Adenosine-1,3-diazaphenoxazine derivative for selective base pair formation with 8-oxo-2'-deoxyguanosine in DNA

The selective detection of 8-oxo-2'-deoxyguanosine (8-oxo-dG) in DNA without chemical or enzymatic treatment is an attractive tool for genomic research. We designed and synthesized the non-natural nucleoside analogue, the adenosine-1,3-diazaphenoxazine (Adap) derivative, for selective recognition of 8-oxo-dG in DNA. This study clearly showed that Adap has a highly selective stabilizing effect on the duplex containing the Adap-8-oxo-dG base pair. Furthermore, the fluorescent property of Adap was shown to be useful for the selective detection of 8-oxo-dG in the duplex DNA. To the best of our knowledge, this is the first successful demonstration of a non-natural nucleoside with a high selectivity for 8-oxo-dG in DNA.     

Biomimetic one-pot preparation of a black tea polyphenol theasinensin A from epigallocatechin gallate by treatment with copper(II) chloride and ascorbic acid

Chromatographic separation of black tea polyphenols is too difficult to supply sufficient quantities of pure compounds for biological experiments. Thus, facile methods to prepare black tea constituents were desired. Treatment of epigallocatechin gallate with copper(II) chloride efficiently afforded an unstable quinone dimer, dehydrotheasinensin A, and subsequent treatment with ascorbic acid stereoselectively yielded theasinensin A. The latter is a dimer with an R-biphenyl bond, one of the major polyphenols found in black tea. The method is simpler and more effective than enzymatic preparation.     

Quantum degenerate mixtures of alkali and alkaline-earth-like atoms

We realize simultaneous quantum degeneracy in mixtures consisting of the alkali and alkaline-earth-like atoms Li and Yb. This is accomplished within an optical trap by sympathetic cooling of the fermionic isotope ?Li with evaporatively cooled bosonic 1??Yb and, separately, fermionic 1?3Yb. Using cross-thermalization studies, we also measure the elastic s-wave scattering lengths of both Li-Yb combinations, |a(?Li-1??Yb)| = 1.0 ± 0.2 nm and |a(?Li-1?3Yb)| = 0.9 ± 0.2 nm. The equality of these lengths is found to be consistent with mass-scaling analysis. The quantum degenerate mixtures of Li and Yb, as realized here, can be the basis for creation of ultracold molecules with electron spin degrees of freedom, studies of novel Efimov trimers, and impurity probes of superfluid systems.     

One‐Pot Synthesis of N‐Acetyl‐ and N‐Glycolylneuraminic Acid Capped Trisaccharides and Evaluation of Their Influenza A(H1 N1) Inhibition

Human lung epithelial cells natively offer terminal N‐acetylneuraminic acid (Neu5Ac) α(2→6)‐linked to galactose (Gal) as binding sites for influenza virus hemagglutinin. N‐Glycolylneuraminic acid (Neu5Gc) in place of Neu5Ac is known to affect hemagglutinin binding in other species. Not normally generated by humans, Neu5Gc may find its way to human cells from dietary sources. To compare their influence in influenza virus infection, six trisaccharides with Neu5Ac or Neu5Gc α(2→6) linked to Gal and with different reducing end sugar units were prepared using one‐pot assembly and divergent transformation. The sugar assembly made use of an N‐phthaloyl‐protected sialyl imidate for chemoselective activation and α‐stereoselective coupling with a thiogalactoside. Assessment of cytopathic effect showed that the Neu5Gc‐capped trisaccharides inhibited the viral infection better than their Neu5Ac counterparts.     

Exploring the Potential of Fulvalene Dimetals as Platforms for Molecular Solar Thermal Energy Storage: Computations,Syntheses, Structures,Kinetics, and Catalysis

A study of the scope and limitations of varying the ligand framework around the dinuclear core of FvRu₂ in its function as a molecular solar thermal energy storage framework is presented. It includes DFT calculations probing the effect of substituents, other metals, and CO exchange for other ligands on ΔH_storage. Experimentally, the system is shown to be robust in as much as it tolerates a number of variations, except for the identity of the metal and certain substitution patterns. Failures include 1,1′,3,3′‐tetra‐tert‐butyl ( 4 ), 1,2,2′,3′‐tetraphenyl ( 9 ), diiron ( 28 ), diosmium ( 24 ), mixed iron‐ruthenium ( 27 ), dimolybdenum ( 29 ), and ditungsten ( 30 ) derivatives. An extensive screen of potential catalysts for the thermal reversal identified AgNO₃–SiO₂ as a good candidate, although catalyst decomposition remains a challenge.     

Design of Weak‐Donor Alkyl‐Functionalized Push–Pull Pyrene Dyes Exhibiting Enhanced Fluorescence Quantum Yields and Unique On/Off Switching Properties

We designed, synthesized, and evaluated environmentally responsive solvatochromic fluorescent dyes by incorporating weak push–pull moieties. The quantum yields of the push (alkyl)–pull (formyl) pyrene dyes were dramatically enhanced by the introduction of alkyl groups into formylpyrene (1‐formylpyrene: Φ_F=0.10; 3,6,8‐tri‐n‐butyl‐1‐formylpyrene: Φ_F=0.90; in MeOH). The new dyes exhibited unique sensitivity to solvent polarity and hydrogen‐bond donor ability, and specific fluorescence turn‐on/off properties (e.g., 3,6,8‐tri‐n‐butyl‐1‐formylpyrene: Φ_F=0.004, 0.80, 0.37, and 0.90 in hexane, chloroform, DMSO, and MeOH, respectively). Here, the alkyl groups act as weak donors to suppress intersystem crossing by destabilizing the HOMOs of 1‐formylpyrene while maintaining weak intramolecular charge‐transfer properties. By using alkyl groups as weak donors, environmentally responsive, and in particular, pH‐responsive fluorescent materials may be developed in the future.     

Supramolecular Phosphatases Formed by the Self‐Assembly of the Bis(Zn2+–Cyclen) Complex,Copper(II), and Barbital Derivatives in Water

In our previous paper, we reported that a dimeric Zn²⁺ complex with a 2,2′‐bipyridyl linker (Zn₂L¹), cyanuric acid (CA), and a Cu²⁺ ion automatically assemble in aqueous solution to form 4:4:4 complex 3 , which selectively catalyzes the hydrolysis of mono(4‐nitrophenyl)phosphate (MNP) at neutral pH. Herein, we report that the use of barbital (Bar) instead of CA for the self‐assembly with Zn₂L¹ and Cu²⁺ induces 2:2:2 complexation of these components, and not the 4:4:4 complex, to form supramolecular complex 6 a , the structure and equilibrium characteristics of which were studied by analytical and physical measurements. The finding show that 6 a also accelerates the hydrolysis of MNP, similarly to 3 . Moreover, inspired by the crystal structure of 6 a , we prepared barbital units that contain functional groups on their side chains in an attempt to produce supramolecular phosphatases that possess functional groups near the Cu₂(μ‐OH)₂ catalytic core so as to mimic the catalytic center of alkaline phosphatase (AP).