Physical Sciences and Mathematics | Open Access Articles

Vitamin E Circular Dichroism Studies: Insights Into Conformational Changes Induced By The Solvent’S Polarity, Drew Marquardt, Brad J. Van Oosten, Mikel Ghelfi, Jeffrey Atkinson, Thad A. Harroun

Chemistry and Biochemistry Publications

We used circular dichroism (CD) to study differences in CD spectra between α-, δ-, and methylated-α-tocopherol in solvents with different polarities. CD spectra of the different tocopherol structures differ from each other in intensity and peak locations, which can be attributed to chromanol substitution and the ability to form hydrogen bonds. In addition, each structure was examined in different polarity solvents using the Reichardt index—a measure of the solvent’s ionizing ability, and a direct measurement of solvent–solute interactions. Differences across solvents indicate that hydrogen bonding is a key contributor to CD spectra at 200 nm. These results are a first …

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Morphology-Induced Defects Enhance Lipid Transfer Rates, Yan Xia, Kamil Charubin, Drew Marquardt, Frederick A. Heberle, John Katsaras, Jianhui Tian, Xiaolin Cheng, Ying Liu, Mu Ping Nieh

Chemistry and Biochemistry Publications

Molecular transfer between nanoparticles has been considered to have important implications regarding nanoparticle stability. Recently, the interparticle spontaneous lipid transfer rate constant for discoidal bicelles was found to be very different from spherical, unilamellar vesicles (ULVs). Here, we investigate the mechanism responsible for this discrepancy. Analysis of the data indicates that lipid transfer is entropically favorable, but enthalpically unfavorable with an activation energy that is independent of bicelle size and long- to short-chain lipid molar ratio. Moreover, molecular dynamics simulations reveal a lower lipid dissociation energy cost in the vicinity of interfaces ("defects") induced by the segregation of the long- …

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Cholesterol's Location In Lipid Bilayers, Drew Marquardt, Norbert Kučerka, Stephen R. Wassall, Thad A. Harroun, John Katsaras

Chemistry and Biochemistry Publications

It is well known that cholesterol modifies the physical properties of lipid bilayers. For example, the much studied liquid-ordered Lo phase contains rapidly diffusing lipids with their acyl chains in the all trans configuration, similar to gel phase bilayers. Moreover, the Lo phase is commonly associated with cholesterol-enriched lipid rafts, which are thought to serve as platforms for signaling proteins in the plasma membrane. Cholesterol's location in lipid bilayers has been studied extensively, and it has been shown – at least in some bilayers – to align differently from its canonical upright orientation, where its hydroxyl group is in the …

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Insights From Molecular Dynamics On Substrate Binding And Effects Of Active Site Mutations In Delta1-Pyrroline-5-Carboxylate Dehydrogenase, Bogdan F. Ion, Mohamed M. Aboelnga, James W. Gauld

Chemistry and Biochemistry Publications

The NAD+-dependent enzyme, 1-pyrroline-5-carboxylate dehydrogenase (P5CDH), has an important role in proline and hydroxyproline catabolism for humans. Specifically, this aldehyde dehydrogenase is responsible for the oxidation of both L-glutamate- -semialdehyde (GSA) and 4-erythro-hydroxy-L-glutamate- -semialdehyde (4-OH-GSA) to their respective L-glutamate product forms. We have performed a detailed molecular dynamics (MD) study of both the reactant and product complex structures of P5CDH to gain insights into ligand binding (i.e., GSA, 4-OH-GSA, NAD+, GLU) in the active site. Moreover, our investigations were further extended to examine the structural impact of S352L, S352A, and E314A mutations on the deficiency in the P5CDH enzymatic activity. …

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Elastomers: Reinventing Butyl Rubber For Stretchable Electronics (Adv. Funct. Mater. 29/2016), Akhil Vohra, Heather L. Filiatrault, Stanley D. Amyotte, R. Stephen Carmichael, Natalie D. Suhan, Conrad Siegers, Lorenzo Ferrari, Gregory J.E. Davidson, Tricia Breen Carmichael

Chemistry and Biochemistry Publications

No abstract provided.

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Polyisobutylene-Paclitaxel Conjugates With Pendant Carboxylic Acids And Polystyrene Chains: Towards Multifunctional Stent Coatings With Slow Drug Release, John F. Trant, Mahmoud M. Abd Rabo Moustafa, Inderpreet Sran, Elizabeth R. Gillies

Chemistry and Biochemistry Publications

Drug-eluting stents are used in the treatment of atherosclerosis, where the incorporation of anti-proliferative or anti-inflammatory drugs decreases the rate of restenosis, the recurrence of artery narrowing. However, these stents can suffer from limitations such as drug depletion and delamination of the drug-eluting coating from the stent surface. Described here is an approach aimed at addressing these issues. Starting from a maleic anhydride adduct of polyisobutylene (PIB) prepared from butyl rubber, ring opening using paclitaxel (PTX) or a combination of PTX and polystyrene (PS) afforded covalent conjugates of PTX and PIB or PIB-PS graft copolymers bearing pendant carboxylic acids. When …

