The State of Biophysics - Biophysical Journal

Probing Nature’s Nanomachines

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perform life’s central functions. Yet these molecules by themselves are not alive, and they function only when they work in the cellular milieu. How living cells come alive through the concerted actions of individual molecules is a major challenge for future research. Researchers are making progress on multiple fronts. On one front we might call ‘‘extreme in vitro,’’ we can measure multiple properties from single-molecular assem- blies. FRET can be extended up to four colors, allowing us to measure six distances simultaneously. This can also be combined with multiaxis optical tweezers to study, for example, DNA replication, which is an amazingly rapid and accurate process that requires more than a dozen different proteins, with single basepair resolution, while at the same time probing how many proteins of which kind are present at each step of the reaction. On another front, we can push the technology to the cellular level, and even to the tissue level, ultimately hoping to view single-mole- cule activities in living cells in full glorious detail. Finally, we might find a third way, where protein complexes can be captured from freshly sacrificed cells or animals, or pa- tient tissues, for detailed single-molecule analysis.

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Biophysical Journal 110(5) 1004–1007