Radial Distribution Function (RDF) analysis shows that the imine group formed in the chemical reaction between MKC9989 and K907 is inaccessible to water molecules and thus the probability of imine hydrolysis is almost zero. The results of the current study explain the high selectivity of the MKC9989 inhibitor towards the K907 residue of IRE1α.

Multicomponent gas separation and purification is an important pre- or post-processing step in industry. Herein, we employed a multiscale computational approach to investigate the possibility of multicomponent low-weight gas (H2, O2, N2, CO2, CH4) separation and purification using novel porous 2D carbonaceous nanomaterials, namely Graphdiyne (GD), Graphenylene (GN), and Rhombic-Graphyne (RG). The dispersion-corrected plane-wave density functional theory (DFT) calculation combined with the Climbing Image Nudged Elastic Band (CI-NEB) method was employed to study the gas/membrane interaction energy and diffusion barrier of different gases passing through the geometrically optimized membranes. The results from CI-NEB calculations were then fitted to the Morse potential function to construct a bridge between quantum mechanics calculations and non-equilibrium molecular dynamics (NEMD) simulation. The selectivity of each membrane for all binary mixtures was calculated using the estimated diffusion energy barriers based on the Arrhenius equation. Finally, a series of extensive NEMD simulations were carried out to evaluate the real word and time dependent separation process. According to the results, CH4 molecules can be completely separated from the other gases using a GD membrane, O2 molecules from CH4, N2, and CO2 by a GN membrane, and H2 molecules from all other gases using a RG membrane.

Novel photoanodes for photoelectrocatalytic water oxidation were designed based on the electrodeposited thin film of palladium and silver-doped graphitic carbon nitride. For the first time, the pho...

Hydrogen storage capacity (HSC) of multilayer graphitic carbon nitride, d-g-C3N4 (d is interlayer spacing), and its palladium nanocomposite, d-Pd@g-C3N4, were investigated using multiscale computational techniques including quantum mechanics calculations and grand canonical Monte Carlo (GCMC) simulation. According to the results, the volumetric HSC of 8-g-C3N4 and 8-Pd@g-C3N4 can reach to DOE target of 30 gH2/L at 177 K, 5.7 MPa, and 177 K, 4.0 MPa, respectively. The gravimetric HSC of 10-g-C3N4 and 12-Pd@g-C3N4 meet the DOE target of 4.5 wt% at 150 K, 3.5 MPa, and 125 K, 4.0 MPa, respectively. The incorporation of Pd atoms enhances the delivery volumetric HSC of 6-, 8-, 10-, and 12-g-C3N4 by 49, 55, 129, and 146%, respectively at 177 K and 0.5 MPa. On the other hand, the incorporation of Pd atoms has a negative effect on the delivery gravimetric HSC of 6- and 8-g-C3N4 and positive effect for 10- and 12-g-C3N4. The estimated isostric heat, Qst, of adsorption is 5.5–8.5 kJ/mol. The maximum value of Qst for both nanoadsorbents belong to those with d = 8 A. The structure of adsorbates and possibility of multilayer adsorption occurrence were also investigated using pair correlation functions and density profiles.

International audience; The Unfolded Protein response is an adaptive pathway triggered upon alteration of endoplasmic reticulum (ER) homeostasis. It is transduced by three major ER stress sensors, among which the Inositol Requiring Enzyme 1 (IRE1) is the most evolutionarily conserved. IRE1 is an ER-resident type I transmembrane protein exhibiting an ER luminal domain that senses the protein folding status and a catalytic kinase and RNase cytosolic domain. In recent years, IRE1 has emerged as a relevant therapeutic target in various diseases including degenerative, inflammatory and metabolic pathologies and cancer. As such several drugs altering IRE1 activity were developed that target either catalytic activity and showed some efficacy in preclinical pathological mouse models. In this review, we describe the different drugs identified to target IRE1 activity as well as their mode of action from a structural perspective, thereby identifying common and different modes of action. Based on this information we discuss on how new IRE1-targeting drugs could be developed that outperform the currently available molecules.