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Assessment Of Hazard Metrics For Predicting Field Benthic Invertebrate Toxicity In The Detroit River, Ontario, Canada, Kerry N. Mcphedren, Alice Grigicak-Mannnion, Gord Paterson, Briggs Tedd, Jan J.H. Ciborowski, G. Douglass Haffner, Ken G. Drouillard

Great Lakes Institute for Environmental Research Publications

Numerical sediment quality guidelines (SQGs) are frequently used to interpret site specific sediment chemistry and predict potential toxicity to benthic communities. These SQGs are useful for a screening line of evidence (LOE) that can be combined with other LOEs in a full weight of evidence (WOE) assessment of impacted sites. Three common multi-chemical hazard quotient methods (PEC-Q_avg, PEC-Q_met and PEC-Q_sum) and a novel (Hazard Score; HZD) approach were used in conjunction with a consensus based set of SQGs to evaluate the ability of different scoring metrics to predict the biological effects of sediment contamination under …

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Is It Appropriate To Composite Fish Samples For Mercury Trend Monitoring And Consumption Advisories?, Ken G. Drouillard, Nilima Gandhi, Satyendra P. Bhavsar, Sarah B. Gewurtz, George B. Arhonditsis, Steve Petro

Great Lakes Institute for Environmental Research Publications

Monitoring mercury levels in fish can be costly because variation by space, time, and fish type/size needs to be captured. Here, we explored if compositing fish samples to decrease analytical costs would reduce the effectiveness of the monitoring objectives. Six compositing methods were evaluated by applying them to an existing extensive dataset and examining their performance in reproducing the fish consumption advisories and temporal trends. The methods resulted in varying amount (average 34-72%) of reductions in samples, but all (except one) reproduced advisories very well (96-97% of the advisories did not change or were one category more restrictive compared to …

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A Chemoenzymatic Route To Chiral Siloxanes, Ravi Naoum, Jacqueline P. Séguin, John F. Trant, Mark B. Frampton, Tomáš Hudlický, Paul M. Zelisko

Chemistry and Biochemistry Publications

An approach employing two enzymes—toluene dioxygenase and immobilized lipase B from Candida antarctica (N435)—was explored as a potential biocatalytic method for the coupling of chiral diols with siloxane species. Analysis of reaction mixtures using1H NMR spectroscopy suggested that up to 66% consumption of the siloxane starting materials had occurred. Oligomeric species were observed and chiral products from the coupling of a cyclic diol with a siloxane molecule were isolated and characterized by MALDI-ToF MS and GPC. Immobilized lipases from Rhizomucor miehei and Thermomyces lanuginosus were also explored as potential catalysts for the coupling reactions, however, their use only returned starting …

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Lipid Bilayer Thickness Determines Cholesterols Location In Model Membranes, Drew Marquardt, Frederick A. Heberle, Denise V. Greathouse, Roger E. Koeppe, Robert F. Standaert, Brad J. Van Oosten, Thad A. Harroun, Jacob J. Kinnun, Justin A. Williams, Stephen R. Wassall, John Katsaras

Chemistry and Biochemistry Publications

Cholesterol is an essential biomolecule of animal cell membranes, and an important precursor for the biosynthesis of certain hormones and vitamins. It is also thought to play a key role in cell signaling processes associated with functional plasma membrane microdomains (domains enriched in cholesterol), commonly referred to as rafts. In all of these diverse biological phenomena, the transverse location of cholesterol in the membrane is almost certainly an important structural feature. Using a combination of neutron scattering and solid-state2H NMR, we have determined the location and orientation of cholesterol in phosphatidylcholine (PC) model membranes having fatty acids of different lengths …

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Fullfact: An R Package For The Analysis Of Genetic And Maternal Variance Components From Full Factorial Mating Designs, Aimee Lee S. Houde, Trevor E. Pitcher

Great Lakes Institute for Environmental Research Publications

Full factorial breeding designs are useful for quantifying the amount of additive genetic, nonadditive genetic, and maternal variance that explain phenotypic traits. Such variance estimates are important for examining evolutionary potential. Traditionally, full factorial mating designs have been analyzed using a two-way analysis of variance, which may produce negative variance values and is not suited for unbalanced designs. Mixed-effects models do not produce negative variance values and are suited for unbalanced designs. However, extracting the variance components, calculating significance values, and estimating confidence intervals and/or power values for the components are not straightforward using traditional analytic methods. We introduce fullfact …

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Quantitative Biomonitoring In The Detroit River Using Elliptio Complanata: Verification Of Steady State Correction Factors And Temporal Trends Of Pcbs In Water Between 1998-2015, Ken G. Drouillard, Mark Cook, Todd A. Leadley, Paul Drca, Ted Briggs, G Douglas Haffner

Great Lakes Institute for Environmental Research Publications

Quantitative biomonitoring methods were applied to determine PCB concentrations in water from the Detroit River over a 17 year period. During 2014, mussels were deployed for and extended duration (21-364 d) and time dependent PCB concentrations were fit to a bioaccumulation model to estimate elimination coefficients (k_tot) and provide site specific calibration of mussel toxicokinetics. The site specific calibration and different k_tot versus K_OW relationships from the literature were used to correct for steady state. ∑PCB concentrations in water were not significantly dependent on the k_tot values used indicating that individual variation exceeds error contributed …

