Observation of individual microtubule motor steps in living cells with endocytosed quantum dots

Xiaolin Nan, Peter A. Sims, Peng Chen, X. Sunney Xie

Research output: Contribution to journalArticle

144 Scopus citations


We report the observation of individual steps taken by motor proteins in living cells by following movements of endocytic vesicles that contain quantum dots (QDs) with a fast camera. The brightness and photostability of quantum dots allow us to record motor displacement traces with 300 /is time resolution and 1.5 nm spatial precision. We observed individual 8 nm steps in active transport toward both the microtubule plus- and minus-ends, the directions of kinesin and dynein movements, respectively. In addition, we clearly resolved abrupt 16 nm steps in the plus-end direction and often consecutive 16 nm and occasional 24 nm steps in minus-end directed movements. This work demonstrates the ability of the QD assay to probe the operation of motor proteins at the molecular level in living cells under physiological conditions.

Original languageEnglish (US)
Pages (from-to)24220-24224
Number of pages5
JournalJournal of Physical Chemistry B
Issue number51
StatePublished - Dec 29 2005


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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