Rapid fermentation of beer using an immobilized yeast multistage bioreactor

The characteristics of yeast sulfite metabolism in a multistage bioreactor system for beer fermentation were investigated. No sulfite was produced in the continuous stirred-tank reactor (CSTR). However, large amounts were produced in the packed-bed reactor (PBR). Production of sulfite in the PBR seems to be inevitable when it is operated continuously. In order to control the sulfite level in the young beer, the yeast needs to be reactivated into the growth phase. One possible strategy to achieve this is to aerate and periodically remove yeast clogged in the reactor once every 6–7 months before the sulfite level exceeds a given concentration (e.g., 20 mg/L). It was confirmed that sulfite production is closely related to the growth condition of the yeast and is therefore important to consider in the control strategy for sulfite when using the immobilized yeast reactor for beer production.     

Electron correlations and transport effective mass in narrow-band systems and the Hubbard model

The Hubbard model is rederived from a tight-binding band calculation, showing that, as long as parameters are properly chosen, the model is justified for calculating electronic properties of narrow-band systems. The treatment is extended by including correlations and it was found that bound solutions called dimers exist. The concept of dimers is found to be very powerful for understanding the unusual properties of heavy fermion systems. However, a Mott-Hubbard-like model may be required to calculate properties of high T_c cuprates. © 1994 John Wiley & Sons, Inc.     

Synthesis and antinociceptive activity of orally active opioid peptides: improvement of oral bioavailability by esterification

To improve the oral bioavailability of a dermorphin tetrapeptide analog, N(alpha)-1-iminoethyl-Tyr-D-MetO-Phe-MebetaAla-OH (III), which has a potent analgesic activity after oral administration, various derivatives were synthesized to increase lipophilicity by esterification of the C-terminal carboxyl group and/or acylation of the phenolic hydroxyl group on Tyr1. Antinociceptive activity was evaluated after subcutaneous or oral administration using the mouse tail pressure test. As a result, increased antinociceptive activity after oral administration as well as an improved ED50(p.o.)/ED50(s.c.) ratio, which is an indicator of oral bioavailability, were found for some compounds. With regard to the improvement of bioavailability, derivatives with acylation of the phenolic hydroxyl group on Tyr1 showed better results than derivatives with esterification of the C-terminal carboxyl group. In particular, an ED50(p.o.)/ED50(s.c.) ratio equivalent to that of morphine was found for an acetylated derivative, N(alpha)-1-iminoethyl-Tyr(COMe)-D-MetO-Phe-MebetaAla-OH (7a), as well as for a methoxycarbonylated derivative, N(alpha)-1-iminoethyl-Tyr(CO2Me)-D-MetO-Phe-MebetaAla-OH (7l).     

Site-directed 13C solid-state NMR studies on membrane proteins: strategy and goals toward revealing conformation and dynamics as illustrated for bacteriorhodopsin labeled with [1-13C]amino acid residues

We have so far demonstrated that well-resolved and site-specifically assigned (13)C peaks as recorded by site-directed NMR study on (13)C-labeled membrane proteins can serve as a convenient probe to reveal their local conformation and dynamics. We attempted here to clarify the extent to which (13)C NMR spectra of (13)C-labeled fully hydrated bacteriorhodopsin (bR) as a typical membrane protein are visible or well resolved in the presence of inherent fluctuation motions with frequency of 10(2)-10(8) Hz, especially at the membrane surfaces. Accordingly, we estimated the relative proportion of (13)C NMR signals from the surface areas with and without peak suppression by the accelerated transverse relaxation effect by surface-bound Mn(2+) ions, which could be effective for residues within 8.7 angstroms of the membrane surface. It turned out that the experimental findings are consistent with the predicted amount of amino acid residues under consideration located within 8.7 angstroms of the surface for [1-(13)C]Val- and Ile-labeled bR and also [3-(13)C]Ala-bR. In contrast, (13)C NMR peaks from such surfaces area are almost completely or partially suppressed for [1-(13)C]Gly-, Ala-, Leu-, Phe- and Trp-labeled bR, as a result of plausible interference of the fluctuation frequency with frequency of magic angle spinning (10(4) Hz). We further assigned several (13)C NMR signals of [1-(13)C] Val-, Trp- and Ile-labeled bR on the basis of a variety of site-directed mutants with reference to those of the wild type. Further, we recorded the (13)C NMR of bR in lipid bilayers to search for the optimal conditions to be able to obtain signals with the highest peak intensities and spectral resolution. Backbone dynamics turn out to be essential for recording (13)C NMR spectra so as to escape from motional frequencies of the order of 10(4)-10(5) Hz, either in the direction of accelerated fluctuation or slowed motions in the direction of forming the 2D array.     

