Using speckles to spot protein dynamics

Pereira et al. describe a new microscopy technique that allows researchers to more precisely mark molecules whose movements they want to track.

Researchers can follow the movements of proteins with several techniques, including fluorescent speckle microscopy (FSM), which relies on the natural variations in signal intensity that occur when levels of fluorescent molecules in a sample are low. These variations result in a speckled pattern on structures such as microtubules, allowing scientists to monitor changes. However, either the contrast or the available signal is low with FSM, making it difficult to distinguish the speckles.

The method Pereira et al. devised, inducible speckle imaging, directs laser light through a diffuser before it reaches the target cell. Constructive and destructive interference create a 3D pattern of speckles that serve as reference points for tracking changes. Unlike FSM, the technique provides a strong signal and high contrast. Another advantage, the researchers note, is that inducible speckle imaging isn’t affected by imperfections in the optical system, which can reduce the resolution of FRAP and other methods of following protein dynamics.

Pereira et al. measured spindle microtubule dynamics in Drosophila cells, which have been difficult to pin down with FSM. Their results support the hypothesis that metaphase duration correlates with the speed of microtubule movement toward the spindle pole. The researchers say that the technique could be applied to other long, fairly homogeneous structures in cells, such as membranes and other types of cytoskeletal filaments.