Plasmonic Nanotorch Helps Detect Ultrafast Biochemical Reactions

Human life relies on exceptional arrays of biochemical reactions. Thus, gaining insights into the functions of biomolecules necessitates real-time tracking of such reactions.

An artistic impression of a plasmonic nanotorch. Image Credit: Yuyang Wang.

Biochemical reactions take place within small fractions of a millisecond and are highly challenging to track even if extremely sensitive optical instruments are used.

Yuyang Wang, a PhD researcher, makes use of a “plasmonic nanotorch”—a single metal nanoparticle for illuminating single fluorescent molecules—enabling the detection of such ultrafast biochemical reactions at present. Wang defended his PhD on June 19th, 2020.

Life is possible with biochemical reactions, specifically those that involve enzymes. The analysis of such reactions is the foundation for advanced biophysical sciences, and a great deal of information has been disclosed on the length scales and the timescales involved.

For a long time, biomolecules and their interactions had been studied only at the ensemble level, where several molecules are analyzed on timescales considerably longer compared to that in the biochemical reaction.

Tackle the Biological Puzzles

Single-molecule fluorescence microscopy (SMFM) is an important tool to achieve a biological understanding of complex molecular systems in which high spatial and temporal resolutions are needed.

By employing SMFM, biological puzzles that are conventionally impossible to solve can be resolved. Single-molecule sensitivity offers access to molecule-to-molecule and time-to-time discrepancies related to complex biological processes, which are concealed in ensemble-level observations.

But the SMFM’s temporal resolution is restricted by the brightness of single molecules as a result of their intrinsic fluorescence saturation at high laser power. Latest methods to improve the brightness are required immediately to extend the applications of SMFM to quicker regimes. Therefore, the usage of single gold nanoparticles was examined by Yuyang Wang to enhance the optimal brightness of single molecules.

Nanoscale Antennas

Noble metal nanoparticles, such as silver or gold particles with a size of less than 100 nm, act like nanoscale antennas. Fluorescence molecules in the proximity of such particles are considerably influenced and seem to be considerably brighter as if being illuminated up by a “plasmonic nanotorch.”

Wang specifically focused on the saturation behavior of single molecules close to the plasmonic particles, as brightness is restricted by saturation. Also, it was discovered that single plasmonic nanoparticles alter the saturation behavior and enhance the maximum brightness of single molecules by up to hundreds of times.

In addition, a systematic method both in theory and in practice was designed by Wang with such nanoparticles.

This is the first time single plasmonic nanotorches have been employed to detect fluorogenic enzyme reactions. It is an essential step in forcing fluorescence improvement to the field of single-molecule enzymology.

The research by Wang improves the insights into plasmon-enhanced fluorescence and provides a method for studying quick biomolecular processes.


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