engleski

Low-temperature epr study of solid trehalose

Trehalose is a disaccharide found in nature which can form crystalline and glassy state. It is well known for its unusual bioprotective properties like ahydrobiosis or cryoprotection. These phenomena are still not fully understood and have prompted the investigation of molecular dynamics in the wide range of trehalose preparations in the solid state. Due to the fact that trehalose exhibits the highest glass transition temperature, Tg, and the most compact hydrogen-bonded network of saccharides, it is interesting to be studied in the context of low-temperature anomalies observed in glasses. The advantage of applying electron paramagnetic resonance (EPR) spectroscopy is in the sensitivity of the electron-spin coupling with the disordered modes in the observed system. Here, electron spin-lattice relaxation times (T1) measured by X-band EPR spectroscopy in irradiated trehalose glass and anhydrous polycrystalline state are presented in the large temperature interval, from 0.012 Tg to 0.7 Tg. The largest difference in T1 is detected below ca. 80 K indicating more efficient energy exchange between the spin system and the lattice for paramagnetic centers in the glassy than anhydrous trehalose polycrystalline state. The involvement of the disordered modes (glassy/soft/boson peak modes), which enhance the energy exchange between the spin system and the lattice in the glassy as compared to the crystalline state, is evaluated in the framework of soft potential model. The results corroborate the idea of boson peak being a universal property of disordered solids.

Trehalose; Glassy state; Molecular dynamics; EPR

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