Host Cell Prediction of Exosomes Using Morphological Features on Solid Surfaces Analyzed by Machine Learning.

Exosomes are extracellular nanovesicles released from any cells and found in any body fluid. Because exosomes exhibit information of their host cells (secreting cells), their analysis is expected to be a powerful tool for early diagnosis of cancers. To predict the host cells, we extracted multidimensional feature data about size, shape, and deformation of exosomes immobilized on solid surfaces by atomic force microscopy (AFM).

Amphiphobic Septa Enhance the Mechanical Stability of Free-Standing Bilayer Lipid Membranes.

Artificial bilayer lipid membranes (BLMs) provide well-defined systems for investigating the fundamental properties of membrane proteins, including ion channels, and for screening the effect of drugs that act on them. However, the application of this technique is limited due to the low stability and low reconstitution efficiency of the process. We previously reported on improving the stability of BLM based on the fabrication of microapertures having a tapered edge in SiO/SiN septa and efficient ion channel incorporation based on vesicle fusion accelerated by a centrifugal force.

Substrate-Induced Structure and Molecular Dynamics in a Lipid Bilayer Membrane.

The solid-substrate-dependent structure and dynamics of molecules in a supported lipid bilayer (SLB) were directly investigated via atomic force microscopy (AFM) and single particle tracking (SPT) measurements. The appearance of either vertical or horizontal heterogeneities in the SLB was found to be strongly dependent on the underlying substrates. SLB has been widely used as a biointerface with incorporated proteins and other biological materials.

Fabrication of Au-Nanoparticle-Embedded Lipid Bilayer Membranes Supported on Solid Substrates.

We fabricated gold nanoparticle (Au-NP)-embedded supported lipid bilayers (SLBs) by two methods. In the vesicle-vesicle fusion method, vesicles with hydrophobized Au-NPs are ruptured and fused on SiO/Si substrates. In the vesicle-membrane fusion method, SLBs without Au-NPs were preformed on the substrate and then vesicles with Au-NPs were fused into the preformed membranes.

Phase separation in lipid bilayer membranes induced by intermixing at a boundary of two phases with different components.

We have demonstrated that dynamic phase separation is induced by coalescence of two self-spreading supported lipid bilayers (SLBs) with different components. Coalescence between a phosphocholine/sphingolipid SLB and a phosphocholine/cholesterol one forms raft-like liquid ordered (Lo) domains, which can be observed by fluorescence microscopy at the boundary of two phases. This phase separation process indicates that lipid molecules, such as sphingolipid and cholesterol, are intermixed.

Amino- and carboxyl-terminal domains of Filamin-A interact with CRMP1 to mediate Sema3A signalling.

Reorganization of the actin cytoskeleton is an early cellular response to various extracellular signals. Sema3A, a repulsive axon guidance molecule, induces the reorganization of actin cytoskeleton in the growth cones. Collapsin response mediator protein 1 (CRMP1) mediates the intracellular Sema3A signalling through its Ser522 phosphorylation.

Protein adsorption to graphene surfaces controlled by chemical modification of the substrate surfaces.

We have investigated effects of the support substrate surfaces on properties of the attached graphene flakes by observing protein adsorption to the graphene surfaces on SiO2/Si substrates that are modified with self-assembled monolayers to control their hydrophilicity. Using atomic force microscopy operated in aqueous environment, we found that high-density clusters of agglomerated avidin molecules form on the graphene flakes in the areas supported by a hydrophobic substrate surface, whereas very low density of large avidin clusters form at the edge of graphene flakes in the area supported by a hydrophilic surface. These results demonstrate that hydrophilicity of the support surface affects hydrophilicity of the graphene surface also in aqueous environment and that surface modification of the support substrate is a useful technique to control protein adsorption phenomena on graphene surfaces for realization of high sensitive graphene biosensors.

Selective adsorption of protein molecules on phase-separated sapphire surfaces.

