Resveratrol Interferes with Fura-2 Intracellular Calcium Measurements

Resveratrol, a naturally occurring polyphenol found in some fruits and especially in grapes, has been reported to provide diverse health benefits. Resveratrol’s mechanism of action is the subject of many investigations, and some studies using the ratiometric calcium indicator Fura-2 suggest that it modulates cellular calcium responses. In the current study, contradictory cellular calcium responses to resveratrol applied at concentrations exceeding 10 μM were observed during in vitro imaging studies depending on the calcium indicator used, with Fura-2 indicating an increase in intracellular calcium while Fluo-4 and the calcium biosensor YC3.60 indicated no response. When cells loaded with Fura-2 were treated with 100 μM resveratrol, excitation at 340 nm resulted in a large intensity increase at 510 nm, but the expected concurrent decline with 380 nm excitation was not observed. Pre-treatment of cells with the calcium chelator BAPTA-AM did not prevent a rise in the 340/380 ratio when resveratrol was present, but it did prevent an increase in 340/380 when ATP was applied, suggesting that the resveratrol response was an artifact. Cautious data interpretation is recommended from imaging experiments using Fura-2 concurrently with resveratrol in calcium imaging experiments.     

Composite Material Based on Macroporous Polyaniline and Osmium Redox Complex for Biosensor Development

Here the feasibility of layers based on the conducting polymer polyaniline (PANI) as component of glucose biosensors using glucose oxidase (GOx) as enzyme and [Os(bpy)₂(4‐aminomethylpyridine)Cl]PF₆ (OsCmplx) as electrochemical mediator, is evaluated. Particularly, PANI was employed to obtain a nanostructured macroporous material (m‐PANI) around polystyrene nanoparticles taken as template and the mediator was co‐immobilized during the polymerizing procedure. The GOx biosensor based on OsCmplx modified m‐PANI provides a linear response to glucose concentration in the range 5 up to 65 mM with a sensitivity of 3.54 µA/mM/cm² (on a projected geometric area=0.07 cm²), an LOD of 0.8 mM and a good precision (%RSD≤7, n=5); the biosensor is stable showing a decrease of 10% to the value of the sensitivity after 15 days of use and of about 50% after 40 days.     

Hexahydroxybenzene–2,2′-bipyridine (1/2)

2,2′-Bi­pyridine (2BPY) and hexa­hydroxy­benzene (HHB) crystallize in a 2:1 ratio as a neutral molecular adduct, C₆H₆O₆·2C₁₀H₈N₂, in space group P with Z = 1 and with the HHB molecule lying on an inversion centre. HHB, of which this is the first single-crystal X-ray structure determination, forms O—H⃛O hydrogen-bonded chains parallel to the a axis, with O⃛O distances of 2.761 (1) and 2.782 (1) Å. O—H⃛N hydrogen bonds to the 2BPY molecules crosslink these chains, with O⃛N distances of 2.707 (1) and 2.735 (1) Å.     

Understanding ligand distributions in modified particle and particlelike systems

Chemical modification of nanoparticles or particlelike systems is ubiquitously being used to facilitate specific pharmaceutical functionalities or physicochemical attributes of nanocrystals, proteins, enzymes, or other particlelike systems. Often the modification process is incomplete and the functional activity of the product depends upon the distribution of functional ligands among the different particles in the system. Here, the distribution function describing the spread of ligands in particlelike systems undergoing partial modification reactions is derived and validated against a conjugated enzyme model system by use of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF). The distribution function is shown to be applicable to describe the distribution of ligands in a wide range of particlelike systems (such as enzymes, dendrimers, or inorganic nanocrystals) and is used to establish guidelines for the synthesis of uniformly modified particle systems even at low reaction efficiencies.     

One step multifunctional micropatterning of surfaces using asymmetric glow discharge plasma polymerization

Micropatterning of surfaces with varying chemical, physical and topographical properties usually requires a number of fabrication steps. Herein, we describe a micropatterning technique based on plasma enhanced chemical vapour deposition (PECVD) that deposits both protein resistant and protein repellent surface chemistries in a single step. The resulting multifunctional, selective surface chemistries are capable of spatially controlled protein adhesion, geometric confinement of cells and the site specific confinement of enzyme mediated peptide self-assembly.     

The 1:1 adduct of 2,5-dihydroxy-1,4-benzoquinone with 4,4′-bipyridine

2,5-Di­hydroxy-1,4-benzo­quinone (DHBQ) and 4,4′-bi­pyridine (BPY) crystallize in a 1:1 ratio as a neutral molecular adduct, C₆H₄O₄·C₁₀H₈N₂, in space group C2/c, with half of each mol­ecule in the asymmetric unit. The mol­ecules are linked by a strong O—H⃛N hydrogen bond [O⃛N 2.6323 (15) Å] and a weak C—H⃛O hydrogen bond [C⃛O 3.2082 (17) Å] to form infinite stacks of parallel one-dimensional hydrogen-bonded ribbons. The two rings of the bi­pyridine are twisted at 28.3° with respect to each other, and the benzo­quinone ring is inclined at an angle of 18.3° with respect to the plane of the neighbouring pyridine ring. The 4,4′-bi­pyridine mol­ecule lies on a twofold axis and the benzo­quinone mol­ecule lies across an inversion centre.