Halogen versus Hydrogen Bonding in Binary Cocrystals: Novel Conformation a Coformer with [2+2] Photoreactivity of Criss-Crossed C=C Bonds

A series of cocrystals involving the hydrogen- and halogen-bond donor coformers catechol ( cat ) and 1,2-diiodotetrafluorobenzene ( 1,2-di-I-tFb ), respectively, is reported. Each coformer forms a cocrystal with each of the three symmetric bipyridines trans-1,2-bis(n-pyridyl)ethylene ( n , n′ -bpe , where: n=n′=2, 3, 4). Four novel cocrystals ( cat ) ⋅ ( 3,3′-bpe ), 2( 1,2-di-I-tFb ) ⋅ ( 2,2′-bpe ), 2( 1,2-di-I-tFb ) ⋅ ( 3,3′-bpe ), and ( 1,2-di-I-tFb ) ⋅ ( 4,4′-bpe ) comprise components that assemble by either O−H⋅⋅⋅N hydrogen bonds ( cat ) or N⋅⋅⋅I halogen bonds ( 1,2-di-I-tFb ). In ( cat ) ⋅ ( 3,3′-bpe ), cat acts as a template to support an intermolecular [2+2] photocycloaddition of 3,3′-bpe . The reactivity occurs via a one-dimensional (1D) hydrogen-bonded tape with stacked and criss-crossed olefins that react stereoselectively and quantitatively to form rctt-tetrakis(3-pyridyl)cyclobutane ( 3,3′-tpcb ). The reactivity of the criss-crossed olefins is facilitated by a hitherto not reported cis-gauche conformation adopted by cat . The stereochemistry of 3,3′-tpcb is confirmed in the cocrystal 2( cat ) ⋅ ( 3,3′-tpcb ).     

Facile preparation of polysaccharide‐coated capillaries using a room temperature ionic liquid for chiral separations

In this study, the dissolution of polysaccharides into an ionic liquid was investigated and applied as a coating onto the capillary walls of a fused‐silica capillary in open‐tubular CEC. The coating was evaluated by examining the chiral separation of two analytes (thiopental, sotalol) with three cellulose derivatives (cellulose acetate, cellulose acetate phthalate, and cellulose acetate butyrate). Baseline separation of thiopental enantiomers was achieved by use of each polysaccharide coating (Rs: 7.0, 8.1, 7.1), while sotalol provided partial resolution (Rs: 0.7, 1.0, 0.9). In addition, reproducibility of the cellulose‐coated capillaries was evaluated by estimating the run‐to‐run and capillary‐to‐capillary RSD values of the EOF. Both stability and reproducibility were very good with RSD values of less than 7%.     

The mole is an Avogadro number of entities,the macroscopic unit for chemical amount

Just as the gram is an Avogadro number of daltons, g = (g/Da) Da, the current definition of the mole can be interpreted as an Avogadro number of entities, as it is often thought of by chemists—and it should be explicitly redefined this way. By introducing a hitherto missing atomic-scale unit for the amount of any substance, the entity (symbol ent), analogous to the dalton for mass, we can then define the mole as: mol = (g/Da) ent—i.e., an Avogadro number of entities. It is argued that the name for the base quantity should be “chemical amount,” by analogy with “electric current.” Recent proposals and counterproposals for redefining the mole (and renaming “amount of substance”) are critically discussed in light of the above intuitively obvious definition.     

Supramolecular ssDNA Templated Porphyrin and Metalloporphyrin Nanoassemblies with Tunable Helicity

Free‐base and nickel porphyrin–diaminopurine conjugates were formed by hydrogen‐bond directed assembly on single‐stranded oligothymidine templates of different lengths into helical multiporphyrin nanoassemblies with highly modular structural and chiroptical properties. Large red‐shifts of the Soret band in the UV/Vis spectroscopy confirmed strong electronic coupling among assembled porphyrin–diaminopurine units. Slow annealing rates yielded preferentially right‐handed nanostructures, whereas fast annealing yielded left‐handed nanostructures. Time‐dependent DFT simulations of UV/Vis and CD spectra for model porphyrin clusters templated on the canonical B‐DNA and its enantiomeric form, were employed to confirm the origin of observed chiroptical properties and to assign the helicity of porphyrin nanoassemblies. Molar CD and CD anisotropy g factors of dialyzed templated porphyrin nanoassemblies showed very high chiroptical anisotropy. The DNA‐templated porphyrin nanoassemblies displayed high thermal and pH stability. The structure and handedness of all assemblies was preserved at temperatures up to +85 °C and pH between 3 and 12. High‐resolution transition electron microscopy confirmed formation of DNA‐templated nickel(II) porphyrin nanoassemblies and their self‐assembly into helical fibrils with micrometer lengths.     

