Time-resolved photoelectron imaging of S2 → S1 internal conversion in benzene and toluene

Ultrafast internal conversion of benzene and toluene from the S(2) states was studied by time-resolved photoelectron imaging with a time resolution of 22 fs. Time-energy maps of the photoelectron intensity and the angular anisotropy were generated from a series of photoelectron images. The photoelectron kinetic energy distribution exhibits a rapid energy shift and intensity revival, which indicates nuclear motion on the S(2) adiabatic surface, while the ultrafast evolution of the angular anisotropy revealed a change in the electronic character of the S(2) adiabatic surface. From their decay profiles of the total photoelectron intensity, the time constants of 48 ± 4 and 62 ± 4 fs were determined for the population decay from the S(2) states in benzene and toluene, respectively.     

Quantitative determination of phenothiazine derivatives in human plasma using monolithic silica solid-phase extraction tips and gas chromatography-mass spectrometry

Solid-phase extraction (SPE) using micropipette tips is a useful technique to prepare samples prior to mass spectrometry. However, most commercial SPE tips have loading capacities that are insufficient for quantitative determination. In this paper, we describe a rapid method for quantitative microanalysis of five phenothiazine derivatives, chlorpromazine, levomepromazine, promazine, promethazine and trimeprazine, using a recently introduced C(18) monolithic silica SPE tip, the MonoTip C(18), for extraction from human plasma. The drugs could be extracted within 5 min from 0.1-mL plasma samples, eluted with methanol, and the eluate injected directly into a gas chromatograph prior to mass spectrometry analysis. Only 0.7 mL of solvent was required for each step of the extraction process. The recoveries of the five phenothiazines spiked into plasma were 91-95% and the limits of quantification for each drug were between 0.25 and 2.0 ng/0.1 mL. The maximum intra- and inter-day coefficient of variation was 11%. The validated method was successfully used to quantify the plasma concentration of levemepromazine in a human subject after oral administration of the drug. This new method is expected to have wide applications as a pretreatment for the rapid, quantitative determination of drug concentrations in plasma samples.     

Development of quality assessment method for optically active food flavor chemicals

A quality assessment method for commercially available, optically active flavor compounds, namely, menthol, menthyl acetate, borneol, perillaldehyde, and 1,8-cineol, was developed. A gas chromatograph equipped with a flame ionization detector and a DB-5ms capillary column was used for the chemical purity test. A GC/MS with a beta-DEX cyclodextrin column was used for the optical purity test, by which the enantiomeric separation of each flavor compound was achieved. Enantiomeric excess was calculated as an expression of optical purity. Of the 25 standard samples subjected to the chemical purity test, six were found to have lower purity than the data provided by the manufacturers. When the same samples were subjected to the optical purity test, 11 were found to have lower purity than that indicated on the reagent labels. These results suggest that there is a need to conduct an optical purity test, in addition to a chemical purity test, for the quality assessment of flavor standards.     

Determination of proline enantiomers in honey and royal jelly by LC-UV

The chiral separation and quantification of D-proline and L-proline in honey and royal jelly were examined by LC with UV detection. Most of the endogenous compounds existing in honey, such as sugars, were removed by using SPE cartridges containing C18 and strong cation-exchange sorbent. Other components, such as primary amino acids, were also removed by two-step derivatization with o-phthalaldehyde (OPA) and 9-fluorenylmethyl chloroformate (FMOC-CI). The components that were derivatized with OPA were separated from proline with a C18 cartridge. Proline was then converted into an FMOC derivative that could be subsequently measured by LC-UV. Sufficient chiral separation of D-proline and L-proline was achieved with an LC chiral column made of a beta-cyclodextrin phase in the polar organic-phase mode. The average recoveries of D-proline and L-proline from honey and royal jelly were in the range of 81.3-98.6% (RSD of < 1.8%). When this method was applied to commercial honey and royal jelly samples, L-proline was detected at concentrations of 369-1930 microg/g, whereas D-proline was not detected.     

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.     

Iron-catalyzed sulfonyl radical formations from sulfonylhydrazides and oxidative addition to alkenes

Generation of sulfonyl radicals from sulfonylhydrazides has been achieved in the presence of a non-toxic iron catalyst and oxygen. The intermolecular addition of resultant sulfonyl radicals to alkenes affords β-hydroxysulfone compounds.     

Emission control by binary energy transfer processes on oligouridine

Fluorescent oligonucleotides have been designed on which two different energy transfer processes were mounted together: excitonic interaction and FRET. The fluorescence emission of the oligonucleotides was controlled well by the two different energy transfer processes, in response to their hybridization to the complementary RNA both in vitro and in cells.     

A novel hydrazide type organocatalyst for enantioselective Diels-Alder reactions

The development of a new class of hydrazide type organocatalyst, (4R,5R)-1,3-bis(isopropylamino)-4,5-dihenylimidazolidin-2-one 2a, for enantioselective Diels-Alder reactions between cyclopentadiene and α,β-unsaturated aldehydes are presented. The new organocatalyst 2a promoted the reaction, affording Diels-Alder adducts in good yields with good levels of enantioselectivity.     

Semiconducting behavior of type-I Si clathrate K8Ga8Si38

A ternary type-I Si clathrate K(8)Ga(8)Si(38) has been revealed to be an indirect band gap semiconducting material with an energy gap (E(g)) of approximately 0.10 eV, which is much smaller than the calculated E(g) value that is 0.15 eV wider than E(g) of elemental Si with the diamond-type structure.