Mixed Valence Tin Oxides as Novel van der Waals Materials: Theoretical Predictions and Potential Applications

Van der Waals (vdW) heterostructures, which can be assembled by combining 2D atomic crystals in a precisely chosen sequence, enable a wide range of potential applications in optoelectronics, photovoltaics, and photocatalysis. However, the difficulty of peeling isolated atomic planes and the lattice mismatch between different materials is the main obstacle to hinder vdW materials from more practical applications. In this work, the mixed valence tin oxides, Sn_xO_y (0.5 < x/y < 1), are proposed as a new member of vdW materials and these mixed valence tin oxides show promise to overcome the above‐mentioned obstacle. Density‐functional theory calculations are combined with an evolutionary algorithm to predict the crystal structures of a series of previously reported tin oxides (Sn₂O₃, Sn₃O₄, Sn₄O₅, and Sn₅O₆), unreported compositions (Sn₇O₈, Sn₉O₁₀, and Sn₁₁O₁₂), and a new β ‐ SnO phase. These structures consist of β‐SnO, Sn₂O₃, and Sn₃O₄ monolayers. Their band gaps can be engineered in the 1.56–3.25 eV range by stacking the monolayers appropriately. The band gap depends linearly on the interlayer distance, as understood from interlayer Sn²⁺–Sn²⁺ and intralayer Sn²⁺–O interactions. Sn_xO_y structures exhibit high photoabsorption coefficients and suitable band‐edge positions for photoexcited H₂ evolution; this indicates potential for environmentally benign solar energy conversion in photovoltaic and photocatalytic applications.     

Change of enzyme activities during the early stage of influenza virus infection

Intracellular activities of various hydrolytic enzymes were investigated in monkey kidney cells infected with the $\text{A}\text{NWS}$ strain of influenza virus. At the early stage of infection, there was a significant decrease in the activity of β-D-galactosidase, α-D-mannosidase, $\text{N}$-acetyl-β-D-glucosaminidase, acid and alkaline phosphatase. The decrease was roughly proportional to the multiplicity of infection, and restored at 2 hr after the infection. Corresponding to this intracellular decrease, there was an increase in the activities of these enzyme outside the cells. The results suggested that these hydrolytic enzymes would be released from the cell membrane or the lysosomes near the membrane in the process of adsorption and penetration of the virus particles.     

Immobilized phenylalanine hydroxylase through the SH groups

Purified rat liver phenylalanine hydroxylase [L-phenylalanine:tetrahydropteridine:oxygen oxidoreductase (4-hydroxylating), EC 1.14.16.1] was immobilized with activated thiol-Sepharose 4B via disulfide bond formation, which is expected to immobilize the enzyme in its activated form through the SH modification. This immobilized enzyme was more stable against thermal denaturation than the free enzyme. When tetrahydrobiopterin was used as the natural cofactor, the K(m) value for phenylalanine was decreased and that for the cofactor was increased. Constant conversion from phenylalanine to tyrosine was demonstrated continuously for over 8 h at 25 degrees C.     

The dissociation between the plasma levels of aminopeptidases A and B in spontaneously hypertensive rats

We performed a longitudinal study for 20 weeks on spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKR) to determine the relationship between peptide metabolism and the age-dependent increase in blood pressure. In both SHR and WKR, the plasma level of aminopeptidase A (AP-A) clearly showed an age-dependent decrease. The plasma level of aminopeptidase B paralleled that of AP-A in WKR, but such an age-dependency was not observed in SHR, thus showing a dissociation between the two aminopeptidases. With age in both strains, the level of angiotensin-converting enzyme tended to decrease, while that of kallikrein activity tended to increase. In addition to these findings, a multivariate study testing the relationship of blood pressure to these enzyme activities, as well as to plasma levels of angiotensin I and renin activity, suggested abnormalities in the networks of proteolytic enzymes and in the peptide metabolism surrounding the renin-angiotensin system in SHR. These abnormalities may play some important roles in pathophysiological mechanisms of hypertension in SHR.     

Synthesis of 5-deoxy-5-fluorosporaricin A

The structures of the O-specific side-chains in the lipopolysaccharides of Salmonella greenside, group Z, and Salmonella adelaide, group O, have been investigated. The former proved to be identical with that of Escherichia coli O 55. The latter, which was more extensively studied, was composed of repeating units having the structure

in which Col is colitose (3,6-dideoxy-l-xylo-hexose). This was also shown to be the biological repeating-unit. The same structure has been proposed for the O-antigen of E. coli O 111. The biological repeating-unit for the S. greenside O-antigen was also defined. The structural studies also confirmed that both lipopolysaccharides contain the hexose region typical for the Salmonella core.     

Synthesis of 4'-deoxy-4'-fluorokanamycin A and B.

4'-Deoxy-4'-fluorokanamycins A (17) and B (25) have been prepared through fluorinative ring-opening of the D-galacto-3',4'-oxiranes (8 and 21) derived from kanamycin A and B with potassium hydrogenfluoride in ethane-1,2-diol. The mechanism of preponderant formation of the 4'-deoxy-4'-fluoro-D-gluco (9 and 22) over the 3'-deoxy-3'-fluoro-D-gulo derivatives was discussed. In the synthesis of 25, the unusual 3',6'-epimine (23) was the main product along with the 4'-deoxy-4'-fluoro derivative. The mechanism of this reaction is also discussed. Both 17 and 25 were active against resistant bacteria producing aminoglycoside-adenylylating enzymes for HO-4'.     

Development of the eggs and larvae of the pike eel,Muraenesox cinereus

Embryonic and larval development of the pike eel,Muraenesox cinereus, are described following natural fertilization in the laboratory. Eggs are pelagic and spherical with diameters from 1.8 to 2.1 mm and have a colorless, transparent chorion and numerous oil globules. Hatching occurs 36 hours after spawning at a water temperature of 25°C. Newly-hatched larvae are 5.8 mm in mean TL, and the number of myomeres averages 86. Absorption of the yolk is completed 8 days after hatching, at 9–10 mm TL. Larvae survive for 10 days without food supply. At this time they are 11.2 mm in mean TL and have 97 + 55=152 myomeres, which is a diagnostic character of this species. They have large eyes and well-developed jaws with sharp teeth.     

Induction by fibroblast growth factor of angiotensin converting enzyme in vascular endothelial cells in vitro

Induction of vascular endothelial cells with pituitary fibroblast growth factor (FGF) provoked an increase in angiotensin converting enzyme activity. The stimulatory effect of FGF on ACE activity was dose-dependent (ED50 = 1.0 ng/ml). Our results suggest a possible role for pituitary FGF in regulation of ACE production in vascular endothelial cells.