Listening In on the Past: What Can Otolith δ18O Values Really Tell Us about the Environmental History of Fishes?

Oxygen isotope ratios from fish otoliths are used to discriminate marine stocks and reconstruct past climate, assuming that variations in otolith δ18O values closely reflect differences in temperature history of fish when accounting for salinity induced variability in water δ18O. To investigate this, we exploited the environmental and migratory data gathered from a decade using archival tags to study the behaviour of adult plaice (Pleuronectes platessa L.) in the North Sea. Based on the tag-derived monthly distributions of the fish and corresponding temperature and salinity estimates modelled across three consecutive years, we first predicted annual otolith δ18O values for three geographically discrete offshore sub-stocks, using three alternative plausible scenarios for otolith growth. Comparison of predicted vs. measured annual δ18O values demonstrated >96% correct prediction of sub-stock membership, irrespective of the otolith growth scenario. Pronounced inter-stock differences in δ18O values, notably in summer, provide a robust marker for reconstructing broad-scale plaice distribution in the North Sea. However, although largely congruent, measured and predicted annual δ18O values of did not fully match. Small, but consistent, offsets were also observed between individual high-resolution otolith δ18O values measured during tag recording time and corresponding δ18O predictions using concomitant tag-recorded temperatures and location-specific salinity estimates. The nature of the shifts differed among sub-stocks, suggesting specific vital effects linked to variation in physiological response to temperature. Therefore, although otolith δ18O in free-ranging fish largely reflects environmental temperature and salinity, we counsel prudence when interpreting otolith δ18O data for stock discrimination or temperature reconstruction until the mechanisms underpinning otolith δ18O signature acquisition, and associated variation, are clarified

Heme Cleavage with Remarkable Ease: Paramagnetic Intermediates Formed by Aerobic Oxidation of a Meso-Amino-Substituted Iron Porphyrin

[[abstract]]Hemes must be oxidatively stable to carry out their functions as biological oxidants, but introduction of a single amino group at a meso position of octaethylheme renders it extremely sensitive to ring opening by dioxygen. Exposure of a red pyridine (py) solution of diamagnetic (py)2FeII(H2N-OEP) (1) (H2N-OEP is the dianion of meso-amino-octaethylporphyrin) to air results in the immediate formation of a green intermediate which is subsequently converted into a second species that has been crystallized and characterized by X-ray diffraction. This process is distinct from coupled oxidation, a model for biological heme cleavage, because it does not require a sacrificial reducing agent to initiate the process

Reactivity of Mono-Meso-Substituted Iron(II) Octaethylporphyrin Complexes with Hydrogen Peroxide in the Absence of Dioxygen. Evidence for Nucleophilic Attack on the Heme.

Treatment of the mono-meso-substituted iron(II) octaethylporphyrin complexes, (py)2FeII(meso-NO2-OEP), (py)2FeII(meso-CN-OEP), (py)2FeII(meso-HC(O)-OEP), (py)2FeII(meso-Cl-OEP), (py)2FeII(meso-OMe-OEP), (py)2FeII(meso-Ph-OEP), and (py)2FeII(meso-Bu-OEP), with hydrogen peroxide in pyridine-d5 at -30° in the strict absence of dioxygen was monitored by 1H NMR spectroscopy. The product oxophlorin complexes are stable as long as the samples are protected from exposure to dioxygen. Hydrogen peroxide reacts cleanly with mono-meso-substituted iron(II) porphyrins in pyridine soln. under an inert atm. to form mixts. of three possible oxygenation products, (py)2Fe(cis-meso-R-OEPO), (py)2Fe(trans-meso-R-OEPO), and (py)2Fe(OEPO). The yields of (py)2Fe(OEPO), which results from replacement of the unique meso substituent, as a function of the identity of the meso substituent decrease in the order NO2 > HC(O) � CN � Cl > OMe > Ph, Bu, which suggests that the species responsible for attack on the porphyrin periphery is nucleophilic in nature. A mechanism involving isoporphyrin formation through attack of hydroxide ion on a cationic iron porphyrin with an oxidized porphyrin ring is suggested. The identity of the unique meso functionality also affects the regiospecificity of substitution when the unique meso group is retained. Although random attack at the two different meso sites is expected to yield a cis/trans product ratio of 2, the obsd. ratios vary in the following order: cyano, 5.0; Bu, 4.9; chloro, 3.2; formyl, 2.6; methoxy, 1.9; Ph 1.4. [on SciFinder(R)

meso Substituent Effects on the Geometric and Electronic Structures of High-Spin and Low-Spin Iron(III) Complexes of Mono-meso-Substituted Octaethylporphyrins.

