For the first time, researchers have been able to confine and study an individual protein, one that plays a key role in photosynthesis, without having to pin it down so tightly as to alter its fundamental behavior.
In the first practical application to proteins of a recently developed technique, two Stanford chemists were able to make detailed observations of the dynamic behavior of the molecule for more than one second, a 50- to 100-fold increase in viewing time compared to other methods, and thereby "set a new standard in single-molecule spectroscopy," according to a commentary in the March issue of Nature Chemistry.
The groundbreaking study is described in a paper by Stanford chemists W. E. Moerner and Randall Goldsmith in that issue, now available online. The commentary was written by researchers not involved in the study.
Observing molecules one at a time is valuable because it lets researchers get a clear picture of that molecule's changing behavior over time, without the picture being confused by the presence of other molecules.
Up until now, researchers have had to remove a molecule from its normal environment typically a solution such as the bloodstream or the fluids inside a cell and "basically staple it to some surface such as a glass slide or a large plastic bead, or imbed it in a synthetic polymer to observe it," said Goldsmith, a postdoctoral researcher in chemistry.
The result, he said, is like trying to discern how a tiger behaves in the wild by watching it pace back and forth in a cage at the zoo. "You have every reason to be suspicious that you might profoundly alter the behavior of the molecule by binding it to a surface," Goldsmith said.
That perspective is buttressed by the results of their study, in which they "trapped" in solution a molecule of a fluorescent photosynthetic protein called allophycocyanin, which is found in red algae and cyanobacteria (formerly known as blue-gre
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