Spin label

  A spin label (SL) is an organic molecule which possesses an unpaired electron, usually on a nitrogen atom, and the ability to bind to another molecule. Spin labels are normally used as tools for probing proteins or biological membrane-local dynamics using EPR spectroscopy. The site-directed spin labeling (SDSL) technique allows one to monitor a specific region within a protein. In protein structure examinations, amino acid-specific SLs can be used.

Additional recommended knowledge

What is the Correct Way to Check Repeatability in Balances?

Don't let static charges disrupt your weighing accuracy

What is the Sensitivity of my Balance?

The goal of spin labeling is somewhat similar to that of isotopic substitution in NMR spectroscopy. There one replaces an atom lacking a nuclear spin (and so is NMR-silent) with an isotope having a spin I 0 (and so is NMR-active). This technique is useful for tracking the chemical environment around an atom when full substitution with an NMR-active isotope is not feasible.

References

Berliner, L.J. (1976). Spin labeling I : theory and applications, Academic Press, New York.

Berliner, L.J. (1979). Spin labeling II : theory and applications, Academic Press, New York.