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2006 MRS Spring Meeting

作者： Mills, Kristen L. Zhu, Xiaoyue Lee, Donghee Takayama, Shuichi Thouless, M.D. Department of Mechanical Engineering University of Michigan Ann Arbor MI 48109 United States Department of Biomedical Engineering University of Michigan Ann Arbor MI 48109 United States Macromolecular Science and Engineering Program University of Michigan Ann Arbor MI 48109 United States Department of Materials Science and Engineering University of Michigan Ann Arbor MI 48109 United States

ISBN: (纸本)1558998810

Exposure of poly(dimethylsiloxane) (PDMS) to oxygen plasma creates a thin, stiff surface-modified layer that reaches a submicron depth. Due to a significant modulus mismatch between the stiff surface-modified layer and the compliant bulk PDMS the surface-modified layer forms intricate patterns of surface buckles when under compressive stress and nano-cracks when under tensile stress. It is desirable to be able to design patterns of nano-cracks, or at least to have an understanding of them. Among the properties necessary to do this are the thickness and elastic modulus of the surface-modified layer. Due to the very small length scale of the surface-modified layer, it is a significant challenge to measure these properties. In this proceedings paper, a two-step method is described for determining the thickness and elastic modulus of the surface-modified layer using the atomic force microscope (AFM). First, nanoindentation is performed from which the bending stiffness of the surface-modified layer is calculated. Second, the surface-modified layer thickness is determined by using phase imaging on the cross-section of oxidized PDMS to map the region of the relatively stiffer surface-modified layer. © 2006 Materials Research Society.

关键词： Silicones

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Assessment of Simple Adhesive Substrates as a Method for Quantifying Microplastics and the Factors Influencing Capture

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SSRN 2022年

作者： Rieland, Julie M. Hu, Zeyuan Deese, Julian S. Love, Brian J. Department of Materials Science and Engineering United States Department of Biomedical Engineering United States Macromolecular Science and Engineering Graduate Program 2300 Hayward St Ann ArborMI48109 United States

Microplastics are a growing environmental concern, with a large body of evidence documenting substantial distribution of plastic material in virtually all environmental compartments. Countermeasures that help to bind, aggregate, or coalesce these distributed particles might result in lower human and animal exposures. Pressure sensitive adhesives (PSAs) have been identified as a viable microplastic (MP) capture mechanism with a range of potential use conditions. As with any countermeasure, there is a need to evaluate their collection efficiency, cost, ease of installation, etc. Expanding on previous work, submerged, spray-coated PSAs were investigated as a quick and low-cost quantitative method to assess MP binding in water. Two molecular weights of poly(2-ethylhexyl acrylate) PSA (92k, 950k, and 50:50 bimodal distribution) were applied as spray-coated substrates to compare MP-adhesive interactions. Thin films of PSA (92k 6 ± 1 μm, 950k 4 ± 2 μm, 50:50 BD 6.5 ± 1 μm) were sprayed on borosilicate glass slides using a commercial air brush. Polydisperse nylon-12 particles varying in size from 15-30 µm in diameter were dispersed in aqueous solution between 0.01 and 5 mg mL -1 and agitated under ambient conditions as quantitative comparisons of adhesive wettability and net capture. Mixed assays were also performed comparing binding of common MP species including polyethylene, polystyrene, and polyester particles and fibers to understand how varying composition, size, and form factor affect adsorption. The glass slide method demonstrated linear trends associated with the MP binding to glass slides with respect both to exposure time and MP concentration. The adhesive wettability demonstrates bounding parameters under which high wettability adhesives excel at MP capture but may compromise the integrity of the adhesive film. © 2022, The Authors. All rights reserved.

关键词： Adhesives

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Direct Interaction between the Transmembrane Helices Stabilize Cytochrome P450 2b4 and Cytochrome B5 Redox Complex

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SSRN 2023年

作者： Ramamoorthy, Ayyalusamy Sahoo, Bikash R. Biophysics Program Department of Chemistry Macromolecular Science and Engineering Biomedical Engineering Michigan Neuroscience Institute The University of Michigan Ann ArborMI48109-1055 United States

The catalytic activity of cytochrome P450 2B4 (CYP2B4) is moderated by its cognate redox partner cytochrome b5 (Cyt-b5). The endoplasmic reticulum (ER) membrane and intermolecular transmembrane (TM) interaction between CYP2B4 and Cyt-b5 regulate the substrate catalysis and the reaction rate. This emphasizes the significance of elucidating the molecular basis of CYP2B4 and Cyt-b5 complexation in a membrane environment to better understand the enzymatic activity of CYP2B4. Our previous solid-state NMR studies revealed the membrane topology of the transmembrane domains of these proteins in the free and complex forms. Here, we show the cross-angle complex formation by the single-pass TM domains of CYP2B4 and Cyt-b5, which is mainly driven by several salt-bridges (E2-R128, R21-D104 and K25-D104), using a multimicrosecond molecular dynamic simulation. Additionally, the leucine-zipper residues (L8, L12, L15, L18 and L19 from CYP2B4) and π-stacking between H23 and F20 residues of CYP2B4 and W110 of Cyt-b5 are identified to stabilize the TM-TM complex in the ER membrane. The simulated tilts of the helices in the free and in the complex are in excellent agreement with solid-state NMR results. The TM-TM packing influences a higher order structural stability when compared to the complex formed by the truncated soluble domains of these two proteins. MM/PBSA based binding free energy estimates nearly 100-fold higher binding affinity (ΔG=-2810.68±696.44 kJ/mol) between the soluble domains of the full-length CYP2B4 and Cyt-b5 when embedded in lipid membrane as compared to the TM-domain-truncated soluble domains (ΔG=-27.406±10.32 kJ/mol). The high-resolution full-length CYP2B4-Cyt-b5 complex structure and its dynamics in a native ER membrane environment reported here could aid in the development of approaches to effectively modulate the drug-metabolism activity of CYP2B4. © 2023, The Authors. All rights reserved.

