Intermolecular communication on a liposomal membrane: enzymatic amplification of a photonic signal with a gemini peptide lipid as a membrane-bound artificial receptor

A supramolecular system that can activate an enzyme through photo-isomerization was constructed by using a liposomal membrane scaffold. The design of the system was inspired by natural signal transduction systems, in which enzymes amplify external signals to control signal transduction pathways. The liposomal membrane, which provided a scaffold for the system, was prepared by self-assembly of a photoresponsive receptor and a cationic synthetic lipid. NADH-dependent L-lactate dehydrogenase, the signal amplifier, was immobilized on the liposomal surface by electrostatic interactions. Recognition of photonic signals by the membrane-bound receptor induced photo-isomerization, which significantly altered the receptor's metal-binding affinity. The response to the photonic signal was transmitted to the enzyme by Cu(2+) ions. The enzyme amplified the chemical information through a catalytic reaction to generate the intended output signal.     

An sp2 and sp3 hybrid nanocrystalline carbon film electrode for anodic stripping voltammetry and its application for electrochemical immunoassay

A hybridized nanocrystalline carbon film electrode consisting of sp(2) and sp(3) bonds was investigated to reveal the reduction properties of Cd(2+) and for application as a highly sensitive and reliable electrochemical immunoassay. Conductive nanocrystalline carbon film consisting of about 60% sp(2) and 40% sp(3) bonds was fabricated using electron cyclotron resonance (ECR) sputtering equipment, and then the Cd(2+) concentrations were measured with an ECR sputtered carbon (ECR nano-carbon) electrode by employing an anodic stripping voltammetry (ASV) technique. The preconcentrated Cd was analyzed with Kelvin probe force microscopy and energy dispersive X-ray spectroscopy while observing the morphology change with an atomic force microscope and a scanning electron microscope. The preconcentrated Cd on the ECR nano-carbon electrode was revealed to be a thin sheet structure, which was significantly different from the Cd on a conventional carbon material that grows with a coralloid structure. The background current during an ASV measurement maintains a low level equivalent to that found with boron-doped diamond because the surface of the ECR nano-carbon is robust and angstrom-level flat. The carbon-electrode performance for ASV was improved by controlling its structure at a nanometer scale without any metal doping or coating. Finally, the ECR nano-carbon was used for biomolecular determination by electrochemical immunoassay with a CdSe nanoparticle label. Electrochemical immunoassay results were successfully obtained with the ECR nano-carbon, and they correlated well with fluorescence results obtained for CdSe nanoparticles.     

Endocytosis-like uptake of surface-modified drug nanocarriers into giant unilamellar vesicles

We had previously developed surface-modified poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) for use as a cellular drug delivery system. The cellular uptake of PLGA-NPs was mediated predominantly by endocytosis, and this uptake was increased by surface modifications with polymers, such as chitosan (CS) and polysorbate 80 (P80). In the present study, we prepared a cell-sized giant unilamellar vesicle (GUV) that mimics a cell membrane to investigate the interaction between cell membranes and NPs. Endocytosis-like uptake of NPs into a GUV was observed when the NPs were modified with nonionic surfactant P80 probably due to change in viscoelasticity and enhanced fusion activity of the membrane induced by P80. In contrast, unmodified NPs and those modified with CS were not internalized into a GUV. These results suggest that surface properties of PLGA-NPs are an important formulation parameter for their interaction with lipid membranes.     

One-Pot Synthesis of Symmetrical and Unsymmetrical Diarylmethanes via Diborylmethane

A one-pot synthesis of diarylmethanes from air-stable diborylmethane via the Suzuki-Miyaura cross-coupling reaction is described. The present approach realizes the synthesis of various symmetrical and unsymmetrical diarylmethanes in good to excellent yields.     

Enantioselective synthesis of tripodal cyclophanes and pyridinophanes by intramolecular [2+2+2] cycloaddition

An enantioselective intramolecular [2+2+2] cycloaddition of 2-aminophenol-tethered triynes and diyne-nitriles proceeded using the chiral Rh catalysts, and tripodal cyclophanes and pyridinophanes with a long ansa chain (up to [16]pyridinophane) were obtained in acceptable yield with high to almost perfect ee. In the reaction of triynes, we elucidated that the oxygen atom at the alkyne terminus is essential for the excellent enantioselectivity. For the construction of cage-type molecule, the choice of rigid tether, which connects 1,6-diyne moiety with a side carbon chain having alkyne or cyano group on its terminus, was important, and 8-amino-2-naphthol moiety was also a preferable tether.     

Low-valent niobium-mediated double activation of C-F/C-H bonds: fluorene synthesis from o-arylated alpha,alpha,alpha-trifluorotoluene derivatives

By the treatment of 0.3 molar amount of NbCl5 and LiAlH4, o-arylated alpha,alpha,alpha-trifluorotoluenes afforded fluorene derivatives in good yields. C-F bonds of the CF3 group and the neighboring ortho C-H bond were doubly activated to give the coupling products.     

Large-aperture focusing of x rays with micropore optics using dry etching of silicon wafers

Large-aperture focusing of Al K(α) 1.49 keV x-ray photons using micropore optics made from a dry-etched 4 in. (100 mm) silicon wafer is demonstrated. Sidewalls of the micropores are smoothed with high-temperature annealing to work as x-ray mirrors. The wafer is bent to a spherical shape to collect parallel x rays into a focus. Our result supports that this new type of optics allows for the manufacturing of ultralight-weight and high-performance x-ray imaging optics with large apertures at low cost.     

Asymmetric Total Synthesis of Heronamides A–C: Stereochemical Confirmation and Impact of Long‐Range Stereochemical Communication on the Biological Activity

Heronamides are biosynthetically related metabolites isolated from marine‐derived actinomycetes. Heronamide C shows potent antifungal activity by targeting membrane phospholipids possessing saturated hydrocarbon chains with as‐yet‐unrevealed modes of action. In spite of their curious hypothesized biosynthesis and fascinating biological activities, there have been conflicts in regard to the reported stereochemistries of heronamides. Here, we describe the asymmetric total synthesis of the originally proposed and revised structures of heronamide C, which unambiguously confirmed the chemical structure of this molecule. We also demonstrated nonenzymatic synthesis of heronamides A and B from heronamide C, which not only proved the postulated biosynthesis, but also confirmed the correct structures of heronamides A and B. Investigation of the structure–activity relationship of synthetic and natural heronamides revealed the importance of both long‐range stereochemical communication and the 20‐membered macrolactam ring for the biological activity of these compounds.