Non‐thermal effects of microwaves on proteins: thermophilic enzymes as model system

Abstract

Two thermophilic and thermostable enzymes, isolated from Sulfolohus solfataricus, S-adenosylhomocysteine hydrolase and 5'-methylthioadenosine phosphorylase, were exposed to 10.4 GHz microwave radiation in order to discriminate between thermal and non-thermal microwave effects. The exposure causes a non-thermal, irreversible and time-dependent inactivation of both enzymes; the inactivation rate is related to the energy absorbed and is independent of the enzyme concentration. The influence of salts on enzyme inactivation has also been investigated. Conformational changes of 5-adenosylhomocysteine hydrolase, detected by fluorescence and circular dichroism techniques, suggest that microwaves induce protein structural rearrangements not related to temperature.

Heat-Induced Antigen Retrieval: An Effective Method to Detect and Identify Progenitor Cell Types during Adult Hippocampal Neurogenesis

“…Thermal denaturation using a microwave promotes an unmasking effect as it disrupts the secondary and tertiary structure of the proteins 6 . Other mechanisms have been proposed including molecular rapid oscillation 6,10,11 . Thus, boiling in the citric acid and tri-sodium citrate buffer is a key step in antigen-retrieval.…”

Microwave-Stimulated Antigen Retrieval. An Update.

“…Hopwood et al [11] concluded that MW irradiation did not produce cleavage or polymerization of proteins and irradiation resulted in an electrophoretic pattern that was similar to that obtained when lysozyme and hemoglobin was heated in formaldehyde to 60°C for 30 min. Interestingly, Porcelli et al [33], more recently, showed results to the contrary. In a study of Sadenosylhomocysteine hydrolase and 5'-methylthioadenosine phosphorylase, two thermophilic and thermostable enzymes, they found that exposure to MWs caused a nonthermal, irreversible and time-dependent inactivation of both enzymes.…”

Preparation of CaZrO₃ powders by a microwave–assisted molten salt method

“…temperature and holding time; and 3) the existence of nonthermal effect from the microwave heating. 27), 36) Shown in Fig. 3 are FESEM images of the asreceived ZrO 2 powders and CaZrO 3 powders prepared by MMSS.…”