In situ photopolymerization of a polymerizable poly(ethylene glycol)-covered phospholipid monolayer on a methacryloyl-terminated substrate

We have prepared a chemically anchored monolayer of PEG (poly(ethylene glycol)) and phospholipid mixture (PEG/phospholipid) on a methacryloyl-terminated substrate by in situ photopolymerization. Both monoacryloyl phospholipid (acryloyl-PC, 1-palmitoyl-2-[12-(acryloyloxy)dodecanoyl]-sn-glycero-3-phosphocholine) and monoacryloyl PEG (acryloyl-PEG, 12-(acryloyloxy)dodecanoyl-PEG) were synthesized by modifyingphospholipid and PEGwith 12-(acryloyloxy)-1-dodecanoic acid and 12-(acryloyloxy)-1-dodecanol, respectively. The surface pressure-area (pi-A) isotherm showed that acryloyl-PEG molecules were stable in the phospholipid monolayer and that they could be evenly inserted into a phospholipid monolayer at the air/water interface. By adding 10 mol % acryloyl-PEG into phosholipid vesicles, we could produce a PEG/phosholipid monolayer on methacryloyl-terminated substrates using vesicle fusion for 3 h. Then, this polymerizable PEG/phospholipid monolayer was in situ photopolymerized onto a methacryloyl-terminated substrate with eosin Y/triethanolamine as co-initiators. Optimal vesicle fusion and irradiation condition were determined with respect to the vesicle fusion time and duration of irradiation. As confirmed by atomic force microscopy and X-ray reflectivity studies, the polymerized PEG/phosholipid surface formed a PEG-covered phospholipid monolayer with thicknesses of 3 and 6 nm for the base phospholipid monolayer and the covering PEG layer, respectively. The chemical anchoring efficiency ofpolymerized PEG and phospholipid molecules, which was calculated by the relative carbon ratio of each surface before and after methanol washing using X-ray photoelectron spectroscopy, was 98%. This polymerized PEG/phosholipid monolayer showed good stability in organic solution due to firm chemical anchoring to a solid surface.     

Hydrogen peroxide oxidation of di(hydroxo)platinum(II) species in carboxylic acids

A facile procedure for synthesizing the mono(hydroxo)tris(carboxylato)platinum(IV) species has been achieved. The reaction of [Pt^II(OH)₂(dmpda)] (dmpda=2,2-dimethyl-1,3-propanediamine) with a 30% aqueous solution of H₂O₂ in the presence of a carboxylic acid produces a stable [Pt^IV(OOCR)₃(OH)(dmpda)] (R=Me, Et) complex in high yield. The crystal structures of [Pt^IV(OOCMe)₃(OH)(dmpda)] . H₂O (triclinic P1 bar, a=8.761(2) Å, b=9.245(3) Å, c=10.659(2) Å, =106.25(2)°, =93.90(2)°, =98.92(2)°, V=813.1(3) ų, Z=2, R= 0.0474) and [Pt^IV(OOCEt)₃(OH)(dmpda)] (monoclinic P2₁/c, a=12.777(4) Å, b=10.514(2) Å, c=14.971(3) Å, =107.40(2)°, V=1919.2(8) ų, Z=4, R=0.0611) show that the hydroxyl group has been selectively positioned at an axial site. The intramolecular hydrogen bond between the OH and C=O moiety exists (O(H)...=C, 2.83 Å for [Pt^IV(OOCMe)₃(OH)(dmpda)] · H₂O; 2.72 Å for [Pt^IV(OOCEt)₃(OH)(dmpda)]. Formation of the axial-mono(hydroxo)tris(carboxylato)platinum(IV) species may be ascribed to a combination of `reactive-equatorial effects' with `cis-addition' in the carboxylic acid.     

Dynamic identification of phosphopeptides using immobilized metal ion affinity chromatography enrichment, subsequent partial beta-elimination/chemical tagging and matrix-assisted laser desorption/ionization mass spectrometric analysis

The enrichment of phosphopeptides using immobilized metal ion affinity chromatography (IMAC) and subsequent mass spectrometric analysis is a powerful protocol for detecting phosphopeptides and analyzing their phosphorylation state. However, nonspecific binding peptides, such as acidic, nonphosphorylated peptides, often coelute and make analyses of mass spectra difficult. This study used a partial chemical tagging reaction of a phosphopeptide mixture, enriched by IMAC and contaminated with nonspecific binding peptides, following a modified beta-elimination/Michael addition method, and dynamic mass analysis of the resulting peptide pool. Mercaptoethanol was used as a chemical tag and nitrilotriacetic acid (NTA) immobilized on Sepharose beads was used for IMAC enrichment. The time-dependent dynamic mass analysis of the partially tagged reaction mixture detected intact phosphopeptides and their mercaptoethanol-tagged derivatives simultaneously by their mass difference (-20 Da for each phosphorylation site). The number of new peaks appearing with the mass shift gave the number of multiply phosphorylated sites in a phosphopeptide. Therefore, this partial chemical tagging/dynamic mass analysis method can be a powerful tool for rapid and efficient phosphopeptide identification and analysis of the phosphorylation state concurrently using only MS analysis data.     

