Literature/202212291648 optical methods for single molecule analysis

First published:

Last Edited:

Number of edits:

The earliest method to get single-molecule data is to interrogate a very small volume. For example, if we consider a $1\mu m^3=1\,\textrm{fl}$ volume with only one molecule inside, we get a concentration of $100\, \textrm{nM}$. However, at a concentration of $1\ \textrm{fM}$, we have 600 molecules per $10^9$ femto-liter volumes.

Therefore, flow-methods (like Flow Cytometry) operate a concentration regimes close to pico-molar: concentrated enough to detect a statistically significant number of molecules, and diluted enough to neglect coincidental detections (known as swarming in flow cytometers).

Low concentrations are important, for example see: literature/202212291643 Errors in amino acid sequences, why pushing sensitivity of assays.

  • Many methods rely on pre-concentration steps, to limit the volume that must be scanned. Examples:

  • Some methods are truly single-molecule sensitive:


These are the other notes that link to this one.


Share your thoughts on this note
Aquiles Carattino
Aquiles Carattino
This note you are reading is part of my digital garden. Follow the links to learn more, and remember that these notes evolve over time. After all, this website is not a blog.
© 2021 Aquiles Carattino
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License
Privacy Policy