Correlations between the number of thiophene units and the photovoltaic behavior of fluorene–oligothiophene copolymers

The photophysical and photovoltaic properties of three alternated fluorene–thiophene copolymers were studied. With similar structure the copolymers differed by the numbers of thiophene units linked to each fluorene group:one, two and three. The electronic properties were analyzed through mobility measurements and the overall properties pointed out to the one containing the three rings as the best material, as anticipated, due to the larger number of thiophene units. However, after thermal annealing the polymer containing two thiophene rings presented the best photovoltaic efficiency, seven fold greater than the pristine material. The morphology, studied by atomic force microscopy, revealed to be one of the key factors for the performance of the materials as solar cells.     

Cyclodextrin-based liquid chromatographic enantiomeric separation of chiral dihydrofurocoumarins, an emerging class of medicinal compounds

A set of 28 racemic dihydrofurocoumarins in which the stereogenic center is located in the furan ring have been synthesized. Currently no effective asymmetric synthesis of this class of compounds exists, although their enantiomers are produced biologically by certain plants. Their diverse medicinal properties are being investigated in several laboratories. The enantioselective separation of these dihydrofurocoumarins by three native and six derivatized cyclodextrins has been evaluated in the reversed-phase mode, the polar organic mode, and normal-phase mode. The hydroxypropyl-beta-cyclodextrin is the most effective chiral stationary phase (CSP) at separating the dihydrofurocoumarins into enantiomers, showing some enantioselectivity for 22 dihydrofurocoumarins, and baseline resolving 16 of the 28 compounds in the reversed-phase mode. The acetyl-beta-cyclodextrin and 2,3-dimethyl-beta-cyclodextrin also showed enantioselectivity for a large number (18 and 17, respectively) of dihydrofurocoumarins in the reversed-phase mode. The native cyclodextrins are ineffective and the aromatic derivatized beta-cyclodextrins are only marginally effective at separating the furocoumarin enantiomers in the reversed-phase mode. The polar organic mode and the normal-phase mode have also been evaluated with these CSPs, but no enantioseparations were observed.     

Charge‐Assisted Halogen Bonding: Donor–Acceptor Complexes with Variable Ionicity

Charge‐assisted halogen bonding is unambiguously revealed from structural and electronic investigations of a series of isostructural charge‐transfer complexes derived from iodinated tetrathiafulvalene and tetracyanoquinodimethane derivatives, (EDT‐TTFI₂)₂(TCNQF_n), n=0–2, which exhibit variable degrees of ionicity. The iodinated tetrathiafulvalene derivative, EDT‐TTFI₂, associates with tetracyanoquinodimethane (TCNQ) and its derivatives of increasing reduction potential (TCNQF, TCNQF₂) through highly directional C? I???N≡C halogen‐bond interactions. With the less oxidizing TCNQ acceptor, a neutral and insulating charge‐transfer complex is isolated whereas with the more oxidizing TCNQF₂ acceptor, an ionic, highly conducting charge‐transfer salt is found, both of 2:1 stoichiometry and isostructural with the intermediate TCNQF complex, in which a neutral–ionic conversion takes place upon cooling. A correlation between the degree of charge transfer and the C? I???N≡C halogen‐bond strength is established from the comparison of the structures of the three isostructural complexes at temperatures from 300 to 20 K, thus demonstrating the importance of electrostatics in the halogen‐bonding interaction. The neutral–ionic conversion in (EDT‐TTFI₂)₂(TCNQF) is further investigated through the temperature dependence of its magnetic susceptibility and the stretching modes of the C≡N groups.     

New approach for the clinical monitoring of 25‐hydroxyvitamin D3 and 25‐hydroxyvitamin D2 by ultra high performance liquid chromatography with MS/MS based on the standard reference material 972

Biomarkers, 25‐hydroxyvitamin D₃ and 25‐hydroxyvitamin D₂, are important indicators of the vitamin D general status and are monitored in several pathophysiological disorders, such as osteoporosis, diabetes, heart disease, etc. A novel ultra‐HPLC with MS/MS methodology for the analysis of 25‐hydroxyvitamin D derivatives coupled with a very simple and highly rapid sample preparation step was developed. Analytical parameters obtained showed linearity (R²) above 0.999 for both vitamins with accuracies between 95.8 and 102%. The LODs were as low as 0.22 and 0.67 nmol/L for 25‐hydroxyvitamin D₃ and 25‐hydroxyvitamin D₂, respectively. Intra‐assay precision (%RSD) was lower than 4.5%, and inter‐assay precision (%RSD) was lower than 6.5%. The feasibility of the developed methodology to be applied in clinical routine analysis has been proved by its application in blood samples from non‐agenarian patients, patients with familial hypercholesterolemia and patients suffering from age‐related macular degeneration.     

