Chemistry Newsblog

Category: Defenses

Evolution of Selected Isoprene Oxidation Products in Dark Aqueous Ammonium Sulfate

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MS Defense:  DM Ashraf Ul Habib
Chemistry Department

Lynn Mazzoleni, Advisor
Thursday, December 4  1pm,  Chem Sci 101
Evolution of Selected Isoprene Oxidation Products in Dark Aqueous Ammonium Sulfate

The climate of the world is changing but our understanding of atmospheric processes is limited. Atmospheric aerosol is a trace but very influential medium of the atmosphere. Especially little is known about the organic aerosol components and their aqueous phase chemical evolution. To address this, the aqueous phase processing of glyoxylic acid, py­ruvic acid, oxalic acid and methylglyoxal was studied simulating dark and radical free atmospheric aqueous aerosol. A novel observation of the cleavage of a carbon-carbon bond in pyruvic acid and glyoxylic acid leading to their decarboxylation was made in the presence of ammonium salts but decarboxylation was not observed from oxalic acid. The empirical rate constants for decarboxylation were determined and are competitive with nighttime OH radical reactions. The structure of the acid, ionic environment of the solu­tions and concentration of species were all found to affect the rate of decarboxylation. A tentative set of reaction mechanisms is proposed involving nucleophilic attack by ammo­nia on the carbonyl carbon leading to fragmentation of the carbon-carbon bond between the carbonyl and carboxyl carbons. Under similar conditions in atmospheric aerosol, the aqueous phase processing may markedly impact the physicochemical properties of aerosol.

 

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Synthetic Oligodeoxynucleotide Purification via Catching by Polymerization

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Suntara (Boat) Fueangfung

Advisor: Dr. Shiyue Fang

Doctoral candidate, Department of Chemistry

Michigan Technological University

Friday, December 5, 2014, 9:00 am

Admin Building, Room 404

PhD Defense

 

Synthetic Oligodeoxynucleotide Purification via Catching by Polymerization

Abstract

Large quantities of pure synthetic oligodeoxynucleotides (ODNs) are important for preclinical research, drug development, and biological studies. These ODNs are synthesized on an automated synthesizer. It is inevitable that the crude ODN product contains failure sequences which are not easily removed because they have the same properties as the full length ODNs. Current ODN purification methods such as polyacrylamide gel electrophoresis (PAGE), reversed-phase high performance liquid chromatography (RP HPLC), anion exchange HPLC, and affinity purification can remove those impurities. However, they are not suitable for large scale purification due to the expensive aspects associated with instrumentation, solvent demand, and high labor costs.

To solve these problems, two non-chromatographic ODN purification methods have been developed. In the first method, the full-length ODN was tagged with the phosphoramidite containing a methacrylamide group and a cleavable linker while the failure sequences were not. The full-length ODN was incorporated into a polymer through radical acrylamide polymerization whereas failure sequences and other impurities were removed by washing. Pure full-length ODN was obtained by cleaving it from the polymer. In the second method, the failure sequences were capped by a methacrylated phosphoramidite in each synthetic cycle. During purification, the failure sequences were separated from the full-length ODN by radical acrylamide polymerization. The full-length ODN was obtained via water extraction. For both methods, excellent purification yields were achieved and the purity of ODNs was very satisfactory. Thus, this new technology is expected to be beneficial for large scale ODN purification.

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A New Biomimetic Approach to Superhydrophobic Nanocomposite Coating Materials Inspired by Natural Materials (Lotus Leaf and Duck Feather)

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Soha M. Albukhari (Advisor: Dr. Patricia Heiden)

Doctoral Student, Department of Chemistry, Michigan Technological University

November  17, 2014 – 8:30 am – Fisher Hall, Room 126

Abstract:

This proposal describes a novel approach to create of superhydrophobic polymeric nanocoating materials, inspired by the water-repellant properties in two natural materials, lotus leaves and duck feathers. The process combines simple synthetic techniques with coaxial electrospinning and ultrasonication techniques to form a novel, reinforced superhydrophobic and self-cleaning coating on a glass substrate. To accomplish this we prepare a PMMA-grafted graphene suspension and a fluorinated silica nanoparticle suspension. These two fluids were used in coaxial electrospinning to produce a novel core-sheath nanofiber coating material with a dual superhydrophobic structure that mimics the critical structures in duck feathers and lotus leaves. These features are expected to give nanocomposite micro-nano core-sheath fibers that will impart superhydrophobic properties by increasing the water contact angle (CA) to more than 150º, and give a self-cleaning surface by having a water roll-off angle of less than 10º. These values are also expected to make the surface resistant to icing. Such a dual biomimetic structure has never been produced before, and by combining these features we will be able to study how these two differently functioning structures interact. The basic purpose of the PMMA-graphene core is to fill the air space in the micro-nano helix of the core-sheath nanocomposite by forming a cushion on the fiber-water interface, decreasing its surface wettability. Moreover, graphene electro-conductivity provides anti-icing properties and adds mechanical strength to the coating, so if the sheath layer fails, the graphene layer will still function independently. Studying this new dual-mimetic material may reveal new information about morphology and nanostructures that impart superhydrophobicity, which has value for coating applications such as airplane wings, sidewalks, car windshields, runways, and roads.

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Molecular characterization of atmospheric organic matter in biogenic secondary organic aerosol, ambient aerosol and clouds

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Chemistry Seminar
Tuesday, September 23, 2014
EERC 314

Molecular characterization of atmospheric organic matter in biogenic secondary organic aerosol, ambient aerosol and clouds

Ms Yunzhu Zhao
(Advisor: Dr. Lynn Mazzoleni)
Doctoral Candidate
Department of Chemistry
Michigan Technological University

ABSTRACT

Atmospheric aerosol affects the Earth’s energy budget, reduces visibility and influences human health. The organic composition of aerosol is quite complex and continuously evolves through various atmospheric processes. To gain a deeper understanding of the molecular composition of atmospheric organic matter (AOM), chamber-generated biogenic secondary organic aerosol (SOA), ambient aerosol and cloud water samples were studied. Ultrahigh resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry was used to provide detailed molecular characterization of the atmospheric samples. Due to the extremely high mass resolution and mass accuracy, thousands of individual molecular formulas were identified in all of the samples studied. Multivariate statistical analysis methods were evaluated to compare the similarities and differences of the sample compositions. The molecular characterization of biogenic SOA, ambient aerosol and clouds will be discussed. This study of the three types of atmospheric samples helps to understand the composition of AOM with respect to atmospheric processes.

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