The structure of scytonemin, an ultraviolet sunscreen pigment from the sheaths of cyanobacteria

P. J. Proteau, W. H. Gerwick, F. Garcia-Pichel, R. Castenholz

Research output: Contribution to journalArticlepeer-review

332 Scopus citations


Despite knowledge of the existence of the pigment called scytonemin for over 100 years, its structure has remained unsolved until now. This pigment, the first shown to be an effective, photo-stable ultraviolet shield in prokaryotes, is a novel dimeric molecule (molec. wt. 544) of indolic and phenolic subunits and is known only from the sheaths enclosing the cells of cyanobacteria. It is probable that scytonemin is formed from a condensation of tryptophan-and phenylpropanoid-derived subunits. The linkage between these units is unique among natural products and this novel ring structure is here termed the 'scytoneman skeleton'. Scytonemin absorbs strongly and broadly in the spectral region 325-425 nm (UV-A-violet-blue, with an in vivo maximum at 370 nm). However, there is also major absorption in the UV-C (λmax=250nm) and UV-B (280-320 nm). The pigment has been recently shown to provide significant protection to cyanobacteria against damage by ultraviolet radiation. The pigment occurs in all phylogenetic lines of sheathed cyanobacteria and possibly represents a UV screening strategy far more ancient than that of plant flavonoids and animal melanins. How diverse organisms deal with UV radiation is considered of vital importance to global ecology.

Original languageEnglish (US)
Pages (from-to)825-829
Number of pages5
Issue number9
StatePublished - Sep 1993
Externally publishedYes


  • Indole alkaloid
  • UV-sunscreen pigment
  • blue green algae
  • cyanobacteria
  • natural products

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


Dive into the research topics of 'The structure of scytonemin, an ultraviolet sunscreen pigment from the sheaths of cyanobacteria'. Together they form a unique fingerprint.

Cite this