Endoplasmic Reticulum (ER) stress is a hallmark of various diseases. Cells cope with ER stress through the activation of an adaptive signaling pathway named the Unfolded Protein Response (UPR) which is mediated by three ER-resident sensors. The most evolutionary conserved of the UPR sensors is IRE1alpha that elicits diverse downstream effects through its kinase and endoribonuclease (RNase) activities. IRE1alpha RNase activity can either catalyze the initial step of XBP1 mRNA unconventional splicing or degrade a number of RNAs through Regulated IRE1-Dependent Decay (RIDD). The degree of exertion of these two activities plays an instrumental role in cells life and death decisions upon ER stress. Until now, the biochemical and biological outputs of IRE1alpha RNase activity have been well documented, however, the precise mechanisms controlling whether IRE1 signaling is adaptive or pro-death (terminal) remain unclear. This prompted us to further investigate those mechanisms and we hypothesized that XBP1 mRNA splicing and RIDD activity could be co-regulated within the context of the IRE1alpha RNase regulatory network. We showed that a key nexus in this pathway is the tRNA ligase RtcB which, together with IRE1alpha is responsible for XBP1 mRNA splicing. We demonstrated that RtcB is tyrosine phosphorylated by c-Abl and dephosphorylated by PTP1B. Moreover, we identified RtcB Y306 as a key residue which, when phosphorylated, perturbs RtcB interaction with IRE1alpha, thereby attenuating XBP1 mRNA splicing and favoring RIDD. Our results demonstrate that the IRE1alpha RNase regulatory network is dynamically fine-tuned by tyrosine kinases and phosphatases upon various stresses and depending on the nature of the stress determines cell adaptive or death outputs.

A novel series of N-functionalized 4-aryl-tetrahydrobiquinoline-2,5-(1H,3H)-diones were synthesized in high yields by a one-pot three-component reaction involving 2-chloroquinoline-3-carbaldehydes, Meldrum’s acid, and enaminones (dimedone-based enaminones) in the presence of K2CO3 in CH3CN under reflux condition. To gain a deep insight on the mechanism of the reaction, an extensive series of quantum mechanics calculations in the framework of density functional theory (DFT) were carried out for supporting the suggested reaction pathway.

Herein, the applicability and efficiency of two types of pillared graphene nanostructures, namely, (6,6)@G and (7,7)@G, were investigated as membranes in reverse osmosis seawater desalination using extensive nonequilibrium molecular dynamics simulations. The water permeability for (6,6)@G and (7,7)@G membranes was estimated at 4.2 and 6.6 L h-1 cm-2 MPa-1, respectively. According to the results, a complete (100%) and pressure-independent salt rejection was estimated for both membranes. In addition, the mechanism of seawater desalination through the pillared graphene membranes was investigated via the density distribution profile of water molecules inside the pillar channels. Furthermore, a series of steered MD simulations were performed to construct the potential of mean force (PMF) profile of water molecules and salt ions passing through the membranes channels. The passing free energy barriers of Na+ and Cl- ions and water molecules are 0.86, 0.62, and 0.22 eV, respectively, for the (6,6)@G membrane. The corresponding quantities for the (7,7)@G membrane are 0.71, 0.44, and 0.11 eV, respectively.

The selectivity of the ligand MKC9989, as inhibitor of the Inositol-Requiring Enzyme 1α (IRE1α) transmembrane kinase/ribonuclease protein, towards the residue K907 in the context of Schiff base formation, has been investigated by employing an array of

Thermo-mechanical properties of boron nitride nanoribbons (BNNRs) were computed using molecular dynamics simulation with optimized Tersoff empirical potential. Thermal conductivity (TC) and heat transport properties of BNNRs were calculated as functions of both temperature and nanoribbon’s length. The results show that TC of BNNRs decreases with raising temperature by T−1.5 up to 1000 K. The phonon–phonon scattering relaxation time, mean free path of phonons, and contribution of high frequency optical phonons in TC of BNNRs were calculated at various temperatures. TC decreases as nanoribbon size increases and it converges to ∼500 W m−1K−1 for nanoribbons with length longer than 30 nm. The mechanical properties, including Gruneisen parameter, stress-strain response curves, Young’s modulus, intrinsic strength, critical strain, and poisson’s ratio were calculated in the temperature range of 137–1000 K. The simulation results show that Gruneisen parameter and poisson’s ratio of BNNRs are −0.092 and 0.245, respectively. The Young’s modulus of BNNRs decreases with raising temperature and its value is 630 GPa at 300 K. According to the results, BNNRs duo to their extraordinary thermo-mechanical properties, are the promising candidate for the future nano-device manufacturing.

In this work, the dispersion behavior of graphene oxide (GO) nanosheets in water was studied by a series of MD simulations for water, GO, and the water/GO mixed systems. The simulation results showed that the water/GO system has a well-ordered structure with strong H-bond interactions. The initial value (4.0 A) of the interlayer distance between two GO sheets at the beginning of the simulation clearly increased (∼7.2 A) in the presence of water as compared to its value after simulation in the absence of water (5.7 A). The solubility parameter of GO was calculated as a function of both temperature and number of layers. The solubility parameter of GO at 300 K reached a plateau at 44.9 MPa1/2 when the number of layers was five. Hence, water is a good solvent for dispersing GO since their solubility parameters are close to each other especially at temperatures close to the freezing point of water. The strong H-bond between water and oxygen-functional groups of GO makes the enthalpy favorable to form stable GO dispersions in water.

