Dependence of the Electrochemical Redox Properties of Fullerenes on Ionic Liquids.

Control of the electrochemical properties of fullerenes via the chemical modification approach has attracted considerable attention. However, surface modification of fullerene cages with various functional groups can lead to the destruction of their original structures. Herein, we report a simple approach for controlling the electrochemical properties of fullerene thin films formed on Au(111) electrodes in various ionic liquids (ILs). A total of eight reversible redox couples for six reductive and two oxidative processes were observed for fullerenes in ammonium- and pyrrolidinium-based ILs. The redox potentials, the differences between two successive redox potentials, the average values of these potential differences for fullerene reduction, and the electrochemical band gaps of fullerene films in various ILs were found to depend on the cation and its alkyl chain length, the anion, and the chemical structure of the fullerene. Highly charged C70 anions were reduced more easily than C60 anions. An increase in the alkyl chain length of the cation led to an increase in the average potential difference between two successive redox potentials for fullerene reduction. The results indicate that the electrochemical band gaps of fullerenes can be manipulated using ILs with appropriate anions, which can be determined based on the size of the anion and the charge distribution.

Electrochemical Sensing of Neurotoxic Agents Based on Their Electron Transfer Promotion Effect on an Au Electrode.

An electrochemical molecular sensor based on a new principle is reported. Nereistoxin (NRT, 4-N,N-dimethylamino-1,2-dithiolane), a naturally occurring neurotoxin (nicotinic acetylcholine receptor agonist), was adsorbed on an Au electrode via Au-S covalent bonding and accelerated the electron transfer between the electrode and the marker, ferricyanide anion. The contrast between the electrochemical responses obtained with the bare and NRT-modified Au electrodes was more pronounced at a low ionic strength of the supporting electrolyte, KCl. In the presence of 1 mM KCl, almost a 0/1 contrast between the signals was obtained through electrostatic interaction between the protonated tertiary amino group of NRT and the anionic ferricyanide ion. No current was observed with an electrode modified with mercaptopropionic acid. An unusually low ionic strength thickened the electric double layer to the degree where current was not observed with the bare electrode. The effect of the electrostatic concentration of the marker ion becomes obvious under such conditions. Commercially available NRT-related pesticides such as Cartap and Bensultap were also detected using the same format after pretreatments by hydrolysis/reduction. The present sensing method was successfully applied to human serum with satisfactory sensitivity.

Dependence of cobaltocenium diffusion in ionic liquids on the alkyl chain length of 1-alkyl-3-methylimidazolium cations.

The electrochemical behavior of cobaltocenium (Cc(+)) on a Au(111) electrode was investigated in five 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([Cnmim][Tf2N], n = 2, 4, 6, 8, or 10) ionic liquids (ILs) in the temperature range from 293.15 to 343.15 K by cyclic voltammetry and chronoamperometry. The redox couple of Cc(+) exhibited a clear reversible one-electron reaction in all the [Cnmim][Tf2N] ILs. The diffusion coefficients of Cc(+) increased with an increase in the alkyl chain length of [Cnmim](+) and a decrease in the viscosity of the IL upon elevating the temperature. The viscosity of the IL plays an important role in determining the activation energy for the diffusion of Cc(+). The obtained results suggested that the alkyl chain length of [Cnmim](+) affects the strength of the interaction between Cc(+) and the surrounding ion species. The results also clarified that the equation proposed by Sutherland adequately describes the diffusion of Cc(+) in ILs when the effect of the type of IL and the temperature on the product of the Stokes radius of Cc(+) and the Sutherland coefficient is considered.

Spontaneous electrodeposition of gold and platinum complexes through a coronene adlayer on Au(111).

The electrodeposition of gold and platinum complexes at the electrochemical interfaces on the coronene-modified Au(111) surface was investigated. Scanning tunneling microscopy revealed the spontaneous deposition of gold and platinum complexes, suggesting that the coronene adlayer plays an important role in the electroreduction of these complexes.

Construction and characterization of molecular nonwoven fabrics consisting of cross-linked poly(γ-methyl-L-glutamate).

Molecular nonwoven fabrics in the form of ultrathin layer-by-layer (LbL) helical polymer films with covalent cross-linking were assembled on substrates by an alternate ester-amide exchange reaction between poly(γ-methyl L-glutamate) (PMLG) and cross-linking agent ethylene diamine or 4,4'-diamino azobenzene. The regular growth of helical monolayers without excessive adsorption and the formation of amide bonds were confirmed by ultraviolet-visible (UV-vis) spectrophotometry, quartz crystal microbalance (QCM), ellipsometry, and infrared reflection-absorption spectroscopy (IR-RAS) measurements. Nanostructures with high uniformity and ultrathin films with few defects formed by helical rod segments of PMLG were characterized by atomic force microscopy (AFM) and Kelvin probe force microscopy (KFM).

