Design and controlled emission properties of bioorganometallic compounds composed of uracils and organoplatinum(II) moieties

The bioorganometallic platinum(II) compounds PtU6 and PtU5 were designed by the conjugation of the corresponding uracil derivative and the organoplatinum(II) compound [4-octyloxy-(C^N^N)PtCl]. The single crystal X-ray structure determination of PtU6 revealed the formation of the dimeric structure through intermolecular hydrogen bonds between the uracil moieties of two independent molecules, wherein each hydrogen-bonded dimer was connected through Pt(II)-Pt(II) and π-π interactions. The tuning of the emission properties of the organoplatinum(II) compounds was achieved by changing the direction of hydrogen bonding sites and the molecular scaffold having two 2,6-dihexamidopyridine moieties as a complementary hydrogen bonding site for the uracil moiety, which depends on the regulation of the aggregated structures, to induce the Pt(II)-Pt(II) and π-π interactions.     

Prenylation of a nonaromatic carbon of indolylbutenone by a fungal indole prenyltransferase

FtmPT1 from Aspergillus fumigatus is a fungal indole prenyltransferase (PT) that normally catalyzes the regiospecific prenylation of brevianamide F (cyclo-L-Trp-L-Pro) at the C-2 position of the indole ring with dimethylallyl diphosphate (DMAPP). Interestingly, FtmPT1 exhibited remarkable substrate tolerance and accepted (E)-4-(1H-indol-3-yl)but-3-en-2-one (1) as a substrate to produce an unnatural novel α-prenylindolylbutenone (1a). This is the first demonstration of the prenylation of a nonaromatic carbon of the acceptor substrate by a fungal indole PT.     

Clarification on the Reactivity of Diaryl Diselenides toward Hexacyclohexyldilead under Light

In this study, the reactivity of organochalcogen compounds toward a representative alkyl-lead bond compound under light was investigated in detail. Under light irradiation, the Cy-Pb bond of Cy₆Pb₂ (Cy = cyclohexyl) undergoes homolytic cleavage to generate a cyclohexyl radical (Cy•). This radical can be successfully captured by diphenyl diselenide, which exhibits excellent carbon-radical-capturing ability. In the case of (PhS)₂ and (PhTe)₂, the yields of the corresponding cyclohexyl sulfides and tellurides were lower than that of (PhSe)₂. This probably occurred due to the low carbon-radical-capturing ability of (PhS)₂ and the high photosensitivity of the cyclohexyl-tellurium bond.     

Imaging of Oral SCC Cells by Raman Micro-Spectroscopy Technique

We used Raman micro-spectroscopy technique to analyze the molecular changes associated with oral squamous cell carcinoma (SCC) cells in the form of frozen tissue. Previously, Raman micro-spectroscopy technique on human tissue was mainly based on spectral analysis, but we worked on imaging of molecular structure. In this study, we evaluated the distribution of four components at the cell level (about 10 μm) to describe the changes in protein and molecular structures of protein belonging to malignant tissue. We analyzed ten oral SCC samples of five patients without special pretreatments of the use of formaldehyde. We obtained cell level images of the oral SCC cells at various components (peak at 935 cm⁻¹: proline and valine, 1004 cm⁻¹: phenylalanine, 1223 cm⁻¹: nucleic acids, and 1650 cm⁻¹: amide I). These mapping images of SCC cells showed the distribution of nucleic acids in the nuclear areas; meanwhile, proline and valine, phenylalanine, and amide I were detected in the cytoplasm areas of the SCC cells. Furthermore, the peak of amide I in the cancer area shifts to the higher wavenumber side, which indicates the α-helix component may decrease in its relative amounts of protein in the β-sheet or random coil conformation. Imaging of SCC cells with Raman micro-spectroscopy technique indicated that such a new observation of cancer cells is useful for analyzing the detailed distribution of various molecular conformation within SCC cells.     

