Quantification of end groups in polystyrenes by pyrolysis–gas chromatography

The determination of end groups in polystyrenes (PSts) polymerized anionically with n-butyllithium as the initiator was carried out by pyrolysis-gas chromatography (Py-GC). The relative proportions of the end groups decrease with increasing molecular weight (MW). Consequently, the peaks which reflect the structure of the end groups can be distinguished by comparing pyrograms of samples with different MW. By comparing the intensities of these peaks relative to total intensities of all the peaks in the pyrogram, the numberaverage molecular weight (M_n) of the polymer can be estimated. The observed M_n values of PSts estimated by this method are compared with those determined by size exclusion chromatography (SEC). By this method it was possible to make direct determination of M_n values of PSts with MWs between 1000 and ca. 1 million. Furthermore, the calibration curve produced by the relative intensity of one of the most characteristic peaks (2-phenyl-1-heptene; C₄H₉? CH₂C (Ph) = CH₂) for the end group to total intensity of all the peaks in the pyrogram, gave rapid and highly reproducible M_n values. © 1994 John Wiley & Sons, Inc.     

n-type organic field-effect transistors with very high electron mobility based on thiazole oligomers with trifluoromethylphenyl groups

Novel thiazole oligomers and thiazole/thiophene co-oligomers with trifluoromethylphenyl groups were developed as n-type semiconductors for OFETs. They showed excellent n-type performances with high electron mobilities. A 5,5'-bithiazole with trifluoromethylphenyl groups forms a closely packed two-dimensional columnar structure leading to a high performance n-type FET. The electron mobility was enhanced to 1.83 cm2/Vs on the OTS-treated substrate.     

Purification and characterization of a nuclease from Lentinus edodes.

An endonuclease with 3'-nucleotidase activity (nuclease Le1) was purified from fruit bodies of Lentinus edodes in a single band on sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The apparent molecular weight of nuclease Le1 was about 27000. The nuclease was inactivated in the presence of ethylenediaminetetraacetic acid (EDTA) and reactivated by the addition of Zn2+. Hydrolysis of poly U by the nuclease showed many intermediate size oligomers prior to the formation of 5'-uridine monophosphate (UMP). Therefore, it was concluded that nuclease Le1 was a Zn(2+)-endonuclease similar to P1-nuclease from Penicillium citrinum. The nuclease was very sensitive to ionic strength, but pH-profiles of the hydrolysis of four 3'-nucleotides were very similar to those of P1 nuclease from P. citrinum.     

Amino acids and peptides. XXXIII. Synthesis of N-terminal epitope peptides of mammalian metallothioneins (MTs).

In order to determine the fine structure of the mammalian metallothionein (MT) epitope to a monoclonal anti-rat Zn-MT-II antibody (MT 189-14-7), N-terminal peptides of various lengths of mammalian metallothioneins (MTs) were synthesized by a conventional solution method using the newly developed beta-2-adamantylaspartate, and their immunological properties were examined. It was found that the N-terminal acetyl group was indispensable for the reaction with the monoclonal antibody and the N-terminally acetylated pentapeptide, Ac-Met-Asp-Pro-Asn-Cys-OH, was the smallest peptide which exhibited a significant reactivity with the antibody.     

Two-photon photochromism of diarylethene dimer derivatives.

Photochromic diarylethene dimer derivatives with large two-photon absorption (TPA) cross-sections have been designed and synthesized. The derivatives have a D-pi-D structure in which indole rings are used as donor units (D) and 1,4-bis(ethynyl)benzene or 1,4-bis(ethenyl)benzene as a pi-conjugated chain unit (pi). Compound 5 a, which has oxazole rings as one of the aryl groups, showed a TPA cross-section of 23 GM at 820 nm and exhibited efficient two-photon photochromic reactivity.     

Polymerization of Styrene Initiated by Photoexcited Charge-Transfer Complex

Photopolymerization of styrene in the presence of pyromellitic dianhydride, an electron acceptor which forms a charge-transfer complex with the monomer, was studied. Polymerization was initiated by illumination with a light of wavelength longer than 350 nm, where only the charge-transfer absorption band exists. It was found that the reaction involves cationic and radical polymerizations and that the reaction course strongly depends on polarity of the system. It was also suggested by the dependence of the rate of polymerization on light intensity and temperature that the cationic polymerization consists of free ion and ion-pair polymerizations. These results were compared with those of the photoinduced cationic polymerization of α-methylstyrene, which has previously been studied.     

Intermolecular Anionic Rearrangement of the Trimethylgerml Group in Trimethylgermylacetonitrile Anions

Intermolecular anionic rearrangement of the trimethylgermyl group in trimethylgermylacetonitrile, bis(trimethylgermyl)acetonitrile, and tris(trimethylgermyl)acetonitrile is described.     

Novel biosensor for the rapid measurement of estrogen based on a ligand-receptor interaction.

A bioaffinity sensor was developed aiming at the detection of estrogen. This biosensor system is based on the specific binding of estrogen to its receptor immobilized on a gold disk electrode. The recombinant DNA encoding human estrogen receptor ligand-binding domain was expressed in bacteria using the histidine-tag fusion system. The expression of the fusion protein was under control of a bacteriophage T7 promoter, and the protein was purified under native conditions by affinity chromatography, which is based on a specific interaction between a histidine-tag, located in the N-terminus of the protein, and the Ni(II) chelate adsorbent. The protein was immobilized on an Au-electrode with Ni(II)-mediated chemisorption using a histidine tag and thiol-modified iminodiacetic acid. Cyclic voltammetric measurements showed that the reversible electrochemical reaction of a ferrocyanide/ferricyanide redox couple was suppressed by the presence of estrogen in a concentration-dependent manner. It seems reasonable to suppose that the electrostatic property of the protein layer on the electrode surface was altered by complexation with estrogen. These data suggest that this biosensor is applicable to the evaluation binding activities of the chemicals toward the human estrogen receptor.     

Eine Integrationsmethode der linearen Differentialgleichung zweiter Ordnung

Ohne Zusammenfassung