The formation of singlet oxygen in surface waters

Wolff, C.J.M.; Halmans, M.T.H.; Heijde, H.B. van der

doi:10.1016/0045-6535(81)90159-4

Cited by 48 publications

(34 citation statements)

References 8 publications

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“…The first pathway leads to the stable triamide, through a rearrangement of the intermediate imino anhydride (Figure 3, purple pathway). In the second case, (Figure 3, green pathway), the imino anhydride undergoes hydrolysis to produce an imide and acetic acid (confirmed by 13 C NMR and HSQC experiments, SI Figure S32). After sensitized photolysis of peptide 1a in H 2 O the expected triamide was not detected.…”

Section: The Journal Of Organic Chemistrymentioning

confidence: 90%

“…Preparative HPLC was performed on a SUPELCO Analytical Ascentis RP-AMIDE 10 cm × 21.2 mm, 5 μm column. 1 H and 13 Synthesis of (S)-3-Hydroxy-1-methoxy-1-oxopropan-2-aminium chloride (11). To a solution of L-serine (1070 mg, 10.2 mmol) in MeOH (15 mL) at 0 °C, SOCl 2 (4.3 mL, 59 mmol) was added dropwise over 15 min, and the mixture was then refluxed for 3 h. The mixture was concentrated under vacuum to give 11 as a yellow solid (1592 mg, 100%).…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…Amino acid-based oxazoles and thiazoles are formed from the cyclization of serine, threonine, and cysteine side chains onto the peptide backbone and are common features of nonribosomal peptides (NRPs) and ribosomally encoded post-translationally modified peptides (RiPPs). , We are particularly interested in NRP and RiPP natural products since they have the potential to act as water contaminants and as ecologically important biomolecules (e.g., metal-binding siderophores). Such oxazole and thiazole peptides have been isolated from sunlight-dwelling photosynthetic algae, cyanobacteria, sea slugs, and sponges. − However, the prevalence of these peptidic heterocycles would seem counterintuitive if they are as reactive toward singlet oxygen ( 1 O 2 ), a ubiquitous oxidant in sunlit natural waters, as previously studied oxazoles and thiazoles. − Indeed, earlier work by Nakamura et al and by Wasserman et al showed that phenyl-substituted oxazoles react quickly with 1 O 2 with rate constants on the order of 10 7 –10 8 M –1 s –1 , translating to a half-life of only 4 days for the highest rate constant in the presence of a typical fresh water 1 O 2 concentration of 1.4 × 10 –14 M (Scheme ). , Beside that, such peptides could be degraded also by intracellular 1 O 2 , which is well-known to be present in both photosynthetic and nonphotosynthetic cells .…”

Section: Introductionmentioning

confidence: 99%

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Singlet Oxygen Photooxidation of Peptidic Oxazoles and Thiazoles

et al. 2019

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Oxazoles and thiazoles are commonly found moieties in nonribosomal peptides (NRPs) and ribosomally synthesized post-translationally modified peptides (RiPPs), which are important biomolecules present in the environment and in natural waters. From previous studies, they seem susceptible to oxidation by singlet oxygen (1O2); therefore, we designed and synthesized model oxazole- and thiazole-peptides and measured their 1O2 bimolecular reaction rate constants, showing slow photooxidation under environmental conditions. We reasoned their stability through the electron-withdrawing effect of the carboxamide substituent. Reaction products were elucidated and support a reaction mechanism involving cycloaddition followed by a series of rearrangements. The first 1O2 bimolecular reaction rate constant for a RiPP, the thiazole-containing peptide Aerucyclamide A, was measured and found in good agreement with the model peptide’s rate constant, highlighting the potential of using model peptides to study the transformations of other environmentally relevant NRPs and RiPPs.

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Section: The Journal Of Organic Chemistrymentioning

confidence: 90%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Singlet Oxygen Photooxidation of Peptidic Oxazoles and Thiazoles

et al. 2019

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“…The photochemically reactive moieties of tyrosine and methionine are highlighted in red and blue, respectively. The light absorbance range and the second-order reaction rate constants with hydroxyl radical and singlet oxygen for tyrosine and methionine are listed with significantly higher steady-state concentrations in sunlit surface waters ranging from 10 −12 to 10 −14 M [55,56], singlet oxygen may be responsible for differences of observed transformation rates among cyanopeptides. The concentration of singlet oxygen in the presented experiment (lake Greifensee water, pH 9) was 1.4 ± 0.05 × 10 -13 M, which is comparable to previous observations of surface waters and supports the possibility that reactions with cyanopeptides could have occurred.…”

