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Summary Efficient and scalable sunlight-driven water-splitting systems are essential for practical renewable hydrogen production. Particulate photocatalyst sheets for Z-scheme water splitting can be printed at low cost using inks containing a hydrogen evolution photocatalyst (HEP), an oxygen evolution photocatalyst (OEP), and conductive metal nanoparticles, and can be applied to large areas. However, the metal nanoparticles lead to backward reactions and light absorption. Herein, we demonstrate printable photocatalyst sheets composed of SrTiO3:La,Rh as the HEP, BiVO4:Mo as the OEP, and nanoparticulate indium tin oxide as a transparent and electrochemically inert conductor, for efficient pure-water splitting. The photocatalyst sheets decompose water with a solar-to-hydrogen energy conversion efficiency of 0.4%, which is one of the highest values among Z-scheme overall water-splitting systems prepared without the requirement for a vacuum process. Printable and efficient photocatalyst sheets obtained using cost-effective and readily extensible procedures spread opportunities toward practical solar hydrogen production via the water-splitting reaction.

Summary Sunlight-driven photocatalytic water splitting has been investigated as a potentially scalable and economically feasible means of producing renewable hydrogen. However, reactors suitable for efficient water splitting and prompt collection of gaseous products on a large scale have yet to be demonstrated. Here, we demonstrate a sunlight-powered water-splitting reactor using a fixed Al-doped SrTiO 3 photocatalyst and address the key issues in the reactor design associated with the scale-up. A panel reactor filled with only a 1-mm-deep layer of water was capable of rapid release of product gas bubbles without forced convection. A flat panel reactor with 1 m 2 of light-accepting area retained the intrinsic activity of the photocatalyst and achieved a solar-to-hydrogen energy conversion efficiency of 0.4% by water splitting under natural sunlight irradiation. The concept of a readily extensible water-splitting panel is a viable means for large-scale production of low-cost renewable solar hydrogen.

Summary Photoelectrochemical (PEC) water oxidation by semiconductor photoanodes plays a fundamental role for sustainable solar fuel and chemical production. Advanced surface and interface engineering has been demonstrated to be of critical importance for the development of highly efficient and stable water oxidation photoanodes. In this review, we briefly introduce the fundamentals and some general considerations in the development and evaluation of water oxidation photoanodes and the assembly of PEC cells. We summarize several most important roles of surface and interface engineering identified in improving the PEC performance of photoanodes and highlight the most prominent research advancements in these fields. Finally, the outlook for the future development of surface and interface engineering for practical photoelectrochemical water oxidation is concisely discussed.

Reverse osmosis membranes based on aromatic polyamide (ar-PA) are widely used in desalination of seawater, yet the microscopic mechanism of water diffusion through a polyamide layer remains elusive. Here, we study the structure and dynamics of polymer chains and water molecules in ar-PA in comparison to nylon 6 (one of aliphatic polyamides) under various water contents (0.0–15.9 wt%). The infrared (IR) difference spectrum between dry and moist ar-PA shows little change in amide A bands, in contrast to that of nylon 6 which yields a prominent dip. Theoretical analyses using molecular dynamics simulations and quantum electronic and vibrational calculations reveal that the dip in nylon 6 is caused by breaking of hydrogen bonds (HBs) among amide groups. The incoming water molecules that break amide-amide HBs are bound to polyamide chains nearby and diffuse slowly. On the other hand, the amide-amide HBs of ar-PA are kept upon hydration. Such polymer structure facilitates growth of large water clusters with more than 100 water molecules and rapid diffusion of water molecules. The amide A band serves as a fingerprint to characterize the water permeability of polyamide materials.

The surface phonon dispersion of a deuterium-terminated Si(110)-(1 × 1) surface [D:Si(110)-(1 × 1)] is investigated by using high-resolution electron-energy-loss spectroscopy (HREELS) and first-principles calculations based on the density functional theory (DFT) with the local density approximation (LDA). The characteristics of D:Si(110)-(1 × 1) are unique compared to those of H:Si(110)-(1 × 1) (Matsushita et al., 2015) in terms of the resolved vibrational modes. By the HREELS, one-dimensional surface phonons consisting of D–Si stretching vibrations are observed above the bulk-phonon band energy edge of 64.5 meV. Ten modes are observed below this value, classified as surface, surface resonant, and bulk phonons according to the calculated energy dispersion as well as the depth profile of spectral density and displacement vectors. In particular, five D–Si bending modes are observed out of the seven theoretically predicted modes. The bending modes are strongly coupled with the displacements across the D and five Si layers. The DFT-LDA surface phonon dispersion is in good agreement with the experimental results except a few frequency/dispersion mismatches, as the structure optimized by DFT-LDA mismatches with the previous scanning tunneling microscopy (STM) results (Matsushita et al., 2015). D:Si(110)-(1 × 1) elucidates the nature of covalently bonded phonons and their characteristics both experimentally and theoretically.