A substantial amount of researches have been carried out on the electron transport properties of gold surfaces. In order to study the role of linkage in the conductive properties of a molecular wire, different linkers such as sulfur, nitrogen, oxygen, CS, SH, NS, and CN are considered in our study. It is found that nitrogen or sulfur linkages can bond Au covalently to cis- and trans-butadiene, whereas on the other hand, oxygen linkage with the same shows a weak interaction and a non-covalent character. Further, this research is also an attempt to study the dependence of the molecular electronic structure of gold-molecule complexes on the external electric field. In addition, electronic conduction has been investigated from the perspective of alteration in shape of molecular orbitals and the development of the HOMO-LUMO gap of moleculegold complexes under the effect of an electric field.

Grand canonical Monte Carlo (GCMC) simulation combined with ab initio quantum mechanics calculations were employed to study hydrogen storage in homogeneous armchair open-ended single walled silicon nanotubes (SWSiNTs), single walled carbon nanotubes (SWCNTs), and single walled silicon carbide nanotubes (SWSiCNTs) in triangular arrays. Two different groups of nanotubes were studied: the first were (12,12) SiNTs, (19,19) CNTs, and (15,15) SiCNTs and the second were (7,7) SiNTs, (11,11) CNTs, and (9,9) SiCNTs with the diameters of ∼26 and ∼15 A for the first and second groups, respectively. The simulations were carried out for different thermodynamic states. The potential energy functions (PEFs) were calculated using ab initio quantum mechanics and then fitted with (12,6) Lennard-Jones (LJ) potential model as a bridge between first principles calculations and GCMC simulations. The absolute, excess, and delivery adsorption isotherms of hydrogen were calculated for two groups of nanotubes. The isosteric heat of adsorption and the radial distribution functions (RDFs) for the adsorbed molecules on different nanotubes were also computed. Different isotherms were fitted with the simulation adsorption data and the model parameters were correlated. According to the results, the hydrogen uptake values in (19,19) CNT array exceeded the US DOE (Department of Energy) target of 6.0 wt% (FY 2010) at 77 K and 1.0 and 2.0 MPa for absolute and excess uptakes, respectively. The results also show that SiNTs and SiCNTs are not more useful materials compared with corresponding CNTs for hydrogen storage.

A complete conformational analysis of doubly-hydrated hexafluoroacetylacetone, 1,1,1,5,5,5-hexafluoropentane-2,2,4,4-tetraol (HFPTO), was carried out by ab initio calculations, at the density functional theory (DFT) level. According to our calculations, 10 stable conformers were obtained. The most stable conformer is stabilized by formation of two intramolecular hydrogen bond (of OHO type) in opposite directions. The calculated geometrical parameters are in agreement with the corresponding values obtained by X-ray diffraction technique. Harmonic and anharmonic vibrational frequencies of the most stable conformer and its deuterated analogue were also calculated and compared with the experimental data. Additionally the Bader theory is applied here showing that characteristics of the bond critical points (BCPs) are useful parameters to estimate the strength of intramolecular hydrogen bonding. Natural bond orbital (NBO) analysis method was performed for the investigation of the relative stability of HFPTO conformers.

In the current work, the issue of re-parameterization of Tersoff empirical potential model was addressed for 2D nanomaterial 'germanene' to be applied in molecular dynamics simulation based studies. The well-known chi-square minimization procedure was used to optimize the original Tersoff potential parameters. Many properties of germanene were extracted using both original and optimized Tersoff potentials and they compared with the corresponding density functional theory data. According to the results, the optimized Tersoff potential provides a significant improvement in many structural, thermodynamic, mechanical, and thermal properties of geramanene.

The electron transport characteristics of a 3, 6-Diphenyl-1, 2, 4, 5-Tetrazine (DPT) single molecular conductor are investigated via the density functional theory (DFT) method. The molecule sandwiched between two gold surfaces. Different linkers such as sulfur, nitrogen, oxygen, CS, CO, CN, NO and NN have been considered to study the role of linkage in the conduction properties of the molecular wire. The charge transfer across the metal–molecule and bonding nature at the interfacial contact were performed by means of the natural bond orbital (NBO) analysis. It is found that Au can covalently bond to DPT through nitrogen or sulfur linkages while its weak interaction through oxygen linkage has non-covalent character in nature. The dependence of the molecular electronic structure of the gold–molecule complexes on the external electric field (EF) has also been studied. It is found that the external EF modifies both the geometry and electronic structure of the molecular wires. The application of EF may increase the molecular conjugation and the induced dipole moment, while decreasing the HOMO–LUMO gap. It may also make the spatial distributions of the frontier molecular orbital's move from a fully delocalized form to a partially localized one depending on the EF strength.

