Highly Asymmetrical Porphyrins with Enhanced Push–Pull Character for Dye‐Sensitized Solar Cells

A porphyrin π‐system has been modulated by enhancing the push–pull character with highly asymmetrical substitution for dye‐sensitized solar cells for the first time. Namely, both two diarylamino moieties as a strong electron‐donating group and one carboxyphenylethynyl moiety as a strong electron‐withdrawing, anchoring group were introduced into the meso‐positions of the porphyrin core in a lower symmetrical manner. As a result of the improved light‐harvesting property as well as high electron distribution in the anchoring group of LUMO, a push–pull‐enhanced, porphyrin‐sensitized solar cell exhibited more than 10 % power conversion efficiency, which exceeded that of a representative highly efficient porphyrin (i.e., YD2)‐sensitized solar cell under optimized conditions. The rational molecular design concept based on highly asymmetric, push–pull substitution will open the possibilities of further improving cell performance in organic solar cells.     

Strong aggregation and directional assembly of aromatic oligoamide macrocycles

Aromatic oligoamide macrocycles exhibit strong preference for highly directional association. Aggregation happens in both nonpolar and polar solvents but is weakened as solvent polarity increases. The strong, directional assembly is rationalized by the cooperative action of dipole-dipole and π-π stacking interactions, leading to long nanotubular assemblies that are confirmed by SEM, TEM, AFM, and XRD. The persistent nanotubular assemblies contain non-collapsible hydrophilic internal pores that mediate highly efficient ion transport observed with these macrocycles and serve as cylindrical sites for accommodating guests such as metal ions.     

An enzymatic assay of chloramphenicol coupled with fluorescence reaction

An alternative method for the assay of chloramphenicol using an enzymatic reaction coupled with a fluorescence detection system has been developed. Chloramphenicol was enzymatically acetylated by chloramphenicol acetyltransferase in the presence of acetyl-coenzyme A (acetyl-CoA) as the acetyl-donor, after which the liberated CoA-SH was derivatized with a fluorogenic reagent, 4-(aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole. The assay was linear over the range of 2.5-40 micrograms/ml. Analytical recoveries of chloramphenicol at concentrations of 7.5 and 22.5 micrograms/ml, added to human serum, plasma, or a slightly hemolyzed serum, were in the range of 93.3 to 106.2%. The enzymatic assay was not affected by the presence of ten other antibiotics tested.     

Potassium-selective membrane electrodes based on macrocyclic metacyclophanes analogous to calixarenes.

The tetrabutyl ester derived from 9,16,25,32-tetrahydroxy[3.1.3.1]metacyclophane was an excellent ionophore for constructing a K+-selective membrane electrode. This ionophore exhibited a much higher selectivity toward K+ than the structurally similar potassium ionophore IV commercially available from Fluka. In particular, the interference from organic ammonium ions decreased remarkably. Potassium ionophore IV possessed oxygen atoms in the ring structure, while the present ionophore changed the oxygen atoms to carbon atoms. Thus, the removal of oxygen atoms in ring constituents of the metacyclophane acted to reduce the interaction with the NH3+ group of organic ammonium ions. The size of the cavity of the present ionophore was between those of calix[4]arene and calix[6]arene derivatives, which act as Na+ and Cs+ ionophores, respectively, demonstrating that the ability to recognize alkali metal cations was strongly cavity size-dependent. The present K+-selective electrode had less interference from Rb+ and Cs+ than an electrode constructed using valinomycin, but suffered greater interference from Na+.     

Highly conducting transmembrane pores formed by aromatic oligoamide macrocycles

Oligoamide macrocycles 1d and 1e, which carry membrane-compatible side chains and contain a hydrophilic, noncollapsible cavity, were found to mediate high ion flux across a lipid bilayer, as demonstrated by results from (23)Na NMR and planar bilayer conductance measurements. The measured transmembrane single channel currents are very high, rivaling those typically associated with pore-forming protein toxins. The obtained results have demonstrated the promise of developing large, highly conducting channels based on nanopores formed by oligoamide macrocycles.     