We have measured the macroscopic and microscopic surface morphology of hydrogen-terminated Si(110)-(1 × 1) [H:Si(110)-(1 × 1)] surfaces prepared by an improved wet chemical process. The observations were performed by high-resolution electron-energy-loss spectroscopy (HREELS), low-energy-electron diffraction (LEED), and scanning tunneling microscopy (STM). At macroscopic scale, it was found that the surface is a mono-hydride terminated surface with a two-dimensional p2mg space group, thus, being a well-defined H:Si(110)-(1 × 1) surface. At microscopic scale, elongated terraces were observed along the [1 1 ¯ 0] direction reflecting surface anisotropy. The terraces extend in frames with sizes up to a few micrometers. We discussed the macroscopic and microscopic surface morphology by combining our LEED and STM results.

A tip-enhanced Raman spectroscopy (TERS) set-up added on a scanning tunneling microscope (STM) was constructed and was used to study the molecular arrangement of 4,4′-bipyridine (4,4′-BiPy) and 4,4′-bipyridine N,N' -dioxide (4,4′-BiPyO 2 ) adsorbed on Au(111). Over a monolayer of 4,4′-BiPy, in the ambient atmosphere, intense TERS signals were recorded, involving Au N stretching vibration at 185 cm − 1 . At the early stage of 4,4′-BiPy adsorption, the Au N stretching signal was not detected. By the aid of the theoretical calculations of the Raman scattering intensities for each vibrational normal mode, a standing-up, tilted orientation at monolayer coverage and a vertical orientation with the longitudinal molecular axis parallel to the surface at low surface coverage was concluded. Adsorption of 4,4′-BiPyO 2 on Au(111) resulted in formation of a (6 × 9) adlattice. Moderately intense TERS signals were observed, containing the N O stretching modes and the in-plane ring vibrational modes. Neither Au O nor Au N stretching modes were observed. 4,4′-BiPyO 2 was laid with the longitudinal axis parallel to the surface, and the molecular plane vertical to the surface. These results demonstrate that STM-TERS is an effective method for simultaneous imaging and vibrational analysis, facilitating identification of the adsorbed layers with the nanometer-scale spatial resolution and monolayer sensitivity.

Pore-forming toxins (PFTs) are soluble proteins that can oligomerize on the cell membrane and induce cell death by membrane insertion. PFT oligomers sometimes form hexagonal close-packed (hcp) structures on the membrane. Here, we show the assembling of the sphingomyelin (SM)-binding PFT, lysenin, into an hcp structure after oligomerization on SM/cholesterol membrane. This process was monitored by high-speed atomic force microscopy. Hcp assembly was driven by reorganization of lysenin oligomers such as association/dissociation and rapid diffusion along the membrane. Besides rapid association/dissociation of oligomers, the height change for some oligomers, possibly resulting from conformational changes in lysenin, could also be visualized. After the entire membrane surface was covered with a well-ordered oligomer lattice, the lysenin molecules were firmly bound on the membrane and the oligomers neither dissociated nor diffused. Our results reveal the dynamic nature of the oligomers of a lipid-binding toxin during the formation of an hcp structure. Visualization of this dynamic process is essential for the elucidation of the assembling mechanism of some PFTs that can form ordered structures on the membrane.

The protonation states and hydration structures of the α-thrombin-bivalirudin complex were studied by joint XN refinement of the single crystal X-ray and neutron diffraction data at resolutions of 1.6 and 2.8Å, respectively. The atomic distances were estimated by carrying out X-ray crystallographic analysis at 1.25Å resolution. The complex represents a model of the enzyme-product (EP) complex of α-thrombin. The neutron scattering length maps around the active site suggest that the side chain of H57/H was deuterated. The joint XN refinement showed that occupancies for Dδ1 and Dε2 of H57/H were 1.0 and 0.7, respectively. However, no significant neutron scattering length density was observed around the hydroxyl oxygen Oγ of S195/H, which was close to the carboxylic carbon atom of dFPR-COOH. These observations suggest that the Oγ atom of S195/H is deprotonated and maintains its nucleophilicity in the EP complex. In addition to the active site, the hydration structures of the S1 subsite and the Exosite I, which are involved in the recognition of bivalirudin, are presented.

