Enzymatic Cell-Surface Decoration with Proteins using Amphiphilic Lipid-Fused Peptide Substrates

Lipid modification of proteins plays a significant role in the activation of cellular signals such as proliferation. Thus, the demand for lipidated proteins is rising. However, getting a high yield and purity of lipidated proteins has been challenging. We developed a strategy for modifying proteins with a wide variety of synthetic lipids using microbial transglutaminase (MTG), which catalyzes the cross-linking reaction between a specific glutamine (Q) in a protein and lysine (K) in the lipid-fused peptide. The synthesized lipid-G₃S-MRHKGS lipid (lipid: fatty acids, tocopherol, lithocholic acid, cholesterol) was successfully conjugated to a protein fused with LLQG (Q-tagged protein) by an MTG reaction, yielding >90 % conversion of the Q-tagged protein in a lipidated form. The purified lipid–protein conjugates were used for labeling the cell membrane in vitro, resulting in best-anchoring ability of cholesterol modification. Furthermore, in situ cell-surface decoration with the protein was established in a simple manner: subjection of cells to a mixture of cholesterol-fused peptides, Q-tagged proteins and MTG.     

Diphenyl phosphate/4‐dimethylaminopyridine as an efficient binary organocatalyst system for controlled/living ring‐opening polymerization of L‐lactide leading to diblock and end‐functionalized poly(L‐lactide)s

The ring‐opening polymerizations (ROPs) of ε‐caprolactone (ε‐CL) and L ‐lactide (LLA) have been studied using the organocatalysts of diphenyl phosphate (DPP) and 4‐dimethylaminopyridine (DMAP). The “dual activation” property of DPP and the “bifunctional activation” property of DPP/DMAP were confirmed by the NMR measurement for ε‐CL and its chain‐end model of poly(ε‐caprolactone) and for LLA and its chain‐end model of poly(L ‐lactide) (PLLA), respectively. The molar ratio of DPP/DMAP was optimized as 1/2 for the ROP of LLA leading to the well‐defined PLLA, such as the molecular weight determined from ¹H NMR measurement of 19,200 g mol^?1 and the narrow polydispersity of 1.10. Additionally, functional initiators were utilized for producing the end‐functionalized PLLAs. The DPP‐catalyzed ROPs of ε‐CL and its analogue cyclic monomers and then the DPP/DMAP‐catalyzed ROP of LLA produced block copolymers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1047–1054     

Selective fabrication of n‐ and p‐type SnO films without doping

Undoped n‐ and p‐type tin monoxide (SnO) films have been selectively fabricated by pulsed laser deposition with a Sn target and careful control of oxygen partial pressure. The films are epitaxially grown in optimal growth conditions on yttria‐stabilized zirconia (YSZ) substrates with out‐of‐plane and in‐plane orientation relationships of (001)_SnO//(001)_YSZ and [110]_SnO//[100]_YSZ, respectively. Both Seebeck and Hall measurements show consistent results on the carrier types of the films. The electron Hall mobility is approximately 11 cm²/Vs at room temperature and the carrier activation energy is 0.14 eV for the n‐type film. The growth at increased oxygen partial pressure yields p‐type films, demonstrating the selective fabrication of both n‐ and p‐type SnO films without doping. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110)

The angular and velocity distributions of desorbing product N(2) were examined over the crystal azimuth in steady-state NO+CO and N(2)O+CO reactions on Pd(110) by cross-correlation time-of-flight techniques. At surface temperatures below 600 K, N(2) desorption in both reactions splits into two directional lobes collimated along 41 degrees -45 degrees from the surface normal toward the [001] and [001] directions. Above 600 K, the normally directed N(2) desorption is enhanced in the NO reduction. Each product desorption component, as well as CO(2), shows a fairly asymmetric distribution about its collimation axis. Two factors, i.e., the anisotropic site structures and the reactant orientation and movements, are operative to induce such asymmetry, depending on the product emission mechanism.     

Cycloaddition reaction of schiff bases with ketenes generated by pyrolysis of 2‐aryl‐substituted 1,5,7‐trioxaspiro[2.5]octane‐4,8‐diones

The α‐oxo ketenes 6 which are generated by the pyrolysis of the 2‐aryl‐substituted 1,5,7‐trioxaspiro[2.5]octane‐4,8‐diones 1 , were reacted with Schiff bases 2 to give spiro compounds constructed between the β‐lactam and 1,3‐dioxolan‐4‐one; i.e., the 2,3,6‐triaryl‐2‐aza‐5,7‐dioxaspiro[3.4]octane‐1,8‐diones 3 and 4 . Hydrogenation of the mixture of 3a and 4a in the presence of catalytic amount of Pd‐C produced the trans‐2‐benzyloxy‐1,4‐diphenyl‐β‐lactam‐3‐carboxylic acid 9 .     