The physisorption of methane in homogeneous armchair open-ended SWCNT triangular arrays for the tubes of diameter of 10.85, 13.57, 16.28 and 19.00 A [(8,8), (10,10), (12,12) and (14,14), respectively] at temperature of 273, 298, 323 and 373 K and at fugacity of 0.5–9.0 Mpa is evaluated by means of Grand Canonical ensemble Monte Carlo simulation. The applied intermolecular forces are modeled using Lennard-Jones potential model. The absolute, excess and delivery adsorption isotherms of methane in various carbon nanotube arrays are calculated. Besides, specific surface areas and the isosteric heats of adsorption, Q st, are studied, also different isotherm models were fitted on the simulation adsorption data, and the model parameters are correlated. A novel geometrical relationship is introduced to calculate accessible interstitial and intratubular volumes. According to our simulation results, one can reaches to 96% of the US Department of Energy target for CH4 storage of 180 v/v at 298 K and 35 bar by using the SWCNT array with nanotube’s diameter of 19 A as adsorbent. For intertube distance equal 3.4 A, no gas adsorption is observed in interstitial channel except for the arrays bigger than 15.4 A in nanotube’s diameter, and multi-layer adsorption starts to form in nanotube’s diameter of 16.28 A at the pressure of 2.0 MPa.

The pyridine–pyridinium cationic complexes [(Py2H) + ], with two different counterions (perchlorate and bromide), were prepared. The vibrational spectra of the complexes have been recorded. We then performed theoretical calculations to aid our understanding of the experimental data. To include the proton tunneling effect in our study, we adopted a simple one-dimensional potential energy surface (PES) for the motion of the hydrogen atom (at the center). This PES was derived from quantum mechanical calculations at the B3LYP/6-311++G �� level of theory for a fixed skeleton geometry. Based on such a PES, we computed the vibrational energy levels, from which a tunneling splitting of 487 ± 2 and 242 ± 2 cm � 1 was

Molecular structure of magnesium bis-acetylacetonate, Mg(acac)2, has been investigated by means of ab initio and density functional theory (DFT) calculations and the results were compared with its gasphase electron diffraction data. For comparison, the structure of Mg(acac)2 was also optimized at the MP2 level using the 6-31G* basis set. The harmonic vibrational frequencies of Mg(acac)2 were obtained at a variety of density functional theory levels using the 6-31G*, 6-311G*, 6-311++G**, and lanL2DZ basis sets. The vibrational frequencies 2,413 C and 213 C derivatives of Mg(acac)2 were also calculated at the B3LYP/6-311++G** level. The calculated frequencies are compared with the experimental Fourier transform IR and Raman spectra. All of the measured IR and Raman bands were interpreted in terms of the calculated vibrational modes. The scaled theoretical frequencies and the structural parameters are in excellent agreement with the experimental data. Analysis of the vibrational spectra indicates a strong coupling between the chelated ring modes. Four bands at the 1021, 664, 569, and 414 cm � 1 are found to be mainly due to the

In the present study, the thermal conductivity (TC) and heat transport properties of nitrogen doped graphene (N-graphene) were investigated as a function of temperature (107-400K) and N-doped concentration (0.0-7.0%) using equilibrium molecular dynamics simulation based on Green-Kubo method. According to the results, a drastic decline in TC of graphene observed at very low N-doped concentration (0.5 and 1.0%). Substitution of just 1.0% of carbon atoms with nitrogens causes a 77.2, 65.4, 59.2, and 53.7% reduction in TC at 107, 200, 300, and 400K, respectively. The values of TC of N-graphene at different temperatures approach to each other as N-doped concentration increases. The results also indicate that TC of N-graphene is much less sensitive to temperature compared with pristine graphene and the sensitivity decreases as N-doped concentration increases. The phonon-phonon scattering relaxation times and the phonon mean free path of phonons were also calculated. The contribution of high frequency optical phonons for pristine graphene and N-graphene with 7.0% N-doped concentration is 0-2% and 4-8%, respectively. These findings imply that it is potentially feasible to control heat transfer on the nanoscale when designing N-graphene based thermal devices.