One‐Pot Enzymatic Synthesis of Merochlorin A and B

The polycycles merochlorin A and B are complex halogenated meroterpenoid natural products with significant antibacterial activities and are produced by the marine bacterium Streptomyces sp. strain CNH‐189. Heterologously produced enzymes and chemical synthesis are employed herein to fully reconstitute the merochlorin biosynthesis in vitro. The interplay of a dedicated type III polyketide synthase, a prenyl diphosphate synthase, and an aromatic prenyltransferase allow formation of a highly unusual aromatic polyketide‐terpene hybrid intermediate which features an unprecedented branched sesquiterpene moiety from isosesquilavandulyl diphosphate. As supported by in vivo experiments, this precursor is furthermore chlorinated and cyclized to merochlorin A and isomeric merochlorin B by a single vanadium‐dependent haloperoxidase, thus completing the remarkably efficient pathway.     

Euler–Lagrange equations governing the flow of solids by extended slip with applications to plane torsion

The paper presents a variational principle based on a new physical law governing the rotationally continuous flow of a solid that flows by means of the recently identified mechanism of extended slip. The Euler–Lagrange equations derived from this principle are applied to the plane torsion problem. Theoretical results so obtained are compared to experimental measurements made using discs of cold-worked aluminium, and excellent agreement between experiment and theory is obtained. Interesting properties of plane torsion are revealed by this investigation. It is shown, for instance, that within the shear annulus in the disc, at each stage of its expansion, the rotation rate is independent of position. Moreover, if we consider the disc centre to be rotating relative to its edge, the rotation rate in the shear annulus is opposite to that in the rigid centre of the disc. At each stage, not only are the senses of rotation of the disc centre and the shear annulus opposite but the products of rotation rate and area for the two domains remain equal.     

A Degradable Sustained-Release Drug Delivery System for Bleb-Forming Glaucoma Surgery

Fibrosis of the filtering bleb is one of the main causes of failure after bleb-forming glaucoma surgery. Intraoperative application of mitomycin C (MMC) is the current gold standard to reduce the fibrotic response. However, MMC is cytotoxic and one-time application is often insufficient. A sustained-release drug delivery system (DDS), loaded with MMC, may be less cytotoxic and equally or more effective. Two degradable (polycaprolactone (PCL) and polylactic-co-glycolic acid (PLGA)) MMC-loaded DDSs are developed. Release kinetics are first assessed in vitro followed by rabbit implants in conjunction with the PRESERFLO MicroShunt. As a control, the MicroShunt is implanted with adjunctive use of a MMC solution. Rabbits are euthanized at postoperative day (POD) 28 and 90. The PLGA and PCL DDSs release (on average) 99% and 75% of MMC, respectively. All groups show functioning blebs until POD 90. Rabbits implanted with a DDS show more inflammation with avascular thin-walled blebs when compared to the control. However, collagen is more loosely arranged. The PLGA DDS shows less inflammation, less foreign body response (FBR), and more complete degradation at POD 90 when compared to the PCL DDS. Further optimization with regard to dosage is required to reduce side effects to the conjunctiva.     

Effect of Carboxymethyl Cellulose (CMC) Functionalization on Dispersion,Mechanical, and Corrosion Properties of CNT/Epoxy Nanocomposites

Carbon nanotube(CNT)/epoxy nanocomposites have a great potential of possessing many advanced properties. However, the homogenization of CNT dispersion is still a great challenge in the research field of nanocomposites. This study applied a novel dispersion agent,carboxymethyl cellulose(CMC), to functionalize CNTs and improve CNT dispersion in epoxy. The effectiveness of the CMC functionalization was compared with mechanical mixing and a commonly used surfactant, sodium dodecylbenzene sulfonate(N...