Dual Esterase‐ and Steroid‐Responsive Energy Transfer Modulation of Ruthenium(II) and Rhenium(I) Complex Functionalized Gold Nanoparticles

A number of adamantane‐containing ruthenium(II) and rhenium(I) complexes have been synthesized, characterized, and noncovalently functionalized with β‐cyclodextrin‐capped gold nanoparticles (β‐CD–GNPs) through the host–guest interaction between cyclodextrin and adamantane. The resultant nanoconjugates have been characterized by transmission electron microscopy (TEM), energy‐dispersive X‐ray analysis (EDX), and 2D ROESY ¹H NMR experiments. The Förster resonance energy transfer (FRET) properties of the nanoconjugates can be modulated by both esterase‐accelerated hydrolysis and competitive displacement of steroid, by monitoring the emission intensity and luminescence lifetime. The FRET efficiencies are found to vary with the nature of the chromophores and the length of the spacer between the transition metal complexes and the GNPs. This work constitutes a “proof‐of‐principle” assay method for the dual‐functional detection of important classes of biomolecules, such as enzymes and steroids.     

Cleavage of a PN Bond in a Urea‐Containing (Ph2P(R)PPh2)‐Bridged Dinuclear Gold(I) Thiolate Complex by Fluoride and a Mechanistic Insight

A urea‐containing, (Ph₂P(R)PPh₂)‐bridged, dinuclear, gold(I) thiolate complex, [Au₂{Ph₂PN(C₆H₄OMe‐4)PPh₂}(SC₆H₄NHCONHC₆H₅)₂] ( 1 ) was designed and synthesized and its photophysical and anion recognition properties studied. The results show that 1 has a high selectivity toward F^?. Upon addition of F^?, the yellow solution was decolorized, and drastic changes of emission and ¹H and ³¹P{¹H} NMR signals were observed. Interestingly, these changes are attributed to fluoride‐assisted P?N bond hydrolysis, instead of the expected hydrogen‐bonding interactions with the urea receptor. Similar changes were observed for two other basic anions, AcO^? and H₂PO₄^?, but to a much lesser extent; and these anions were found to bind to the urea receptor at the same time. On the other hand, Cl^? was found to only bind to the urea moiety through hydrogen‐bonding interactions. Further studies with the control complex [Au₂{Ph₂PN(C₆H₄OMe‐4)PPh₂}Cl₂] ( 2 ) indicate that F^? assists the hydrolysis process via cleavage of the P?N bond. DFT calculations were performed to study the reaction mechanism for the fluoride‐assisted P?N bond hydrolysis of 2 ; these provide a better insight into the role of fluoride in the hydrolysis.     

Nonlinear Taylor stability of viscoelastic fluids

Using Stuart's energy method, the torque on the inner cylinder, for a second order fluid, in the supercritical regime is calculated. It is found that when the second normal stress difference is negative, the flow is more stable than for a Newtonian fluid and the torque is reduced. If the second normal stress difference is positive, then the flow is more stable and there is no torque reduction. Experimental data related to the present work are discussed.Nomenclature a amplitude of the fundamentals - A _ij ⁽¹⁾ , A _ij ⁽²⁾ first and second Rivlin-Ericksen tensors - d r ₂–r ₁ - D d/dx - E - F - g _ij metric tensor - G torque on the inner cylinder in the supercritical regime - h height of the cylinders - k ₀ /d ² - k ₁ /d ² - I ₁ - I ₂ - I ₃ - I ₄ - r ₁, r ₂ radii of inner and outer cylinders respectively - r ₀ 1/2(r ₁+r ₂) - R Reynolds number ₁ r ₁ d/ ₀ - R _c critical Reynolds number - T Taylor number r _{1 1} ² d ^{3 2}/ ₀ ² *) - T _c critical Taylor number - u ₁, v ₁, w ₁ Fundamentals of the disturbance - u _i , v _i , w _i , (i>1) harmonics - mean velocity (not laminar velocity) - u –u ₁/ar _{1 1} - v v ₁/Rar _{1 1} - x (r–r ₀)/d - , material constants - 0 viscosity - wave number d - density - ₁ angular velocity of inner cylinder - tilde denotes complex conjugate     

Eluent-Induced Separation of Inorganic Cations in Capillary Liquid Chromatography with Contactless Conductivity Detector

