Cesium-133 NMR longitudinal relaxation study of ion binding to the Gramicidin transmembrane channel

Urry, Dan W.; Trapane, Tina L.; Brown, R.A; Venkatachalam, C. M.; Prasad, K. U.

doi:10.1016/0022-2364(85)90374-9

Cited by 14 publications

(11 citation statements)

References 31 publications

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“…These cells, which can be found in the Dead Sea, tolerate extremely high concentrations of salt. Ba 1 cells were grown in a series of 30 used a similar analysis to determine Cs þ binding constants to the channel-forming peptide gramicidin A (60 M À1 tight and 4 M À1 weak).…”

Section: Chemical Shiftmentioning

confidence: 99%

Biomedical applications of133Cs NMR

Goodman

Ackerman

2005

NMR Biomed.

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133 Cs NMR is a valuable tool for non-invasively probing biological systems. As a congener of potassium, it accumulates in the intracellular space, primarily through the action of the Na þ -K þ pump (ATPase). In addition, it is possible to resolve the MR signal of 133 Cs in different tissue compartments on the basis of chemical shift or MR relaxation properties. This compartmental resolution applies not only to the intra-and extracellular spaces, but to subcellular compartments as well. In this review, we discuss the studies defining the ion transport, chemical shift and relaxation characteristics of 133 Cs in living systems. We also review the application of 133 Cs NMR to evaluation of ion transport across membranes and the kinetic/ chemical environment of the intracellular space in systems ranging from red blood cells to rat brain.

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Section: Chemical Shiftmentioning

confidence: 99%

Biomedical applications of133Cs NMR

Goodman

Ackerman

2005

NMR Biomed.

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“…The physical method data on this channel-lyso-PC system, instead, demonstrate a tight binding process giving rise to single ion occupancy and a weak binding process resulting in double ion occupancy. This has been demonstrated from the viewpoint of the ion using lithium-7 [16], sodium-23 [20,21] and cesium-133 [15] NMR and from within the channel (3) for potassium and thallium ions using synthetic gramicidin A molecules in which a single carbonyl carbon was enriched [17]. If the off-rate constant for the singly occupied channel were sufficiently small (for example 3 x 105/sec as reported for sodium ion, reference 21) that it did not contribute significantly to the measured ion fluxes, then cy-cling between singly and doubly occupied states could be occurring with little evidence for the initial ion occupancy.…”

Section: Discussionmentioning

confidence: 90%

“…For the malonyl dimer of gramicidin, the fitted value of kcb for sodium ion was found to be essentially the same as that experimentally determined by dielectric relaxation measurements for the thallium ion [6]. Subsequently, two binding constants for the lithium ion interaction with the gramicidin channel have been determined using lithium-7 NMR [16], and more recently two binding constants have been estimated for cesium ion using cesium-133 NMR [15], and K~' and ko~f have been estimated for rubidium ion using rubidium-87 NMR [19]. In the present effort K[ and koWff are estimated by means of potassium-39 NMR, the former using longitudinal relaxation time data and the latter using an appropriate ratio of longitudinal to transverse relaxation times.…”

Section: Introductionmentioning

confidence: 86%

“…The potassium-39 chemical shift for 0.3 mM channels and 100 mM KCI was 14.7 ppm upfield from 100 mM KCI in -~H20. These results indicate essentially complete channel formation [6,15,16]. The potassium ion titrations were carried out by addition of dry KC1 (J.T.…”

Section: Methodsmentioning

confidence: 99%

“…The procedures for channel incorporation and for determination of channel concentration were as previously described [6,15,16]. Verification of the ioninteracting channel state for this preparation was achieved by observing the circular dichroism spectrum and by determining the ion NMR chemical shift at 30~ The CD spectrum for the preparation used in the potassium-39 NMR studies is given in Fig.…”

Section: Methodsmentioning

confidence: 99%

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Potassium-39 NMR of K+ interaction with the gramicidin channel and NMR-derived conductance ratios for Na+, K+ and Rb+

1986

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A potassium-39 NMR study of potassium ion interaction with the gramicidin transmembrane channel in phospholipid bilayers at high ion activity is reported which allows determination of a weak binding constant, Kwb approximately equal to 8.3/M, and an off-rate constant for the weak site, kwoff approximately equal to 2.6 X 10(7)/sec. These values are interpreted with the aid of additional NMR data as the binding constant for formation of the doubly occupied channel state and the rate constant for an ion leaving the doubly occupied state. Considering the singly occupied channel state for the potassium ion to be "electrically silent" at 1 molar ion activity, as with the sodium ion, the single-channel conductance for 100 mV and 30 degrees C calculated to be 29 pS, and using the same approximation with previous NMR results on the sodium and rubidium ions, reasonable conductance ratios were calculated. Further experimental estimates of the other three constants with the experimental location of binding sites and Eyring rate theory to introduce voltage dependence allowed a more complete calculation of the two-site channel. The single-channel conductance for potassium ion is calculated to be 24 pS at 1 M activity and 26 pS at 0.6 M activity, which compares for diphytanoyl phosphatidylcholine membranes to an experimental most probable single-channel conductance of 25 pS and a mean channel conductance of 20 pS. The calculated conductance ratios using NMR-derived constants were gamma (K)/gamma (Na) = 2.0 and gamma (Rb)/gamma (Na) = 4.3.(ABSTRACT TRUNCATED AT 250 WORDS)

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Nuclear magnetic resonance studies of cesium-133 in the halophilic halotolerant bacterium Ba1. Chemical shift and transport studies

Sakhnini

Gilboa

1998

NMR Biomed.

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Ba1 bacteria (Holomonas israelensis ) were grown on different salt concentrations 0.2–4 M. When the cells were transferred to a medium containing 25 mM CsCl without potassium there was an uptake of cesium by the cells. The intracellular cesium signal was shifted from the cesium signal in the medium without the use of a shift reagent. The shift was depended on the salt concentration in the growth medium. The intracellular cesium shift showed a much smaller dependence on the concentration of salts in the medium than the extracellular cesium; the same results were detected for cells grown on a medium containing 25 mM CsCl. The cesium transport through the cell membrane was mostly by active transport. The cesium concentration in the cell was higher than that of the medium, ∼100 mM intracellular concentration compared to 25 mM in the medium. The first order constants for influx or efflux of cesium were from 2 × 10−4 and up to 24 × 10−4 /min for the different medium concentrations. © 1998 John Wiley & Sons, Ltd.

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Cesium-133 NMR longitudinal relaxation study of ion binding to the Gramicidin transmembrane channel

Cited by 14 publications

References 31 publications

Biomedical applications of133Cs NMR

Biomedical applications of133Cs NMR

Potassium-39 NMR of K+ interaction with the gramicidin channel and NMR-derived conductance ratios for Na+, K+ and Rb+

Nuclear magnetic resonance studies of cesium-133 in the halophilic halotolerant bacterium Ba1. Chemical shift and transport studies

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