Protein Crystallization Irradiated by Audible Sound: The Effect of Varying Sound Frequency

Abstract

Protein crystallization is a process that is very sensitive to the physical environment. Audible sound is an environmental characteristic that can significantly affect the crystallization process. Previously, it was found that the crystallization result is frequency dependent, that is, the crystallization of protein under different sound frequencies yields different results. Here, we further investigate the effect of varying frequency (or a frequency program) on protein crystallization. Twelve different frequency programs and six proteins were used to test the effect of varying sound frequency on protein crystallization. The results showed that varying the audible sound frequency from high to low exhibited the most significant improvement in protein crystallization. Varying frequency linearly from 15 000 to 100 Hz in 12 h best promoted crystallization, with the average number of crystallization hits 36.5% higher than in the control. Crystal quality was improved with sound irradiation using STW2 program. Our study showed that varying the sound frequency has positive effects on facilitating protein crystallization and purposely optimizing sound frequency programs may be helpful for obtaining protein crystals.

Pilot Aquaphotomic Study of the Effects of Audible Sound on Water Molecular Structure

“…The change in temperature might be a result of absorbed heat generated by the sound perturbation. Previous works have shown that at least part of the audible sound energy is transformed into heat that can be absorbed by water, and spent on the reorganization of water molecular structure, causing the change in its temperature [ 6 , 10 ].…”

“…Our findings, even though based on investigation of sound effects on the simplest aqueous systems and only two frequencies, may prove to have wider implications, especially considering the major role water plays as a matrix for biological systems. Recent scientific reports showed that audible sound promotes crystallization of proteins, which is frequency-dependent, and shows some variation based on protein type; this was found to be connected with the change of temperature and evaporation of protein solution [ 6 , 10 ]. Although the mentioned studies were performed using different frequencies and even variable-frequency sound perturbation, there is a common link with our study—sound affects water-based systems and changes their molecular structure in a frequency- and sample-type-dependent manner.…”

“…There are many records documenting how sound affects biomolecules in water solutions, single-cells and even whole organisms, plants especially [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. One study showed that audible sound in the form of music (38–689 Hz) was able to affect growth, metabolism and antibiotic susceptibility of prokaryotic as well as eukaryotic microbes [ 8 , 9 ].…”

“…The effects of sound on biological structures was also investigated in vitro, showing, for example, that crystallization of proteins is sensitive to audible sound and is frequency-dependent [ 6 , 10 ]. Sound, however, has not only been seen to induce changes by pure mechanical means, it has also been shown to have an impact on the signal paths of plants and the nervous system of animals.…”