Intralipid is a lipid emulsion used in photodynamic therapy (
Alkylation patterns and excited‐state properties of pterins were examined both experimentally and theoretically. 2D
- NSF-PAR ID:
- 10075028
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Photochemistry and Photobiology
- Volume:
- 94
- Issue:
- 5
- ISSN:
- 0031-8655
- Page Range / eLocation ID:
- p. 834-844
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract PDT ) for its light scattering and tissue‐simulating properties. The purpose of this study is to determine whether or not Intralipid undergoes photooxidation, and we have carried out an Intralipid peroxide trapping study using a series of phosphines [2′‐dicyclohexylphosphino‐2,6‐dimethoxy‐1,1′‐biphenyl‐3‐sulfonate, 3‐(diphenylphosphino)benzenesulfonate, triphenylphosphine‐3,3′,3′′‐trisulfonate and triphenylphosphine]. Our new findings are as follows: (1) An oxygen atom is transferred from Intralipid peroxide to the phosphine traps in the dark, after the photooxidation of Intralipid. 3‐(Diphenylphosphino)benzenesulfonate is the most suitable trap in the series owing to a balance of nucleophilicity and water solubility. (2) Phosphine trapping and monitoring by31PNMR are effective in quantifying the peroxides in H2O. An advantage of the technique is that peroxides are detected in H2O; deuteratedNMR solvents are not required. (3) The percent yield of the peroxides increased linearly with the increase in fluence from 45 to 180 J cm−2based on our trapping experiments. (4) The photooxidation yields quantitated by the phosphines and31PNMR are supported by the direct1HNMR detection using deuteratedNMR solvents. These data provide the first steps in the development of Intralipid peroxide quantitation afterPDT using phosphine trapping and31PNMR spectroscopy. -
Rationale It is imperative to understand how chemical preservation alters tissue isotopic compositions before using historical samples in ecological studies. Specifically, although compound‐specific isotope analysis of amino acids (CSIA‐AA) is becoming a widely used tool, there is little information on how preservation techniques affect amino acid
δ 15N values.Methods We evaluated the effects of chemical preservatives on bulk tissue
δ 13C andδ 15N and amino acidδ 15N values, measured by gas chromatography/isotope ratio mass spectrometry (GC/IRMS), of (a) tuna ( ) and squid (Thunnus albacares ) muscle tissues that were fixed in formaldehyde and stored in ethanol for 2 years and (b) two copepod species,Dosidicus gigas andCalanus pacificus , which were preserved in formaldehyde for 24–25 years.Eucalanus californicus Results Tissues in formaldehyde‐ethanol had higher bulk
δ 15N values (+1.4, ; +1.6‰,D. gigas ), higherT. albacares δ 13C values for (+0.5‰), and lowerD. gigas δ 13C values for (−0.8‰) than frozen samples. The bulkT. albacares δ 15N values from copepods were not different those from frozen samples, although theδ 13C values from both species were lower (−1.0‰ for and −2.2‰ forE. californicus ) than those from frozen samples. The mean amino acidC. pacificus δ 15N values from chemically preserved tissues were largely within 1‰ of those of frozen tissues, but the phenylalanineδ 15N values were altered to a larger extent (range: 0.5–4.5‰).Conclusions The effects of preservation on bulk
δ 13C values were variable, where the direction and magnitude of change varied among taxa. The changes in bulkδ 15N values associated with chemical preservation were mostly minimal, suggesting that storage in formaldehyde or ethanol will not affect the interpretation ofδ 15N values used in ecological studies. The preservation effects on amino acidδ 15N values were also mostly minimal, mirroring bulkδ 15N trends, which is promising for future CSIA‐AA studies of archived specimens. However, there were substantial differences in phenylalanine and valineδ 15N values, which we speculate resulted from interference in the chromatographic resolution of unknown compounds rather than alteration of tissue isotopic composition due to chemical preservation. -
1. Ants are widely regarded as ‘ecosystem engineers’ because their nest construction and contributions to nutrient cycling change the biological, chemical, and physical properties of the soil around their nests. Despite increasing attention to ant manipulation of soil ecosystems, the extent to which many common species influence soil properties, as well as nutrient uptake and community composition of plants near nests, is still unknown.
