Low-temperature immobilization of water in Antarctic Turgidosculum complicatulum and in Prasiola crispa. Part I. Turgidosculum complicatulum.
Colloids Surf B Biointerfaces
; 173: 869-875, 2019 Jan 01.
Article
em En
| MEDLINE
| ID: mdl-30551303
ABSTRACT
The studies of low-temperature immobilization of bound water in Antarctic lichenized fungus Turgidosculum complicatulum were performed using 1H NMR and DSC over a wide range of thallus hydration. 1H NMR free induction decays were decomposed into a solid component well described by the Gaussian function and two exponentially decaying components coming from a tightly bound water and from a loosely bound water fraction. 1H NMR spectra revealed one averaged mobile proton signal component. 1H NMR measurements recorded in time and in frequency domain suggest the non-cooperative bound water immobilization in T. complicatulum thallus. The threshold of the hydration level estimated by 1H NMR analysis at which the cooperative bound water freezing was detected was Δm/m0 ≈ 0.39, whereas for DSC analysis was equal to Δm/m0 = 0.375. Main ice melting estimated from DSC measurements for zero hydration level of the sample starts at tm = -(19.29 ± 1.19)°C. However, DSC melting peak shows a composed form being a superposition of the main narrow peak (presumably melting of mycobiont areas) and a broad low-temperature shoulder (presumably melting of isolated photobiont cells). DSC traces recorded after two-hour incubation of T. complicatulum thallus at -20 °C suggest much lower threshold level of hydration at which the ice formation occurs (Δm/m0 = 0.0842). Presumably it is a result of diffusion induced migration of separated water molecules to ice microcrystallites already present in thallus, but still beyond the calorimeter resolution.
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01-internacional
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MEDLINE
Assunto principal:
Ascomicetos
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Microbiologia da Água
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Água
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Temperatura Baixa
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Clorófitas
Idioma:
En
Revista:
Colloids Surf B Biointerfaces
Assunto da revista:
QUIMICA
Ano de publicação:
2019
Tipo de documento:
Article