Quartz crystal microbalance with dissipation monitoring can be used to study hydration of biopolymers [1-3]. In humidity-scanning modification of this method, the water activity is set up by a non-saturated solution of lithium chloride, which is continuously diluted during the experiment. Thus, water activities are scanned from low values (close to those of saturated LiCl solutions) to very high values [2]. Here we report a further development of the method that allows performing not only continuous increase but also continuous decrease of humidities in QCM-D experiments. We applied this method to study sorption-desorption hysteresis in three biopolymers: hen egg white lysozyme, porcine gastric mucin (PGM) and bovine submaxillary gland mucin (BSM). The experiments were conducted in films of biopolymers, applied on solid surfaces of QCM-D sensors. All three biopolymers showed pronounced sorption-desorption hysteresis, although the nature of the hysteresis was different in case of lysozyme compared to PGM and BSM. Earlier it was suggested that lysozyme may have two hysteresis loops: one due to the glass transition and the other one due to changes in aggregation of lysozyme molecules [4]. This idea is discussed based on the obtained QCM-D data using results of Raman studies of hydration of lysozyme [5].
References:
1. Znamenskaya, Y.; Sotres, J.; Gavryushov, S.; Engblom, J.; Arnebrant, T.; Kocherbitov, V. J.Phys.Chem.B. (2013), 117, 2554−2563
2. Graf, G.; Kocherbitov, V. J.Phys.Chem.B. (2013), 117, 10017−10026
3. Kocherbitov, V. Current Opinion in Colloid & Interface Science (2013), 18, 510–516
4. Kocherbitov, V.; Arnebrant, T.; Söderman, O. J.Phys.Chem.B.(2004), 108 (49), 19036 – 19042
5. Kocherbitov, V.; Latynis, J.; Misiunas, A.; Barauskas, J.; Niaura, G. J.Phys.Chem.B. (2013), 117 (17), 4981–4992
vitaly.kocherbitov@mah.se
