Ultra-photostable DNA FluoroCubes: Mechanism of Photostability and Compatibility with FRET and Dark Quenching

Ultrafast Super-Resolution Imaging Exploiting Spontaneous Blinking of Static Excimer Aggregates

Single-molecule localization methods have been popularly exploited to obtain super-resolved images of biological structures. However, the low blinking frequency of randomly switching emission states of individual fluorophores greatly limits the imaging speed of single-molecule localization microscopy (SMLM). Here we present an ultrafast SMLM technique exploiting spontaneous fluorescence blinking of cyanine dye aggregates confined to DNA framework nanostructures. The DNA template guides the formation of static excimer aggregates as a "light-harvesting nanoantenna", whereas intermolecular excitation energy transfer (EET) between static excimers causes collective ultrafast fluorescence blinking of fluorophore aggregates. This DNA framework-based strategy enables the imaging of DNA nanostructures with 12.5-fold improvement in speed compared to conventional SMLM. Further, we demonstrate the use of this strategy to track the movement of super-resolved DNA nanostructures for over 20 min in a microfluidic system. Thus, this ultrafast SMLM holds great potential for revealing the dynamic processes of biomacromolecules in living cells.

Lumos maxima - How robust fluorophores resist photobleaching?

Fluorescent dyes synergize with advanced microscopy for researchers to investigate the location and dynamic processes of biomacromolecules with high spatial and temporal resolution. However, the instability of fluorescent dyes, including photobleaching and photoconversion, represent fundamental limits for super-resolution and time-lapse imaging. In this review, we discuss the latest advances in improving the photostability of fluorescent dyes. We summarize the primary photobleaching processes of cyanine and rhodamine dyes and highlight a range of strategies developed in recent years to strengthen these fluorophores. Additionally, we discuss the influence of protein microenvironments and labeling methods on the photostability of fluorophores. We aim to inspire next-generation robust and bright fluorophores that ultimately enable the routine practice of time-lapse super-resolution imaging of live cells.

DNA Origami Fiducial for Accurate 3D Atomic Force Microscopy Imaging

Atomic force microscopy (AFM) is a powerful technique for imaging molecules, macromolecular complexes, and nanoparticles with nanometer resolution. However, AFM images are distorted by the shape of the tip used. These distortions can be corrected if the tip shape can be determined by scanning a sample with features sharper than the tip and higher than the object of interest. Here we present a 3D DNA origami structure as fiducial for tip reconstruction and image correction. Our fiducial is stable under a broad range of conditions and has sharp steps at different heights that enable reliable tip reconstruction from as few as ten fiducials. The DNA origami is readily codeposited with biological and nonbiological samples, achieves higher precision for the tip apex than polycrystalline samples, and dramatically improves the accuracy of the lateral dimensions determined from the images. Our fiducial thus enables accurate and precise AFM imaging for a broad range of applications.