Phase-modulation fluorometer using a phase-modulated excitation light source

We propose a phase-modulation fluorometer (PMF) with a light-emitting diode (LED) or a laser diode (LD) used as an excitation light source (ELS) that is driven in the phase-modulation (PM) mode. The PM-ELS generates many frequency sidebands that spread in the vicinity of carrier frequency f _c with the interval of modulation frequency f _m depending on the maximum phase deviation Δφ. The scheme enables us to derive fluorescence lifetime values of a multicomponent sample at one time. We show a typical numerical simulation result for explaining the principle of operation. To demonstrate the effectiveness of the proposed PMF, we have measured fluorescence lifetimes of three kinds of inorganic fluorescent glasses and that of a mixture solution of 1 × 10^?6M rhodamine 6G and 1 × 10^?6 M coumarin 152 in ethanol with a volume ratio of 1: 1.     

Asymmetric total synthesis of halicholactone.

The asymmetric total synthesis of the marine metabolite, halicholactone 1, is described. The bisallylic triol 6 with three chiral centers at C8, C12, and C15 was constructed by [2,3]-sigmatropic rearrangement of the sulfoxide 18, which was prepared stereoselectively using the chirality of (diene)Fe(CO)3 complexes. Introduction of the trans-substituted cyclopropane subunit into 21 was successfully achieved using the modified regio- and stereoselective Simmons-Smith reaction. The use of RCM (ring-closing metathesis) methodology (4-->35) was pivotal for the formation of a nine-membered unsaturated lactone fragment of halicholactone 1. As this approach is flexible and stereoselective, other oxylipins could be synthesized by the protocol described herein.     

Solvent‐ and concentration‐sensitive fluorescence of 2‐(3,4,5,6‐tetrafluoro‐2‐hydroxyphenyl)benzoxazole

2‐(3,4,5,6‐Tetrafluoro‐2‐hydroxyphenyl)benzoxazole ( 2 ) emits the long wavelength fluorescence around 500 nm in nonpolar solvent via the intramolecular proton transfer process in the excited state of 2 (enol‐form) and also emits the intermediate wavelength fluorescence around 440 nm in polar solvent, which is assumed to originate from the excited state of 2 (anion). The ease of formation of 2 (anion), compared to 2‐(2‐hydroxyphenyl)benzoxazole ( 1 ), is explained by the strongly inductive fluorine atoms. In a solvent with the intermediate polarity, 2 emits both fluorescences and their relative intensity is dependent on the concentration of 2 , which is supposed to be caused by the high sensitivity of the intermediate wavelength emission to the concentration quenching.     

Mechanical Properties of Uniaxially Cold-Drawn Films of Poly[(R)-3-hydroxybutyrate] and Its Copolymers

Uniaxially oriented films of poly[(R)-3-hydroxybutyrate] (P(3HB)) and two kind of copolymers, poly[(R)-3-hydroxybutyrate-co-8%-[R]-3-hydroxyvalerate] (P(3HB-co-8%-3HV)), and poly[(R)-3-hydroxybutyrate-co-[R]-5%-3-hydroxyhexanoate] (P(3HB-co-5%-3HH)), were prepared by cold-drawing from amorphous preforms at temperatures near to the respective glass transition temperatures. Melt-quenched films in a rubber state could be stretched reproducibly to a draw ratio of 500%∼1800%, and subsequent annealing under tension led to improvement of the tensile strength and Young's modulus. Two-step drawing resulted in further improvement of the mechanical properties. The mechanical properties remained unchanged after storing for 6 months at room temperature, suggesting that high orientation and crystallinity suppress the secondary crystallization.     

On approximating electron repulsion integrals with linear combination of atomic-electron distributions

We recently investigated some features of atomic-electron distributions which are products of atomic orbitals without linear redundancies. Then, the atomic-electron distributions were employed as expansion functions of molecular charge distributions in the three-center expansion method for electron repulsion integrals. It turned out that the method is very accurate even after substantial reductions of required integrals. We shall illustrate the method and discuss its applicability to many electron theories. © 1996 John Wiley & Sons, Inc.     

Experiment at SPring-8

The GeV photon beam at SPring-8 is produced by backward-Compton scattering of laser photons from 8 GeV electrons. The maximum energy of the photon will be above 3 GeV, and the beam intensity will be 10⁷ photons/sec. Polarization of the photon beam will be 100 % at the maximum energy with fully polarized laser photons. We report the outline of the quark nuclear physics project with this high-quality high-intensity beam.     

Real-time enzymatic degradation study of poly[(R)-3-hydroxybutyric acid] copolymer thin film by atomic force microscopy in buffer solution

In situ observation of lamellar crystals during the enzymatic degradation by poly(hydroxybutyrate) (PHB) depolymerase is carried out on the thin films of poly[((R)-3-hydroxybutyric acid)-co-(16 mol-%-(R)-3-hydroxypentanoic acid)] using atomic force microscopy in buffer solution. Erosion of lamellar crystals and formation of splintered morphology along the crystal growth direction are directly observed during the course of the enzymatic degradation process. The changes in lamellar morphologies caused by enzymatic degradation are discussed in terms of lamellar crystal growth process.

AFM images of a P[(R)-3HB-co-(R)-3HV] thin film before and during enzymatic degradation.     

Suppressed Migration and Enhanced Cisplatin Chemosensitivity in Human Cancer Cell Lines by Tuning the Molecular Mobility of Supramolecular Biomaterials

Cancer cells recognize physical cues transmitted from the surrounding microenvironment, and accordingly alter the migration and chemosensitivity. Cell adhesive biomaterials with tunable physical properties can contribute to the understanding of cancer cell responses, and development of new cancer therapies. Previously, it was reported that polyrotaxane-based surfaces with molecular mobility effectively modulate cellular functions via the yes-associated protein (YAP)-related signaling pathway. In the present study, the impact of molecular mobility of polyrotaxane surfaces on the migration and chemosensitivity of lung (A549), pancreatic (BxPC-3), and breast cancer (MDA-MB-231) cell lines is investigated, and it is found that the cellular spreading of adherent A549 and BxPC-3 cells and nuclear YAP translocation are promoted on low-mobility surfaces, suggesting that cancer cells alter their subcellular YAP localization in response to molecular mobility. Furthermore, low-mobility surfaces suppress cellular migration more than high-mobility surfaces. Additionally, low-mobility surfaces promote the cisplatin chemosensitivity of each cancer cell line to a greater extent than high-mobility surfaces. These results suggest that the molecular mobility of polyrotaxane surfaces suppresses cellular migration and enhances chemosensitivity via the subcellular translocation of YAP in cancer cells. Biointerfaces based on polyrotaxanes can thus be a new platform for elucidating cancer cell migration and chemoresistance mechanisms.     

ChemInform Abstract: Theoretical Study on Spectroscopic Properties of Positive,Neutral, and Negative Species of BCl2 and AlCl2: The Stability of the Negative Species.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Theoretical Studies of Group 1 Metal Complexes with Hydrogen Fluoride,M(HF)n,M: Li,Na, and K: A New Type of Electrides.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.