Exploring the photodegradation of pyrroles
Jennifer Apell has recently published a paper in Environmental Science & Technology exploring the photodegradation of the pesticide fludioxonil and compounds that contain pyrrole in general. Pyrrole moieties were able to undergo direct photodegradation as well as indirect photodegradation with singlet oxygen (1O2) and triplet state organic matter (3CDOM*). The occurrence of these photodegradation pathways and the rate at which they occurred depended heavily on the substituent
Can we predict indirect photochemical reactions?
Rachele Ossola recently published her master thesis work on the competing reactivity of singlet oxygen (1O2) and triplet chromophoric dissolved organic matter (3CDOM*) in Environmental Science and Technology. In this work, we investigated the indirect photochemistry of furan carboxamides, a class of compounds derived from the fungicide fenfuram, with a combination of steady-state and laser flash photolysis experiments. Our results showed that 1O2 reactivity observed in the st
Photochemical product of steroid hormone with novel hexacyclic ring system
While studying the environmental fate of potent endocrine-active steroid hormones, we observed the formation of an intramolecular [2+2] photocycloaddition product with a novel hexacyclic ring system following photolysis of altrenogest. The structure and absolute configuration were established by X-ray diffraction analysis. Theoretical computations identified a barrierless two-step cyclization mechanism for the formation of the photoproduct upon photoexcitation. The product e
A deeper understanding of the triplet probe sorbic acid
Kyle Moor and Markus Schmitt published a set of papers in Environmental Science & Technology on sorbic acid as a probe for triplet-excited dissolved organic matter (3DOM*). These papers use two recently developed laser spectroscopy techniques to measure: (1) the quenching rate constants of 3DOM* with sorbic acid and (2) the pool of triplets in DOM captured when using sorbic acid. By comparing the results between the two measurement approaches, we examine the major differences
N-cyclopropylanilines to probe oxidative properties of triplet-state photosensitizers
We have developed a set of N-cyclopropylaniline (CPA) analogs to probe the oxidative properties of triplet-state photosensitizers in aqueous solutions. After an initial single electron transfer (SET) oxidation, anilines without a cyclopropyl group are susceptible to radical cation quenching by antioxidant moieties present in DOM, causing an underestimation in the rate of oxidation during steady-state experiments. In this work, we show that CPAs undergo a spontaneous, irreve
Updated and validated solar spectrum irradiance values
Jennifer Apell has a new paper in Environmental Science: Processes & Impacts providing updated values for spectral irradiance that can be used to calculate photodegradation rates in environmental systems. These irradiance values are available for every 10° latitude in the northern and southern hemisphere, for four seasons, at solar noon and day-averaged, and for wavelengths from 280 to 800 nm in 1 nm increments. Updated and validated solar irradiance reference spectra for est
Addressing singlet oxygen reactivity of environmentally relevant NRPs
Alessandro Manfrin published a paper in The Journal of Organic Chemistry on the singlet oxygen reactivity of oxazoles and thiazoles included in peptidic chains. Oxazoles and thiazoles are five-membered aromatic rings, found in natural peptides, and known to undergo rapid oxidation in the presence of singlet oxygen. In this work we synthesized model oxazole- and thiazole-peptides and demonstate that their singlet oxygen reactivity dramatically changes when they are included in
Newly discovered non-singlet oxygen kinetic solvent isotope effects
Caroline Davis has a new paper in Environmental Science & Technology on the newly discovered non-singlet oxygen kinetic solvent isotope effect important for the determination of a compound’s reactivity with singlet oxygen. Traditionally, reactivity of a pollutant with singlet-oxygen is demonstrated by faster degradation kinetics in heavy water (D2O) vs. H2O, due to longer lifetimes and therefore higher steady-state concentrations of the highly reactive oxygen species in D2O.
New probe for triplet-state dissolved organic matter reactivity
Kyle Moor recently published a paper in Environmental Science & Technology on using singlet oxygen phosphorescence as a probe for measuring triplet-excited state dissolved organic matter (3DOM*) reactivity. The concept for this project originated more than a decade ago when Kris was a faculty member at University of Minnesota! This indirect observation method allows access to measuring 3DOM* quenching rate constants and photophysical properties. We determined rate constants
Direct photochemical degradation of extracellular enzymes
Christine Egli has a new paper in in Environmental Science & Technology on photochemically induced site-specific damage in aquatic extracellular enzymes. This work presents an optimized proteomics approach to study simultaneous inactivation and site-specific molecular changes in environmentally relevant model enzymes. We report site-specific degradation fingerprints in the three dimensional proteins and reveal subsequent intramolecular processes, such as antioxidant effects.