@article {2635,
	title = {Probing General Acid Catalysis in the Hammerhead Ribozyme},
	journal = {Journal of the American Chemical Society},
	volume = {131},
	number = {3},
	year = {2009},
	note = {ISI Document Delivery No.: 427PQTimes Cited: 5Cited Reference Count: 58Thomas, Jason M. Perrin, David M.},
	month = {Jan},
	pages = {1135-1143},
	type = {Article},
	abstract = {Recent crystallographic and computational studies have provided fresh insights into the catalytic mechanism of the RNA-cleaving hammerhead ribozyme. Based on these findings, specific ribozyme functional groups have been hypothesized to act directly as the general acid and base catalysts, although the catalytic role of divalent metal cations (M2+) remains uncertain: We now report a functional characterization of the general acid catalysis mechanism and the role of an M2+ cofactor therein, for the S. mansoni hammerhead (an "extended" hammerhead ribozyme). We have compared hammerhead cleavage of substrates with natural (ribo-phosphodiester) versus bridging-5{\textquoteright}-phosphorothioate scissile linkages, in the contexts of active site mutations and M2+ substitution. Cleavage of the natural substrate is inhibited by modification of the G8 2{\textquoteright}-OH ribozyme residue and depends strongly upon the presence and identity of an M2+ cofactor; in contrast, cleavage of the bridging-phosphorothioate substrate is conspicuously insensitive to any of these factors. These results imply that (1) both an M2+ cofactor and the G8 2{\textquoteright}-OH play crucial roles in hammerhead general acid catalysis and (2) the M2+ cofactor does not contribute to general acid catalysis via Lewis acid stabilization of the leaving group. General acid pK(a) perturbation was also demonstrated for both M2+ substitution and G8 2{\textquoteright}-OH modification, which suggests transition state M2+ coordination of the G8 2{\textquoteright}-OH, to lower its pK(a) and improve its ability to transfer a proton to the leaving group. We also report a simple method for synthesizing radiolabeled bridging-5{\textquoteright}-phosphorothioate substrates.},
	keywords = {2{\textquoteright}-HYDROXYL GROUP, ACTIVE-SITE, BASE CATALYSIS, CATIONS, MEDIATED CLEAVAGE, METAL-ION, MONOVALENT, P-31 NMR, PHOSPHOLIPASE-C, RIBONUCLEASE-A, SUBSTRATE-ANALOG},
	isbn = {0002-7863},
	url = {<Go to ISI>://000264791600054},
	author = {Thomas, J. M. and Perrin,David M.}
}
@article {2117,
	title = {Lipid-specific binding of the calcium-dependent antibiotic daptomycin leads to changes in lipid polymorphism of model membranes},
	journal = {Chemistry and Physics of Lipids},
	volume = {154},
	number = {2},
	year = {2008},
	note = {ISI Document Delivery No.: 336MXTimes Cited: 8Cited Reference Count: 41Jung, David Powers, Jon Paul Straus, Suzana K. Hancock, Robert E. W.},
	month = {Aug},
	pages = {120-128},
	type = {Article},
	abstract = {Daptomycin is a cyclic anionic lipopeptide with an antibiotic activity that is completely dependent on the presence of calcium (as Ca2+). In a previous study [Jung et al., 2004. Chem. Biol. 11, 949-957], it was concluded that daptomycin underwent two Ca2+-dependent structural transitions, whereby the first transition was solely dependent on Ca2+, while the second transition was dependent on both Ca2+ and the presence of negatively charged lipids that allowed daptomycin to insert into and perturb bilayer membranes with acidic character. Differences in the interaction of daptomycin with acidic and neutral membranes were further investigated by spectroscopic means. The lack of quenching of intrinsic fluorescence by the water-soluble quencher, KI, confirmed the insertion of the daptomycin Trp residue into the membrane bilayer, while the kynurenine residue was inaccessible even in an aqueous environment. Differential scanning calorimetry (DSC) indicated that the binding of daptomycin to neutral bilayers occurred through a combination of electrostatic and hydrophobic interactions, while the binding of daptomycin to Mayers containing acidic lipids primarily involved electrostatic interactions. The binding of daptomycin to acidic membranes led to the induction of non-lamellar lipid phases and membrane fusion. (C) 2008 Elsevier Ireland Ltd. All rights reserved.},
	keywords = {ANTIMICROBIAL PEPTIDES, Daptomycin, DSC, FLUORESCENCE, lipopeptide, LY146032, membrane fusion, MIMETIC SYSTEMS, MODEL MEMBRANES, P-31 NMR, PHASE-TRANSITIONS, PHOSPHOLIPIDS, RESONANCE ENERGY-TRANSFER, STAPHYLOCOCCUS-AUREUS, X-RAY-DIFFRACTION},
	isbn = {0009-3084},
	url = {<Go to ISI>://000258369200006},
	author = {Jung, D. and Powers, J. P. and Straus, S. K. and Hancock, R. E. W.}
}
@article {382,
	title = {Combined solid state NMR and X-ray diffraction investigation of the local structure of the five-coordinate silicon in fluoride-containing as-synthesized STF zeolite},
	journal = {Journal of the American Chemical Society},
	volume = {124},
	number = {26},
	year = {2002},
	note = {ISI Document Delivery No.: 567YYTimes Cited: 41Cited Reference Count: 48},
	month = {Jul},
	pages = {7770-7778},
	type = {Article},