Determination of Penicillins in Milk by a Dual-Optrode Biosensor

Penicillins are the most frequently found antibiotic residues in milk, as they are commonly used for the treatment of bacterial infections in cows. In the present study, we introduce a method for the rapid detection of penicillin residues in raw milk based on the determination of glucose concentration in milk with a dual flow-through biosensor. The molar concentration of glucose in milk is typically over 500 times lower than the concentration of lactose and is highly dependent on the rate of lactose hydrolysis, which is catalyzed by β-galactosidase. Glucose concentrations in milk change with variation in the β-galactosidase activity. β-Galactosidase is an enzyme produced in the microbiota in milk and its activity is inhibited by benzylpenicillin. Spiking milk with benzylpenicillin lowers glucose concentrations in comparison to high-quality milk after short storage intervals. The presence of penicillin in the milk of treated animals resulted in decreased glucose concentrations in comparison with high-quality milk that contained no antibiotics. The glucose concentration in milk samples was followed by the system enabling the elimination of the effects of bacterial respiration in the output with reliable results in less than 1?min.     

Energy exchange network of inter‐residue interactions within a thermally fluctuating protein molecule: A computational study

Protein function is regulated not only by the structure but also by physical dynamics and thermal fluctuations. We have developed the computer program, CURrent calculation for proteins (CURP), for the flow analysis of physical quantities within thermally fluctuating protein media. The CURP program was used to calculate the energy flow within the third PDZ domain of the neuronal protein PSD‐95, and the results were used to illustrate the energy exchange network of inter‐residue interactions based on atomistic molecular dynamics simulations. The removal of the α3 helix is known to decrease ligand affinity by 21‐fold without changing the overall protein structure; nevertheless, we demonstrated that the helix constitutes an essential part of the network graph. © 2015 Wiley Periodicals, Inc.     

Pyrene‐Based Y‐shaped Solid‐State Blue Emitters: Synthesis,Characterization, and Photoluminescence

A series of pyrene‐based Y‐shaped blue emitters, namely, 7‐tert‐butyl‐1,3‐diarylpyrenes 4 were synthesized by the Suzuki cross‐coupling reaction of 7‐tert‐butyl‐1,3‐dibromopyrene with a variety of p‐substituted phenylboronic acids in good to excellent yields. These compounds were fully characterized by X‐ray crystallography, UV/Vis absorption and fluorescence spectroscopy, DFT calculations, thermogravimetric analysis, and differential scanning calorimetry. Single‐crystal X‐ray analysis revealed that the Y‐shaped arylpyrenes exhibited a low degree of π stacking owing to the steric effect of the bulky tert‐butyl group in the pyrene ring at the 7‐position, and thus, the intermolecular π–π interactions were effectively suppressed in the solid state. Despite the significantly twisted nonplanar structures, these molecules still displayed efficient intramolecular charge‐transfer emissions with clear solvatochromic shifts on increasing solvent polarity. An intriguing fact is that all of these molecules show highly blue emissions with excellent quantum yields in the solid state. Additionally, the two compounds containing the strongest electron‐accepting groups, CN ( 4d ) and CHO ( 4f ), possess high thermal stability, which, together with their excellent solid‐state fluorescence efficiency, makes them promising potential blue emitters in organic light‐emitting device applications.     

Remarkable effect of hydrogen bonding between ring and axle components on deslipping reactions of rotaxanes

A series of rotaxanes 1·5, 2·5, 3·5, and 4·5 bearing a different substituent (X = NO₂, Br, H, and OMe, respectively) at para position on the phenol moiety of the ring component exhibit clear difference in deslipping behavior. The difference in the deslipping rates is consistent with the difference in intercomponent hydrogen bonding strength estimated from the O-H stretching vibration wavenumbers. The para substituent dictates the relative strength of the intra- and intermolecular hydrogen bonds. Thus the incorporation of an intramolecular hydrogen bond allows for tunability of the strength of the intercomponent interaction.