The graphene nanoribbons (GNRs) are promising candidate for next-generation electronic materials. Herein, the thermal conductivity (TC) and heat transport properties of GNRs were investigated as a function of temperature and nanoribbon size using equilibrium molecular dynamics simulation based on Green–Kubo method. According to the results, by increasing temperature, the TC decreases monotonically by T −1.52. The size dependence of TC was studied using a series of GNRs with 2 nm in width and 2–30 nm in length. The results showed that the TC decreases with longitudinal extension to reach a plateau at ~1,500 W m−1 K−1 based on an exponential curve fitting. The phonon scattering relaxation time, the average group velocity of phonons, and the phonon mean free paths were also calculated. The contribution of high frequency optical phonons to the total TC is negligible (0.3–2.0 %) below 400 K and exponentially increases at higher temperatures. When the quantum corrections for temperature were considered to the calculated results, the maximum value for TC (~5,500 W m−1 K−1) was obtained at 130 K.

Grand canonical Monte Carlo (GCMC) simulation combined with ab initio quantum mechanics calculations were employed to study methane storage in homogeneous armchair open-ended single-walled silicon nanotubes (SWSiNTs), single-walled carbon nanotubes (SWCNTs), and single-walled silicon carbide nanotubes (SWSiCNTs) in triangular arrays. Two different groups of nanotubes were studied: the first were (12,12) SiNTs, (19,19) CNTs, and (15,15) SiCNTs and the second were (7,7) SiNTs, (11,11) CNTs, and (9,9) SiCNTs with the diameters of 26 and 15 A for the first and second groups, respectively. The simulations were carried out at different thermodynamic states. The potential energy functions were calculated using ab initio quantum mechanics and then fitted with (12,6) Lennard–Jones potential model as a bridge between first-principles calculations and GCMC simulations. The absolute, excess, and delivery adsorption isotherms of methane were calculated for two groups of nanotubes. The specific surface area and the isosteric heat of adsorption were computed. The radial distribution functions for the adsorbed molecules on different nanotubes were also calculated. Different isotherm models were fitted with the simulation adsorption data. According to the results, the excess uptake value of methane adsorption in (11,11) CNT array exceeded the US Department of Energy target (180 V/V at 298 K and 35 bar). The results also indicate that SiNTs and SiCNTs are not desirable materials compared with corresponding CNTs for natural gas storage.

The physisorption of methane in homogeneous armchair open-ended SWBNNT triangular arrays was evaluated using grand canonical ensemble Monte Carlo simulation for tubes 11.08, 13.85, 16.62, and 19.41 A [(8,8), (10,10), (12,12), and (14,14), respectively] in diameter, at temperatures of 273, 298, 323, and 373 K, and at fugacities of 0.5–9.0 Mpa. The intermolecular forces were modeled using the Lennard–Jones potential model. The absolute, excess, and delivery adsorption isotherms of methane were calculated for the various boron nitride nanotube arrays. The specific surface areas and the isosteric heats of adsorption, Q st, were also studied, different isotherm models were fitted to the simulated adsorption data, and the model parameters were correlated. According to the results, it is possible to reach 108% and 140% of the US Department of Energy’s target for CH4 storage (180 v/v at 298 K and 35 bar) using the SWBNNT array with nanotubes 16.62 and 19.41 A in diameter, respectively, as adsorbent. The results show that for a van der Waals gap of 3.4 A, there is no interstitial adsorption except for arrays containing nanotubes with diameters of >15.8 A. Multilayer adsorption starts to occur in arrays containing nanotubes with diameters of >16.62 A, and the minimum pressure required for multilayer adsorption is 1.0 MPa. A brief comparison of the methane adsorption capacities of single-walled carbon and boron nitride nanotube arrays was also performed.

Cells are constantly exposed to various chemical and physical stimuli. While much has been learned about the biochemical factors that regulate secretory trafficking from the endoplasmic reticulum (ER), much less is known about whether and how this trafficking is subject to regulation by mechanical signals. Here, we show that subjecting cells to mechanical strain both induces the formation of ER exit sites (ERES) and accelerates ER-to-Golgi trafficking. We found that cells with impaired ERES function were less capable of expanding their surface area when placed under mechanical stress and were more prone to develop plasma membrane defects when subjected to stretching. Thus, coupling of ERES function to mechanotransduction appears to confer resistance of cells to mechanical stress. Furthermore, we show that the coupling of mechanotransduction to ERES formation was mediated via a previously unappreciated ER-localized pool of the small GTPase Rac1. Mechanistically, we show that Rac1 interacts with the small GTPase Sar1 to drive budding of COPII carriers and stimulates ER-to-Golgi transport. This interaction therefore represents an unprecedented link between mechanical strain and export from the ER.