	abstract = {The local structure of the [SiO4/2F](-) unit in fluoride-containing as-synthesized STF zeolite has been experimentally determined by a combination of solid-state NMR and microcrystal X-ray diffraction to be very close to trigonal bipyramidal. Because the fluoride ions are disordered over two sites, the resulting local structure of the [SiO4/2F](-) unit from a conventional XRD refinement is an average between tetrahedral SiO4/2 and five-coordinate [SiO4/2F](-), giving an apparent F-Si distance longer than expected. The correct F-Si distance was determined by slow spinning MAS and fast spinning F-19/Si-29 CP and REDOR solid-state NMR experiments and found to be between 1.72 and 1.79 Angstrom. In light of this, the X-ray structure was re-refined, including the disorder at Si3. The resulting local structure of the [SiO4/2F]- unit was very close to trigonal bipyramidal with a F-Si distance of 1.744 (6) Angstrom, in agreement with the NMR results and the prediction of Density Functional Theory calculations. In addition, further evidence for the existence of a covalent F-Si bond is provided by a F-19{\textendash}>Si-29 refocused INEPT experiment. The resonance for the five-coordinate species at -147.5 ppm in the Si-29 Spectrum is a doublet due to the F-19/Si-29 J-coupling of 165 Hz. The peaks in this doublet have remarkably different effective chemical shift anisotropies due to the interplay of the CSA, dipolar coupling, and J-coupling tensors. The distortions from tetrahedral geometry of the neighboring silicon atoms to the five-coordinate Si3 atom are manifested in increased delta(aniso) values. This information, along with F-Si distances measured by F-19{\textendash}>Si-29 CP experiments, makes it possible to assign half of the Si-29 resonances to unique tetrahedral sites. As well as determining the local geometry of the [SiO4/2F](-) unit, the work presented here demonstrates the complementarity of the solid-state NMR and X-ray diffraction techniques and the advantages of using them together.},
	keywords = {5-COORDINATE SILICON, C-13 NMR, CONTAINING OCTADECASIL, CROSS-POLARIZATION, DISTANCE DETERMINATIONS, LOCATION, MOLECULAR-SIEVES, P-31 NMR, POLARIZATION TRANSFER, PROTON-ENHANCED NMR},
	isbn = {0002-7863},
	url = {<Go to ISI>://000176516400032},
	author = {Fyfe, C. A. and Brouwer, D. H. and Lewis, A. R. and Villaescusa, L. A. and Morris, R. E.}
}
@article {3976,
	title = {1D and 2D solid state NMR investigations of the framework structure of As-synthesized AlPO4-14},
	journal = {Solid State Nuclear Magnetic Resonance},
	volume = {9},
	number = {2-4},
	year = {1997},
	note = {ISI Document Delivery No.: YU021Times Cited: 46Cited Reference Count: 21},
	month = {Dec},
	pages = {97-106},
	type = {Article},
	abstract = {The framework structure of As-synthesized ALPO(4)-14 has been investigated with a combination of different one-dimensional Al-27 and P-31 solid State NMR techniques and Al-27/P-31 double resonance methods. The results are found to be fully consistent with the assumed structural model. Al-27 MAS and DOR experiments at three different magnetic field strengths together with simulations show the presence of two tetrahedral sites, one pentacoordinated and one octahedral aluminum site. The Al-27 quadrupolar coupling constants and the P-31 isotropic chemical shifts of the tetrahedral sites correlate well with tetrahedral shear-strain parameters and mean P-O-Al bond angles, respectively. These correlations allow one to assign all of the NMR resonances to specific T-sites in the proposed framework structure. The assignments are then further confirmed by the application of three different two-dimensional heteronuclear correlation methods (i.e., Al-27 {\textendash}> P-31 TEDOR, CP, and INEPT) which reveal the connectivities between AlOx and PO4 polyhedra. The two-dimensional INEPT experiment is applied here for the first time in the solid state. (C) 1997 Published by Elsevier Science B.V.},
	keywords = {AL-27, Al-27 nuclear magnetic resonance spectroscopy, aluminophosphate, ANGLE, double resonance, MOLECULAR, MOLECULAR-SIEVE VPI-5, NUCLEI, P-31 NMR, P-31 nuclear magnetic, QUADRUPOLAR, RESOLUTION, resonance spectroscopy, sieve, SPIN},
	isbn = {0926-2040},
	url = {<Go to ISI>://000071671900004},
	author = {Fyfe, C. A. and Altenschildesche, H. M. Z. and Wong-Moon, K. C. and Grondey, H. and Chezeau, J. M.}
}
@article {3610,
	title = {Synthesis and spectroscopic characterization of bis(trifluorophosphinyl)-gold(I) undecafluorodiantimonate(V) [Au(PF3)(2)][Sb2F11]},
	journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie},
	volume = {74},
	number = {11},
	year = {1996},
	note = {ISI Document Delivery No.: WC124Times Cited: 3Cited Reference Count: 20},
	month = {Nov},
	pages = {2392-2394},
	type = {Article},
	abstract = {The synthesis of [Au(PF3)(2)][Sb2F11], the first trample of a linear, thermally stable metal bis(trifluorophosphine) complex is achieved by CO substitution of [Au(CO)(2)][Sb2F11] by PF3. The [A(PF3)(2)](+) cation can also be generated by reductive phosphorylation by an excess of PF3 in fluorosulfuric acid. Spectroscopic characterization involves F-19 and P-31 NMR in HSO3F and SO2 solution including spectral simulation by the WIN-DAISY method and FT-IR and Raman spectra. Spectroscopic evidence suggests that the metal-ligand bond involves predominantly sigma-bonding with drastically reduced pi-back-donation.},
	keywords = {CHEMISTRY, F-19 NMR, gold(I) complex, gold(I) PF3 complex, linear, P-31 NMR, SPECTRA, vibrational spectra},
	isbn = {0008-4042},
	url = {<Go to ISI>://A1996WC12400054},
	author = {Bley, B. and Bodenbinder, M. and Balzer, G. and Willner, H. and Hagele, G. and Mistry, F. and Aubke, F.}
}
