Measurements of residual stress in semi-insulating GaAs by Cr-related luminescence lines

We have measured systematically the Cr-related zero-phonon lines in the 0.839 eV region in a series of plastically-bent semi-insulating GaAs:Cr with compressive or tensile stress along various bending axes. As a result, it has been found that the residual stress in semi-insulating GaAs:Cr wafers can be sensitively characterized from a splitting and energy shift of the 0.839 eV Cr-related luminescence lines in the low-temperature photoluminescence spectra. Furthermore, we have applied this method to the characterization of the interface stress of OMVPE-grown ZnSe/GaAs:Cr heterostructure and found that anomalous stress exists at the ZnSe/GaAs interface, which is inconsistent with stress predicted by the lattice mismatch of the heterojunctions.     

Naturally-occurring nitro compounds

Naturally-occurring nitro compounds display great structural diversity, and a wide range of biological activities. This review summarizes current information on the structures of naturally-occurring nitro compounds and on the biosynthesis of the nitro group.     

Synthesis of polyfunctionalized furans from 3-acetyl-1-aryl-2-pentene-1,4-diones

The BF₃-catalyzed cyclization of 3-acetyl-1-aryl-2-pentene-1,4-diones 1a-e in the presence of water in boiling tetrahydrofuran gave bis(3-acetyl-5-aryl-2-furyl)methanes 2a-e in 26-79% yields along with a small amount of 3-acetyl-5-aryl-2-methylfurans 3a-e. The exact structure of 2a was determined by X-ray crystallography. The use of a half volume of the solvent for the reaction of 1a resulted in the formation of 2,4-bis(3-acetyl-5-phenyl-2-furfuryl)-3-acetyl-5-phenylfuran (4) together with 2a and 3a. A similar reaction of 1a was carried out in the presence of 3-acetyl-5-(4-methylphenyl)-2-methylfuran (3d) to afford 4-(3-acetyl-5-phenyl-2-furfuryl)-3-acetyl-5-(4-methylphenyl)-2-methylfuran (5) in 49% yield. The BF₃-catalyzed reaction of 1a with 2,4-pentanedione in dry tetrahydrofuran at 23°C gave 3-(3-acetyl-5-phenyl-2-furfuryl)-4-hydroxy-3-penten-2-one (6a) and 3-(3-acetyl-2-methyl-4-phenyl-5-furyl)-4-hydroxy-3-penten-2-one (7a) in 66 and 24% yields, respectively. The product distribution depended on the reaction temperature. A similar reaction of 1b-e also yielded the corresponding trisubstituted furans 6b-e and tetrasubstituted furans 7b-e in good yields. These results suggested the presence of the furfuryl carbocation intermediate A during the reaction. The one-pot synthesis of 6a and 7a was also achieved by a similar reaction using phenylglyoxal. The deoxygenation of 1a with triphenylphosphine gave 3a in 88% yield, while 1a was treated with concentrated hydrochloric acid to yield 3-acetyl-2-chloromethyl-5-phenylfuran (8) which was quantitatively transformed in ethanol into 3-acetyl-2-ethoxymethyl-5-phenylfuran (9) and in water into 3-acetyl-5-phenylfurfuryl alcohol (10), respectively. In addition, the Diels-Alder reaction of cyclopantadiene with 1a gave the corresponding [4+2] cycloaddition products 11 and 12.     

Exploring leptonic CP violation by reactor and neutrino superbeam experiments

We point out the possibility that reactor measurement of θ₁₃, when combined with high-statistics ν_e appearance accelerator experiments, can detect leptonic CP violation. Our proposal is based on a careful statistical analysis under reasonable assumptions on systematic errors, assuming 2 years running of the neutrino mode J-PARC → Hyper-Kamiokande experiment and a few years running of a reactor experiment with 100 t detectors at the Kashiwazaki–Kariwa nuclear power plant. We show that the method can be arranged to be insensitive to the intrinsic parameter degeneracy but is affected by the one due to unknown sign of Δm²₃₁.     

Symmetrization of Nonsymmetric Macdonald Polynomials and Macdonald's Inner Product Identities

We study the Macdonald polynomials that give eigenstates of some quantum many-body system with long-range interactions. Scalar products of the nonsymmetric Macdonald polynomials are algebraically evaluated through their Rodrigues-type formulas. We present a new proof of Macdonald's inner product identities without recourse to the shift operators; that is, we calculate square norms of the Macdonald polynomials through Weyl-symmetrization of those of the nonsymmetric Macdonald polynomials.     

