Living cationic polymerization of 2‐adamantyl vinyl ether

Living cationic polymerization of 2‐adamantyl vinyl ether (2‐vinyloxytricyclo[3.3.1.1]^3,7decane; 2‐AdVE) was achieved with the CH₃CH(OiBu)OCOCH₃/ethylaluminum sesquichloride/ethyl acetate [CH₃CH(OiBu)OCOCH₃/Et_1.5AlCl_1.5/CH₃COOEt] initiating system in toluene at 0 °C. The number‐average molecular weights (M_n's) of the obtained poly(2‐AdVE)s increased in direct proportion to monomer conversion and produced the polymers with narrow molecular weight distributions (MWDs) (M_w/M_n = ～1.1). When a second monomer feed was added to the almost polymerized reaction mixture, the added monomer was completely consumed and the M_n's of the polymers showed a direct increase against conversion of the added monomer. Block and statistical copolymerization of 2‐AdVE with n‐butyl vinyl ether (CH₂?CH? O? CH₂ CH₂CH₂CH₃; NBVE) were possible via living process based on the same initiating system to give the corresponding copolymers with narrow MWDs. Grass transition temperature (T_g) and thermal decomposition temperature (T_d) of the poly(2‐AdVE) (e.g., M_n = 22,000, M_w/M_n = 1.17) were 178 and 323 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1629–1637, 2008     

Muon spin relaxation for Ar+NO2 systems in transverse and longitudinal magnetic fields

Surface muons produced in UT-MSL were introduced into argon gas of 4.0±0.2 atm with NO₂ (0–30 ppm), and muonium signals were detected in the presence of a transverse (1.7–3.4 G) and a longitudinal magnetic field (0–3.5 kG) at 295±1 K. The cross section for the transverse relaxation was (11.0±1.0)×10⁻¹⁶ cm². The relaxation rates in different longitudinal magnetic fields show that the rate does not follow the conventional equation which assumes that the relaxation occurs mainly by spin-exchange interaction. Similar measurements were performed for the Mu+O₂ system. These findings indicate that chemical reactions contribute to these relaxation rates.     

A sensitive and quantitative technique for detecting autophagic events based on lysosomal delivery

We sought to develop a sensitive and quantitative technique capable of monitoring the entire flux of autophagy involving fusion of lysosomal membranes. We observed the accumulation inside lysosomal compartments of Keima, a coral-derived acid-stable fluorescent protein that emits different-colored signals at acidic and neutral pHs. The cumulative fluorescent readout can be used to quantify autophagy at a single time point. Remarkably, the technique led us to characterize an autophagy pathway in Atg5-deficient cells, in which conventional LC3-based autophagosome probes are ineffective. Due to the large Stokes shift of Keima, this autophagy probe can be visualized in conjunction with other green-emitting fluorophores. We examined mitophagy as a selective autophagic process; time-lapse imaging of mitochondria-targeted Keima and GFP-Parkin allowed us to observe simultaneously Parkin recruitment to and autophagic degradation of mitochondria after membrane depolarization.     

Observations of surface modifications induced by the multiple pulse irradiation using a soft picosecond x-ray laser beam

To study the interactions between picosecond soft x-ray laser (SXRL) beams and material surfaces, gold (Au), copper (Cu), and silicon (Si) surfaces were irradiated with SXRL pulses having a wavelength of 13.9 nm and a duration of ～7 ps. Following irradiation, the surfaces of the substrates were observed using a scanning electron microscope and an atomic force microscope. With single pulse irradiation, ripple-like structures were formed on the Au and Cu surfaces. These structures were different from previously investigated conical structures formed on an Al surface. In addition, it was confirmed that the development of modified structures, i.e., growth of hillocks on the Au and Cu surfaces, was observed after multiple SXRL pulse exposures. However, on the Si surface, deep holes that seemed to be melted structures induced by the accumulation of multiple pulses of irradiations were found. Therefore, it was concluded that SXRL beam irradiation of various material surfaces causes different types of surface modifications, and the changes in the surface behaviors are attributed to the differences in the elemental properties, such as the attenuation length of x-ray photons.     

Intermolecular coupling of alkynes, isocyanates, and acyl chlorides: an efficient method for the synthesis of 5-hydroxypyrrol-2(5H)-ones

New insights into the reaction of diethylzirconocene with an alkyne, an isocyanate, and an acyl chloride in this order are reported. The products of 5-hydroxypyrrol-2(5H)-ones are obtained in good yields after hydrolysis. It is an efficient method for the synthesis of 5-hydroxypyrrol-2(5H)-ones.     

A three carbon homologation by the ring-opening of β-propiolactones with diorganocuprates

Various organocuprates react with β-propiolactones to give β-substituted propionic acids in high yields.