B-F interaction

The fl2" symmetry of the B 2p orbital matches that of LGO(5) and an in-phase orbital interaction gives rise to an MO that has 7r-bonding character delocalized over all three B—F interactions. 

Electron Transport Between Photosystem I and Photosystem II Inhibitors. The interaction between PSI and PSII reaction centers (Fig. 1) depends on the thermodynamically favored transfer of electrons from low redox potential carriers to carriers of higher redox potential. This process serves to communicate reducing equivalents between the two photosystem complexes. Photosynthetic and respiratory membranes of both eukaryotes and prokaryotes contain stmctures that serve to oxidize low potential quinols while reducing high potential metaHoproteins (40). In plant thylakoid membranes, this complex is usually referred to as the cytochrome b /f complex, or plastoquinolplastocyanin oxidoreductase, which oxidizes plastoquinol reduced in PSII and reduces plastocyanin oxidized in PSI (25,41). Some diphenyl ethers, eg, 2,4-dinitrophenyl 2 -iodo-3 -methyl-4 -nitro-6 -isopropylphenyl ether [69311-70-2] (DNP-INT), and the quinone analogues,... 

Luisi, B.F., et al. Crystallographic analysis of the interaction of the glucocorticoid receptor with DNA. 

In be complexes bci complexes of mitochondria and bacteria and b f complexes of chloroplasts), the catalytic domain of the Rieske protein corresponding to the isolated water-soluble fragments that have been crystallized is anchored to the rest of the complex (in particular, cytochrome b) by a long (37 residues in bovine heart bci complex) transmembrane helix acting as a membrane anchor (41, 42). The great length of the transmembrane helix is due to the fact that the helix stretches across the bci complex dimer and that the catalytic domain of the Rieske protein is swapped between the monomers, that is, the transmembrane helix interacts with one monomer and the catalytic domain with the other monomer. The connection between the membrane anchor and the catalytic domain is formed by a 12-residue flexible linker that allows for movement of the catalytic domain during the turnover of the enzyme (Fig. 8a see Section VII). Three different positional states of the catalytic domain of the Rieske protein have been observed in different crystal forms (Fig. 8b) (41, 42) ... 

Cross-peaks A and B represent interactions of the C-4 proton (H ) resonating at 8 2.20 with the C-3 and C-5 carbons (8 72.2 and 43.7, respectively). Cross-peak C corresponds to the coupling between the C-4 proton (8 2.70) (H ) with the C-2 iminic carbon (8 160.4). Crosspeaks D, E, and F represent long-range correlations between the C-5a... 

Sawicki, J.A., Sawicka, B.D., Wagner, F.E. Nucl. Instrum. Meth. Phys. Res. Sect. B-Beam Interact. Mater. Atoms 62, 253 (1991)... 

The Wyboume crystal field parameters B (f, f), B (d, d), and Bjj(f, d), which describe the interaction due to the presence of the ligands onto the electrons of the lanthanide center. They are deduced from the ligand field energies and wave functions obtained from Kohn—Sham orbitals of restricted DFT calculations within the average of configuration (AOC) reference by placing evenly n — 1 electrons in the 4f orbitals and one electron in the 5d.33... 

Shen, W.-E., Sridhar, K., Bernlohr, D.A. and Kraemer, F.B. (1999) Interaction of rat hormone-sensitive lipase with adipocyte lipid-binding protein. Proceedings of the National Academy of Sciences USA 96, 5528—5532. 

Petersen, H. U., Roll, T., Grunberg-Manago, M., and Clark, B. F. (1979). Specific interaction of initiation factor IF2 of E. coli with formylmethionyl-tRNA 1 1. Biochem. Biophys. Res. Commun. 91, 1068—1074. 

During, H.J. and Van Tooren, B.F. (1990). Bryophyte interactions with other plants. Botanical Journal of the Linnean Society 104 79-98. 

It is readily apparent that the three a bonds are capable of holding the six bonding electrons in the a t and e molecular orbitals. The possibility of some 7r-bonding is seen in the molecular orbital diagram as a result of the availability of the a2" orbital, and in fact there is some experimental evidence for this type of interaction. The sum of the covalent radii of boron and fluorine atoms is about 152 pm (1.52 A), but the experimental B-F bond distance in BF3 is about 129.5 pm (1.295 A). Part of this "bond shortening" may be due to partial double bonds resulting from the 7r-bonding. A way to show this is by means of the three resonance structures of the valence bond type that can be shown as... 

Calu-3 (American type culture collection ATCC HTB-55) is a human bronchial epithelial cell line derived from an adenocarcinoma of the lung [59], This cell line has been shown to exhibit serous cell properties and form confluent monolayers of mixed cell phenotypes, including ciliated and secretory cell types [60], but the cilia are formed very irregularly and seem to disappear with increasing passage number (unpublished observations, C.E. and B.F.). Calu-3 cells have shown utility as a model to examine transport [61-63] and metabolism in human bronchial epithelial cells for many therapeutic compounds [64], Furthermore, they have been used in a number of particlecell interaction studies [65-67], The interactions between respiratory epithelial cells and particulates are discussed more in detail in Chap. 19. 

Jin, H., Zastawny, R., George, S. R., and O Dowd, B. F. (1997) Elimination of palmitoylation sites in the human dopamine receptor does not affect receptor-G protein interaction. Eur. J. Pharmacol. 324, 109-116. 

Lee, S. P., O Dowd, B. F., Rajaram, R. D., Nguyen, T., and George, S. R. (2003) D2 dopamine receptor homodimeiization is mediated by multiple sites of interaction, including an intermo-lecular interaction involving transmembrane domain 4. Biochemistry. 42, 11023-11031. 

In order to allow for a closer approach of the boron centers, the introduction of flat cyclic boryl moieties with reduced steric hindrance has also been pursued. Thus, the reaction of 26 with 9-chloro-9-borafluorene and 5-bromo-10,l 1-di-hydrodibenzo[b,f]borepin resulted in the formation of diboranes 31 and 32 which bear two different boryl moieties at the pen-positions of naphthalene (Scheme 13). " These diboranes have been characterized by multinuclear NMR spectroscopy and X-ray single-crystal analysis. In 31, the boron center of the borafluorenyl moiety is 7i-coordinated by the zp o-carbon of a mesityl group with which it forms a contact of 2.730(3) A (Fig. 8). As a result of this interaction, the boron center involved in this contact is slightly pyramidalized (Xangie = 355.7°). In the case of 32 (Fig. 9), the distance between the boron center of the boracylic moiety and the zpio-carbon of... 

---