We studied the light emission induced by tunneling electrons of scanning tunneling microscopy (STM) from well-defined 3,4,9,10-perylenetertracarboxylic dianhydride (PTCDA) bilayer, vapor deposited under ultrahigh vacuum condition on Au(111) single crystal surface. We detected visible fluorescence over the second layer of PTCDA. The light emission spectrum contained a fluorescence peak at 1.75 eV of photon energy at STM bias voltages below 2.5 V. When the bias voltage was set above 2.5 V, another fluorescent peak was observed at 2.35 eV. This peak is out of the range of Au local plasmon excitation, and is attributed to the transition from S 1 excited state to S 0 ground state of PTCDA molecule excited by direct electron injection. The fluorescence near 2.35 eV was reported in dilute solution of PTCDA by optical excitation. This intrinsic molecular fluorescence indicates that the 2nd layer PTCDA molecules were significantly isolated from environment over the presence of the 1st layer on Au(111).

SDH (l-serine dehydratase, EC 4.3.1.17) is a pyridoxal-5'-phosphate (PLP)-dependent enzyme that catalyzes dehydration of l-Ser/Thr to yield pyruvate/ketobutyrate and ammonia. A SDH isoform (cSDH) found in human cancer cell lines has relatively low catalytic activity in comparison with the liver enzyme (hSDH). The crystal structure of cSDH has been determined at 2.8 angstroms resolution. A PLP is covalently attached to K48 by Schiff-base linkage in the active site. The ring nitrogen of PLP is involved in a H-bonding with C309, but is apparently not protonated. Twenty-three amino residues that compose the active site surfaces were identified. The human and rat liver enzymes (hSDH and rSDH) have the same residues, while residues G72, A172, and S228 in cSDH are replaced with A66, S166, and A222, respectively, in hSDH. These residues in hSDH and cSDH were mutated to make complementary pairs of mutated enzymes, and their kinetic parameters were determined. C303 of hSDH and C309 of cSDH which are H-bonding partner of the ring nitrogen of PLP were mutated to alanine and their kinetic parameters were also determined. The crystal structures and the mutation data suggest that having a glycine at residue 72 of cSDH is the major reason for the reduction of catalytic activity of cSDH. Changing alanine to glycine at residue 72 increases the flexibility of the substrate binding-loop (71S(G/A)GN74), so that the bound substrate and PLP are not pushed deep into the active cleft. Consequently, the proton transfer rate from S(G) of C309 to N1 of the bound PLP is decreased, which determines the rate of catalytic reaction.

Adsorption of purine DNA bases (guanine and adenine) on Cu(1 1 0) was studied by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine-structure spectroscopy (NEXAFS), and density-functional theory (DFT) calculation. At coverages near 0.2 monolayers, Angular-resolved NEXAFS analysis revealed that adenine adsorbates lie almost flat and that guanine adsorbates are tilted up on the surface with the purine ring parallel to the atom rows of Cu(1 1 0). Referring to the previous studies on pyrimidine DNA bases [M. Furukawa, H. Fujisawa, S. Katano, H. Ogasawara, Y. Kim, T. Komeda, A. Nilsson, M. Kawai, Surf. Sci. 532–535 (2003) 261], the isomerization of DNA bases on Cu(1 1 0) was found to play an important role in the adsorption geometry. Guanine, thymine and cytosine adsorption have an amine-type nitrogen next to a carbonyl group, which is dehydrogenated into imine nitrogen on Cu(1 1 0). These bases are bonded by the inherent portion of –NH–CO– altered by conversion into enolic form and dehydrogenation. Adenine contains no CO group and is bonded to Cu(1 1 0) by participation of the inherent amine parts, resulting in nearly flatly-lying position.

d-Eritadenine (DEA) is a potent inhibitor of S-adenosyl-l-homocysteine hydrolase (SAHH) and has hypocholesterolemic activity. We have hypothesized that 3-deaza-DEA (C3-DEA) and its analogues retain high level of SAHH inhibitory activity and have resistance to deamination and glycosidic bond hydrolysis in vivo. Such C3-DEA analogues would have much higher hypocholesterolemic activity. C3-DEA, and its methyl ester (C3-OMeDEA) and its methyl amido (C3-NMeDEA) were synthesized to examine their SAHH inhibitory and hypocholesterolemic activities. A crystal structure of SAHH containing C3-DEA was determined and confirmed that DEA and C3-DEA bound to the same site of SAHH with the same binding mode. The SAHH inhibitory activities of C3-DEA (K(I)=1.5 microM) and C3-OMeDEA (K(I)=1.5 microM) are significantly lower than that of DEA (K(I)=30 nM), while rats fed by C3-DEA and C3-OMeDEA decrease the total plasma cholesterol and phospholipids by 36-40% and 23%, respectively, which is similar to the level of reductions (42% and 27%) by DEA. C3-NMeDEA lost most of the SAHH inhibitory activity (K(I)=30 microM) and dietary C3-NMeDEA does not decrease cholesterol and phospholipid in plasma but decreases the triacylglycerol level by 16%. DEA and C3-DEA analogues are neither substrates nor inhibitors of adenosine deaminase.