Synthesis of heterometal cluster complexes by the reaction of cobaltadichalcogenolato complexes with groups 6 and 8 metal carbonyls

Metalladichalcogenolate cluster complexes [{CpCo(S2C6H4)}2Mo(CO)2] (Cp = eta(5)-C5H5) (3), [{CpCo(S2C6H4)}2W(CO)2] (4), [CpCo(S2C6H4)Fe(CO)3] (5), [CpCo(S2C6H4)Ru(CO)2(P(t)Bu3)] (6), [{CpCo(Se2C6H4)}2Mo(CO)2] (7), and [{CpCo(Se2C6H4)}(Se2C6H4)W(CO)2] (8) were synthesized by the reaction of [CpCo(E2C6H4)] (E = S, Se) with [M(CO)3(py)3] (M = Mo, W), [Fe(CO)5], or [Ru(CO)3(P(t)Bu3)2], and their crystal structures and physical properties were investigated. In the series of trinuclear group 6 metal-Co complexes, 3, 4, and 7 have similar structures, but the W-Se complex, 8, eliminates one cobalt atom and one cyclopentadienyl group from the sulfur analogue, 4, and does not satisfy the 18-electron rule. 1H NMR observation suggested that the CoW dinuclear complex 8 was generated via a trinuclear Co2W complex, with a structure comparable to 7. The trinuclear cluster complexes, 3, 4, and 7, undergo quasi-reversible two-step one-electron reduction, indicating the formation of mixed-valence complexes Co(III)M(0)Co(II) (M = Mo, W). The thermodynamic stability of the mixed-valence state increases in the order 4 < 3 < 7. In the dinuclear group 8 metal-Co complexes, 5 and 6, the CpCo(S2C6H4) moiety and the metal carbonyl moiety act as a Lewis acid character and a base character, respectively, as determined by their spectrochemical and redox properties. Complex 5 undergoes reversible two-step one-electron reduction, and an electron paramagnetic resonance (EPR) study indicates the stepwise reduction process from Co(III)Fe(0) to form Co(III)Fe(-I) and Co(II)Fe(-I).     

New linear-parabolic rate equation for thermal oxidation of silicon

We propose a new oxidation rate equation for silicon supposing only a diffusion of oxidizing species but not including any rate-limiting step by interfacial reaction. It is supposed that diffusivity is suppressed in a strained oxide region near SiO(2)/Si the interface. The expression of a parabolic constant in the new equation is the same as that of the Deal-Grove model, while a linear constant makes a clear distinction with that of the model. The estimated thickness using the new expression is close to 1 nm, which compares well with the thickness of the structural transition layers.     

Synthetic Studies on Palau'amine. Construction of the Cyclopentane Core via an Asymmetric 1,3-Dipolar Cycloaddition

The cyclopentane core of palau’amine has been constructed in optically pure form through the use of an asymmetric azomethine ylid [1,3]-dipolar cycloaddition reaction.     

Preparation of Titania/PDMS Hybrid Films and the Conversion to Porous Materials

Transparent films of titania/poly(dimethylsiloxane) (PDMS) hybrids were prepared by the solvent evaporation from the precursor solution prepared by the co-hydrolysis and co-condensation of titanium tetraisopropoxide and a methoxy-functionalized PDMS. The hybrid films were flexible and had high homogeneity of the composition. The organic groups of PDMS were decomposed at 400°C in air to form porous films. Though the heated films were rather brittle compared to the as-synthesized films, they were still transparent and homogeneous. The BET surface areas of the films after the heat treatment at 400°C were over 300 m²/g, while the as-synthesized hybrid films were non porous. According to the BDDT classification, the nitrogen adsorption/desorption isotherms of the calcined films were Type I, showing that the films were microporous. The titania domains were still amorphous after the heat treatment at 400°C and transformed to anatase after the heat treatment at 1,000°C.     

Experimental studies of the liquid junction potential between electrolyte solutions in different solvents part IV. A study using mixed-solvent salt bridges

The problem of the liquid junction potential (ljp) between different solvents was studied by measuring the emf's of a cell with a mixed-solvent salt bridge: Ag65 mM AgClO₄, 5 mM Et₄NClO₄ (S₁);1 mM Et₄ NClO₄ (S₁); 0.1 M MX (S₃ + S′₃); 1 mM Et₄NClO₄ (S₂);5 mM Et₄NClO₄, 5 mM AgClO₄ (S₂)6Ag. For 130 different combinations of solvents S₁, S₂, and (S₃+S′₃), the emf's were measured by changing the composition of (S₃ + S′₃) from pure S₃ to S′₃. Though there were exceptions, the emf's in many cases changed linearly or nearly linearly with the volume fraction of the mixed solvents. It was considered that the results were obtained because the component of the Ijp which was due to the solvent-solvent interactions at the mixed solvent/pure solvent junctions often changed in linear or near-linear relations with the volume fraction of the mixed solvent. A preliminary experiment showed some possibility of similar relations also to hold for mixed solvent/mixed solvent junctions.