Ferromagnetic anomaly associated with the antiferromagnetic transitions in (donor)[Ni(mnt)2]-type charge-transfer salts

Three newly prepared [Ni(mnt)2] complexes, (HMTTF)[Ni(mnt)2], (ChSTF)[Ni(mnt)2], and (DBTTF)2[Ni(mnt)2], are reported (DBTTF = dibenzotetrathiafulvalene, ChSTF = 2,3-cyclohexylenedithio-1,4-dithia-5,8-diselanafulvalene, HMTTF = bis(trimethylene)-tetrathiafulvalene, and mnt = maleonitrile dithiolate). The former two compounds have usual DA-type (D = donor, A = acceptor) mixed stacks, whereas the DBTTF complex has DDDDAA-type 6-fold columns. These compounds are electrical insulators, but the HMTTF and ChSTF complexes exhibit chiT minima at 16 and 55 K, respectively, followed by chiT peaks at 8 and 16 K. Below these temperatures the ESR signal disappears, indicating antiferromagnetic transitions. The origin of the ferromagnetic interaction is explained either from the difference of the g values between the donor and the anion or from the intrinsic ferromagnetic interaction of the [Ni(mnt)2] anions.     

The effect of humidity on thermal process of zinc acetate

The thermal decomposition of zinc acetate dihydrate Zn(CH₃CO₂)₂·2H₂O in some humidity-controlled atmospheres has been successfully investigated by novel thermal analyses, which are sample-controlled thermogravimetry (SCTG), thermogravimety combined with evolved gas analysis using mass spectrometry (TG–MS) and simultaneous measurement of differential scanning calorimetry and X-ray diffractometry (XRD–DSC). The thermal processes of anhydrous zinc acetate in dry gas atmosphere by conventional linear heating experiment initiated with the sublimation around 180 °C, followed by the fusion and the decomposition over 250 °C. SCTG was useful to interpret clearly the successive reaction because the high-temperature parallel decompositions were effectively inhibited. The thermal behavior changed dramatically by introducing water vapor in the atmosphere and the thermal process was quite different from that in dry gas atmosphere. Zinc oxide (ZnO) was formed only in a humidity-controlled atmosphere, and could be easily synthesized at temperatures below 300 °C. XRD–DSC equipped with a humidity generator revealed directly the crystalline change from Zn(CH₃CO₂)₂ to ZnO. A detailed thermal process of Zn(CH₃CO₂)₂·2H₂O and the effect of water vapor are discussed.     

Novel ring transformation reactions of xanthine derivatives

The novel ring transformation reactions were found in the reactions of 1,3,7,9-tetra-alkyl-8,9-dihydroxanthines and acetylenic compounds. The reaction of the dihydroxanthine with DMAD gave a propellane type compound and with methyl propiolate afforded the similar type compound and a pyrimido[4,5-b]diazepine derivative. The mechanism of these reactions was also discussed.     

Cyclic dithio-carbenium ion salts and their conversion to ketene dithioacetals

1,2-Ethanedithiol and 1,3-propanedithiol were treated with perchloric acid in acetic anhydride to give 2-methyl-1,3-dithiolan-2-yl and 2-methyl-1,3-dithian-2-yl perchlorates, respectively, which were converted to ketene dithioacetals by deprotonation with tertiary amines.     

Large-scale separation of metallic and semiconducting single-walled carbon nanotubes

In the applications of single-walled carbon nanotubes (SWNTs), it is extremely important to separate semiconducting and metallic SWNTs. Although several methods have been reported for the separation, only low yields have been achieved at great expense. We show a separation method involving a dispersion-centrifugation process in a tetrahydrofuran solution of amine, which makes metallic SWNTs highly concentrated to 87% in a simple way.