Cyst Reduction by Melatonin in a Novel Drosophila Model of Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) causes progressive cystic degeneration of the renal tubules, the nephrons, eventually severely compromising kidney function. ADPKD is incurable, with half of the patients eventually needing renal replacement. Treatments for ADPKD patients are limited and new effective therapeutics are needed. Melatonin, a central metabolic regulator conserved across all life kingdoms, exhibits oncostatic and oncoprotective activity and no detected toxicity. Here, we used the Bicaudal C (BicC) Drosophila model of polycystic kidney disease to test the cyst-reducing potential of melatonin. Significant cyst reduction was found in the renal (Malpighian) tubules upon melatonin administration and suggest mechanistic sophistication. Similar to vertebrate PKD, the BicC fly PKD model responds to the antiproliferative drugs rapamycin and mimics of the second mitochondria-derived activator of caspases (Smac). Melatonin appears to be a new cyst-reducing molecule with attractive properties as a potential candidate for PKD treatment.     

Complex Pore Structure of Mesoporous Zeolites: Unambiguous TEM Imaging Using Platinum Tracking

The article proposes a new way for visualization of mesopores and quantitative evaluation of the pore structure in zeolite crystals. The approach is based on platinum tracking inside the zeolite material after its incorporation from a gaseous precursor using an electron beam prior to preparing a TEM specimen by the focused ion beam technique. The pores in mesoporous silica and purely microporous zeolite Y were visualized in TEM images in a demonstration of the capabilities of the approach. Finally, platinum tracking was used for studying the pore structure of zeolite Y (CBV 720) containing mesopores both inside the crystal and those emerging at its surface, which were unambiguously distinguished from each other. The obtained sizes of the mesopores and the calculated material porosity are in good agreement with the results obtained by the low-temperature argon sorption isotherms method.     

Ruthenium tetrazene complexes bearing glucose moieties on their periphery: Synthesis,characterization, and in vitro cytotoxicity

Ruthenium tetrazene complexes with general formula [Cp*RuCl(1,4-R₂N₄)] (Cp* = η⁵-C₅Me₅), where R = benzyl ( 1 ), 2-fluorobenzyl ( 2 ), β-d -glucopyranosyl-unprotected ( 3a ) and acyl-protected ( 3b – d ), 2-acetamido-β-d -glucopyranosyl-unprotected ( 4a ) and acyl-protected ( 4b – d ), propyl-β-d -glucopyranoside-unprotected ( 5a ), and O-acetylated ( 5b ), were synthesized and characterized using nuclear magnetic resonance and electrospray ionization–mass spectrometry. In addition, the molecular structure of 3b was determined using X-ray crystallography. The cytotoxicity of complexes against ovarian (A2780, SK-OV-3) and breast (MDA-MB-231) cancer cell lines and noncancerous cell line HEK-293 was evaluated and compared to cisplatin activity. The carbohydrate-modified complexes bearing acyl-protecting groups exhibited higher efficacy (in low micromolar range) than unprotected ones, where the most active 4d was superior to cisplatin up to five times against all investigated cancer cell lines; however, no significant selectivity was achieved. The complex induced apoptotic cell death at low micromolar concentrations (0.5 μM for A2780 and HEK293; 2 μM for SK-OV-3 and MDA-MB-231).     

Structure of Supramers Formed by the Amphiphile Biotin-CMG-DOPE

The synthetic function-spacer-lipid (FSL) amphiphile biotin-CMG-DOPE is widely used for delicate ligation of living cells with biotin residues under physiological conditions. Since this molecule has an “apolar-polar-hydrophobic” gemini structure, the supramolecular organization is expected to differ significantly from the classical micelle. Its organization is investigated with experimental methods and molecular dynamics simulations (MDS). Although the linear length of a single biotin-CMG-DOPE molecule is 9.5 nm, the size of the dominant supramer globule is only 14.6 nm. Investigations found that while the DOPE tails form a hydrophobic core, the polar CMG spacer folds back upon itself and predominantly places the biotin reside inside the globule or planar layer. MDS demonstrates that <10 % of biotin residues on the highly water dispersible globules and only 1 % of biotin residues in layer coatings are in an linear conformation and exposing biotin into the aqueous medium. This explains why in biotin-CMG-DOPE apolar biotin residues both in water dispersible globules and coatings on solid surfaces are still capable of interacting with streptavidin.     

Amphiphilic water soluble cationic ring opening metathesis copolymer as an antibacterial agent

Bacterial infection is a global problem, especially resistance acquired by bacteria against to antibiotics; there is urgent need for the development of antibiotics. Here, we proposed dendron-grafted polymers via ring opening metathesis polymerization (ROMP) featuring different with tailored hydrophobicity/hydrophilicity and cationic charges. Dendritic oxanorbornene derivatives were synthesized having two and six carbon linkers and their corresponding random and block copolymers were prepared having pendant pyridinium salt moieties via ROMP. In total, 12 different water-soluble dendronized cationic polymers featuring hexyl pyridinium moieties were prepared and investigated. Six carbon linker possessing triple charge density and hexyl pyridinium functionality each repeating unit copolymers exhibited high antibacterial activity against Gram-positive bacteria (S. aureus). However, all the polymers were inactive against Gram-negative bacteria (E. coli). Most of the copolymers are non-hemolytic (>HC ₅₀ = 1,000 μg/ml). It was also observed that, there is no significant effect between block copolymers and random copolymers keeping hydrophobicity and cationic charge density constant. Zeta potential was measured to investigate the mechanism in solution via the interaction of polymers with S. aureus, while scanning electron microscope (SEM) measurements image confirms damage of the bacterial cell wall after implementation of biocidal polymer.