Switching of the enzymatic activity synchronized with signal recognition by an artificial DNA receptor on a liposomal membrane

We constructed a supramolecular system on a liposomal membrane that is capable of activating an enzyme via DNA hybridization. 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, providing a platform for the system, was prepared by the self-assembly of an oligonucleotide lipid, a phospholipid and a cationic synthetic lipid. The enzyme was immobilized on the liposomal surface through electrostatic interactions. Selective recognition of DNA signals was achieved by hybridizing the DNA signals with the oligonucleotide lipid embedded in the liposome. The hybridized DNA signal was sent to the enzyme by a copper ion acting as a mediator species. The enzyme then amplified the event by the catalytic reaction to generate the output signal. In addition, our system demonstrated potential for the discrimination of single nucleotide polymorphisms.     

Quinoxaline-embedded polyacenoquinone esters: synthesis, electronic properties, and crystal structure

The development of an expedient synthesis toward quinoxaline ring-embedded polyacenoquinone esters with the generic structure A is demonstrated by the synthesis of penta- and hexacenoquinone esters. They are potential n-type small molecules, capable of undergoing successive reductions and self-assembling in face-to-face π-stacks.     

Development of imaging mass spectrometry (IMS) dataset extractor software,IMS convolution

Imaging mass spectrometry (IMS) is a powerful tool for detecting and visualizing biomolecules in tissue sections. The technology has been applied to several fields, and many researchers have started to apply it to pathological samples. However, it is very difficult for inexperienced users to extract meaningful signals from enormous IMS datasets, and the procedure is time-consuming. We have developed software, called IMS Convolution with regions of interest (ROI), to automatically extract meaningful signals from IMS datasets. The processing is based on the detection of common peaks within the ordered area in the IMS dataset. In this study, the IMS dataset from a mouse eyeball section was acquired by a mass microscope that we recently developed, and the peaks extracted by manual and automatic procedures were compared. The manual procedure extracted 16 peaks with higher intensity in mass spectra averaged in whole measurement points. On the other hand, the automatic procedure using IMS Convolution easily and equally extracted peaks without any effort. Moreover, the use of ROIs with IMS Convolution enabled us to extract the peak on each ROI area, and all of the 16 ion images on mouse eyeball tissue were from phosphatidylcholine species. Therefore, we believe that IMS Convolution with ROIs could automatically extract the meaningful peaks from large-volume IMS datasets for inexperienced users as well as for researchers who have performed the analysis.     

Ring cleavage reactions of methyl α-D-allopyranoside derivatives with phenylboron dichloride and triethylsilane

In the course of our studies on the regioselective carbon-oxygen bond cleavage of the benzylidene acetal group of hexopyranosides with a reducing agent, we found that a combination of a Lewis acid and a reducing agent triggered a ring-opening reaction of the pyranose ring of methyl α-D-allopyranosides. The formation of an acyclic boronate ester by the attachment of a hydride ion at C-1 indicated that the unexpected endocyclic cleavage of the bond between the anomeric carbon atom and the pyranose ring oxygen atom proceeded via an oxacarbenium ion intermediate produced by the chelation between O5/O6 of the pyranoside and the Lewis acid, followed by nucleophile substitution with a hydride ion at C1.     

The experimental visualisation of molecular structural changes during both photochemical and thermal reactions by real-time vibrational spectroscopy

Have you ever hoped to observe transition states? Chemists have long desired to monitor the deformation of molecular structures via transition states to understand the mechanisms of complicated reactions. Detailed knowledge of transition states helps find strategies to develop novel reaction schemes for introducing new functionalities to chemicals. Molecular structural changes via transition states can be observed by real-time vibrational spectroscopy using sub-5 fs laser pulses. In this paper, I report the direct observation of time-dependent frequency shifts of relevant molecular vibrational modes, which allowed for the clear visualization of ultrafast structural changes in molecules during bond breaking and bond reformation steps. Various mechanisms for photochemical reactions were clarified using sub-5 fs laser pulses. Moreover, a non-thermal vibrational excitation method for efficiently driving chemical reactions in the electronic ground state in solution with the use of broadband visible sub-5 fs laser pulses has been developed. The respective chemical reaction processes were directly observed, including transition states during not only "photochemical" but also "thermal" reactions. Time-resolved spectroscopy with a time resolution of a few femtoseconds enables observation of real-time vibrational amplitudes of complicated molecules and opens up new ways for clarifying reaction mechanisms and developing new chemical transformations.     

Stereoselective [3,3]-sigmatropic rearrangement promoted by the metal [1,3]-shift of binuclear Fischer carbene complexes

Reaction of chiral homobinuclear Fischer chromium carbene complexes with allyl alcohol in the presence of NaH and the following oxidative demetalation gave alpha-allyl esters in up to 97% ee via [3,3]-sigmatropic rearrangement reaction promoted by the metal 1,3-shift. On the other hand, chiral heterobinuclear tungsten carbene complexes with arene chromium complexes afforded alpha-allyl-beta-hydroxy esters as a major product in up to 92/8 dr by the same reaction sequence.     

Total Synthesis of Vancomycin Aglycon—Part 3: Final Stages

A triazene-based synthetic strategy for the construction of the complex biaryl ethers and a Suzuki coupling reaction were the key steps in the synthesis of precursor 1 of the aglycon of vancomycin, which already contains the complete skeleton of the target compound. The cleavage of the triazene unit from the D ring and the removal of the other protecting groups led to the aglycon of vancomycin. These strategies should be particularly valuable for the synthesis of other naturally occurring glycopeptide antibiotics and offer opportunities for the synthesis of combinatorial libraries of compounds of the vancomycin family for chemical biology studies.     

Heat transfer and thermographic analysis of catalyst surface during multiphase phenomena under spray-pulsed conditions for dehydrogenation of cyclohexane over Pt catalysts

Dehydrogenation of cyclohexane over Pt/alumite and Pt/activated carbon catalysts has been carried out for hydrogen storage and supply to fuel cell applications. An unsteady state has been created using spray pulsed injection of cyclohexane over the catalyst surface to facilitate the endothermic reaction to occur efficiently. Higher temperature of the catalyst surface is more favorable for the reaction, thus the heat transfer phenomena and temperature profile under alternate wet and dry conditions created using spray pulsed injection becomes important. IR thermography has been used for monitoring of temperature profile of the catalyst surface simultaneously with product analysis. The heat flux from the plate-type heater to the catalyst has been estimated using a rapid temperature recording and thermocouple arrangement. The estimated heat flux under transient conditions was in the range of 10-15 kW/m(2), which equates the requirement for endothermic reactions to the injection frequency of 0.5 Hz, as used in this study. The analysis of temperature profiles, reaction products over two different supports namely activated carbon cloth and alumite, reveals that the more conductive support such as alumite is more suitable for dehydrogenation of cyclohexane.