Monolayers of organic adsorbates formed on Si wafers are prospective materials for nanometer-scale fabrication, chemical functionalization and biochemical analysis. We have been studying the methods of preparing organic monolayers by activating hydrogen-terminated H:Si(1 1 1). In this report, the method of photo-assisted adsorption of allylamine (CH 2 CH–CH 2 –NH 2 ) and 1-butene (CH 2 CH–CH 2 –CH 3 ) onto H:Si(1 1 1) is described. The adsorbates were identified by high-resolution electron energy loss spectroscopy and Auger electron spectroscopy. The functional group, NH 2 in allylamine, was observed reserved in the adlayer. Mixed adlayers of allylamine and 1-butene, which is practically favorable, were also prepared.

The covalent attachment of alkyl groups to silicon surfaces, via carbon–silicon bond formation, has been attempted using gas-surface reactions starting from Cl-terminated Si(1 1 1) or H:Si(1 1 1) under ultraviolet light irradiation. The formation of Cl-terminated Si(1 1 1) and its resulting stability were examined prior to deposition of organic molecules. High-resolution electron energy loss spectroscopy (HREELS) was utilized for detecting surface-bound adsorbates. The detection of photo-deposited organic species on Cl:Si(1 1 1) from gas-phase CH4 or CH2CH2 was not significant. On H:Si(1 1 1), it was evident that after the photoreaction with gas-phase C2H5Cl, C2H5 groups were chemically bonded to the surface Si atoms through single covalent bonds. The C2H5 groups were thermally stable at temperatures below 600 K. Alkyl monolayers prepared on silicon surfaces by dry process will lead to a new prospective technology of nanoscale fabrication and biochemical applications.

S-adenosylhomocysteine hydrolase (AdoHcyase) catalyzes the hydrolysis of S-adenosylhomocysteine (AdoHcy) to form adenosine and homocysteine. The crystal structure of the K185N mutated enzyme, which has weak catalytic activity (0.1%), has been determined at 2.8 A resolution and supports the previously predicted mechanism [Takata, Y., Yamada, T., Huang, Y., Komoto, J., Gomi, T., Ogawa, H., Fujioka, M., & Takusagawa, F. (2002). Catalytic mechanism of S-adenosylhomocysteine hydrolase. Site-directed mutagenesis of Asp-130, Lys-185, Asp-189, and Asn-190. J. Biol. Chem. 277, 22670-22676]. The mutated enzyme has an intermediate structure between the open and closed conformation, observed in the substrate-free enzyme and in the inhibitor complexes, respectively. H54, H300, and H352 were mutated to asparagine, respectively, to identify the roles of the histidine residues in catalysis. The kinetic data of H54N, H300N, and H354N mutated enzymes suggest that H54 is the amino acid residue that acts as a general acid/base to cleave the C5'-S(D) bond of AdoHcy. The E155Q mutated enzyme retained a large portion of the catalytic activity (31%), while the E155D mutated enzyme lost most of it (0.3%). The NADH accumulation measurements of the mutated enzymes indicated that the C3'-oxidation and the C4'-proton abstraction are a concerted event and the C5'-S(D) bond cleavage is an independent event. The C4'-proton exchange measurements indicate that the enzyme has an open conformation when AdoHcy is converted to 3'-keto-4', 5'-dehydro-Ado in the active site. With the results of this study and those of the previous studies, a detailed catalytic mechanism of AdoHcyase is described. K185 facilitates the C3'-oxidation, D130 abstracts the C4'-proton, D189, and E155 act as a communicator between the concerted C3'-oxidation and C4'-proton abstraction, and H54 plays as a general acid to cleave the C5'-S(D) bond of AdoHcy.