Control of dominant conduction orbitals by peripheral substituents in paddle-wheel diruthenium alkynyl molecular junctions

Control of charge carriers that transport through the molecular junctions is essential for thermoelectric materials. In general, the charge carrier depends on the dominant conduction orbitals and is dominantly determined by the terminal anchor groups. The present study discloses the synthesis, physical properties in solution, and single-molecule conductance of paddle-wheel diruthenium complexes 1R having diarylformamidinato supporting ligands (DArF: p-R-C₆H₄-NCHN-C₆H₄-R-p) and two axial thioanisylethynyl conducting anchor groups, revealing unique substituent effects with respect to the conduction orbitals. The complexes 1R with a few different aryl substituents (R = OMe, H, Cl, and CF₃) were fully characterized by spectroscopic and crystallographic analyses. The single-molecule conductance determined by the scanning tunneling microscope break junction (STM-BJ) technique was in the 10⁻⁵ to 10⁻⁴G₀ region, and the order of conductance was 1OMe > 1CF3 ≫ 1H ∼ 1Cl, which was not consistent with the Hammett substituent constants σ of R. Cyclic voltammetry revealed the narrow HOMO–LUMO gaps of 1R originating from the diruthenium motif, as further supported by the DFT study. The DFT-NEGF analysis of this unique result revealed that the dominant conductance routes changed from HOMO conductance (for 1OMe) to LUMO conductance (for 1CF3). The drastic change in the conductance properties originates from the intrinsic narrow HOMO–LUMO gaps.

Dominant conduction orbitals of paddle-wheel organodiruthenium complexes can be facilely controlled by the substituents embedded in the amidinato ligands.     

Reconfigurable Photonic Crystal Reversibly Exhibiting Single and Double Structural Colors

Unlike absorption-based colors of dyes and pigments, reflection-based colors of photonic crystals, so called “structural colors”, are responsive to external stimuli, but can remain unfaded for over ten million years, and therefore regarded as a next-generation coloring mechanism. However, it is a challenge to rationally design the spectra of structural colors, where one structure gives only one reflection peak defined by Bragg's law, unlike those of absorption-based colors. Here, we report a reconfigurable photonic crystal that exhibits single-peak and double-peak structural colors. This photonic crystal is composed of a colloidal nanosheet in water, which spontaneously adopts a layered structure with single periodicity (407 nm). After a temperature-gradient treatment, the photonic crystal segregates into two regions with shrunken (385 nm) and expanded (448 nm) periodicities, and thus exhibits double reflection peaks that are blue- and red-shifted from the original one, respectively. Notably, the transition between the single-peak and double-peak states is reversible.     

Preparation of 2-formyl-4-nitropyrroles

The Vilsmeier reaction of 3-nitropyrroles which are prepared by the reaction of nitroalkenes with the sodium salt of tosylmethylisocyanide gives 2-formyl-4-nitropyrroles in good yields.     

Membrane-Vesicle-Mediated Interbacterial Communication Activates Silent Secondary Metabolite Production

Most bacterial biosynthetic gene clusters (BGCs) are “silent BGCs” that are expressed poorly or not at all under normal culture conditions. However, silent BGCs, even in part, may be conditionally expressed in response to external stimuli in the original bacterial habitats. The growing knowledge of bacterial membrane vesicles (MVs) suggests that they could be promising imitators of the exogenous stimulants, especially given their functions as signaling mediators in bacterial cell-to-cell communication. Therefore, we envisioned that MVs added to bacterial cultures could activate diverse silent BGCs. Herein, we employed Burkholderia multivorans MVs, which induced silent metabolites in a wide range of bacteria in Actinobacteria, Bacteroidetes and Proteobacteria phyla. A mechanistic analysis of MV-induced metabolite production in Xenorhabdus innexi suggested that the B. multivorans MVs activate silent metabolite production by inhibiting quorum sensing in X. innexi. In turn, the X. innexi MVs carrying some MV-induced peptides suppressed the growth of B. multivorans, highlighting the interspecies communication between B. multivorans and X. innexi through MV exchange.