Measuring the behavior of single molecules enables the discovery of states and dynamics obscured by bulk measurements. However, molecules in solution rapidly diffuse in three dimensions, precluding long-duration and high-temporal resolution measurement. In a new breakthrough, Shangguo (aka the TrackFather) has developed 3D single-molecule active real-time tracking (3D-SMART), which can “lock-on” to freely diffusing single molecules in solution for up to minutes at a time! This new single molecule tracking can be applied to continuously monitor single proteins and nucleic acids, including real-time measurement of transcription on a freely diffusing, single-dye labelled DNA strand. See the entire work in the recent paper in Nature Communications!

The structure and dynamics of intracellular water constitute the cornerstone for understanding all aspects of cellular function. However, direct visualization of subcellular solvation heterogeneity has remained elusive. To explore this question, graduate student Xiaoqi Lang has demonstrated a vibrational-shift imaging approach to probe solvation at the microscopic level by combining spectral-focusing hyperspectral stimulated Raman scattering (hsSRS) with an environmentally-sensitive nitrile probe. When applied to quantitatively measure the spatial variation of solvation in live cells, this new method reveals significantly reduced solvation in the cytoplasm compared to the nuclear compartment and bulk water! This work sheds light on heterogenous solvation at the subcellular level and opens up new avenues to explore solvation variance in complex systems. For more, check out the recent publication in the Journal of Chemical Physics.

Our collaborators in the Sahay lab (sahaylab.org) have recently reported that naturally occurring cholesterol analogues can increase the delivery efficiency of lipid nanoparticles (LNPs)! Way to go Gaurav and team! Josie and Shangguo applied 3D-DyPLoT to differentiate the intracellular trafficking behavior of different LNP constructs, showing that increased delivery efficiency correlated with increased linear directed motion of individual LNPs in live cells.

Link: www.nature.com/articles/s41467-020-14527-2

Courtney has developed a new strategy for improving the speed of laser scanning microscopy. The technique, called 3D Fast Acquisition Scan by z-Translating Raster (3D-FASTR), uses an electrically tunable lens (ETL) to generate a reproducible 3D sparse sampling pattern which fully and efficiently scans a volume in the fastest possible time without repeating until the volume is complete. This method has shown a 4-fold improvement in the volumetric imaging rate of live cells. The theory underlying 3D-FASTR is completely general and can be applied to any scanning imaging method. Find details in the recent publication in Optics Express!

Link: doi.org/10.1364/OE.27.036241