Protein crystals form in supersaturated solutions via a nucleation and growth mechanism. The amyloid fibrils of denatured proteins also form via a nucleation and growth mechanism. This similarity suggests that, although protein crystals and amyloid fibrils are distinct in their morphologies, both processes can be controlled in a similar manner. We show that ultrasonication is one of the most effective methods of agitation for accelerating spontaneous fibrillation. We also show that ultrasonication is also useful for forming crystals of proteins. We address the underlying mechanism of the ultrasonication-dependent breakdown of supersaturation, leading to the formation of amyloid fibrils or protein crystals.
Many scientists have investigated taste nerve responses without regarding the tonicity of taste stimulating solutions that varies in a wide range. We increased the tonicity by adding nonelectrolytes that elicited no taste nerve responses in bullfrogs, and investigated hypertonicity effects on the taste nerve responses to inorganic salts and bitter substances. Here, we show that the hypertonicity opens tight junctions surrounding taste receptor cells and changes the magnitude and firing pattern of taste nerve responses. We quantitatively suggest that the changes result from the magnitude and direction of local circuit currents generated by diffusion potentials across the tight junctions.
Aureochromes in stramenopiles contain a basic leucine zipper (bZIP) domain in the central region and a light-oxygen-voltage-sensing (LOV) domain, and are thought to function as light-regulated transcription factors. To understand the molecular mechanism, we investigated the photoreactions, oligomeric structures, and DNA binding of recombinant aureochrome-1 (AUREO1). The results suggest that monomeric AUREO1 is present in reduced conditions and undergoes dimerization upon illumination. Blue light-induced dimerization enhances the affinity for the target sequence. Our N-terminally truncated mutants may be useful molecular tools as a photoactivatable-bZIP module (Photozipper) for optogenetics and biophysical analyses.
Stimulated Raman scattering (SRS) microscopy allows real-time biomedical imaging based on vibrational contrast, leading to various emerging applications to label-free imaging and Raman-labeled imaging. This review explains the principle, features, and applications of SRS microscopy, and introduces our recent development of SRS spectral microscopy for multicolor, real-time, stain-free tissue imaging.