The molecular internal vibration modes and orientation of the DNA base molecules (cytosine, thymine, guanine and adenine) adsorbed on copper(1 1 0) clean single crystal surface were investigated by infrared reflection adsorption spectroscopy in ultrahigh vacuum. The adsorption was performed by thermal evaporation of powder of each species onto Cu(1 1 0) at room temperature. The surface uptakes of the molecules were determined by Auger electron spectroscopy. Cytosine exhibited characteristic asymmetric and symmetric NH2 stretching signal. The asymmetric stretching signal was missing in the submonolayer region, indicating that the whole molecule was standing upright, with the NH2 group sticking out of the surface. Thymine was also proved to stand upright at surface. Guanine exhibited weakened infrared signals, indicating that the core purine ring was tilted on the surface, with an interaction of NHCO side of the molecule. Adenine at coverages below one monolayer gave no absorption signals, evidencing the molecules laid flat along the surface. The vibrational information obtained will be helpful in developing the future methods of surface DNA sequencing.

Pretreating Si wafer surfaces with hydrochloric acid and hydrogen peroxide mixture (HPM) or ethanol was found to enhance the reactivity of chemical Ni deposition on Si(100) wafers in a simple bath of NiSO 4 –(NH 4 ) 2 SO 4 at pH 9.0. This phenomenon was identified as the acceleration of anodic reaction involved in chemical Ni deposition reaction on Si wafer surfaces, namely oxidation process of surface Si. Just after immersing into the alkaline bath, a reactive surface where oxidation reaction of Si was accelerated was formed on Si wafer surface with HPM or ethanol pretreatment. On the reactive surface, uniform and glossy Ni deposition film was obtained. In order to clarify the effects of HPM- or ethanol-pretreatment on anodic reaction, the pretreated Si(100) wafers were immersed into aqueous alkaline solution excluding NiSO 4 , resulting acceleration of Si oxidation compared to the unpretreated Si(100) surface. The progress of surface reactivity was also clarified by open circuit potentials (OCP), XPS, and ex-situ ATR FTIR. Moreover, by using this pretreatment, selective deposition onto nano-patterned Si substrate was performed. A two-dimensional array of fine Ni dots (diameter ca. 80 nm) was successfully fabricated.

The processes of thermal desorption and photo-induced desorption were investigated for nitric oxide (NO) molecules from the adlayers on bare diamond C(1 1 1) (2×1) surface formed at 110 K. The surface coverage of NO was monitored by X-ray photoelectron spectroscopy (XPS). The kinetics of thermal desorption of NO was of first-order (the activation energy of desorption=9.8 kcal mol −1 ) at coverages below one monolayer, and of zeroth-order (9.2 kcal mol −1 ) for multilayer. Time-of-flight (TOF) detection of photo-induced desorption of NO was performed by laser beams of wavelengths 193, 248 and 308 nm. The photo-excitation that drives NO desorption was attributed to the band-gap excitation of substrate and/or surface for the NO coverages below one monolayer, and to the direct absorption by NO multilayer consisting of (NO) 2 species.

Photochromic reactivity of a dithienylethene dimer, 5-(2-(3,4-dimethyl-2-thienyl))-3,3,4,4,5,5-hexafluorocyclopent-1-enyl-2-(2-(2,4-dimethyl-3-thienyl))-3,3,4,4,5,5-hexafluorocyclopent-1-enyl-3,4-dimethylthiophene, was studied in solution as well as in the crystalline phase. In solution two kinds of closed-ring form isomers were reversibly produced upon irradiation with ultraviolet light, while in the crystalline phase only one kind of closed-ring form isomer was produced. The different reactivity was attributed to the difference in the distance between two reactive centers in the crystal.

A process of electron-beam patterning of the surface of a Si(111) wafer was developed by utilizing alkyl monolayers as ultrathin patterning media. We performed chemical benchmark tests of the electron-beam patterning of alkyl monolayers on Si(111) in ambient oxygen, followed by the deposition of a metal on bombarded areas by immersion into an aqueous solution containing metal ions of the metal to be deposited. We investigated practically important issues related to this process, such as the robustness of organic monolayers against oxidation in aqueous media, the contrast enhancement of the bombarded areas by metal deposition, and the detectability of electron-bombarded areas of the monolayers by scanning tunneling microscopy (STM). The alkyl-covered Si(111) surface was significantly resistant to the oxidation by dissolved O2 in pure water, compared to hydrogen-terminated Si(111). By immersion into a solution containing CuSO4+HF+NH4F, electron-bombarded areas were visualized by the presence of the deposit of Cu. Electron-bombarded areas were also distinguishable from intact areas in terms of height contrast or roughness measured by STM. These results indicate the usefulness of alkyl monolayers for nano-scale patterning on silicon wafers.

