Label-free molecular beacon system based on DNAs containing abasic sites and fluorescent ligands that bind abasic sites

A new class of label-free molecular beacon (MB) system based on DNA strands that contain abasic (AP) sites (AP-DNA) and adopt stem-loop structures, in combination with fluorescent ligands that bind these AP sites, has been developed. Unlike a conventional MB, which requires covalent labeling of the MB with a fluorophore and a quencher, the developed system (APMB) does not require covalent attachment of signal transduction units. Detailed sensing functions of a series of APMB systems were examined with the aid of the fluorescent ligand named ATMND to provide insight into the design strategy for APMB systems. The effects of the stem length and the position of the AP site in the stem moiety on the fluorescence response of the APMB system were examined. Genotyping of a G/C SNP of PCR amplification products was successfully demonstrated with the APMB system and blue-fluorescent ATMND as a ligand. The APMB system was further extended to a system that utilized green-fluorescent lumiflavin.     

Shape- and size-controlled synthesis in hard templates: sophisticated chemical reduction for mesoporous monocrystalline platinum nanoparticles

Here we report a novel hard-templating strategy for the synthesis of mesoporous monocrystalline Pt nanoparticles (NPs) with uniform shapes and sizes. Mesoporous Pt NPs were successfully prepared through controlled chemical reduction using ascorbic acid by employing 3D bicontinuous mesoporous silica (KIT-6) and 2D mesoporous silica (SBA-15) as a hard template. The particle size could be controlled by changing the reduction time. Interestingly, the Pt replicas prepared from KIT-6 showed polyhedral morphology. The single crystallinity of the Pt fcc structure coherently extended over the whole particle.     

Systematic study of protein detection mechanism of self-assembling 19F NMR/MRI nanoprobes toward rational design and improved sensitivity

(19)F NMR/MRI probe is expected to be a powerful tool for selective sensing of biologically active agents owing to its high sensitivity and no background signals in live bodies. We have recently reported a unique supramolecular strategy for specific protein detection using a protein ligand-tethered self-assembling (19)F probe. This method is based on a recognition-driven disassembly of the nanoprobes, which induced a clear turn-on signal of (19)F NMR/MRI. In the present study, we conducted a systematic investigation of the relationship between structure and properties of the probe to elucidate the mechanism of this turn-on (19)F NMR sensing in detail. Newly synthesized (19)F probes showed three distinct behaviors in response to the target protein: off/on, always-on, and always-off modes. We clearly demonstrated that these differences in protein response could be explained by differences in the stability of the probe aggregates and that "moderate stability" of the aggregates produced an ideal turn-on response in protein detection. We also successfully controlled the aggregate stability by changing the hydrophobicity/hydrophilicity balance of the probes. The detailed understanding of the detection mechanism allowed us to rationally design a turn-on (19)F NMR probe with improved sensitivity, giving a higher image intensity for the target protein in (19)F MRI.     

Carboxylic acid recognition of diamidine having a fluorescent 1,8-diphenylanthracene unit and its detection of amidinium-carboxylate and amidinium formation

A diphenylanthracene-based diamidine (1a) fluorescent probe for the detection of dicarboxylic acids has been designed and synthesized, which has an extended π-conjugation rather than a simple anthracene ring, in order to observe highly different fluorescence wavelengths after complex formation with dicarboxylic acids. The fluorescence spectra of the mixed solution of the diamidine 1a and carboxylic acids showed two different fluorescence bands, which corresponded to the complex formation (amidinium-carboxylate formation, λ_em?=?450?nm, light blue color) and dissociated amidinium formation (λ_em?=?510?nm as a broad band, green color). The complexed and dissociated states were confirmed by DOSY NMR and TD-DFT calculations. These different fluorescence wavelengths may come from the differences in the dihedral angles between the phenyl rings at the 1,8-position and anthracene ring (difference in π-conjugation) of 1a under complex formation and dissociated amidinium formation. The proposed mechanism for the observation of the different fluorescence wavelengths (complex formation and amidinium formation) was also confirmed by the fluorescence study of diamidine 1b which causes restricted rotation of the phenyl rings by substitution of the steric methyl groups, and observed the same fluorescence spectra for the complex formation and amidinium formation (400, 420, 450?nm as a vibrational structure of anthracene ring). These fluorescence characteristics of the diamidine 1a are also applicable for the detection of α,ω?dicarboxylic acids.     

