Biophysics Letter

European Biophysics Journal

, Volume 31, Issue 7, pp 559-562

First online:

Membrane water-penetration profiles from spin labels

  • Derek MarshAffiliated withMax-Planck-Institut für biophysikalische Chemie, Abteilung Spektroskopie, 37070 Göttingen, Germany

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Spin label hyperfine splittings in mixtures of protic and aprotic solvents are used to obtain association constants K A,h for hydrogen bonding to oxazolidine nitroxides. With the Onsager approach to account for the variation in local dielectric constant, these results are used to determine the effective penetration profile of water into fluid phospholipid membranes, from recent electron paramagnetic resonance (EPR) studies on phospholipids spin-labelled systematically down the sn-2 chain. Water penetration is appreciable, depends on chain unsaturation, and is strongly affected by cholesterol.

Hydrogen bonding Nitroxide Polarity profile Local dielectric constant Water permeation