In situ crystallization of bacterial cellulose II. Influences of different polymeric additives on the formation of celluloses Iα and Iβ at the early stage of incubation

Effects of polymeric additives with different degrees of polymerization (DP) or substitution (DS) on the crystallization of celluloses I and I have been examined at an early stage of the incubation of Acetobactor xylinum by using newly developed FT-IR spectroscopy. It was found that the mass fraction of cellulose I is greatly decreased with increasing concentrations of carboxymethyl cellulose sodium salt (CMC) or xyloglucan (XG) in the incubation medium. Such a decrease in the mass fraction of cellulose I, which corresponds to the enhanced crystallization of cellulose I, is more prominent for CMC or XG with lower DPs, but the additives with too low DPs are not so effective probably due to higher solubility and the lower adhesion on the surface of microfibrils. Moreover, the mass fractions of celluloses I and I are highly correlated with the crystallite size of microfibrils, indicating that I is crystallized in larger-size microfibrils while I is produced in smaller-size microfibrils. On the basis of these experimental results, the mechanism of the crystallization of celluloses I and I is discussed in the Acetobactor xylinum system.     

Electrophoretic analysis of the cleaved form of serpin,squamous cell carcinoma antigen-1 in normal and malignant squamous epithelial tissues

The aim of this study was to detect the cleaved form of serine proteinase inhibitor (serpin), squamous cell carcinoma (SCC) antigen-1 in normal and malignant squamous epithelial tissues, which implies the presence of its target proteinase. The cleaved SCC antigen-1 in normal squamous epithelium was identified as a single spot with pI 6.35 and M(r) 40,000 by two-dimensional electrophoresis (2-DE) combined with immunoblotting. Interestingly, the cleaved form showed different biochemical properties in heat stability or immunoreactivity with a monoclonal antibody for SCC antigen (Mab 426) compared to intact SCC antigen-1. Furthermore, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of tissue extracts showed an abundant 40 kDa band of cleaved SCC antigen-1 in tumor tissue compared to normal tissue. Among the potential target proteinase of SCC antigen-1, immunoblotting analyses revealed that cathepsin L2 was remarkably overexpressed in tumor tissue, while cathepsin L was expressed in both normal and tumor tissues. These findings indicate that SCC antigen-1 interacts with specific endogenous proteinases such as cathepsins L and L2 in physiological and pathological states of squamous epithelium.     

High‐Pressure Synthesis of Manganese Oxyhydride with Partial Anion Order

The high‐pressure synthesis of a manganese oxyhydride LaSrMnO_3.3H_0.7 is reported. Neutron and X‐ray Rietveld analyses showed that this compound adopts the K₂NiF₄ structure with hydride ions positioned exclusively at the equatorial site. This result makes a striking contrast to topochemical reductions of LaSrMnO₄ that result in only oxygen‐deficient phases down to LaSrMnO_3.5. This suggests that high H₂ pressure plays a key role in stabilizing the oxyhydride phase, offering an opportunity to synthesize other transition‐metal oxyhydrides. Magnetic susceptibility revealed a spin‐glass transition at 24 K that is due to competing ferromagnetic (Mn²⁺–Mn³⁺) and antiferromagnetic (Mn²⁺–Mn², Mn³⁺–Mn³⁺) interactions.     

Thermodynamic Control of Intramolecular Singlet Fission and Exciton Transport in Linear Tetracene Oligomers

We newly synthesized a series of homo- and hetero-tetracene (Tc) oligomers to propose a molecular design strategy for the efficient exciton transport in linear oligomers by promoting correlated triplet pair (TT) dissociation and controlling sequential exciton trapping process of individual doubled triplet excitons (T+T) by intramolecular singlet fission. First, entropic gain effects on the number of Tc units are examined by comparing Tc-homo-oligomers [(Tc)_n: n=2, 4, 6]. Then, a comparison of (Tc)_n and Tc-hetero-oligomer [TcF₃-(Tc)₄-TcF₃] reveals the vibronic coupling effect for entropic gain. Observed entropic effects on the T+T formation indicated that the exciton migration is rationalized by number of possible TT states increased both by increasing the number of Tc units and by the vibronic levels at the terminal TcF₃ units. Finally, we successfully observed high-yield exciton trapping process (trapped triplet yield: Φ_TrT=176 %).     

A new family of glucose-1-phosphate/glucosamine-1-phosphate nucleotidylyltransferase in the biosynthetic pathways for antibiotics

Aminoglycoside antibiotics are composed of aminosugars and a unique aminocyclitol aglycon including 2-deoxystreptamine (DOS), streptidine, actinamine, etc., and nucleotidylyltransferases, sugar modifying enzymes, and glycosyltransferases appear to be essential for their biosynthesis. However, the genes encoding those enzymes were unable to be identified by a standard homology search in the butirosin biosynthetic btr gene cluster, except that the btrM gene appeared to be a glycosyltransfease. Disruption studies of the btrD gene indicated that BtrD was involved in the supply of a glycosyl donor immediately prior to the glycosylation of DOS giving paromamine. As anticipated, BtrD expressed in Escherichia coli was able to catalyze UDP-D-glucosamine formation from D-glucosamine-1-phosphate and UTP. Both dTTP and UTP were good NTP substrates, and D-glucose-1-phosphate and D-glucosamine-1-phosphate were good sugar phosphates for the enzyme reaction. This finding is the first to identify an enzyme which activates a sugar donor in the DOS-containing antibiotics. Interestingly, BtrD homologues have been reported as functionally unknown open reading frames (ORFs) in the biosynthetic gene clusters for several antibiotics including teicoplanin, balhimycin, chloroeremomycin, and mitomycin C. It appears therefore that gene clusters for antibiotic biosynthesis provide their own nucleotidylyltransferases, and the BtrD homologues are among the secondary metabolism specific enzymes.     

Direct observation of a pair decay of neutral charmed particles produced in 400 GeVc proton interaction

The second evidence of a pair decay of charmed particles has been obtained in an emulsion chamber exposed to $\text{400}\text{GeV}\text{c}$ protons. The life time and production cross section of the charmed particles have been evaluated as several times 10^?13 s and several tens of microbarns.     

On a unified double zeta function of Mordell–Tornheim type*

Lithuanian Mathematical Journal - We introduce a double zeta function of Mordell–Tornheim type and compute its values at nonpositive integer points. We then discuss a possible generalization...