How do your crystals grow?
"Another advantage of fluorescence is that it provides a high signal-to-noise ratio," says author Shinpei Tanaka of Hiroshima University in Japan. "We are able to measure very dilute solutions at the crystal interface."
The researchers found that when single tetragonal crystals of egg-white lysozyme formed, there was no concentration gradient between the solution and the crystal surface. However, in formation of clumps of needle-like branched crystals, called spherulites, the observed concentration at the surface was several times higher than that of the bulk solution. The authors attributed the difference to aggregates of loosely bound molecules near the interface.
Characterization of the dynamics near the crystal by FCS may provide direction for improving the crystallization process - currently as much an art as a science, based on trial and error - because the spherulites are not usable for structural characterizations.
"Although we knew something was different between the two crystal forms, the degree of concentration of the molecules in spherulites compared to that of the homogeneous state around tetragonal single crystals was surprising," says Tanaka.
The analytical result could lead to improvements in isolation of good crystals of biomolecules. For example, the results suggest that local heating by a laser could be used to control local concentrations and avoid spherulite formation.
Original publication: Shinpei Tanaka et al.; "Slow molecular dynamics close to crystal surfaces during crystallization of a protein lysozyme studied by fluorescence correlation spectroscopy"; The Journal of Chemical Physics 2010.
Other news from the department science
Get the life science industry in your inbox
From now on, don't miss a thing: Our newsletter for biotechnology, pharma and life sciences brings you up to date every Tuesday and Thursday. The latest industry news, product highlights and innovations - compact and easy to understand in your inbox. Researched by us so you don't have to.