Combining high mass resolution and velocity imaging in a time-of-flight ion spectrometer using pulsed fields and an electrostatic lens

We describe a momentum resolving time-of-flight ion mass spectrometer that combines a high mass resolution, a velocity focusing condition for improved momentum resolution, and field-free conditions in the source region for high resolution electron detection. It is used in electron-ion coincidence experiments to record multiple ionic fragments produced in breakup reactions of small to medium sized molecules, such as F(3)SiCH(2)CH(2)Si(CH(3))(3). These breakup reactions are caused by soft x rays or intense laser fields. The ion spectrometer uses pulsed extraction fields, an electrostatic lens, and a delay line detector to resolve the position. Additionally, we describe a simple analytical method for calculating the momentum from the measured hit position and the time of flight of the ions.     

Site-specific functionalization of proteins by organopalladium reactions

A new carbon-carbon bond has been regioselectively introduced into a target position (position 32 or 174) of the Ras protein by two types of organopalladium reactions (Mizoroki-Heck and Sonogashira reactions). Reaction conditions were screened by using a model peptide, and the stability of the Ras protein under the reaction conditions was examined by using the wild-type Ras protein. Finally, the iF-Ras proteins containing a 4-iodo-L-phenylalanine residue were subjected to organopalladium reactions with vinylated or propargylated biotin. Site-specific biotinylations of the Ras protein were confirmed by Western blot and LC-MS/MS.     

Adhesion Properties of Nanometer-Thick Perfluoropolyether Films Confined Between Solid Surfaces: A Coarse-Grained Molecular Dynamics Study

Lubrication with thin liquid films is essential to ensure the tribological reliability of technologically advanced devices, such as micro-electro-mechanical systems and hard disk drives. However, the adhesion and friction properties of thin films and the underlying mechanism remain elusive due to our limited understanding of film structures and motions at the molecular scale. Here, we investigate the adhesion behavior of nanometer-thick perfluoropolyether (PFPE) films confined between two solid surfaces as a function of film thickness using coarse-grained molecular dynamics simulations. Consistent with typical experimental results, our simulations show that the adhesive force exerted by the PFPE films reaches a maximum and then decreases with increasing solid–solid spacing. The maximum adhesive force increases sharply for PFPE films thinner than 4 nm. When exhibiting the maximum adhesive force, PFPE films are slightly stretched within a solid–solid spacing a little larger than the initial film thickness and thereby show lower density than the original equilibrium density. Conventional theories of adhesion, which assume equilibrium density for liquid films, are not applicable in such case. Therefore, we construct a theoretical model that takes decreasing liquid density into account to discuss the underlying mechanism of the adhesive force exerted by nanometer-thick PFPE films on solid surfaces. We infer from the theoretical analyses that the maximum adhesive force originates mainly from solid–liquid interaction for thin films and liquid–liquid interaction for thick films.     

Electrostatic properties of ultra-thin polyimide Langmuir-Blodgettfilms biased in a needle-plane electrode system

Surface potentials of polyimide (PI) Langmuir-Blodgett (LB) films on metal (Al, Ag and Au) electrodes, charged at various voltages, were examined under a needle-plane electrode system. It was found that PI LB films were negatively charged when the biasing voltage applied to the needle-electrode increased. The surface potentials saturated when the number of deposited layers was 20 to 30, and they were dependent on the nature of the metal electrodes. The temperature dependence of the surface potential also was examined, and it was concluded that the tendency to accept electrons increases as the temperature increases. These results suggest that the presence of interfacial electrostatic space charges in as-deposited PI LB films at the metal/film interface made a significant contribution to the creation of the additional electrostatic potential when the films were biased under a needle-plane electrode system     

Sulfated Hyaluronan Binds to Heparanase and Blocks Its Enzymatic and Cellular Actions in Carcinoma Cells

We examined whether sulfated hyaluronan exerts inhibitory effects on enzymatic and biological actions of heparanase, a sole endo-beta-glucuronidase implicated in cancer malignancy and inflammation. Degradation of heparan sulfate by human and mouse heparanase was inhibited by sulfated hyaluronan. In particular, high-sulfated hyaluronan modified with approximately 2.5 sulfate groups per disaccharide unit effectively inhibited the enzymatic activity at a lower concentration than heparin. Human and mouse heparanase bound to immobilized sulfated hyaluronan. Invasion of heparanase-positive colon-26 cells and 4T1 cells under 3D culture conditions was significantly suppressed in the presence of high-sulfated hyaluronan. Heparanase-induced release of CCL2 from colon-26 cells was suppressed in the presence of sulfated hyaluronan via blocking of cell surface binding and subsequent intracellular NF-κB-dependent signaling. The inhibitory effect of sulfated hyaluronan is likely due to competitive binding to the heparanase molecule, which antagonizes the heparanase-substrate interaction. Fragment molecular orbital calculation revealed a strong binding of sulfated hyaluronan tetrasaccharide to the heparanase molecule based on electrostatic interactions, particularly characterized by interactions of (−1)- and (−2)-positioned sulfated sugar residues with basic amino acid residues composing the heparin-binding domain-1 of heparanase. These results propose a relevance for sulfated hyaluronan in the blocking of heparanase-mediated enzymatic and cellular actions.     

