{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,13]],"date-time":"2026-05-13T20:57:35Z","timestamp":1778705855493,"version":"3.51.4"},"reference-count":33,"publisher":"Wiley","issue":"2","license":[{"start":{"date-parts":[[2005,11,18]],"date-time":"2005-11-18T00:00:00Z","timestamp":1132272000000},"content-version":"vor","delay-in-days":5039,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Magnetic Resonance in Med"],"published-print":{"date-parts":[[1992,2]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>The diffusive permeability to water molecules, P<jats:sub>d<\/jats:sub>, of lipid vesicles with entrapped paramagnetic solute ions can be determined rapidly from analysis of the magnetic field dependence (nuclear magnetic relaxation dispersion, or NMRD profile) of T<jats:sub>1<\/jats:sub> of exterior solvent water protons. Such data yield \u03c4 the mean lifetime of solvent molecules inside the vesicles, from \u03c4 = (fT<jats:sub>lpara<\/jats:sub>) \u2013 T<jats:sub>1ves<\/jats:sub>, where f is the volume fraction of entrapped water, T<jats:sub>1Para<\/jats:sub> is the observed T<jats:sub>1<\/jats:sub> corrected for buffer background, and T<jats:sub>1Ves<\/jats:sub> is the relaxation time of water protons in the entrapped solution. For small spherical unilamellar vesicles of inner radius R, P<jats:sub>d<\/jats:sub> = R\/3\u03c4. f can be obtained accurately from knowledge of both the concentration of Gd(DTPA)<jats:sup>2\u2212<\/jats:sup> in the solution in which the vesicles were formed and the average concentration of ions in the final sample. At low temperatures, in the limit of slow exchange, T<jats:sub>1Para<\/jats:sub> becomes independent of field and \u03c4 = f T<jats:sub>1Para<\/jats:sub>; the observation of a field independent profile is a control that confirms that no paramagnetic material is external to the vesicles. We have measured T<jats:sub>1Para<\/jats:sub>, using a field\u2010cycling relaxometer, for suspensions of POPC (1\u2010palmitoyl\u20102\u2010oleoyl\u2010lecithin) vesicles with 100\u2013500 mM entrapped Gd(DTPA)<jats:sup>2\u2212<\/jats:sup> and membrane concentrations of cholesterol ranging from 0 to 40 mol %. These profiles, which span the field range 0.01\u201350 MHz proton Larmor frequency, were taken at 5, 15, 25, and 35\u00b0C. Concentrations of Gd(DTPA)<jats:sup>2\u2212<\/jats:sup> were determined independently by both ICP analyses and NMRD methods. Values for P<jats:sub>d<\/jats:sub> for vesicles with 100 mM Gd(DTPA)<jats:sup>2\u2212<\/jats:sup> and outer diameters 100 nm \u00b1 20%, as determined by quasielastic light scattering, are 63, 47, 24, 16, and 8.7 \u00d7 10<jats:sup>\u22124<\/jats:sup>cm s<jats:sup>\u22121<\/jats:sup>, at 25\u00b0C, for cholesterol concentrations of 0, 10, 20, 30, and 40%, respectively. The corresponding activation enthalpies are 14, 14, 14, 17, and 17 kcal\/M. Comparison with <jats:sup>2<\/jats:sup>H NMR studies of deuterated POPC vesicles with no cholesterol at 20\u00b0C, and with 10% at 40\u00b0C, which yielded the same order parameter for the palmitoyl acyl chains, gives no indication of a correlation between order parameter and permeability.<\/jats:p>","DOI":"10.1002\/mrm.1910230208","type":"journal-article","created":{"date-parts":[[2007,3,5]],"date-time":"2007-03-05T13:19:36Z","timestamp":1173100776000},"page":"275-286","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":62,"title":["Permeability of liposomal membranes to water: Results from the magnetic field dependence of T<sub>1<\/sub> of solvent protons in suspensions of vesicles with entrapped paramagnetic ions"],"prefix":"10.1002","volume":"23","author":[{"given":"Seymour H.","family":"Koenig","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Quet F.","family":"Ahkong","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"suffix":"III","given":"Rodney D.","family":"Brown","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Michael","family":"Lafleur","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marga","family":"Spiller","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Evan","family":"Unger","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Colin","family":"Tilcock","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2005,11,18]]},"reference":[{"key":"e_1_2_1_2_2","doi-asserted-by":"publisher","DOI":"10.1002\/mrm.1910050409"},{"key":"e_1_2_1_3_2","doi-asserted-by":"publisher","DOI":"10.1002\/mrm.1910080111"},{"key":"e_1_2_1_4_2","doi-asserted-by":"publisher","DOI":"10.1002\/mrm.1910030309"},{"key":"e_1_2_1_5_2","doi-asserted-by":"publisher","DOI":"10.1148\/radiology.171.1.2928550"},{"key":"e_1_2_1_6_2","doi-asserted-by":"publisher","DOI":"10.1002\/mrm.1910060410"},{"key":"e_1_2_1_7_2","doi-asserted-by":"publisher","DOI":"10.1016\/0009-3084(86)90069-1"},{"key":"e_1_2_1_8_2","doi-asserted-by":"publisher","DOI":"10.1085\/jgp.68.2.127"},{"key":"e_1_2_1_9_2","doi-asserted-by":"publisher","DOI":"10.1038\/216717a0"},{"key":"e_1_2_1_10_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi00294a018"},{"key":"e_1_2_1_11_2","doi-asserted-by":"publisher","DOI":"10.1016\/0006-291X(74)90313-1"},{"key":"e_1_2_1_12_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0021-9258(18)93126-1"},{"key":"e_1_2_1_13_2","first-page":"75","volume-title":"NMR Spectroscopy of Cells and Organisms","author":"Koenig S. 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