2. This study tested hypotheses that activities of a common subalpine ant,
, alter soil moisture and pH, redistribute nitrogen around nests, and affect plant species abundance and ground cover.Formica podzolica 3. A combination of field sampling techniques showed that distance from a nest had a positive relationship with soil moisture and a negative relationship with plant abundance next to and downhill from nests. Slope aspect also affected plant communities, with downhill transects having higher plant cover and above‐ground biomass than uphill transects. A stable isotope analysis did not reveal that plants near nests had enriched15N, but there were substantial differences in15N among sites.
4. Overall, this study uncovers significant impacts of
on the subalpine microhabitats directly surrounding their nests.F. podzolica -
Abstract Rationale The use of secondary ion mass spectrometry (SIMS) to perform micrometer‐scale
in situ carbon isotope (δ13C) analyses of shells of marine microfossils called planktic foraminifers holds promise to explore calcification and ecological processes. The potential of this technique, however, cannot be realized without comparison to traditional whole‐shell δ13C values measured by gas source mass spectrometry (GSMS).Methods Paired SIMS and GSMS δ13C values measured from final chamber fragments of the same shell of the planktic foraminifer
are compared. The SIMS–GSMS δ13C differences (Δ13CSIMS‐GSMS) were determined via paired analysis of hydrogen peroxide‐cleaned fragments of modern cultured specimens and of fossil specimens from deep‐sea sediments that were either untreated, sonicated, and cleaned with hydrogen peroxide or vacuum roasted. After treatment, fragments were analyzed by a CAMECA IMS 1280 SIMS instrument and either a ThermoScientific MAT‐253 or a Fisons Optima isotope ratio mass spectrometer (GSMS).Orbulina universa Results Paired analyses of cleaned fragments of cultured specimens (
n = 7) yield no SIMS–GSMS δ13C difference. However, paired analyses of untreated (n = 18) and cleaned (n = 12) fragments of fossil shells yield average Δ13CSIMS‐GSMSvalues of 0.8‰ and 0.6‰ (±0.2‰, 2 SE), respectively, while vacuum roasting of fossil shell fragments (n = 11) removes the SIMS–GSMS δ13C difference.Conclusions The noted Δ13CSIMS‐GSMSvalues are most likely due to matrix effects causing sample–standard mismatch for SIMS analyses but may also be a combination of other factors such as SIMS measurement of chemically bound water. The volume of material analyzed via SIMS is ~105times smaller than that analyzed by GSMS; hence, the extent to which these Δ13CSIMS‐GSMSvalues represent differences in analyte or instrument factors remains unclear.
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Abstract Compound‐specific stable isotope analysis (
CSIA ) of amino acids (AA ) has rapidly become a powerful tool in studies of food web architecture, resource use, and biogeochemical cycling. However, applications to avian ecology have been limited because no controlled studies have examined the patterns inAA isotope fractionation in birds. We conducted a controlledCSIA feeding experiment on an avian species, the gentoo penguin (Pygoscelis papua ), to examine patterns in individualAA carbon and nitrogen stable isotope fractionation between diet (D) and consumer (C) (Δ13CC‐Dand Δ15NC‐D, respectively). We found that essentialAA δ 13C values and sourceAA δ 15N values in feathers showed minimal trophic fractionation between diet and consumer, providing independent but complimentary archival proxies for primary producers and nitrogen sources respectively, at the base of food webs supporting penguins. Variations in nonessentialAA Δ13CC‐Dvalues reflected differences in macromolecule sources used for biosynthesis (e.g., protein vs. lipids) and provided a metric to assess resource utilization. The avian‐specific nitrogen trophic discrimination factor (TDF Glu‐Phe= 3.5 ± 0.4‰) that we calculated from the difference in trophic fractionation (Δ15NC ‐D) of glutamic acid and phenylalanine was significantly lower than the conventional literature value of 7.6‰. Trophic positions of five species of wild penguins calculated using a multi‐TDFG lu‐Pheequation with the avian‐specificTDFG lu‐Phevalue from our experiment provided estimates that were more ecologically realistic than estimates using a singleTDFG lu‐Pheof 7.6‰ from the previous literature. Our results provide a quantitative, mechanistic framework for the use ofCSIA in nonlethal, archival feathers to study the movement and foraging ecology of avian consumers.