The initial stages of Umbilicaria aprina Nyl. hydration (starting from the hydration level Dm/m 0 ¼ 0.048 AE 0.004) were observed using hydration kinetics, sorption isotherm and proton NMR. The thalli were hydrated from gaseous phase. The total saturation hydration level obtained at the relative humidity p/p 0 ¼ 100% was Dm/m 0 ¼ 0.848 AE 0.009. The hydration courses revealed i) a fraction of very tightly bound water (Dm/m 0 ¼ 0.054 AE 0.011, short hydration time constant, t hyd ), ii) a fraction of tightly bound water [Dm/m 0 ¼ 0.051 AE 0.038, t hyd ¼ (4.7 AE 2.6) h], and iii) a loosely bound water pool [ t hyd ¼ (31.0 AE 1.9) h] for higher values of target humidity. The sorption isotherm of U. aprina was fitted well using Dent model. The relative mass of water saturating primary binding sites was DM/m 0 ¼ 0.054, which is close to the water fractions. Proton FIDs detected (i þ ii) the immobilized tightly bound water fraction, L 1 , and iii) the mobile, loosely bound water pool L 2 . The hydration dependence of the proton liquid signal suggests the presence of a significant contribution from a water soluble solid fraction in the thallus. Sorption isotherm fitted to NMR data showed the absence of 'sealed' water fraction trapped in pores of the thallus.

Hydration kinetics, sorption isotherm, and proton free induction decays are measured for Leptogium puberulum Hue thalli hydrated from gaseous phase. Very tightly, tightly and loosely bound water fraction are distinguished. The hydration dependence of mobile NMR signal component is non-linear and fitted well by rational function, which suggest the presence of water soluble solid (presumably carbohydrate) fraction in thallus structures of L. puberulum.

Gaseous phase hydration effect of extremely dehydrated thallus of the Antarctic lichenized fungus Turgidosculum complicatulum and of green alga Prasiola crispa was observed using hydration kinetics, sorption isotherm, H-NMR spectroscopy and relaxometry. Three bound water fractions were distinguished: (1) very tightly bound water, (2) tightly bound water and (3) a loosely bound water fraction detected at higher levels of hydration. Sorption isotherm was sigmoidal in form and well fitted using Dent model. The relative mass of water saturating primary water binding sites was ΔM/m = 0.055 for T. complicatulum and ΔM/m = 0.131 for P. crispa.H-NMR free induction decays (FIDs) for T. complicatulum and for P. crispa were superpositions of a solid signal component, and one averaged liquid signal component for P. crispa thallus ([Formula: see text] ≈ 80 µs) or two liquid signal components coming from a tightly bound ([Formula: see text]≈ 71 µs) and from a loosely bound water fraction ([Formula: see text]≈ 278 µs) for T. complicatulum. H-NMR spectra recorded for T. complicatulum and for P. crispa thalli revealed one averaged mobile proton signal component L. The total liquid signal component expressed in units of solid (L + L )/S suggests the presence of water soluble fraction in T. complicatulum thallus.

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AbstractThe effect of low temperature onUmbilicaria aprinacollected from Schirmacher Oasis, East Antarctica, was determined over a wide range of hydration using proton free induction decays, proton nuclear magnetic resonance (NMR) spectra and differential scanning calorimetry methods. The proton NMR line is a superposition of the broad component from the solid matrix of the thallus and a narrower component from the averaged bound water pool. Proton free induction decays may be resolved into three components: a solid component well described by the Abragam function and two exponentially decaying components from water loosely bound and water tightly bound in the thallus. With decreased temperature the loosely bound water pool (freezing water) is transferred to the tightly bound water pool (non-freezing water), and vanishes below -40°C. Bound water freezing and melting temperatures decrease with the decrease of hydration level, suggesting that heterogeneous ice nucleation is responsible for water freezing. The onset of bound water freezing temperature isc.10°C lower than the melting temperature. TheU. aprinathalli do not reveal the ability to stimulated ice nucleation at higher temperature. Freeze-thaw cycles showed that forn> 5 cycles no substantial change occurs in the difference between melting and freezing temperatures.

Hydration kinetics, sorption isotherm, and proton free induction decays are measured for Ramalina terebrata thalli rehydrated from gaseous phase. Very tightly, tightly, and loosely bound water fractions are distinguished. Sorption isotherm is sigmoidal in form with the mass of water saturating primary water binding sites equal to ∆m/m 0 = 0.046. Proton free induction decays show the presence of immobilized water fraction (T * 2L 1 ≈ 100 µs) and mobile water pool (T * 2L 2 ≈ 330 µs). Sorption isotherm fitted to the NMR data shows the absence of water fraction "sealed" in pores of dry thallus.

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The initial stages of rehydration of digalactosyldiacylglycerol model membrane lyophilizates were observed using hydration kinetics, sorption isotherm, and high power proton relaxometry (at 30 MHz). Hydration time courses are single exponential and the sorption isotherm is sigmoidal in form. The mass of water saturating primary binding sites equals ∆M/m0 = 0.019 ± 0.001. Proton free induction decays distinguish (i) immobilized protons of solid matrix of lyophilizate, signal S0; (ii) protons of water fraction tightly bound to the lyophilizate surface, L1; and (iii) mobile protons of loosely bound water pool, L2. Hydration dependence of total water signal (L1 + L2)/S0 shows the presence of water fraction "sealed" in liposome structures, which equals ∆MS/m0 = 0.092 ± 0.007.