How do your crystals grow?

September 14, 2010

Washington, D.C. (September 14, 2010) -- Because one of the main bottlenecks in determining the structure of protein molecules is producing good isolated single crystals, improved crystallization techniques would be useful in a wide range of genomics and pharmaceutical research.

Research reported in The Journal of Chemical Physics uses fluorescence correlation spectroscopy (FCS) to investigate the processes at the surface of a growing crystal. By focusing a laser on the crystal surface and measuring the resulting fluorescence, FCS can resolve dimensions as small as a single wavelength of the light.

"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.
-end-
The article, "Slow molecular dynamics close to crystal surfaces during crystallization of a protein lysozyme studied by fluorescence correlation spectroscopy" by Shinpei Tanaka appears in The Journal of Chemical Physics. http://link.aip.org/link/jcpsa6/v133/i9/p095103/s1

Journalists may request a free PDF of this article by contacting jbardi@aip.org

NOTE: An image is available for journalists. Please contact jbardi@aip.org

ABOUT THE JOURNAL OF CHEMICAL PHYSICS

The Journal of Chemical Physics publishes concise and definitive reports of significant research in methods and applications of chemical physics. Innovative research in traditional areas of chemical physics such as spectroscopy, kinetics, statistical mechanics, and quantum mechanics continue to be areas of interest to readers of JCP. In addition, newer areas such as polymers, materials, surfaces/interfaces, information theory, and systems of biological relevance are of increasing importance. Routine applications of chemical physics techniques may not be appropriate for JCP. Content is published online daily, collected into four monthly online and printed issues (48 issues per year); the journal is published by the American Institute of Physics. See: http://jcp.aip.org/

ABOUT AIP

The American Institute of Physics is a federation of 10 physical science societies representing more than 135,000 scientists, engineers, and educators and is one of the world's largest publishers of scientific information in the physical sciences. Offering partnership solutions for scientific societies and for similar organizations in science and engineering, AIP is a leader in the field of electronic publishing of scholarly journals. AIP publishes 12 journals (some of which are the most highly cited in their respective fields), two magazines, including its flagship publication Physics Today; and the AIP Conference Proceedings series. Its online publishing platform Scitation hosts nearly two million articles from more than 185 scholarly journals and other publications of 28 learned society publishers.

American Institute of Physics

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