Evidence of xenon transport through the gramicidin channel: a 129Xe-NMR study

McKim, Steve; Hinton, James F.

doi:10.1016/0005-2736(94)90348-4

Cited by 23 publications

(12 citation statements)

References 21 publications

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“…These polymers were successfully used in the past to determine the effective diameters of a number of polyene-, polypeptide- and protein-channels reconstituted into lipid bilayers [13]–[23]. This method avoids the potentially strong Coulomb interactions that occur when ions were used to probe ion channels containing fixed charges.…”

Section: Introductionmentioning

confidence: 99%

Use of Nonelectrolytes Reveals the Channel Size and Oligomeric Constitution of the Borrelia burgdorferi P66 Porin

et al. 2013

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In the Lyme disease spirochete Borrelia burgdorferi, the outer membrane protein P66 is capable of pore formation with an atypical high single-channel conductance of 11 nS in 1 M KCl, which suggested that it could have a larger diameter than ‘normal’ Gram-negative bacterial porins. We studied the diameter of the P66 channel by analyzing its single-channel conductance in black lipid bilayers in the presence of different nonelectrolytes with known hydrodynamic radii. We calculated the filling of the channel with these nonelectrolytes and the results suggested that nonelectrolytes (NEs) with hydrodynamic radii of 0.34 nm or smaller pass through the pore, whereas neutral molecules with greater radii only partially filled the channel or were not able to enter it at all. The diameter of the entrance of the P66 channel was determined to be ≤1.9 nm and the channel has a central constriction of about 0.8 nm. The size of the channel appeared to be symmetrical as judged from one-sidedness of addition of NEs. Furthermore, the P66-induced membrane conductance could be blocked by 80–90% by the addition of the nonelectrolytes PEG 400, PEG 600 and maltohexaose to the aqueous phase in the low millimolar range. The analysis of the power density spectra of ion current through P66 after blockage with these NEs revealed no chemical reaction responsible for channel block. Interestingly, the blockage of the single-channel conductance of P66 by these NEs occurred in about eight subconductance states, indicating that the P66 channel could be an oligomer of about eight individual channels. The organization of P66 as a possible octamer was confirmed by Blue Native PAGE and immunoblot analysis, which both demonstrated that P66 forms a complex with a mass of approximately 460 kDa. Two dimension SDS PAGE revealed that P66 is the only polypeptide in the complex.

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Section: Introductionmentioning

confidence: 99%

Use of Nonelectrolytes Reveals the Channel Size and Oligomeric Constitution of the Borrelia burgdorferi P66 Porin

et al. 2013

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“…[35][36][37] Recently, extensive reviews regarding the history and development of hyperpolarized xenon NMR have been published. 38,39 Biological systems studied with 129 Xe NMR include globular proteins such as myoglobin and hemoglobin, [40][41][42][43][44][45][46] membrane associated peptides such as gramicidin, 47 and lipid membranes themselves. 48 While xenon shows appreciable binding to many proteins, as evidenced by its use in making heavy atom derivatives of protein crystals for x-ray crystallography, 49 In spite of the favorable attributes of xenon interacting with proteins in solution, high-sensitivity molecular sensing is not compatible with the fast-exchange characteristic of xenon-protein interactions.…”

Section: Introductionmentioning

confidence: 99%

Development of a Functionalized Xenon Biosensor

et al. 2004

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NMR-based biosensors that utilize laser-polarized xenon offer potential advantages beyond current sensing technologies. These advantages include the capacity to simultaneously detect multiple analytes, the applicability to in vivo spectroscopy and imaging, and the possibility of "remote" amplified detection. Here we present a detailed NMR characterization of the binding of a biotin-derivatized caged-xenon sensor to avidin. Binding of "functionalized" xenon to avidin leads to a change in the chemical shift of the encapsulated xenon in addition to a broadening of the resonance, both of which serve as NMR markers of ligand-target interaction. A control experiment in which the biotin-binding site of avidin was blocked with native biotin showed no such spectral changes, confirming that only specific binding, rather than nonspecific contact, between avidin and functionalized xenon leads to the effects on the xenon NMR spectrum. The exchange rate of xenon (between solution and cage) and the xenon spin-lattice relaxation rate were not changed significantly upon binding. We describe two methods for enhancing the signal from functionalized xenon by exploiting the laser-polarized xenon magnetization reservoir. We also show that the xenon chemical shifts are distinct for xenon encapsulated in different diastereomeric cage molecules. This demonstrates the potential for tuning the encapsulated xenon chemical shift, which is a key requirement for being able to multiplex the biosensor.

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“…Xenon has been shown to bind to various proteins in crystals and in solution [66,125,126,81,127,128,129,130,131,132]. The formation of xenon clathrates has also been investigated extensively with both thermally polarized and laser-polarized xenon (see for example, Refs.…”

Section: Introductionmentioning

confidence: 99%