Condensation reactions to form oxazoline-substituted potassium organotrifluoroborates.

A library of oxazoline-substituted potassium organotrifluoroborates was prepared via the condensation of various potassium formyl-substituted aryl- and heteroaryltrifluoroborates with tosylmethyl isocyanide under basic conditions. The efficient Suzuki-Miyaura cross-coupling of products thus formed to various aryl bromides was achieved in good yields. The method allows the facile preparation of oxazole-containing triaromatic products in two steps from simple potassium formyl-substituted aryl- or heteroaryltrifluoroborates.

Structure of functional Staphylococcus aureus alpha-hemolysin channels in tethered bilayer lipid membranes.

We demonstrate a method for simultaneous structure and function determination of integral membrane proteins. Electrical impedance spectroscopy shows that Staphylococcus aureus alpha-hemolysin channels in membranes tethered to gold have the same properties as those formed in free-standing bilayer lipid membranes. Neutron reflectometry provides high-resolution structural information on the interaction between the channel and the disordered membrane, validating predictions based on the channel's x-ray crystal structure.

Facile synthesis of highly functionalized ethyltrifluoroborates.

Organotrifluoroborates are generating increased interest because of their ease of preparation and purification and indefinite shelf life. Herein we report the preparation of organotrifluoroborates bearing functional groups that can be manipulated at different stages of the synthetic route, exploiting the inertness of their carbon-boron bonds. The alkylation of 2,2-dicyanoethyltrifluoroborate with a variety of electrophiles and of (EWG)2CH2 with potassium iodomethyltrifluoroborate resulted in di- and trisubstituted ethyltrifluoroborates in good to excellent yields.

Lateral diffusion coefficients of an eicosanyl-based bisglycerophosphocholine determined by PFG-NMR and FRAP.

We report the lateral diffusion properties of 2,2'-di-O-decyl-3,3'-di-O-(eicosanyl)-bis-(rac-glycero)-1,1'-diphosphocholine (C20BAS) using pulsed-field gradient NMR (PFG-NMR) and fluorescence recovery after photobleaching (FRAP). C20BAS membranes display a melting transition at Tm = 15.7 degrees C, as determined by differential scanning calorimetry and 31P NMR chemical shift anisotropy.

Molecular-scale structural and functional characterization of sparsely tethered bilayer lipid membranes.

Surface-tethered biomimetic bilayer membranes (tethered bilayer lipid membranes (tBLMs)) were formed on gold surfaces from phospholipids and a synthetic 1-thiahexa(ethylene oxide) lipid, WC14. They were characterized using electrochemical impedance spectroscopy, neutron reflection (NR), and Fourier-transform infrared reflection-absorption spectroscopy (FT-IRRAS) to obtain functional and structural information. The authors found that electrically insulating membranes (conductance and capacitance as low as 1 microS cm(-2) and 0.

Functional reconstitution of the integral membrane enzyme, isoprenylcysteine carboxyl methyltransferase, in synthetic bolalipid membrane vesicles.

Three bipolar archaeal-type diglycerophosphocholine tetraether lipids (also known as bolalipids) have been prepared to determine (1) the influence of molecular structure on the physical properties of bolalipid membranes and (2) their impact on the functional reconstitution of Ste14p, a membrane-associated isoprenylcysteine carboxyl methyltransferase from Saccharomyces cerevisiae. Three bolalipids were synthesized: C20BAS, C32BAS, and C32phytBAS. These bolalipid structures differ in that the C20BAS derivative has a short sn-1 glyceryl diether C20H40 transmembrane alkyl chain and two ether-linked sn-2 n-decyl chains, whereas the C32BAS and C32phytBAS derivatives have a longer sn-1 diether C32H64 membrane-spanning chain and two ether-linked sn-2 n-hexadecyl or phytanyl chains, respectively.

Enzyme activity to augment the characterization of tethered bilayer membranes.

The rate of Ca2+ -triggered phospholipase A2 (PLA2) degradation of tethered bilayer membranes (tBLMs), composed of a synthetic lipid, beta-mercaptoethanol, and palmitoyloleoylphosphatidylcholine (POPC), is approximately 80 times greater than for those prepared with diphytanoylphosphatidylcholine (DPhyPC). Electrochemical impedance spectroscopy (EIS) and neutron reflectivity (NR) data indicate complete, water-free tBLMs that exhibit near ideal capacitive behavior and the presence of a water reservoir in the bilayer subspace proximal to the substrate (Au) surface for both tBLMs. Together these data indicate that the POPC and the DPhyPC tBLMs are structurally similar along the surface normal but markedly different at the outer leaflet/solution interface and that PLA2 is a sensitive probe of short length scale structural differences not revealed by EIS and NR.