Dominant factors affecting the pressure dependence of melting temperatures in homologous series of aliphatic polyesters

The pressure dependence of the melting temperature of six aliphatic polyesters belonging to two different homologous series, poly(x-succinate) and poly(x-adipate) having even number of methylene groups (2,4,6) in the alkylene segment (x) was investigated by high pressure differential thermal analysis (HP-DTA) up to 500 MPa. The phase diagrams of these polyesters were newly determined except for poly(ethylene adipate). The dT_m/dp_o at atmospheric pressure was obtained from the quadratic equation and the trend of dT_m/dp_o with respect to the number of methylene groups in the monomer unit in each homologous series is discussed. Amorphous densities at 25 °C, expansion and compressibility coefficients in the melt of these polyesters are also reported. The entropy of fusion (ΔS_m), enthalpy of fusion (ΔH_m), volume change on melting (ΔV_m), conformational entropy (ΔS^or) and volume entropy (ΔS^v) were correlated with respect to the number of methylene groups in the alkylene segment. ΔV_m and ΔS^v displayed a similar trend as that of dT_m/dp_o while ΔS_m, ΔS^or and ΔH_m showed an increasing trend. The influence of these parameters on dT_m/dp_o is discussed in the context of the Clapeyron equation.     

Enhanced bile canaliculi formation enabling direct recovery of biliary metabolites of hepatocytes in 3D collagen gel microcavities

Analysis of biliary metabolites is essential to predict pharmacokinetics and hepatotoxicity during drug development. In this paper, we present a hepatocyte culture configuration that enables the direct recovery of bile acid that accumulates in bile canaliculi by embedding the hepatocytes in a 3D micropatterned collagen gel substrate. We investigated the formation of bile canaliculi in hepatocytes embedded in circular microcavities of various sizes and made from collagen gel. Image analyses using fluorescently labeled bile acid revealed that the area of bile canaliculi in embedded hepatocytes in a microcavity of 60 or 80 μm in diameter was enlarged when compared with other sized microcavities and those of hepatocytes cultured using conventional hepatocyte sandwich cultures. We successfully recovered bile acid from the enlarged bile canaliculi of hepatocytes cultured in microcavities using a glass capillary and quantified the amount recovered. Using our approach, the direct recovery of biliary metabolites, using hepatocyte cultures with enhanced biliary excretion and geometrically enlarged bile canaliculi, may enable accurate screening of pharmacokinetics and drug-drug interactions against drug transporters.     

Imidazo[1,5-a]pyridine-1-ylalkylalcohols: synthesis via intramolecular cyclization of N-thioacyl 1,2-aminoalcohols and their silyl ethers and molecular structures

Iodine-mediated cyclization of N-thioacyl 1,2-aminoalcohols derived from aromatic aldehydes and ketones mainly produced bis(1-imidazo[1,5-a]pyridyl)arylmethanes, whereas the reaction of N-thioacyl 1,2-aminoalcohols derived from aliphatic aldehydes and N-thioacyl 1,2-aminoalcohols protected with a silyl group with iodine gave imidazo[1,5-a]pyridine-1-ylalkylalcohols as a major product.     

Formation of positive and negative anisotropic holographic gratings depending on recording energy in photoreactive liquid crystalline copolymer films

Anisotropic diffractive gratings formed by birefringent molecular alignment are fabricated by a holographic technique using a photo-cross-linkable liquid crystalline copolymer (PLCCP). Depending on the exposure energy used for holographic recording, bright or dark regions of the interference fringe can be chosen for the molecular-aligned region, analogous to positive- and negative-type photoresist processing in photolithography. In conjunction with simultaneously generated surface relief gratings, the anisotropic refractive index modulation inherent in the PLCCP film exhibits different diffraction properties depending on the incident beam polarization. The anisotropic refractive index grating profiles are quantitatively presented for two cases determined by the exposure energy, based on the Fourier analysis of diffractive optics. The selection of different grating formations selected by varying only the exposure energy could provide a strategy for the fabrication of functionalized diffractive optical elements.     

Concise total synthesis of (-)-myxalamide A

The MIDA touch: A concise and highly convergent protecting-group-free total synthesis of (-)-myxalamide?A involves a stereoselective vinylogous Mukaiyama aldol reaction of a vinylketene silyl N,O-acetal, together with a one-pot Stille/Suzuki-Miyaura cross-coupling reaction using Burke's N-methyliminodiacetic acid (MIDA) boronate to connect left- and right-hand fragments of the molecule (see scheme).     

Specific uptake of aromatic compounds from aqueous solution by montmorillonite modified with tetraphenylphosphonium

Montmorillonite (MT) modified with tetraphenylphosphonium (TPP·MT) had specific uptake behavior for aromatics in aqueous solution. This is attributed to the extent of π–π stacking interactions between the benzene rings of intercalated TPP⁺ and the benzene rings of aromatics with different electronic states. The uptake order of aromatics by TPP·MT was in contrast to that by layered double hydroxide (LDH) intercalated with 2,7-naphthalene disulfonate. The selective uptake of target aromatic compounds from aqueous solution can be achieved by combining appropriate inorganic layered compounds and modified aromatic ions.     

Photoreprogrammable dual-function grating based on photochromism and selective metal deposition

We introduce photoreprogrammable dual-function gratings, which show different diffraction in transmission and reflection. Parallel metal lines on the photochromic diarylethene (DAE) surface were prepared by selective metal deposition, enabling one-dimensional diffraction in transmission and reflection. Then, another isomerization pattern was programmed on the DAE layer by light irradiation. This grating generated unique diffraction: one-dimensional diffraction in the reflection but two-dimensional diffraction in the transmission, and a dual-function grating was achieved. This programmed state on the DAE layer could be erased by UV irradiation and could be reprogrammed to generate different diffraction by visible laser scanning. This result shows the great potential of the photoreprogrammable dual-function grating as a key element in various future optical devices and systems.     

Concise total synthesis of calothrixins A and B

The concise total synthesis of calothrixins A and B has been accomplished by utilizing the one-pot formation of hexatriene as a key intermediate via the palladium-catalyzed tandem cyclization/cross-coupling reaction of triethyl(indol-2-yl)borate. In another key transformation, the indolo[3,2-j]phenanthridine core was prepared in high yield via Cu(I)-mediated 6π-electrocyclization.     

Spontaneous and selective CO2 sorption under ambient conditions in seemingly nonporous molecular crystal of azacalix[5]arene pentamethyl ether

Described are the syntheses, crystal structures, and solid-gas adsorption behaviors of azacalix[4]arene tetramethyl ether and azacalix[5]arene pentamethyl ether. While the former compound exhibited no adsorption of four main atmospheric components, the latter selectively and rapidly adsorbed CO(2) at ambient temperature and pressure. X-ray crystallographic and potential energy distribution analysis revealed that azacalix[5]arene created an energetically favorable space for CO(2) in its seemingly nonporous crystal, leading to the observed selective CO(2) uptake under ambient conditions.     

Thermodynamic stability of Hoogsteen and Watson-Crick base pairs in the presence of histone H3-mimicking peptide

We found that Hoogsteen base pairs were stabilized by molecular crowding and a histone H3-mimicking peptide, which was not observed for Watson-Crick base pairs. Our findings demonstrate that the type of DNA base pair is critical for the interaction between DNA and histones.