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45214-G7
Diffusion and Adsorption of Single Dendrimers for Gas Hydrate Prevention
Our Type-G PRF grant was awarded for the two-year period of Spet 1, 06-Aug 31, 08. The major goal of this research is to understand the molecular level interaction between dendrimers and hydrocarbon for the prevention of gas hydrates in the oil pipeline, a practical problem which is costing the petroleum industry at least one million dollars a day.
Over the past one year multiple students, including my graduate student Karthikeyan Pasupathy, undergraduate students Aaron Jones (senior, graduated this May) and Donovan Jones (freshman), and NSF-REU (Research Education for Undergraduates) student Justin Ching from UCLA have all participated in this research. In particular, Aaron and Donovan were partially supported by this grant. This research has resulted in an ongoing collaboration between my experimental group and Prof Monica Lamm's theoretical group at Iowa State University. In addition, John Lyons, an undergraduate student from the University of Wisconsin, Madison, also participated in this research as an REU student of Prof Lamm.
So far we have successfully labeled PAMAM dendrimers with fluorescent dye TRITC. We have measured the absorbance spectra of TRITC-labeled PAMAM and Squalane hydrocarbon, and the binding between PAMAM and Squalane. For these measurements we have used combined techniques of UV-vis spectrophotometry and transmission electron microscopy. Using total-internal-reflection single-molecule fluorescence microscopy, we have discovered the approaching, association, and dissociation kinetics for single PAMAM and Squalane molecules on the subsecond time scale. We have found experimentally and through molecular dynamics simulations that pH is a major factor affecting the binding affinity between the PAMAM and the Squalane, possibly because of pH-induced variation of charge density on the outer rims of the dendrimers. We believe the underlining mechanism between dendrimers and hydrocarbon is predominantly hydrophobic and van der Waals interactions, in which the branches of the dendrimer molecules are attached to the backbones of the hydrocarbons. We also believe the flexibity of the PAMAM dendrimers is altered because of the change in pH. Such conformational change is expected to affect the binding capacity of dendrimers for hydrocarbon.
So far this research has generated a paper entitled "Single-Molecule Study of Dendrimer-Hydrocarbon Interaction" presented by Pasupathy at the NSTI 2007 conference in San Jose this May. A manuscript is in preparation and will be submitted in this August to one of the leading journals in physical chemistry. In addition, two REU students, Ching and Lyons, have presented their REU research at Clemson University and at Iowa State University, respectively. One of my students, Donovan Jones, was awarded an SUMR award earlier this year.
Overall our project has made significant progress in advancing our knowledge on the interaction between dendrimers and hydrocarbons at the single-molecule level. Within one year this grant has enabled the training of a number of graduate and undergraduate students. Neither of these would have been possible without the support of this Type-G grant. As the PI of this project I sincerely thank the PRF fund for this crucial support at this early stage of my career and believe this grant will pave the way for my future funding opportunities.