A non-suppressed contactless conductivity detector has been used as a capillary detector in a capillary ion chromatograph, combining a reversed-phase C30 column permanently modified with ionic surfactant. The C30 column (100 × 0.32 mm. id) was modified with sodium dodecyl sulfate (SDS) for the separation of inorganic cations. Monovalent cations could be separated by the proposed system, in which methanesulfonic acid (MSA) and SDS were employed as the mobile phase component, but divalent cations could not be eluted under this condition. As for the case of SDS used as the eluent, an H⁺-cation-exchange column was placed before the sample injector to convert the Na⁺ from the eluent into H⁺, and when the mixture of MSA and dodecyl sulfuric acid was used as the eluent, the retention of cations was improved and baseline separation of the cations was achieved within 23 min. The effect of the eluent composition on the retention behavior of inorganic cations was investigated. The repeatability of retention time and peak height varied from 0.39 to 0.58 and 2.21 to 3.25 % as relative standard deviation, respectively.

     

Increased stability and size of a bubble on a superhydrophobic surface

Computational and theoretical models of millimeter-sized bubbles placed on upright hydrophobic and superhydrophobic surfaces are compared with experimental data here. Although the experimental data for a hydrophobic surface corroborated the computational and theoretical data, the case of a superhydrophobic surface showed the bubbles to be able to contain significantly larger volumes than predicted. This is attributed to the greater ability of the bubble contact line to advance compared with its tendency to detach from the surface because of buoyancy. We surmise that a static model therefore describes only an unstable equilibrium for these bubbles, which unless heavily isolated from external influences are more likely to assume a larger stable size.     

Photoelectron spectroscopy of the molecular anions, Li3O- and Na3O-

The molecular anions, Li(3)O(-) and Na(3)O(-) were produced by laser vaporization and studied via anion photoelectron spectroscopy. Li(3)O(-) and Na(3)O(-) are the negative ions of the super-alkali neutral molecules, Li(3)O and Na(3)O. A two-photon process involving the photodetachment of electrons from the Li(3)O(-) and Na(3)O(-) anions and the photoionization of electrons from the resulting Li(3)O and Na(3)O neutral states was observed. The assignment of the Li(3)O(-) photoelectron spectrum was based on computational results provided by Zein and Ortiz [J. Chem. Phys. 135, 164307 (2011)].     

Ensembles of engineered cardiac tissues for physiological and pharmacological study: heart on a chip

Traditionally, muscle physiology experiments require multiple tissue samples to obtain morphometric, electrophysiological, and contractility data. Furthermore, these experiments are commonly completed one at a time on cover slips of single cells, isotropic monolayers, or in isolated muscle strips. In all of these cases, variability of the samples hinders quantitative comparisons among experimental groups. Here, we report the design of a "heart on a chip" that exploits muscular thin film technology--biohybrid constructs of an engineered, anisotropic ventricular myocardium on an elastomeric thin film--to measure contractility, combined with a quantification of action potential propagation, and cytoskeletal architecture in multiple tissues in the same experiment. We report techniques for real-time data collection and analysis during pharmacological intervention. The chip is an efficient means of measuring structure-function relationships in constructs that replicate the hierarchical tissue architectures of laminar cardiac muscle.     

Rubesanolides A and B: diterpenoids from Isodon rubescens

From the medicinal plant Isodon rubescens, we isolated two novel diterpenes, rubesanolides A (1) and B (2). The compounds contain a unique β-lactone subgroup. This is the first discovery for a natural diterpene having rings A, B, and C in chair, boat, and twist-chair conformations, respectively. The structures were elucidated by analysis of spectroscopic data, and the absolute configuration of 1 was determined by X-ray diffraction.     

A natural product-like inhibitor of NEDD8-activating enzyme

The natural product-like 6,6″-biapigenin has been identified as only the second inhibitor of NEDD8-activating enzyme using virtual screening. This compound was active in enzyme and cell-based assays, with potency in the micromolar range.     

Preparation of unsymmetrical distyryl BODIPY derivatives and effects of the styryl substituents on their in vitro photodynamic properties

A series of unsymmetrical distyryl BODIPYs have been prepared which function as highly potent photosensitisers with in vitro IC(50) values as low as 15 nM. Their cellular uptake, subcellular localisation and photocytotoxicity depend greatly on the styryl substituents.