es1c04194_si_001.pdf (2.45 MB)
Cyanobacterial Toxins and Cyanopeptide Transformation Kinetics by Singlet Oxygen and pH-Dependence in Sunlit Surface Waters
journal contribution
posted on 2021-10-29, 19:43 authored by Regiane Natumi, Christoph Dieziger, Elisabeth M.-L. JanssenTo assess the risks
associated with cyanobacterial blooms, the
persistence and fate processes of cyanotoxins and other bioactive
cyanobacterial metabolites need to be evaluated. Here, we investigated
the reaction with photochemically produced singlet oxygen (1O2) for 30 cyanopeptides synthesized by Dolichospermum
flos aquae, including 9 anabaenopeptins, 18 microcystins,
2 cyanopeptolins, and 1 cyclamide. All compounds were stable in UVA
light alone but in the presence of a photosensitizer we observed compound-specific
degradation. A strong pH effect on the decay was observed for 18 cyanopeptides
that all contained tyrosine or structurally related moieties. We can
attribute this effect to the reaction with 1O2 and triplet sensitizer that preferentially react with the deprotonated
form of tyrosine moieties. The contribution of 1O2 to indirect phototransformation ranged from 12 to 39% and second-order
rate constants for 9 tyrosine-containing cyanopeptides were assessed.
Including the pH dependence of the reaction and system-independent
second-order rate constants with 1O2 will improve
the estimation of half-lives for multiclass cyanopeptide in surface
waters. Our data further indicates that naturally occurring triplet
sensitizers are likely to oxidize deprotonated tyrosine moieties of
cyanopeptides and the specific reactivity and its pH dependence needs
to be investigated in future studies.
History
Usage metrics
Categories
Keywords
uva light aloneorder rate constantsindirect phototransformation rangedstructurally related moietiescyanopeptide transformation kineticssunlit surface waters30 cyanopeptides synthesized2 sub1 supstrong ph effectph dependence needssurface waterstyrosine moietiesmulticlass cyanopeptide2 cyanopeptolins1 cyclamideph dependencetriplet sensitizerspecific reactivityspecific degradationsinglet oxygenrisks associatedpreferentially reactfuture studiesfate processesdeprotonated formcyanobacterial toxinscyanobacterial bloomscontaining cyanopeptidescontained tyrosine9 tyrosine18 microcystins18 cyanopeptides