title: Non-cooperative immobilization of residual water bound in lyophilized photosynthetic lamellae.
abstract: This study applied 1H-NMR in time and in frequency domain measurements to monitor the changes that occur in bound water dynamics at decreased temperature and with increased hydration level in lyophilizates of native wheat photosynthetic lamellae and in photosynthetic lamellae reconstituted from lyophilizate. Proton relaxometry (measured as free induction decay = FID) distinguishes a Gaussian component S within the NMR signal (o). This comes from protons of the solid matrix of the lamellae and consists of (i) an exponentially decaying contribution L1 from mobile membrane protons, presumably from lipids, and from water that is tightly bound to the membrane surface and thus restricted in mobility; and (ii) an exponentially decaying component L2 from more mobile, loosely bound water pool. Both proton relaxometry data and proton spectroscopy show that dry lyophilizate incubated in dry air, i.e., at a relative humidity (p/p0) of 0% reveals a relatively high hydration level. The observed liquid signal most likely originates from mobile membrane protons and a tightly bound water fraction that is sealed in pores of dry lyophilizate and thus restricted in mobility. The estimations suggest that the amount of sealed water does not exceed the value characteristic for the main hydration shell of a phospholipid. Proton spectra collected for dry lyophilizate of photosynthetic lamellae show a continuous decrease in the liquid signal component without a distinct freezing transition when it is cooled down to -60ºC, which is significantly lower than the homogeneous ice nucleation temperature [Bronshteyn, V.L. et al. Biophys. J. 65 (1993) 1853].
authors.forename: Hubert
authors.initials: H
authors.lastname: Harańczyk
authors.forename: Ewelina
authors.initials: E
authors.lastname: Baran
authors.forename: Piotr
authors.initials: P
authors.lastname: Nowak
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Florek-Wojciechowska
authors.forename: Anna
authors.initials: A
authors.lastname: Leja
authors.forename: Dorota
authors.initials: D
authors.lastname: Zalitacz
authors.forename: Kazimierz
authors.initials: K
authors.lastname: Strzałka
mesh_terms: D005612:Freeze Drying; D009682:Magnetic Resonance Spectroscopy; D016011:Normal Distribution; D010788:Photosynthesis; D011522:Protons; D013696:Temperature; D020524:Thylakoids / Q000378:metabolism*; D014908:Triticum / Q000378:metabolism; D014867:Water / Q000737:chemistry*
chemical_list: D011522:Protons; D014867:Water