关键词： Lipid bilayers

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Comparisons and development of electrochemical sensors using G-PANI composite based on filter paper and transparency film substrate

Comparisons and development of electrochemical sensors using...

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Nanotechnology 2014: Graphene, CNTs, Particles, Films and Composites - 2014 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2014

作者： Ruecha, N. Rodthongkum, N. Cate, D.M. Chailapakul, O. Henry, C.S. Program in Macromolecular Science Faculty of Science Chulalongkorn University Pathumwan Bangkok 10330 Thailand Metallurgy and Materials Science Research Institute Chulalongkorn University Pathumwan Bangkok 10330 Thailand School of Biomedical Engineering Colorado State University Fort Collins CO 80523 United States Electrochemistry and Optical Spectroscopy Research Unit Department of Chemistry Chulalongkorn University Pathumwan Bangkok 10330 Thailand Department of Chemistry Colorado State University Fort Collins CO 80523 United States

ISBN: (纸本)9781482258264

Electrochemical sensors based on filter paper and transparency film substrates have been prepared using screen-printing method for the detection of the heavy metals ions including Pb2+, Cd2+ and Zn 2+. The electrochemical characteristics of these electrodes were analyzed using cyclic voltammetry (CV) and anodic stripping voltammetry (ASV) while the surface roughness were measured using an optical profilometer. For electrochemical characterization by CV, electrodes on paper give a higher current response for ferri/ferrocyanide than transparency-based electrodes. When using ASV for the detection of heavy metals, the transparency-based device gave higher current response than paper-based device. Moreover, for the surface characterization using optical profilometry, carbon ink penetrated into the porous of filter paper but coated on the transparency film substrate affecting to surface roughness in transparency-based electrodes is higher than electrodes on paper. To improve the sensitivity of these devices, graphene (G) and polyaniline (PANI) nanocomposite was prepared by polymerization of aniline monomer in the presence of G and used for electrode modification. G/PANI nanocomposite-modified electrode was characterized by CV and used for heavy metals detection by ASV. This system will be very useful for portable environmental monitoring.

关键词： Graphene

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Cross-linked low EW PFSA for high temperature fuel cell

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作者： Ghassemi, H. Zawodzinski, T. Schiraldi, D. Hamrock, S. Department of Macromolecular Science and Engineering Case Western Reserve University Cleveland OH 44106 United States Department of Chemical and Biomolecular Engineering University of Tennessee Knoxville TN 37996 United States 3M Fuel Cell Components Program 3M Company St. Paul MN 55144 United States

ISBN: (纸本)9780841226319

Several approaches have been studied to prepare ionomers for a high temperature proton exchange membrane (PEM) fuel cell. These ionomers were designed to be very low equivalent weight (EW), chemically stable, solvent resistant and highly conductive. The synthetic approaches include grafting, hybrid formation and cross-linking. The most interesting results were obtained from cross-linking of functionalized PFSA ionomers with various cross-linking compounds. New side-chain component multifunctional ionomers have been developed that were cross-linkable during or after membrane fabrication. As a result of this approach, a suite of polymers have been synthesized that, after membrane casting and cross linking show improved solvent resistant, low swelling and excellent proton conductivity. An obvious approach to increase proton conductivity in PSFA materials is to lower the equivalent weight (EW) by increasing the number of protogenic groups. PFSA membranes with EW

关键词： Ionomers

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Properties of the surface-modified layer of plasma-oxidized poly(dimethylsiloxane)

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MRS Online Proceedings Library 2006年第1期924卷 1-6页

作者： Kristen L. Mills Xiaoyue Zhu Donghee Lee Shuichi Takayama M. D. Thouless Department of Mechanical Engineering University of Michigan Ann Arbor USA Department of Biomedical Engineering University of Michigan Ann Arbor USA Macromolecular Science and Engineering Program University of Michigan Ann Arbor USA Department of Materials Science and Engineering University of Michigan Ann Arbor USA

关键词： nanoscale elastic properties film

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A quantitative assessment of nanoparticle-ligand distributions: Implications for targeted drug and imaging delivery in dendrimer conjugates

A quantitative assessment of nanoparticle-ligand distributio...