In situ disorder-order transformation in synthetic gallosilicate zeolites with the NAT topology

Here, we report that synthetic gallosilicate molecular sieves with the NAT topology and Si/Ga ratios close to but slightly higher than 1.50 undergo an in situ transformation under their crystallization conditions. The materials have been studied ex situ by using powder X-ray diffraction, elemental and thermal analyses, and multinuclear MAS NMR. The transformation is characterized by a change in the distribution of Si and Ga of the NAT framework, from a quite (but not completely) disordered phase to a very highly (but not completely) ordered one, accompanied by a change from tetragonal to orthorhombic symmetry. During most of the solution-mediated transformation, no noticeable signs of fresh precipitation, phase segregation, or changes in the chemical composition are detected. Intermediate materials show variations in the degree of Si-Ga ordering and orthorhombic distortion and are not physical mixtures of the disordered and ordered phases. Ab initio calculations strongly suggest a preferential siting of Si in the tetrahedral sites involved in a smaller number of 4-rings in the NAT topology (i.e., the low multiplicity site). The cost of violations of Loewenstein's rule has also been calculated. For this topology and chemical composition the preferential siting and Loewenstein's rule drive together the system to the ordered configuration. A Monte Carlo sampling procedure affords a reasonable model for the initial, mainly disordered state, which fits well within the experimental disorder-order series.     

Novel supramolecular isomerism in coordination polymer synthesis from unsymmetrical bridging ligands: solvent influence on the ligand placement orientation and final network structure

The assembly of Co(NCS)(2) with 1-methyl-1'-(3-pyridyl)-2-(4-pyridyl)ethene (L(1)) exhibits a novel supramolecular isomerism of [Co(L(1))(2)(NCS)(2)](infinity) caused by different placement orientation of L(1) around metal centers. The reaction in MeOH/H(2)O and EtOH/H(2)O resulted in a double chain structure of 1, and that in EtOH/CH(3)NO(2) led to an open framework structure of 2. The reaction in MeOH/CH(3)NO(2) solvent system concomitantly afforded 1 and 2. The assemblies of 1-(3-pyridyl)-2-(4-pyrimidyl)ethene (L(2)) with Co(NCS)(2) created the water-coordinated complexes of Co(L(2))(2)(H(2)O)(2)(NCS)(2) (3 and 4), an MeOH coordinated complex of Co(L(2))(2)(H(2)O)(2)(NCS)(2) (5), and an open framework coordination polymer of [Co(L(1))(2)(NCS)(2)](infinity) (6) depending on the reaction solvent system. From these observations, it is suggested that in the formation of 1, the solvent-coordinated intermediate species would be generated first and its trans coordination configuration should define the placement orientation of L(1) in the resulting polymer of 1. On the other hand, it is presumed that the solvent-coordinated intermediate would not be produced during the formation of 2 due to the weaker coordination ability of EtOH and CH(3)NO(2) molecules. The open framework coordination polymers of 2 and 6 are converted in the solid state into the isomeric coordination polymer of 1 and hydrogen bonded network structure of 3, respectively.     

Reactivity of amido ligands on a dinuclear Ru(II) center: formation of imido complexes and C-N coupling reaction with alkyne

Treatment of a dinuclear Ru(II) amido complex [Cp*Ru(mu2-NHPh)]2 (Cp* = eta5-C5Me5) with small organic substrates including CO, tert-butyl isocyanide, a sulfur ylide Ph2S=CH2, and diphenylacetylene resulted in an unexpected disproportionation reaction of the bridging amido ligands to produce a free amine and a series of imido-bridged diruthenium complexes [(Cp*Ru)2(mu2-L)(mu2-NPh)] (L = CO, t-BuNC, CH2). In the case of diphenylacetylene, the bridging imido ligand underwent subsequent coupling reaction with the coordinated alkyne to form an iminoalkenyl complex [(Cp*Ru)2(mu2-PhNCPhCPh)].     

Mesocellular polymer foams with unprecedented uniform large mesopores and high surface areas

Mesocellular polymer foams with uniform approximately 17 nm cellular pores were fabricated using mesocellular silica foams as inorganic templates. The mesocellular polymer foams have high surface areas up to approximately 600 m(2)g(-1) and pore volumes of 1.6 cm(3)g(-1).     

Directing Polymorphism in the Helical Nanofilament Phase

Herein, it is reported that the polymorphism in the helical nanofilament (HNF, B₄) liquid-crystalline phase depends on the fabrication methods, that is, UV-driven formation and template-assisted self-assembly in the nanoconfined geometry. As a result, uniaxially oriented HNFs with different helical structures were obtained, in which generation of the twisted-ribbon and cylindrical-ribbon polymorphs showed that even the molecular lattice has a different orientation. The detailed structures were directly observed by SEM and grazing-incidence X-ray diffraction with synchrotron radiation. The resultant polymorphs could be used in chiro-optical applications due to the capability for fine control of the helical structures.     

Hemoglobin as a Diagnosing Molecule for Biological Effects of Atmospheric-Pressure Plasma

The studies with proteins are necessary to understand the biological effects of atmospheric pressure plasma (APP). Among proteins, those with transient metal ions play key roles in many biological events and they are very sensitive to environmental redox states. Iron-containing hemoglobin (Hb) is investigated in this study, after APP treatments under two environmental gas conditions of pure N₂ and N₂?+?O₂ mixture. Monitoring the intensity change for absorption spectra could lead to a quantitative assessment of the effect of discharge plasma on Hb. Redox states of Hb are classified into five states including O₂-bound Hb (oxy-Hb), deoxy-Hb, met-Hb, NO-bound Hb (NO-Hb), and hemichrome. Chemically generated reactive species and some scavengers are applied to understand the chemical reactions. Our experimental results confirm the complex chemical reactions of APP and suggest the possible use of Hb as a model protein for the visualization of APP biological effects.