Mn(III)-initiated facile oxygenation of heterocyclic 1,3-dicarbonyl compounds

The Mn(III)-initiated aerobic oxidation of heterocyclic 1,3-dicarbonyl compounds, such as 4-alkyl-1,2-diphenylpyrazolidine-3,5-diones, 1,3-dialkylpyrrolidine-2,4-diones, 3-alkyl-1,5-dimethylbarbituric acids, and 3-butyl-4-hydroxy-2-quinolinone gave excellent to good yields of the corresponding hydroperoxides, which were gradually degraded by exposure to the metal initiator after the reaction to afford the corresponding alcohols. The synthesis of 30 heterocyclic 1,3-dicarbonyl compounds, the corresponding hydroperoxides and the 10 alcohols, their characterization, and the limitations of the procedure are described. In addition, the mechanism of the hydroperoxidation and the redox decomposition of the hydroperoxides are discussed.     

Organometallic Molecular Wires with Thioacetylene Backbones,trans-{RS-(C≡C)n}2Ru(phosphine)4: High Conductance through Non-Aromatic Bridging Linkers

In this work, the design, synthesis, and single-molecule conductance of ethynyl- and butadiynyl-ruthenium molecular wires with thioether anchor groups [RS=n-C₆H₁₃S, p-tert-Bu−C₆H₄S), trans-{RS−(C≡C)_n}₂Ru(dppe)₂ (n=1 ( 1^R ), 2 ( 2^R ); dppe: 1,2-bis(diphenylphosphino)ethane) and trans-(n-C₆H₁₃S−C≡C)₂Ru{P(OMe)₃}₄ 3^hex ] are reported. Scanning tunneling microscope break-junction study has revealed conductance of the organometallic molecular wires with the thioacetylene backbones higher than that of the related organometallic wires having arylethynylruthenium linkages with the sulfur anchor groups, trans-{p-MeS−C₆H₄-(C≡C)_n}₂Ru(phosphine)₄ 4 ⁿ (n=1, 2) and trans-(Th−C≡C)₂Ru(phosphine)₄ 5 (Th=3-thienyl). It should be noted that the molecular junctions constructed from the butadiynyl wire 2^R , trans-{ Au −RS−(C≡C)₂}₂Ru(dppe)₂ ( Au : gold metal electrode), show conductance comparable to that of the covalently linked polyynyl wire with the similar molecular length, trans-{ Au −(C≡C)₃}₂Ru(dppe)₂ 6³ . The DFT non-equilibrium Green's function (NEGF) study supports the highly conducting nature of the thioacetylene molecular wires through HOMO orbitals.     

Pattern enrichment analysis for phage selection of stapled peptide ligands

Phage display is the most widely used technique to discover de novo peptides that bind to target proteins. However, it is associated with some challenges such as compositional bias. In this study, to overcome these difficulties, we devised a ‘pattern enrichment analysis.’ In this method, two samples (one obtained by affinity selection, the other simply amplified without selection) are prepared, and the two sequence datasets read on next-generation sequencer are compared to find the three-residue pattern most enriched in the selected sample. This allows us to compare two sequence datasets with high coverage and facilitates the identification of peptide sequences and the key residues for binding. We also demonstrated that this approach in the combination with structured peptide libraries allowed spatial mapping of the enriched sequence patterns. Here, we prepared a phage library displaying chemically stapled helical peptides with the X₁C₂X₃X₄X₅X₆X₇X₈C₉X₁₀ sequence, where X is any amino acid. To validate our method, we performed screening against the HDM2 protein. The results showed that the hydrophobic residues (Phe, Tyr, Trp and Leu) that are key to interactions with HDM2 were clearly identified by the pattern enrichment analysis. We also performed selection targeting the SARS-CoV-2 spike RBD in the same manner. The results showed that similar patterns were enriched among the hit peptides that inhibited the protein–protein interaction.

To effectively identify helical peptide binders from a phage library, we developed “pattern enrichment analysis,” which finds the enriched three-residue patterns by comparison with a control sample.     

Fluorescent Cyclodextrin/Peptide Hybrids with a Novel Guest‐Responsive Chemosensor in the Peptide Side Chain

Peptides bearing β‐cyclodextrin and 4‐(N,N‐dimethylamino)benzoyl (DMAB) units in the peptide side chains were prepared as chemosensors for molecule detection. The DMAB unit was expected to be included into the cyclodextrin cavity intramolecularly. However, these peptides exhibited no twisted intramolecular charge transfer fluorescence and the normal fluorescence intensity decreased upon the addition of 1‐adamantanol as an exogenous guest, indicating that the DMAB units are shallowly included in the cyclodextrin cavities.     

Nukleare Wechselwirkung und Feinstrukturen von kolloidalen Goldteilchen

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