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作者： Mullen, Douglas G. Fang, Ming Desai, Ankur Baker Jr., James R. Orr, Bradford G. Banaszak Holl, Mark M. Program in Macromolecular Science and Engineering University of Michigan Ann Arbor MI 48109 United States Michigan Nanotechnology Institute for Medicine and Biological Sciences University of Michigan Ann Arbor MI 48109 United States Program in Applied Physics University of Michigan Ann Arbor MI 48109 United States Department of Physics University of Michigan Ann Arbor MI 48109 United States Department of Chemistry University of Michigan Ann Arbor MI 48109 United States

Functional nanoparticles often contain ligands including targeting molecules, fluorophores, and/or active moieties such as drugs. Characterizing the number of these ligands bound to each particle and the distribution of nanoparticle-ligand species is important for understanding the nanomaterial's function. In this study, the amide coupling methods commonly used to conjugate ligands to poly(amidoamine) (PAMAM) dendrimers were examined. A skewed Poisson distribution was observed and quantified using HPLC for two sets of dendrimer-ligand samples prepared using the amine-terminated form of the PAMAM dendrimer and a partially acetylated form of the PAMAM dendrimer that has been used for targeted in vivo drug delivery. The prepared samples had an average number of ligands per dendrimer ranging from 0.4 to 13. Distributions identified by HPLC are in excellent agreement with the mean ligand/dendrimer ratio, measured by 1H NMR, gel permeation chromatography (GPC), and potentiometric titration. These results provide insight into the heterogeneity of distributions that are obtained for many classes of nanomaterials to which ligands are conjugated and belie the use of simple cartoon models that present the "average" number of ligands bound as a physically meaningful representation for the material. © 2010 American Chemical Society.

关键词： Ligands

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SYNTHESIS OF INHERENTLY DISSYMMETRIC POLYAMIDES

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JOURNAL OF POLYMER science PART A-1-POLYMER CHEMISTRY 1970年第8期8卷 2275-+页

作者： OVERBERGER, CG YOSHIMUR.T OHNISHI, A GOMES, AS Department of Chemistry and the Macromolecular Research Center University of Michigan Ann Arbor Michigan 48104 Fellow of the Brazilian National Research Council and the National Academy of Science overseas research fellowship program.

The preparation of polyamides from derivatives of optically active biphenic acid is described. The diacid chlorides chosen were 2,2′-dinitro-6,6′-dimethylbiphenyl-4,4′-dicarbonyl chloride and 2,2′-dichloro-6,6′-dimethylbiphenyl-4,4′-dicarbonyl chloride, the diamines were phenyldiamines ( o -, m -, p -) piperazine, trans -2,5-dimethylpiperazine, and 1,2-piperaazolidine. Polymerization was carried out by the method of interfacial polycondensation. The polymers of aromatic diamines were insoluble in common organic solvents but soluble in dimethylformamide containing 5% lithium chloride, triesters of phosphoric acid, and methanesulfonic acid. The polymers of aliphatic diamines were also insoluble in common organic solvents but soluble in trifluoroethanol. All polymers had melting points higher than 280°C.

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Fluorescence lifetime imaging microscopy (FLIM) measures oxygen gradients in microfluidic bioreactors

Fluorescence lifetime imaging microscopy (FLIM) measures oxy...

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Biomedical Topical Meeting, BIO 2006

作者： Sud, Dhruv Mehta, Geeta Mehta, Khamir Linderman, Jennifer Takayama, Shuichi Mycek, Mary-Ann Dept. of Biomedical Engineering University of Michigan Ann Arbor MI 48109-2099 United States Dept. of Chemical Engineering University of Michigan Ann Arbor MI 48109-2099 United States Macromolecular Science and Engineering Program University of Michigan Ann Arbor MI 48109-2099 United States Applied Physics Program University of Michigan Ann Arbor MI 48109-2099 United States Comprehensive Cancer Center University of Michigan Ann Arbor MI 48109-2099 United States

A unique FLIM system was employed to quantitatively image extracellular oxygen distributions in perfused micro-bioreactors. We report effects of cell density on oxygen consumption and the first such measurement of oxy... 详细信息

ISBN: (纸本)1557528071

关键词： Oxygen

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Design and Optimization of the Porous Metamaterial EM Absorbers in X-band

Design and Optimization of the Porous Metamaterial EM Absorb...

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IEEE International Symposium on Electromagnetic Compatibility (EMC)

作者： Kanat Anurakparadorn Alan Taub Eric Michielssen Macromolecular Science and Engineering Program Department of Material Science and Engineering University of Michigan Ann Arbor Michigan USA Department of Mechanical Engineering University of Michigan Ann Arbor Michigan USA Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor Michigan USA

A strategy that combines experiment and simulation to design and optimize electromagnetic (EM) metamaterial absorbers containing a periodic porous structure is described. The approach provides the ability to produce absorbers that meet multiple user-specified objectives. Using the measured intrinsic properties of the baseline materials as an input to EM-field based computational modelling and optimization, absorption by the studied metamaterials measured by their reflection loss (RL) increases significantly. The resulting metamaterials have the potential for lower cost and lighter weight while providing greater protection than traditional metal gaskets and foams.

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