Guanidinoacetate methyltransferase (GAMT) is the enzyme that catalyzes the last step of creatine biosynthesis. The enzyme is found in abundance in the livers of all vertebrates. Recombinant rat liver GAMT has been crystallized with S-adenosylhomocysteine (SAH), and the crystal structure has been determined at 2.5 A resolution. The 36 amino acid residues at the N terminus were cleaved during the purification and the truncated enzyme was crystallized. The truncated enzyme forms a dimer, and each subunit contains one SAH molecule in the active site. Arg220 of the partner subunit forms a pair of hydrogen bonds with Asp134 at the guanidinoacetate-binding site. On the basis of the crystal structure, site-directed mutagenesis on Asp134, and chemical modification and limited proteolysis studies, we propose a catalytic mechanism of this enzyme. The truncated GAMT dimer structure can be seen as a ternary complex of protein arginine methyltransferase (one subunit) complexed with a protein substrate (the partner subunit) and the product SAH. Therefore, this structure provides insight into the structure and catalysis of protein arginine methyltransferases.

S-Adenosylhomocysteine hydrolase (AdoHcyase) catalyzes the hydrolysis ofS-adenosylhomocysteine to form adenosine and homocysteine. On the bases of crystal structures of the wild type enzyme and the D244E mutated enzyme complexed with 3′-keto-adenosine (D244E·Ado*), we have identified the important amino acid residues, Asp-130, Lys-185, Asp-189, and Asn-190, for the catalytic reaction and have proposed a catalytic mechanism (Komoto, J., Huang, Y., Gomi, T., Ogawa, H., Takata, Y., Fujioka, M., and Takusagawa, F. (2000) J. Biol. Chem. 275, 32147–32156). To confirm the proposed catalytic mechanism, we have made the D130N, K185N, D189N, and N190S mutated enzymes and measured the catalytic activities. The catalytic rates (k cat) of D130N, K185N, D189N, and N190S mutated enzymes are reduced to 0.7%, 0.5%, 0.1%, and 0.5%, respectively, in comparison with the wild type enzyme, indicating that Asp-130, Lys-185, Asp-189, and Asn-190 are involved in the catalytic reaction. K m values of the mutated enzymes are increased significantly, except for the N190S mutation, suggesting that Asp-130, Lys-185, and Asp-189 participate in the substrate binding. To interpret the kinetic data, the oxidation states of the bound NAD molecules of the wild type and mutated enzymes were measured during the catalytic reaction by monitoring the absorbance at 340 nm. The crystal structures of the WT and D244E·Ado*, containing four subunits in the crystallographic asymmetric unit, were re-refined to have the same subunit structures. A detailed catalytic mechanism of AdoHcyase has been revealed based on the oxidation states of the bound NAD and the re-refined crystal structures of WT and D244E·Ado*. Lys-185 and Asp-130 abstract hydrogen atoms from 3′-OH and 4′-CH, respectively. Asp-189 removes a proton from Lys-185 and produces the neutral Nζ (–NH2), and Asn-190 facilitates formation of the neutral Lys-185. His-54 and His-300 hold and polarize a water molecule, which nucleophilically attacks the C5′- of 3′-keto-4′,5′-dehydroadenosine to produce 3′-keto-Ado.

In-situ electrochemical scanning tunnelling microscopy (STM) was applied to the investigation of the adsorption of iodine (I) on a well-defined Ni(111) single crystal electrode in an aqueous solution of 10 mM HF+1 mM KI under electrochemical potential control. The (√3×√3)R30° adlattice of I was observed by in-situ STM and confirmed by low-energy electron diffraction (LEED) using an ultrahigh vacuum-electrochemical apparatus. Adsorption of I took place in the potential region of the second anodic peak, and the I adlayer remained on the surface even with the anodic dissolution in progress. The I adatoms were desorbed upon sweeping the potential into the negative region, in which the Ni(111)–(1×1) structure was discerned clearly by in-situ STM. The anodic dissolution of Ni(111) with the adlayer of I was found to proceed by the layer-by-layer mode. Reactivity of the steps is discussed based on the geometrical configuration of Ni and I atoms near the step edges.

The effect of oxidation of silicon surface on chemical deposition of nickel was investigated in aqueous basic baths containing Ni2+. On H-terminated Si(100), Ni was deposited obviously but partially. On oxidized Si(100), Ni was deposited on the whole surface with a higher rate than on H–Si (100). The deposits were examined by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). Selective nickel deposition was performed on oxidized Si(100) patterned with a layer of plasma-CVD SiO2. Ni dots with diameters about 1 μm were formed by dipping the patterned Si(100) wafers first into a Ni bath containing no reducing agent for nuclei formation, and then into a Ni bath with reducing agent for growing particles.

