Rehydration of Digalactosyldiacylglycerol Model Membrane Lyophilizates Observed by NMR and Sorption Isotherm

Abstract

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.

Initial Phases of DNA Rehydration by NMR and Sorption Isotherm

“…The value of the spin-spin relaxation time for solid is close to that value for the solid matrices of several dry microheterogeneous biological systems (e.g. model DGDG membranes [12], photosynthetic membranes [13], bark and bast [14], wheat seed [15], lichen thallus [11,[16][17][18][19], dentine and dental enamel [20]). Moreover, similar values of spin-spin relaxation time are recorded for dry solid polymer matrices [21].…”

Initial Phases of Antarctic Ramalina terebrata Hook f. & Taylor Thalli Rehydration Observed by Proton Relaxometry

“…The L 1 signal component with the value T * 2L 1 ≈ 100 µs is characteristic of tightly bound water fraction either lichen thalli or for many other biological systems [19,[22][23][24][25][26][27][28][29][30]. The L 2 signal with T * 2L 2 ≈ 330 µs, shortened by B 0 inhomogeneities [31], comes from water loosely bound on thallus surfaces and/or from free water fraction (Fig.…”

“…For some dry biological systems (e.g. freeze-dried photosynthetic membranes) a fraction of loosely (and tightly) bound water remains in pores of dry system [25,28,29]. Its presence manifests in NMR--sorption isotherm as a constant liquid signal already detected at h = 0.…”

Non-cooperative immobilization of residual water bound in lyophilized photosynthetic lamellae

“…In contrast to animal cell membranes, photosynthetic membranes are dominated by galactolipids, which prefer the formation of the lyotropic inverted hexagonal H II phase over the lamellar L phase [9]. For example, the main photosynthetic membrane lipid MGDG with unsaturated fatty acids forms in water phase H II .…”

“…For the lowest hydration levels, the L 2 component was not detected. The 1/e-value allows a direct comparison between the characteristic time constant describing the solid signal and the relaxation times describing the liquid signal components[9,16,17].…”