Dendrimers as scaffolds for the synthesis of spherical porphyrin arrays

This communication describes a self assembled porphyrin sphere. The globular macromolecular assembly contains 12 terminal porphyrins and has a molecular mass in excess of 15,000 g mol-1.     

An example in affine pi-rings

An example is given of a prime p.i. ringR finitely generated over a field, with a prime idealQ which is not finitely generated as a two-sided ideal ofR. Supported in part by the National Science Foundation.     

Crystal and molecular structure of the spin-crossover complex bis(pyridine) [N,N′-ethylenebis (3-carboxysalicylaldimine)] cobalt (II)

The average structure of the title compound, Co(H₂fsa₂en)(py)₂, which has been shown previously to exhibit a thermally induced high-spin low-spin crossover, has been investigated by single-crystal X-ray diffraction. This structure has been solved in the monoclinic space groupC2/c (No. 15), with cell dimensionsa=16.641(5),b=9.496(4),c=16.329(6) Å, and=95.47(3)°;V=2569(3) ų,M _r =571.46,Z=4,D _x =1.478 mg m^–3; MoK radiation (graphite crystal monochromator),=0.71073 Å,(MoK)=7.138 cm^–1;T=295 K andR=0.081 for 681 observed [I>3(I)] independent reflections. The cobalt(II) ion resides on a twofold axis in an elongated octahedral environment, the length of the apical bond (formed with pyridine) being 2.262(12) Å and the mean length of the equatorial bonds (formed with the Schiff base) 2.079(12) Å. These values are consistent with the magnetic behavior, which suggested a distorted surrounding for the metal atom. The packing is essentially governed by the parallelism of the salicylaldimine ligands. The two pyridine rings of the molecule are twisted by ~98° on each side of the basal plane; they are probably affected by orientational disorder or, if ordered, they might be described in a superstructure not yet established.     

A convenient synthesis of a porphyrin cross-linked polymer,its application as a size selective heterogeneous catalyst and a comparison with a porphyrin-cored hyperbranched polymer

This paper describes how the polymeric structure and environment surrounding supported catalysts can be used to affect the product outcome from a reaction. As well as reporting a size/shape selectivity, we also describe a significant effect on product distribution. Specifically, how the polymeric environment can favour or disfavour particular products. As such, these results illustrate how it may be possible to target more or less of a specific compound (from a possible mix) by careful choice of the polymer architecture surrounding a catalyst.     

Thermal degradation of β‐carotene studied by ion mobility atmospheric solid analysis probe mass spectrometry: full product pattern and selective ionization enhancement

Atmospheric solid analysis probe mass spectrometry has the capability of capturing full product patterns simultaneously including both volatile and semi‐volatile compounds produced at elevated temperatures. Real‐time low‐energy collision‐induced fragmentation combined with ion mobility separations enables rapid identification of the chemical structures of products. We present here for the first time the recognition of full product patterns resulting from the thermal degradation of β‐carotene at temperatures up to 600 °C. Solvent vapor‐induced ionization enhancement is observed, which reveals parallel thermal dissociation processes that lead to even‐ and odd‐numbered mass products. The drift‐time distributions of high mass products, along with β‐carotene, were monitored with temperature, showing multiple conformations that are associated with the presence of two β‐rings. Products of masses 346/347, however, show a single conformation distribution, which indicates the separation of two β‐rings resulting from the direct bond scission at the polyene hydrocarbon chain. The thermal degradation pathways are evaluated and discussed. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.     

DFT studies on the vibrational and electronic spectra of acetylsalicylic acid

The following is a theoretical and experimental study on the vibrational and electronic properties of acetylsalicylic acid (ASA). Vibrational information was obtained by FT-IR and Raman spectroscopy which agree well with harmonic vibrational frequency calculations. The calculations were carried out using density functional theory B3LYP methods with 6-311G** and LANL2DZ basis sets. The vibrational assignments were calculated by Gaussview. Absorption UV-Vis experiments of ASA reveal three maximum peaks at 203, 224 and 277 nm, which are in agreement with calculated electronic transitions using TD-B3LYP/6-311G**.     

Formation of A2B2 supramolecular porphyrin co-polymers

New supramolecular A2B2 co-polymers formed in solution from a rigid diporphyrin monomer (the A2 unit) and a short flexible dipyridine monomer (the B2 unit) are reported; NMR experiments show that complete binding occurs at mM concentrations; UV titrations reveal that the dipyridine unit and a monomeric control ligand have identical binding constants, confirming that linear polymers were generated (in preference to small cyclic oligomers); at 2 x 10(-2) M polymers with an average molecular weight of 17,100 g mol-1 and containing approximately 14 porphyrin units have formed.     

E-cadherin tethered to micropatterned supported lipid bilayers as a model for cell adhesion

Cell-cell adhesion is a dynamic process requiring recruitment, binding, and reorganization of signaling proteins in the plane of the plasma membrane. Here, we describe a new system for investigating how this lateral mobility influences cadherin-based cell signaling. This model is based on tethering of a GPI-modified E-cadherin protein (hEFG) to a supported lipid bilayer. In this report, membrane microfluidics and micropatterning techniques are used to adopt this tethered protein system for studies with the anchorage-dependent cells. As directly formed from proteoliposomes, hEFG exhibits a diffusion coefficient of 0.6 +/- 0.3 microm(2)/s and mobile fraction of 30-60%. Lateral structuring of the supported lipid bilayer is used to isolate mobile proteins from this mixed mobile/immobile population, and should be widely applicable to other proteins. MCF-7 cells seeded onto hEFG-containing bilayers recognize and cluster this protein, but do not exhibit cell spreading required for survival. By micropatterning small anchors into the supported lipid bilayer, we have achieved cell spreading across the bilayer surface and concurrent interaction with mobile hEFG protein. Together, these techniques will allow more detailed analysis of the cellular dynamics involved in cadherin-dependent adhesion events.