Ion channel complex of antibiotics as viewed by NMR

2009 ◽  
Vol 81 (6) ◽  
pp. 1123-1129 ◽  
Author(s):  
Michio Murata ◽  
Yusuke Kasai ◽  
Yuichi Umegawa ◽  
Naohiro Matsushita ◽  
Hiroshi Tsuchikawa ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Fluorine Atom ◽  
Double Resonance ◽  
Conformational Search ◽  
Pharmacological Effects ◽  
Dipolar Interactions ◽  
Acyl Chains ◽  
Bimolecular Interaction ◽  
Covalent Conjugates

Amphotericin B (AmB) exerts its pharmacological effects by forming a barrel-stave assembly in fungal membranes. To examine the interaction between AmB and ergosterol or cholesterol, 13C- and 19F-labeled covalent conjugates were prepared and subjected to solid-state NMR measurements. Using rotor-synchronous double resonance experiments such as REDOR and RDX, we estimated the distance between the fluorine atom and its nearest carbon in the heptaene moiety to be less than 8.6 Å, indicating that the B ring of ergosterol comes close to the AmB polyene moiety. Conformational search of the AmB-ergosterol conjugate using the NMR-derived constraints suggested that ergosterol molecules surround the AmB assembly in contrast to the conventional image where ergosterol is inserted into AmB molecules. AmB-AmB bimolecular interaction was examined by using 13C- and 19F-labeld AmBs in dimyritoylphosphatidylcholine membrane without sterols. 13C-19F dipolar interactions deriving from both head-to-head and head-to-tail orientations were observed in the REDOR experiments. The interactions between AmB and acyl chains of the phospholipid were also detected.

scholarly journals Use of Solid-State NMR Spectroscopy for the Characterization of Molecular Structure and Dynamics in Solid Polymer and Hybrid Electrolytes

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1207
Author(s):  
Gabrielle Foran ◽  
Nina Verdier ◽  
David Lepage ◽  
Cédric Malveau ◽  
Nicolas Dupré ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Solid State Nmr ◽  
Pulse Sequence ◽  
Dynamic Properties ◽  
Double Resonance ◽  
Solid Polymer ◽  
Pulse Field ◽  
Solid State Nmr Spectroscopy

Solid-state NMR spectroscopy is an established experimental technique which is used for the characterization of structural and dynamic properties of materials in their native state. Many types of solid-state NMR experiments have been used to characterize both lithium-based and sodium-based solid polymer and polymer–ceramic hybrid electrolyte materials. This review describes several solid-state NMR experiments that are commonly employed in the analysis of these systems: pulse field gradient NMR, electrophoretic NMR, variable temperature T1 relaxation, T2 relaxation and linewidth analysis, exchange spectroscopy, cross polarization, Rotational Echo Double Resonance, and isotope enrichment. In this review, each technique is introduced with a short description of the pulse sequence, and examples of experiments that have been performed in real solid-state polymer and/or hybrid electrolyte systems are provided. The results and conclusions of these experiments are discussed to inform readers of the strengths and weaknesses of each technique when applied to polymer and hybrid electrolyte systems. It is anticipated that this review may be used to aid in the selection of solid-state NMR experiments for the analysis of these systems.

Solid State NMR Studies of the Adsorbed States of Formic Acid on Y Zeolites

1980 ◽  
Vol 3 ◽  
Author(s):  
T. Michael Duncan ◽  
Robert W. Vaughan
Keyword(s):  
Solid State ◽  
Formic Acid ◽  
Solid State Nmr ◽  
Double Resonance ◽  
Chemical Shift Anisotropy ◽  
Surface States ◽  
Cross Polarization ◽  
Nmr Studies ◽  
Y Zeolites ◽  
Nmr Techniques

ABSTRACTSeveral multiple-pulse double-resonance NMR techniques have been applied to isolate and characterize the spectra of the adsorbed states of formic acid on two Y zeolites. The two surface states, bidentatT3 and ynidentate, possess different motional properties and 13C - H cross-polarization techniques may be used to separate the spectra. The 13C chemical shift anisotropy is founa to iorrelate with the symmetry of the formate species. The H spectrum of the carbonyl hydrogen, selectively observed with the dipolardifference method, indicates that this hydrogen becomes more acidic upon adsorption.

scholarly journals Structure and Orientation of Pardaxin Determined by NMR Experiments in Model Membranes

2004 ◽  
Vol 279 (44) ◽  
pp. 45815-45823 ◽  
Author(s):  
Fernando Porcelli ◽  
Bethany Buck ◽  
Dong-Kuk Lee ◽  
Kevin J. Hallock ◽  
Ayyalusamy Ramamoorthy ◽  
...  
Keyword(s):  
Solid State ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Solid State Nmr ◽  
Double Resonance ◽  
Slow Motion ◽  
Solution Nmr ◽  
Helical Conformation ◽  
Hydrophobic Core ◽  
Nmr Studies

Pardaxins are a class of ichthyotoxic peptides isolated from fish mucous glands. Pardaxins physically interact with cell membranes by forming pores or voltage-gated ion channels that disrupt cellular functions. Here we report the high-resolution structure of synthetic pardaxin Pa4 in sodium dodecylphosphocholine micelles, as determined by1H solution NMR spectroscopy. The peptide adopts a bend-helix-bend-helix motif with an angle between the two structure helices of 122 ± 9°, making this structure substantially different from the one previously determined in organic solvents. In addition, paramagnetic solution NMR experiments on Pa4 in micelles reveal that except for the C terminus, the peptide is not solvent-exposed. These results are complemented by solid-state NMR experiments on Pa4 in lipid bilayers. In particular,13C-15N rotational echo double-resonance experiments in multilamellar vesicles support the helical conformation of the C-terminal segment, whereas2H NMR experiments show that the peptide induces considerable disorder in both the head-groups and the hydrophobic core of the bilayers. These solid-state NMR studies indicate that the C-terminal helix has a transmembrane orientation in DMPC bilayers, whereas in POPC bilayers, this domain is heterogeneously oriented on the lipid surface and undergoes slow motion on the NMR time scale. These new data help explain how the non-covalent interactions of Pa4 with lipid membranes induce a stable secondary structure and provide an atomic view of the membrane insertion process of Pa4.

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