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Determination Of Pcb Elimination Coefficients In Round Goby And Tubenose Goby, Xin Sun, Tim B. Johnson, Ken G. Drouillard

Great Lakes Institute for Environmental Research Publications

Whole-body elimination coefficients of polychlorinated biphenyls (PCBs) were determined in two Great Lakes invasive fish species, round goby (Neogobius melanostomus) and tubenose goby (Proterorhinus semilunaris). Elimination rates were determined for a set of model PCB congeners (n=12 congeners) dosed to fish by intraperitoneal injection and allowed to depurate at a temperature of 21.4^oC for 90 d. Eight PCBs (PCB 6, 13, 21, 57, 62, 68, 89, 112 and 125) exhibited significant elimination by round goby and had corresponding half lives ranging from 13 to 39.8 d. For tubenose goby, four congeners (PCBs 21, 58, …

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Full-Text Articles in Physical Sciences and Mathematics

Vitamin E Circular Dichroism Studies: Insights Into Conformational Changes Induced By The Solvent’S Polarity, Drew Marquardt, Brad J. Van Oosten, Mikel Ghelfi, Jeffrey Atkinson, Thad A. Harroun

Chemistry and Biochemistry Publications

Morphology-Induced Defects Enhance Lipid Transfer Rates, Yan Xia, Kamil Charubin, Drew Marquardt, Frederick A. Heberle, John Katsaras, Jianhui Tian, Xiaolin Cheng, Ying Liu, Mu Ping Nieh

Chemistry and Biochemistry Publications

Cholesterol's Location In Lipid Bilayers, Drew Marquardt, Norbert Kučerka, Stephen R. Wassall, Thad A. Harroun, John Katsaras

Chemistry and Biochemistry Publications

Insights From Molecular Dynamics On Substrate Binding And Effects Of Active Site Mutations In Delta1-Pyrroline-5-Carboxylate Dehydrogenase, Bogdan F. Ion, Mohamed M. Aboelnga, James W. Gauld

Chemistry and Biochemistry Publications

Elastomers: Reinventing Butyl Rubber For Stretchable Electronics (Adv. Funct. Mater. 29/2016), Akhil Vohra, Heather L. Filiatrault, Stanley D. Amyotte, R. Stephen Carmichael, Natalie D. Suhan, Conrad Siegers, Lorenzo Ferrari, Gregory J.E. Davidson, Tricia Breen Carmichael

Chemistry and Biochemistry Publications

Polyisobutylene-Paclitaxel Conjugates With Pendant Carboxylic Acids And Polystyrene Chains: Towards Multifunctional Stent Coatings With Slow Drug Release, John F. Trant, Mahmoud M. Abd Rabo Moustafa, Inderpreet Sran, Elizabeth R. Gillies

Chemistry and Biochemistry Publications

Assessment Of Hazard Metrics For Predicting Field Benthic Invertebrate Toxicity In The Detroit River, Ontario, Canada, Kerry N. Mcphedren, Alice Grigicak-Mannnion, Gord Paterson, Briggs Tedd, Jan J.H. Ciborowski, G. Douglass Haffner, Ken G. Drouillard

Great Lakes Institute for Environmental Research Publications

Is It Appropriate To Composite Fish Samples For Mercury Trend Monitoring And Consumption Advisories?, Ken G. Drouillard, Nilima Gandhi, Satyendra P. Bhavsar, Sarah B. Gewurtz, George B. Arhonditsis, Steve Petro

Great Lakes Institute for Environmental Research Publications

A Chemoenzymatic Route To Chiral Siloxanes, Ravi Naoum, Jacqueline P. Séguin, John F. Trant, Mark B. Frampton, Tomáš Hudlický, Paul M. Zelisko

Chemistry and Biochemistry Publications

Lipid Bilayer Thickness Determines Cholesterols Location In Model Membranes, Drew Marquardt, Frederick A. Heberle, Denise V. Greathouse, Roger E. Koeppe, Robert F. Standaert, Brad J. Van Oosten, Thad A. Harroun, Jacob J. Kinnun, Justin A. Williams, Stephen R. Wassall, John Katsaras

Chemistry and Biochemistry Publications

Fullfact: An R Package For The Analysis Of Genetic And Maternal Variance Components From Full Factorial Mating Designs, Aimee Lee S. Houde, Trevor E. Pitcher

Great Lakes Institute for Environmental Research Publications

Quantitative Biomonitoring In The Detroit River Using Elliptio Complanata: Verification Of Steady State Correction Factors And Temporal Trends Of Pcbs In Water Between 1998-2015, Ken G. Drouillard, Mark Cook, Todd A. Leadley, Paul Drca, Ted Briggs, G Douglas Haffner

Great Lakes Institute for Environmental Research Publications

Determination Of Pcb Elimination Coefficients In Round Goby And Tubenose Goby, Xin Sun, Tim B. Johnson, Ken G. Drouillard

Great Lakes Institute for Environmental Research Publications