Direct formation of a 2D redox-active adlayer based on a bisterpyridine derivative and Co2+ on a Au(111) electrode.

The direct assembly of single component 4',4''''-(1,4-phenylene)bis(2,2' : 6',2''-terpyridine) (PTPy) and Co(2+) and PTPy mixed arrays was examined on a Au(111) surface by a simple immersion method. A redox active 2D adlayer consisting of a bisterpyridine derivative and cobalt ions was found to form directly on Au(111) from solution, suggesting that new nanostructures and/or adlayers with electrochemical activity can be precisely designed and controlled by selection of the metal ion and ligand.

Conformational change in 4-pyridineethanethiolate self-assembled monolayers on Au(111) driven by protonation/deprotonation in electrolyte solutions.

Self-assembled monolayers (SAMs) of 4-pyridineethanethiol (4-PyEtS) formed on a Au(111) surface were investigated in aqueous electrolyte solutions by cyclic voltammetry and in situ scanning tunneling microscopy (STM). On the basis of reductive desorption of 4-PyEtS on Au(111), the reduction peak potential was found to be -0.86 V vs. Ag/AgCl (sat. KCl). The surface excess was calculated from the reductive desorption peak area to be 5.4 x 10(-10) mol cm(-2). High-resolution STM images revealed that a p(5 x radical3 R-30 degrees ) lattice including two molecules was found in 0.1 M NaClO(4), whereas the 4-PyEtS-SAMs formed a p(10 x radical3 R-30 degrees ) lattice constituting four molecules in 0.05 M HClO(4). The transition from a p(10 x radical3 R-30 degrees ) to a p(5 x radical3 R-30 degrees ) in the 4-PyEtS-SAMs was directly observed by changing pH of the electrolyte solution, indicating that the conformational change in 4-PyEtS-SAMs is driven by protonation/deprotonation. The present results obtained by STM observation are also supported by the clear pH dependence of the pyridine moiety in the surface-enhanced infrared spectrum.

Thermal behavior of luciferase on nanofabricated hydrophilic Si surface.

The thermal behavior of luciferase on nanofabricated hydrophilic Si surface was investigated using molecular dynamics simulations. At high temperature, LUC_CHANGES (structural changes in the active site of luciferase) were smaller on the nanofabricated hydrophilic Si surface than on a non-nanofabricated hydrophilic Si surface, although LUC_CHANGES were slightly larger on the nanofabricated hydrophilic Si surface than on a non-nanofabricated hydrophobic Si surface. At room temperature, LUC_CHANGES were smaller on the nanofabricated hydrophilic Si surface than on a non-nanofabricated and wet-treated Si surface. Thus, nanofabricated hydrophilic Si surface would be preferable for practical applications.

Formation of oriented polypeptides on Au(111) surface depends on the secondary structure controlled by peptide length.

We synthesized three different lengths of poly(L-lysine) containing an -SH group at the terminal (PLL(n)-SH, n (polymerization degree) = 4, 10, 30) and adsorbed them on an Au(111) surface. To analyze the formation process and the structure of self-assembled monolayers (SAMs), we used atomic force microscopy (AFM) and Fourier transform infrared reflection absorption spectra (FT-IR RAS). At the initial stage of SAM growth, formation of nanosize domains was confirmed by AFM imaging. The alpha-helical PLL(30)-SH exhibited a well-defined SAM structure after adsorption reached equilibrium. The alpha-helical PLL(30)-SH was almost perpendicular to the gold surface and exhibited interesting molecular packing due to the secondary structure of PLL(30)-SH and the underlying Au(111) array. The tilt angle of the helix axis from the substrate normal was estimated to be about 50 degrees (AFM) and 44 degrees (FT-IR RAS) respectively. On the other hand, PLL(4)-SH and PLL(10)-SH formed beta-sheet-type SAMs on the Au(111) surface based on the structure determined by FT-IR RAS spectrum.

Frequent hemizygous deletion at 1p36 and hypermethylation downregulate RUNX3 expression in human lung cancer cell lines.