Introduction of a single meso substituent into ClFeIII(OEP) or K[(NC)2Fe(OEP)] results in significant changes in the geometric and/or spectroscopic properties of these complexes. The mono-meso-substituted iron(III) complexes ClFeIII(meso-Ph-OEP), ClFeIII(meso-Bu-OEP), ClFeIII(meso-MeO-OEP), ClFeIII(meso-Cl-OEP), ClFeIII(meso-NC-OEP), ClFeIII(meso-HC(O)-OEP), and ClFeIII(meso-O2N-OEP) were isolated and characterized by their UV/visible and paramagnetically shifted 1H NMR spectra. The structures of both ClFeIII(meso-Ph-OEP) and ClFeIII(meso-NC-OEP) were detd. by x-ray crystallog. Both mols. have five-coordinate structures typical for high-spin (S = 5/2) iron(III) complexes. However, the porphyrins themselves no longer have the domed shape seen in ClFeIII(OEP), and the N4 coordination environment possesses a slight rectangular distortion. These high-spin, mono-meso-substituted iron(III) complexes display 1H NMR spectra in chloroform-d soln. which indicate that the conformational changes seen in the solid-state structures are altered by normal mol. motion to produce spectra consistent with Cs mol. symmetry. In pyridine soln. the high-spin six-coordinate complexes {(py)ClFeIII(meso-R-OEP)} form. In methanol soln. in the presence of excess potassium cyanide, the low-spin six-coordinate complexes K[(NC)2FeIII(meso-R-OEP)] form. The 1H NMR spectra of these show that electron-donating substituents produce an upfield relocation of the meso-proton chem. shifts. This relocation is interpreted in terms of increased contribution from the less common (dxz,dyz)4(dxy)1 ground electronic state as the meso substituent becomes more electron donating. [on SciFinder(R)

Comparison of Transfection Agents in Forming Complexes with Ferumoxides, Cell Labeling Efficiency, and Cellular Viability

By complexing ferumoxides or superparamagnetic iron oxide (SPIO) to transfection agents (TAs), it is possible to magnetically label mammalian cells. There has been no systematic study comparing TAs complexed to SPIO as far as cell labeling efficiency and viability. This study investigates the toxicity and labeling efficiency at various doses of FEs complexed to different TAs in mammalian cells. Different classes of TAs were used, such as polycationic amines, dendrimers, and lipid-based agents. Cellular toxicity was measured using doses of TAs from 1 to 50 μg/mL in incubation media. Iron incorporation efficiency was measured by combining various amounts of FEs and different doses of TAs. Lipofectamine2000 showed toxicity at lowest dose (1 μg/mL), whereas FuGENE6 and low molecular weight poly- L -lysine (PLI.) showed the least toxicity. SPIO labeling efficiency was similar with high-molecular-weight PIX (388.1 kDa) and superfect, whereas FuGENE6 and low-molecular-weight PLL were inefficient in labeling cells. Concentrations of 25 to 50 μg/mL of FEs complexed to TAs in media resulted in sufficient endocytosis of the SPIO into endosomes to detect cells on cellular magnetic resonance imaging

Color Transformation and Fluorescence of Prussian Blue–Positive Cells: Implications for Histologic Verification of Cells Labeled with Superparamagnetic Iron Oxide Nanoparticles

Superparamagnetic iron oxide (SPIO) nanoparticles, either modified or in combination with other macromolecules, are being used for magnetic labeling of stem cells and other cells to monitor cell trafficking by magnetic resonance imaging (MRI) in experimental models. The correlation of histology to MRI depends on the ability to detect SPIO-labeled cells using Prussian blue (PB) stain and fluorescent tags to cell surface markers. Exposure of PB-positive sections to ultraviolet light at a wavelength of 365 nm commonly used fluorescence microscopy can result in color transformation of PB-positive material from blue to brown. Although the PB color transformation is primarily an artifact that may occur during fluorescence microscopy, the transformation can be manipulated using imaging process software for the detection of low levels of iron labeled cells in tissues sample