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A Guide to Build a Highly Inclined Swept Tile Microscope for Extended Field-of-view Single-molecule Imaging

Single-molecule imaging has greatly advanced our understanding of molecular mechanisms in biological studies. However, it has been challenging to obtain ...

University of Central Florida

We report a simple single-molecule fluorescence imaging method that increases the temporal resolution of any type of array detector by >5-fold with full field-of-view. We spread single-molecule spots to adjacent pixels by rotating a mirror in the detection path during the exposure time of a single frame, which encodes temporal information into the spatial domain. Our approach allowed us to monitor fast blinking of an organic dye, the dissociation kinetics of very short DNA and conformational changes of biomolecules with much improved temporal resolution than the conventional method. Our technique is useful when a large field-of-view is required, for example, in the case of weakly interacting biomolecules or cellular imaging.

Spatially encoded fast single-molecule fluorescence spectroscopy with full field-of-view.

The single-molecule pull-down (SiMPull) assay analyzes molecular complexes in physiological conditions from cell or tissue lysates. Currently the approach requires a lengthy sample preparation process, which has largely prevented the widespread adoption of this technique in bioanalysis. Here, we present a simplified SiMPull assay based upon dichlorodimethylsilane-Tween-20 passivation and F(ab) fragment labeling. Our passivation is a much shorter process than the standard polyethylene glycol passivation used in most single-molecule studies. The use of F(ab) fragments for indirect fluorescent labeling rather than divalent F(ab') or whole IgG antibodies allows for the pre-incubation of the detection antibodies, reducing the sample preparation time for single-molecule immunoprecipitation samples. We examine the applicability of our approach to recombinant proteins and endogenous proteins from mammalian cell lysates.

Facile single-molecule pull-down assay for analysis of endogenous proteins.

Although the formation of RNA-protein bodies has been studied intensively, their mobility and how their number and size are regulated are still poorly understood. Here, we show significant increased mobility of nuclear speckles after transcriptional inhibition, including long-range directed motion of one speckle towards another speckle, terminated by speckle fusion, over distances up to 4 um and with velocities between 0.2-1.5 µm/min. Frequently, 3 or even 4 speckles follow very similar paths, with new speckles appearing along the path followed by a preceding speckle. Speckle movements and fusion events contribute to fewer but larger speckles after transcriptional inhibition. These speckle movements are not actin-dependent, but occur within chromatin-depleted channels enriched with small granules containing the speckle-marker protein SON. Similar long-range speckle movements and fusion events were observed after heat-shock, heavy-metal stress, and during late G2 and early prophase. Our observations suggest a mechanism for long-range, directional nuclear speckle movements, contributing to overall regulation of nuclear speckle number and size as well as overall nuclear organization.

Kyu Young Han

CREOL,
The College of Optics and Photonics,
CREOL, The College of Optics and Photonics

University of Central Florida

A Guide to Build a Highly Inclined Swept Tile Microscope for Extended Field-of-view Single-molecule Imaging

Kyu Young Han

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University of Central Florida

A Guide to Build a Highly Inclined Swept Tile Microscope for Extended Field-of-view Single-molecule Imaging

CREOL,
The College of Optics and Photonics,
CREOL, The College of Optics and Photonics