The structure of the iodine adlattice formed on Ag(111) in aqueous solutions containing iodide ions has been determined as a function of the electrode potential by in situ scanning tunneling microscopy (STM) and ex situ low energy electron diffraction (LEED). In KI solutions buffered with KF-KOH at pH 10, continuous compression of the iodine adlattice from square (√3 × √3R-30°), via (√3qRβ° × √3R-30°), to (√3 × √3)R30° was observed as the electrode potential was increased; this was then followed by an abrupt phase transition into a rotated hexagonal (√3r × √3r)R(30° + α°) phase. Coadsorption of K was observed by Auger electron spectroscopy (AES) at potentials negative of that for the phase transition. In acid solutions (0.1mM HI) the continuous compression from (√3 × √3)R30°, via c(p × √3R-30°), into (√3r × √3r)R(30° + α°) was observed. The Moire pattern observed for the (√3r × √3r)R(30° + α°) adlattice, as well as the flatness of other adlattices observed in STM images, is explained in terms of lattice registry on the basis of a “hard ball contact model”.

Iodine adlayers formed on Au(111) in aqueous KI solution have been studied by ex situ Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and in situ scanning tunneling microscopy (STM). The LEED patterns are described as c ( p × 3 R − 30 ° ) where p decreases continuously with increasing emersion potential. By in situ STM, a series of rotated hexagonal structures was observed at positive potentials in addition to the c ( p × 3 R − 30 ° ) structures. This rotated hexagonal adlattice was also compressed with increasing electrode potential. These results in general confirm the phenomenon of electrocompression of the iodine adlayer on Au(111) observed by in situ surface X-ray scattering.

Reconstruction of the arteries of the foot in patients with severe chronic arterial occlusive disease has become a routine and valuable procedure. However, it is frequently difficult to select the optimal site for the distal arterial anastomosis. In order to determine the most important anatomic variations of foot arteries and the relationship of the dorsalis pedis artery to crossing tendons, the following study was performed in 30 cadaver limbs of 17 persons (9 men and 8 women). Their mean age at death was 69.8 years (range: 42 to 93 years). Methods to evaluate anatomy included anatomic dissection, arteriography, and preparation of corrosion cast models. The latter was performed by injection of liquid plastic and catalyst into the tibial arteries followed by chemical débridement of the soft tissue of the foot. Photographs of the corrosion cast models were taken at various stages of soft tissue dissolution. The dorsalis pedis artery was absent in 6.7% of the cases, and the arcuate artery was absent in 33%. The dorsalis pedis artery arose from the peroneal artery in 6.7%. The dorsalis pedis artery crossed under the extensor hallucis longus tendon at the ankle in 54%, above the ankle in 43%, but below the ankle in only 3%. Our study suggests that the optimal site for the dorsalis pedis artery anastomosis on the foot is the segment distal to the ankle.

It has become increasingly apparent that basic information regarding the interaction of the relevant gaseous species at the diamond surface is important for a better understanding of the chemical vapor deposition (CVD) process. The non-linear phenomena of second-harmonic generation (SHG) and sum frequency generation (SFG) have the potential of probing the surface in situ during diamond CVD. We have initiated a program of investigating the low index planes of the diamond single crystal using conventional surface science techniques in conjunction with SHG and SFG measurements. As a first step in this effort, Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy, spectroscopy and low energy electron diffraction (LEED) temperature-programmed desorption have been used to study the interactions of H and CHx species with the reconstructed diamond C(111) (2 × 1) surface. It is found that a very small quantity of chemisorbed H atoms (0.05 ML (monolayer) or less) can induce the (2 × 1)-to-(1 × 1) phase transformation and uphold the sp3 structure up to nearly 1400 K. SHG measurements during the exposure of the surface to hydrogen showed direct correlation with observations by LEED and AES. The vibrational spectrum of the surface hydrogen is obtained using IR visible SFG. On a fully relaxed (1 × 1) surface a single sharp peak at about 2830 cm−1 is observed which can be identified as the CH stretching mode from H on top sites. The SFG spectrum after exposure of the (2 × 1) surface to methane through a hot filament shows the dominant adsorbed species to be the methyl group.

Pd(100), Rh(100) and PtRh(100) are inert for the dissociative adsorption of N 2 . We succeeded to prepare a surface nitride with a c(2 × 2) structure on Pd(100), Rh(100) and Pt-Rh(100) surfaces by performing the catalytic reaction of NO + H 2 → N(a) + H 2 O. On Pt(100), however, the accumulation of N atoms was difficult. Formation of c(2 × 2)-N on a PtRh(100) surface indicates equal affinity of N atoms to the Pt and Rh atoms on the alloy surface. When the c(2 × 2)-N surface is exposed to H 2 . a prominent loss-peak appears at 3200–3240 cm −1 . In situ EELS experiments of the c(2 × 2) surfaces in 10 −7 -10 −8 Torr of H 2 showed that the loss peak intensity for the N-H vibration obeys to a half order dependence in hydrogen pressure, which suggests that the predominant N-hydrogen adsorption complex is NH and not NH 2 . The isotope effect for equilibrium of NH and ND is very small on Pd(100), Rh(100) and Pt-Rh(100) surfaces.