Self‐Degradable Lipid‐Like Materials Based on “Hydrolysis accelerated by the intra‐Particle Enrichment of Reactant (HyPER)” for Messenger RNA Delivery

RNA‐based therapeutics is a promising approach for curing intractable diseases by manipulating various cellular functions. For eliciting RNA (i.e., mRNA and siRNA) functions successfully, the RNA in the extracellular space must be protected and it must be delivered to the cytoplasm. In this study, the development of a self‐degradable lipid‐like material that functions to accelerate the collapse of lipid nanoparticles (LNPs) and the release of RNA into cytoplasm is reported. The self‐degradability is based on a unique reaction “Hydrolysis accelerated by intra‐Particle Enrichment of Reactant (HyPER).” In this reaction, a disulfide bond and a phenyl ester are essential structural components: concentrated hydrophobic thiols that are produced by the cleavage of the disulfide bonds in the LNPs drive an intraparticle nucleophilic attack to the phenyl ester linker, which results in further degradation. An oleic acid‐scaffold lipid‐like material that mounts all of these units (ssPalmO‐Phe) shows superior transfection efficiency to nondegradable or conventional materials. The insertion of the aromatic ring is unexpectedly revealed to contribute to the enhancement of endosomal escape. Since the intracellular trafficking is a sequential process that includes cellular uptake, endosomal escape, the release of mRNA, and translation, the improvement in each process synergistically enhances the gene expression.     

Water-Soluble contrast enhancing materials—new photobleachable dyes

Many styrylpyridinium compounds (SPC), which are very stable in the dark, were prepared and evaluated as photobleachable dyes for contrast enhanced lithography (CEL). The photobleaching characteristics of water-soluble contrast enhancing materials composed of SPC and water-soluble polymer depend on the structure of the SPC and the kind of polymers used. The technique using SPC-based CEL proved to be very effective for the resist pattern profiles.     

ANALYSIS OF CUTTING CHARACTERISTIC OF POLYCARBONATE SHEET SUBJECTED TO WEDGE INDENTATION BY KNIFE EDGE AND GROOVED PLATE

Asymmetric plunge cutting by using a grooved knife edge plate was proposed for advanced die cutting of a polycarbonate (PC) sheet. By varying the tip angle α_U and the tip thickness w _U of knife edge in the counter plate, and combining a standard steel cutting rule of 42° center bevel blade, a cutting load response of PC sheet was experimentally investigated, and the deformation was also observed by a CCD camera. Furthermore, an FEM simulation was carried out by varying the lower tip thickness for revealing the effect of interference of lower grooved counter plate. Through this work, the following were found: 1) there were two deformation modes of sheared profile; 2) the lower tip thickness w _U was a primary factor, compared to the lower tip angle of α_U; 3) the equivalent wedge angle effect was revealed with respect to the upper/lower angles α and α_U, while the PC sheet was bent up by the lower knife indentation.     

Evaluations of tribological characteristics of PFPE lubricants on DLC surfaces of magnetic disks

This article presents measurements of adhesion and friction of perfluoropolyether (PFPE) lubricant films dip-coated on magnetic disks covered with diamond-like carbon (DLC) film. We have developed a custom-built pin-on-disk type micro-tribotester to perform the tribological measurements. The adhesion tests were performed by pulling down/up a 1.5-mm-diameter glass ball on a stationary disk surface, and the friction tests were carried out by sliding the glass ball on a rotating disk surface without changing head-disk interface conditions from the adhesion tests. Experiments were performed for the different kinds of 2- and 6-nm-thick PFPE lubricants (polar: Zdol4000 and Zdol2000; nonpolar: Z03) under lightly loaded and slow sliding conditions to minimize disturbance against the molecular layered structure. The adhesive forces were found to decrease with increasing film thickness in the order of Z03 > Zdol2000 > Zdol4000 (decreasing rate), which closely corresponds to the order of monolayer thickness, and then to saturate to almost the same calculated values. As for the friction forces of 2-nm-thick films, Zdol2000 featured extraordinarily large friction in comparison with Zdol4000 and Z03, while Zdol4000 was slightly larger than Z03. The largest friction of Zdol2000 reveals that the 2-nm-thick Zdol2000 formed a monolayer that served as an immobile layer. With the increase in film thickness, the friction force of Zdol2000 decreased, indicating that extra lubricant molecules served as a mobile layer, while that of Z03 remained unchanged as the lowest value. By extrapolating the loading force versus friction force relationship into a negative loading force region, it is found that the friction force of Z03 tended to zero at zero net load (loading force plus adhesion force), while those for Zdol2000 and Zdol4000 exhibited finite values, indicating formation of an immobile layer, which shows similar characteristics to those of adhesive rubber material. The dewetted surface is found to feature violently changing friction force only at the first stage of sliding, and it then becomes stable after several sliding passes.     

Effect of Ultraviolet Irradiation on the Interactions between Perfluoropolyether Lubricant and Magnetic Disk Surfaces

To tailor the characteristics of molecularly thin lubricant films, magnetic disk surfaces coated with nanometer-thick perfluoropolyether AM3001 lubricant films were irradiated with 184.9 and 253.7 nm ultraviolet (UV) rays. We elucidated the effect of UV irradiation on the interactions between the lubricant and the magnetic disk surface via surface energy, bonded lubricant thickness and lubricant spreading measurements for films with and without UV irradiation. We found that UV irradiation decreased the dispersive and polar surface energies of the lubricant films by 20 and 80%, respectively; increased bonded lubricant thickness; and decelerated lubricant spreading. These results indicated that dispersion and polar interactions between lubricant molecules and the magnetic disk surface were strengthened by UV irradiation.