ZINC TETRAPHENYLPORPHYRIN-SENSITIZED PHOTOREDUCTION OF ANTHRAQUINONESULFONATE IN AQUEOUS MICELLAR SOLUTIONS*

Abstract— Zn-tetraphenylporphyrin (ZnTPP), solubilized in non-ionic surfactant micelles, was found to sensitize photoreductions of some sodium anthraquinonesulfonatesz in the presence of ascorbic acid under anaerobic conditions. The reaction rate was increased by the addition of an anionic surfactant, while retardation was observed with a cationic surfactant. The pH-reaction rate profiles showed maxima located in the order corresponding to pK_a-values for the semiquinone of each anthraquinone-sulfonate. A reaction scheme involving the formation of ZnTPP⁺ at the primary step, followed by back-reduction with ascorbic acid, is proposed. The reaction scheme is in good agreement with the results of flash photolysis. The surfactant micelles are suggested to aid the charge-separation between the ionic species just after the redox reaction involving the photoexcited ZnTPP and anthraquinonesulfonates.     

Phase-separation and distribution of phenyl groups for PhTES-TEOS coatings prepared on polycarbonate substrate

Phenyltriethoxysilane (PhTES) and tetraethoxysilane (TEOS) coatings [xPhTES·(100 − x)TEOS (mol%)] (x = 0 − 80) were prepared on polycarbonate (PC) substrate, and adhesion, surface hardness and distribution of phenyl groups were studied. The coatings with more than 60 mol% of PhTES showed good adhesion (≈ 100%), and the pencil hardness of PC substrate (4B) improved to 2B or B after the coatings. Bulk gels with the same compositions were also prepared, and distribution of phenyl groups were estimated using fourier transform infrared (FT-IR) spectroscopy (KBr method for bulk gels and attenuated total reflection (ATR) method for coatings). A significant difference for the distribution of phenyl groups was clearly observed between bulk gels and coatings, suggesting PC substrate affects the distribution of phenyl groups in coatings. The adhesion and FTIR results revealed that there is an interaction caused by π-electrons between benzene rings on PC substrate and phenyl groups of PhTES-TEOS coatings. It was found that the adhesion was strongly correlated with the phenylsilsesquioxane networks formed around PC substrate side.     

Hyperpolarized 13C Magnetic Resonance Imaging of Fumarate Metabolism by Parahydrogen-induced Polarization: A Proof-of-Concept in vivo Study

Hyperpolarized [1-¹³C]fumarate is a promising magnetic resonance imaging (MRI) biomarker for cellular necrosis, which plays an important role in various disease and cancerous pathological processes. To demonstrate the feasibility of MRI of [1-¹³C]fumarate metabolism using parahydrogen-induced polarization (PHIP), a low-cost alternative to dissolution dynamic nuclear polarization (dDNP), a cost-effective and high-yield synthetic pathway of hydrogenation precursor [1-¹³C]acetylenedicarboxylate (ADC) was developed. The trans-selectivity of the hydrogenation reaction of ADC using a ruthenium-based catalyst was elucidated employing density functional theory (DFT) simulations. A simple PHIP set-up was used to generate hyperpolarized [1-¹³C]fumarate at sufficient ¹³C polarization for ex vivo detection of hyperpolarized ¹³C malate metabolized from fumarate in murine liver tissue homogenates, and in vivo ¹³C MR spectroscopy and imaging in a murine model of acetaminophen-induced hepatitis.     

Photo-Induced Dihydroxylation of Alkenes with Diacetyl,Oxygen, and Water

Herein reported is a photo-induced production of vicinal diols from alkenes under mild reaction conditions. The present dihydroxylation method using diacetyl (= butane-2,3-dione), oxygen, and water dispenses with toxic reagents and intractable waste generation.