Section: Phototransformation Kinetics Of Cyanopeptidesmentioning

confidence: 99%

Phototransformation kinetics of cyanobacterial toxins and secondary metabolites in surface waters

2021

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Background Cyanobacteria and their toxins occur in high concentrations during the so-called bloom events in surface waters. To be able to assess the risks associated with cyanobacterial blooms, we need to understand the persistence and fate processes of these toxins and other bioactive metabolites. In this study, we investigated the photochemical fate of 54 cyanopeptides extracted from two strains of Microcystis aeruginosa (PCC7806 and UV006), Planktothrix rubescens, and Dolichospermum flos aquae. We determined half-lives during sunlight exposure in lake water and inspected the effect of pH on transformation kinetics for 27 microcystins, 8 anabaenopeptins, 14 cyanopeptolins, 2 cyclamides, and 3 aeruginosins. Results For cyanopeptides from D. flos aquae and P. rubescens, we observed the highest removal of 28 and 26%, respectively, after 3-h sunlight exposure. Most cyanopeptides produced by the two M. aeruginosa strains were rather persistent with only up to 3% removal. The more reactive cyanopeptides contained amino acids known to undergo phototransformation, including methionine and tyrosine moieties or their derivatives. Photochemical half-lives of 14 tyrosine-containing cyanopeptides decreased by one order of magnitude from nearly persistent conditions at pH 7 (half-life > 70 h) to shorter half-lives at pH 10 (< 10 h). Conclusions More work is needed to distinguish the contribution of different photochemical reaction pathways including the contributions to the pH effect. To the best of our knowledge, this is the first assessment of transformation kinetics of such a wide range of cyanopeptides. The abundant and persistent cyanopeptides that have not been studied in detail yet should be prioritized for the evaluation of their ecosystem and human health risks and for their abatement during drinking water treatment.

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“…However, the more selectively reacting 1 O 2 has a significantly higher steady-state concentration in sunlit surface waters ranging from 10 −12 to 10 −14 M compared to hydroxyl radical (10 −15 to 10 −17 M). 9,10,[12][13][14] In proteins, 1 O 2 reacts predominantly with five amino acids: histidine (His, H), methionine (Met, M), cysteine (Cys, C), tyrosine (Tyr, Y) and tryptophan (Trp, W). 8,15 While the reaction mechanisms and modifications for the reaction with 1 O 2 have long been identified for freely dissolved amino acids, more recently, differences of oxidation rates have been observed for amino acid residues incorporated in proteins.…”

Section: Introductionmentioning

confidence: 99%

Inactivation and Site-specific Oxidation of Aquatic Extracellular Bacterial Leucine Aminopeptidase by Singlet Oxygen

Egli

Stravs

Janssen

2020

Environ. Sci. Technol.

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Extracellular enzymes are master recyclers of organic matter and to predict their functional lifetime, we need to understand their environmental transformation processes. In surface waters, direct and indirect photochemical transformation is a known driver of inactivation. We investigated molecular changes that occur along with inactivation in aminopeptidase, an abundant class of extracellular enzymes. We studied the inactivation kinetics and localized oxidation caused by singlet oxygen, 1 O 2 , a major photochemically-derived oxidant towards amino acids. Aminopeptidase showed second order inactivation rate constants with 1 O 2 comparable to those of free amino acids. We then visualized site-specific oxidation kinetics within the three-dimensional protein and demonstrated that fastest oxidation occurred around the active site and at other reactive amino acids. However, second order oxidation rate constants did not correlate strictly with the 1 O 2 -accessible surface areas of those amino acids.We inspected site-specific processes by a comprehensive suspect screening for 723'288 possible transformation products. We concluded that histidine involved in zinc coordination at the active site reacted slower than expected by its accessibility and we differentiated between two competing reaction pathways of 1 O 2 with tryptophan residues. This systematic analysis can be directly applied to other proteins and transformation reactions.

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The formation of singlet oxygen in surface waters

Cited by 48 publications

References 8 publications

Singlet Oxygen Photooxidation of Peptidic Oxazoles and Thiazoles

Singlet Oxygen Photooxidation of Peptidic Oxazoles and Thiazoles

Phototransformation kinetics of cyanobacterial toxins and secondary metabolites in surface waters

Inactivation and Site-specific Oxidation of Aquatic Extracellular Bacterial Leucine Aminopeptidase by Singlet Oxygen

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