16 research outputs found
Reveromycins revealed: New polyketide spiroketals from Australian marine-derived and terrestrial Streptomyces spp. A case of natural products vs artifacts
No full textChemical analysis of fermentation products from two Australian Streptomyces isolates yielded all four known and twelve new examples of the rare reveromycin class of polyketide spiroketals, including hemi-succinates, hemi-fumarates and hemi-furanoates. Reveromycins were identified with the aid of HPLC-DAD-MS and HPLC-DAD-SPE-NMR methodology, and structures were assigned by detailed spectroscopic analysis. The structural and mechanistic requirements for an unprecedented hemi-succinate : ketal-succinyl equilibrium were defined and provided a basis for proposing that reveromycin 4′-methyl esters and 5,6-spiroketals were artifacts. A plausible reveromycin polyketide biosynthesis is proposed, requiring a 2-methylsuccinyl-CoA starter unit, with flexible incorporation of a C6–8 polyketide chain extension and diacid esterification units. Structure activity relationship investigations by co-metabolites were used to assess the anticancer, antibacterial and antifungal properties of reveromycins
C3 and 2D C3 Marfey’s methods for amino acid analysis in natural products
No full textWe validate the improved resolution and sensitivity of the C Marfey's method, including an ability to resolve all Ile isomers, against an array of amino acids commonly encountered in natural products and by comparison to an existing Marfey's method. We also describe an innovative 2D C Marfey's method as an analytical approach for determining the regiochemistry of enantiomeric amino acid residues in natural products. The C and 2D C Marfey's methods represent valuable tools for probing and defining the stereocomplexity of hydrolytically accessible amino acid residues in natural products
Developing Methods for Assessing Trophic Magnification of Perfluoroalkyl Substances within an Urban Terrestrial Avian Food Web
No full textWe investigated the trophic magnification potential of
perfluoroalkyl
substances (PFAS) in a terrestrial food web by using a chemical activity-based
approach, which involved normalizing concentrations of PFAS in biota
to their relative biochemical composition in order to provide a thermodynamically
accurate basis for comparing concentrations of PFAS in biota. Samples
of hawk eggs, songbird tissues, and invertebrates were collected and
analyzed for concentrations of 18 perfluoroalkyl acids (PFAAs) and
for polar lipid, neutral lipid, total protein, albumin, and water
content. Estimated mass fractions of PFCA C8–C11 and PFSA C4–C8 predominantly
occurred in albumin within biota samples from the food web with smaller
estimated fractions in polar lipids > structural proteins >
neutral
lipids and insignificant amounts in water. Estimated mass fractions
of longer-chained PFAS (i.e., C12–C16) mainly occurred in polar lipids with smaller estimated fractions
in albumin > structural proteins > neutral lipids > and water.
Chemical
activity-based TMFs indicated that PFNA, PFDA, PFUdA, PFDoA, PFTrDA,
PFTeDA, PFOS, and PFDS biomagnified in the food web; PFOA, PFHxDA,
and PFHxS did not appear to biomagnify; and PFBS biodiluted. Chemical
activity-based TMFs for PFCA C8–C11 and
PFSA C4–C8 were in good agreement with
corresponding TMFs derived with concentrations normalized to only
total protein in biota, suggesting that concentrations normalized
to total protein may be appropriate proxies of chemical activity-based
TMFs for PFAS, which predominantly partition to albumin. Similarly,
TMFs derived with concentrations normalized to albumin may be suitable
proxies of chemical activity-based TMFs for longer-chained PFAS, which
predominantly partition to polar lipids
Developing Methods for Assessing Trophic Magnification of Perfluoroalkyl Substances within an Urban Terrestrial Avian Food Web
No full textWe investigated the trophic magnification potential of
perfluoroalkyl
substances (PFAS) in a terrestrial food web by using a chemical activity-based
approach, which involved normalizing concentrations of PFAS in biota
to their relative biochemical composition in order to provide a thermodynamically
accurate basis for comparing concentrations of PFAS in biota. Samples
of hawk eggs, songbird tissues, and invertebrates were collected and
analyzed for concentrations of 18 perfluoroalkyl acids (PFAAs) and
for polar lipid, neutral lipid, total protein, albumin, and water
content. Estimated mass fractions of PFCA C8–C11 and PFSA C4–C8 predominantly
occurred in albumin within biota samples from the food web with smaller
estimated fractions in polar lipids > structural proteins >
neutral
lipids and insignificant amounts in water. Estimated mass fractions
of longer-chained PFAS (i.e., C12–C16) mainly occurred in polar lipids with smaller estimated fractions
in albumin > structural proteins > neutral lipids > and water.
Chemical
activity-based TMFs indicated that PFNA, PFDA, PFUdA, PFDoA, PFTrDA,
PFTeDA, PFOS, and PFDS biomagnified in the food web; PFOA, PFHxDA,
and PFHxS did not appear to biomagnify; and PFBS biodiluted. Chemical
activity-based TMFs for PFCA C8–C11 and
PFSA C4–C8 were in good agreement with
corresponding TMFs derived with concentrations normalized to only
total protein in biota, suggesting that concentrations normalized
to total protein may be appropriate proxies of chemical activity-based
TMFs for PFAS, which predominantly partition to albumin. Similarly,
TMFs derived with concentrations normalized to albumin may be suitable
proxies of chemical activity-based TMFs for longer-chained PFAS, which
predominantly partition to polar lipids