Site-selective adsorption of protein molecules was found on sapphire surfaces that exhibit a phase separation into two domains: weakly charged hydrophobic domain and negatively charged hydrophilic one. Ferritin and bovine serum albumin molecules, which are negatively charged in a buffer solution, are adsorbed to the hydrophobic domains. Avidin molecules, which are positively charged, are adsorbed to the other domain.

Evolution of supported planar lipid bilayers on step-controlled sapphire surfaces.

Self-organized step/terrace structures on a sapphire surface were used to investigate interface properties between a solid surface and a supported planar lipid bilayer (SPB). We prepared random-stepped, single-stepped and multistepped sapphire surfaces. Some multistepped surfaces covered with crossing steps exhibit phase-separation into hydrophilic and hydrophobic domains.

Recombinant nucleocapsid protein-based IgG enzyme-linked immunosorbent assay for the serological diagnosis of SARS.

The recombinant nucleocapsid protein (rNP) of severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) was expressed in a baculovirus system. The purified SARS-CoV rNP was used as an antigen for detection of SARS-CoV antibodies in IgG enzyme-linked immunosorbent assay (ELISA). The ELISA was evaluated in comparison with neutralizing antibody assay and the authentic SARS-CoV antigen-based IgG ELISA.

An experimental and theoretical study on the substituent effect of the permanganate oxidation of styrenes.

The kinetic data obtained for the cycloadditions of the permanganate ion to a series of styrene derivatives in dichloromethane solution in the presence of a quaternary ammonium ion were examined with two theoretical approaches, on the assumption that the reactions proceed via a concerted [3 + 2] mechanism. The semi-quantitative frontier molecular orbital analysis of the kinetic data shows a linear free energy relationship with better correlation than the Hammett plot with a values when the point for p-NO2 group is omitted. Further examination of the results of the FMO analysis reveals that the deviation of the point for p-nitrostyrene is attributed to the transition structure being more reactant-like than that of the other derivatives.

Atomic structures of the Ge/Si(113)-(2 x 2) surface.

Based on scanning tunneling microscopy observations of the epitaxial growth of Ge on Si(113) and first-principles total energy and band calculations, we demonstrate that the Ge/Si(113)-(2 x 2) surface is made up of alternating [1;10]-oriented rows of rebonded atoms and tilted pentamers of five atoms, where each pentamer is stabilized by an interstitial atom at the subsurface. From the existence of stacking defects in rows of tilted pentamers observed at room temperature, we have deduced that at epitaxial temperatures the pentamers frequently change their tilting orientations between two minimum energy states.

Dephosphorylation failure of tyrosine-phosphorylated STAT1 in IFN-stimulated Sendai virus C protein-expressing cells.

Sendai virus C protein (SeV C) has been reported to counteract the antiviral activities of interferons (IFNs) by inhibiting the expression of IFN-stimulated gene products. In SeV C-expressing cells, formation of an active ISGF3 complex and translocation of STAT1 into the nucleus were not observed. STAT1 was continuously phosphorylated at tyrosine 701 by IFN signaling; however, its serine phosphorylation was suppressed.

Semiquantitative FMO Analysis of Substituent Effect on the Reaction of Permanganate Ion with Unsymmetrical Alkenes.

The substituent effects on the reactions of permanganate ion with unsymmetrical alkenes are analyzed on the assumption of a concerted (3 + 2) cycloaddition model by using an equation obtained by approximation based on the FMO theory in which development and localization of the frontier molecular orbitals at the reaction sites with progress of the reaction are considered. The Hammett plots are successfully reproduced with the newly obtained rate data for the reactions of trans-chalcone and its derivatives and the data for methyl cinnamates, cinnamate ions, and alkyl vinyl ethers taken from the literature using FMO energies and orbital coefficients calculated by the PM3 method. It was indicated that a factor introduced to the basic equation in order to estimate the extent of localization of the molecular orbitals at the transition state is closely related to the position of the transition state along the reaction path.