The phonon dispersion relations of monolayer graphite on Ni(111) and on Ni(001) were measured by using electron energy loss spectroscopy. Both samples gave almost the same results. The data were analysed with a force constant model in a slab geometry, and it was revealed that the vertical bond bending force constant and the bond twisting force constant were greatly softened. These force-constant changes are comparable with the previously reported case of monolayer graphite on (111) surfaces of transition-metal carbides. However, the interaction between the Ni substrate and the graphite overlayer is not so strong as that on the carbide (111) surface. The similar phonon structures between graphitic layers on Ni(111) and on Ni(001) suggest that both substrates have similar charge transfer capability.

A nitrogen overlayer (N(a)) was synthesized on Pd(100) by catalytic reduction of NO by CO or H 2 in the total pressure range of 10 −7 −10 1 Torr at crystal temperatures higher than 500 K. The process of the formation of N(a) was monitored by AES, LEED, HREELS and TDS. N(a) formed a c (2 × 2) superlattice, and desorbed at 600–700 K. N(a) was hydrogenated by gas-phase H 2 . HREELS revealed the reversible formation of NH x (a) species on the surface.

The catalytic reduction of NO by H 2 on a Pt 0.25 Rh 0.75 (100) alloy single crystal was investigated by monitoring the surface species while the reaction was proceeding. Adsorption of NO at 500 K formed an O-covered surface with p(3 × 1) structure. Enrichment of Rh on the surface induced by adsorption of O was observed, and a Rh-rich alloy surface forms the p(3 × 1)-O faster. The nature of the p(3 × 1) overlayer is discussed. The NO + H 2 reaction formed a c(2 × 2) overlayer of N(a). The hydrogenated adsorbate NH x (a) was observed under the presence of gas-phase H 2 . The hydrogenation reaction of N(a) to NH x (a) was reversible, and faster than complete hydrogenation to NH 3 (g).

The assembling of the sphingomyelin (SM)-binding pore-forming toxin (PFT), lysenin, to SM/cholesterol bilayer was examined by high-speed atomic force microscopy (HS-AFM) [1]. The HS-AFM images of SM/cholesterol bilayer preincubated with lysenin exhibited the hexagonal close packed (hcp) assembly of lysenin oligomers (Fig. 1A). The in-situ AFM images revealed that the formation of the hcp structure took place quickly (Fig. 1B). Before the full coverage of the membrane surface with a stable hcp assembly of lysenin oligomers, most of the oligomers underwent reorganization either by dissociating into monomers or by rapidly diffusing along the membrane in less than a second. The assembling of lysenin oligomers was also followed on SM/DOPC/cholesterol bilayer. Oligomers firstly formed at the edges of the SM-rich domains and covered these domains similarly to the SM/cholesterol bilayer. Our results revealed the dynamic nature of the oligomers of a lipid binding toxin during its assembling on SM-containing membranes.Reference[1] N. Yilmaz, T. Yamada, P. Greimel, T. Uchihashi, T. Ando, and T. Kobayashi, Biophys. J. 105, 1397-1405 (2013).View Large Image | View Hi-Res Image | Download PowerPoint Slide

When a clean Pt-Rh(100) alloy surface was exposed to NO at T > 440 K, the LEED pattern changed sequentially as p(1 × 1) → c(2 × 2) → c(2 × 2) + p(3 × 1) → p(3 × 1), where the c(2 × 2) pattern appeared immediately after the exposure to NO. In contrast to this, the appearance time for the p(3 × 1) depends strongly on the initial Rh concentration on the surface adjusted by annealing. When the p(3 × 1) surface was exposed to H2 by mixing H2 into NO gas, the AES intensity of O(a) decreased and of N(a) increased markedly and the LEED pattern changed from p(3 × 1) to c(2 × 2). These results suggest that N(a) has equal affinity to Pt and Rh atoms so that the N(a) does not distinguish the Pt and Rh sites on the alloy surface. On the other hand, O(a) makes a stronger bond with Rh atoms so that Rh atom segregation onto the surface is induced. By reacting randomly distributed Rh atoms on the Pt-Rh(100) surface with oxygen, a surface compound in a p(3 × 1) arrangement is built on the surface.