Runt-related transcription factor 3 (RUNX3) has been recognized as a tumor suppressor gene in gastric cancer because its expression level was reduced or disappeared due to epigenetic changes. To evaluate the usefulness of the RUNX3 gene as a biomarker of lung cancer, we have analyzed the expression of the RUNX3 gene in 15 lung cancer cell lines by real-time reverse transcription-polymerase chain reaction (RT-PCR), and demonstrated that RUNX3 gene expression was reduced or disappeared in all cell lines examined (100%). In addition, we have attempted to classify all the cell lines into three groups according to the expression level; less than 10% (group I), 10-30% (group II) and approximately 50% (group III). We further investigated methylation status of the CpG sites in the exon 1 region of RUNX3 by methylation specific PCR (MSP), and studied the correlation between the expression level and hemizygous deletion as revealed by bicolor fluorescence in situ hybridization (FISH). The CpG sites were hypermethylated in 8 cell lines (53%) and the RUNX3 loci were hemizygously deleted in another 8 cell lines (53%). Furthermore group I, II, and III corresponded well to methylation-positive cell lines, cell lines showing hemizygous deletion, and the rest of cell lines without methylation or hemizygous deletion, respectively. These results suggest that a comprehensive study on RUNX3 using real-time RT-PCR, MSP, and FISH could be beneficial in understanding the pathogenetic mechanisms of human lung cancer at the molecular level.

Direct electrochemistry of engineered cytochrome b562 molecules with a ligand binding pocket.

The rapid and reversible electron transfer reaction of cytochrome b562 was observed at an In2O3 electrode. The estimated heterogeneous electron transfer rate constant (k0') was k0' > or = 5.0 x 10(-3) cm s(-1) at pH 6.5. When the methionine-7 (Met-7) residue, which coordinates to the heme iron as an axial ligand, of the wild-type cytochrome b562 was replaced by an Ala or Gly residue, a water molecule bound to the heme iron and the electron transfer rate constants decreased to 1.3 x 10(-3) and 1.8 x 10(-3) cm s(-1), respectively. This decrease in the electron transfer rate would be due to the larger reorganization energy for the structural change at the redox site. The midpoint potential of cytochrome b562 was shifted negatively by approximately 135 mV by replacing Met-7 with Ala or Gly. Similar dissociation kinetics of cyanide for the mutated molecules as compared to native myoglobin was obtained.

Notable deuterium effect on the electron transfer rate of myoglobin.

The electron transfer reaction of wild-type myoglobin at an electrode was significantly facilitated in a D2O buffer as compared with that in an H2O buffer, with k(0)'(H2O)/k(0)'(D2O)= 0.13, while a minimal deuterium kinetic isotope effect on the myoglobin with modification at distal histidine (His-64) was observed.

Functional evaluation of heme vinyl groups in myoglobin with symmetric protoheme isomers.

We replaced protoheme-IX in native myoglobin with the symmetric protohemes-III and -XIII, in order to investigate the role of heme vinyl-globin contacts on Mb function. The UV-visible spectra and the resonance Raman spectra in the high-frequency region (containing oxidation, spin, and coordination state marker lines) of the two reconstituted Mbs were very similar. However, the signal intensity of the Soret band in the CD spectra and the resonance Raman lines for vinyl bending modes in the low-frequency region notably differed, thereby reflecting altered heme peripheral contacts. The redox potentials, formal heterogeneous electron-transfer rates, and thermal denaturation temperatures of the two reconstituted Mbs were also indistinguishable. In addition, the oxygen binding properties of the ferrous deoxy Mbs were comparable. These results demonstrate that altered heme vinyl-globin interactions only slightly affect the physical properties of Mb. It is therefore likely that the orientation of protoheme-IX about the alpha,gamma-axis in the heme pocket is not necessarily a crucial factor for oxygen binding to native Mb.

Detection of C-Si covalent bond in CH3 adsorbate formed by chemical reaction of CH3MgBr and H:Si(111).

High-resolution electron energy loss spectroscopy (HREELS) yielded evidence for the formation of single covalent bonds between Si(111) surface atoms and CH(3) groups from the reaction of CH(3)MgBr and hydrogen-terminated H:Si(111)(1 x 1). The vibration at 678 cm(-)(1), assigned to the C-Si bond, was isolated within the spectrum of CH(3) on deuterium-terminated D:Si(111)(1 x 1). The CH(3) groups were thermally stable at temperatures below 600 K. The C-Si bonds are essential for enhancing the usefulness of alkyl moieties, which will lead to a new prospective technology of nanoscale fabrication and biochemical application.

Off-pump coronary artery bypass grafting in a patient with chronic myelomonocytic leukemia.

We report the case of a 71-year-old man with chronic myelomonocytic leukemia who developed cardiogenic shock twice due to a stenosis of the left main trunk of the coronary artery. We performed coronary artery bypass grafting to the left anterior descending artery with the left internal thoracic artery without using a cardiopulmonary bypass. The patient had no infection, leukemic transformation, or cardiac event after the surgery. Off-pump coronary artery bypass grafting is safe and useful for high risk patients, such as those with leukemia.