Marjan Dolatmoradi, Graduate Student, Vertes Lab & Rhys Dickhudt, Graduate Student, Boyes Lab, Graduate Students, GW Department of Chemistry

Fri, 3 December, 2021 2:00pm

The Department of Chemistry Presents, via Online and In-person Presentation: Marjan Dolatmoradi, Graduate Student, Vertes Lav & Rhys Dickhudt, Graduate Student, Boyes Lab, Graduate Students, GW Department of Chemistry

Mapping Biological Nitrogen Fixation One Cell at a Time

Metabolic heterogeneity is an inherent property of cell populations, including isogenic populations, that can be manifested in phenotypic differences. Metabolite levels determined by single-cell analysis provide information on the functioning of metabolic pathways in individual cells and can reveal much of the cellular phenomena that are masked in cell-population studies. Single-cell metabolomics based on mass spectrometry (MS) has become a powerful platform that allows for studying spatiotemporal dynamics of metabolite levels at cellular resolution. To achieve the statistical characterization of heterogeneity in metabolic cell states, numerous cells must be analyzed, and for that, high-throughput techniques are needed. In our study, we utilized optical fiber-based laser ablation electrospray ionization (f-LAESI) mass spectrometry (MS) with ion mobility separation (IMS) combined with a dual-channel microscope, capable of simultaneous brightfield and fluorescence imaging, for microscopy guided high-throughput single-cell analysis. To explore metabolic heterogeneity in biological nitrogen fixation, soybean (Glycine max) root nodule cells infected by rhizobia (Bradyrhizobium japonicum) were studied. The f-LAESI sampling method allows for direct analysis of tissue-embedded single cells in their native state, resulting in reduced artifacts due to high metabolite turnover and diffusion rates. Using high-resolution IMS, structural isomers can be separated on a millisecond timescale thereby improving the molecular coverage and confidence in metabolite identification. Population-wide heterogeneity, rare cells and hidden subpopulations can also be discovered using this technique.

Bio

Marjan Dolatmoradi received her M.S. degree in computational chemistry from American University in Washington, DC in 2018. In 2019, she joined the research group of Prof. Akos Vertes at the George Washington University. Her current work focuses on single-cell metabolomics using mass spectrometry-based techniques under ambient conditions.

Rhys Dickhudt, Graduate Student, Boyes Lab, GW Department of Chemistry

Naphthalene Polyamide Brushes via Chain Growth Condensation Polymerization

Conventional polymer brushes typically consist of surface-grafted random coil polymers, synthesized via the grafting from method using a living chain-growth polymerization technique. While successful, this technique primarily limits the preparation of polymer brushes to those from vinyl-based monomers. However, the discovery of the chain-growth condensation (CGC) polymerization technique allows for synthesis of a new class of polymer brush based on rigid-rod aromatic polymers. Previously published research from our research group was the first demonstration of aromatic polyamide brushes synthesized using the CGC polymerization technique. Recent advances in our lab includes the development of high Young’s modulus polymer brushes, which has opened the door for an investigation into the effect of the polymer backbone structure on the physical properties of the final brush. Modifying the aromatic backbone to introduce conjugation via the naphthalene unit has the potential to produce thin, covalently attached polymer films with both interesting optical properties and excellent mechanical properties. These new polymer brush systems have prospective applications as polymer light emitting devices and scratch resistant surfaces.

Bio

Rhys graduated with a B.S. in chemistry from Grove City College in Grove City, PA. In fall 2019, he began work on his Ph.D. in the Boyes lab at GWU. Rhys' current research is on functionalizing aromatic polyamide brushes for applications in membrane separations, optical devices, and high-strength surfaces.