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Abstract:

Insulin and the blood-brain barrier (BBB) interact in at least two distinct ways that are related to cognitive impairment.  Insulin plays important roles in cognition, neurogenesis, and CNS mediated metabolic regulation. Yet nearly all of the insulin is produced by the pancreas and dependent on transport by the BBB.  Evidence suggests that impaired insulin transport at the BBB and resistance within the brain occur in Alzheimer’s disease.  Additionally, the BBB deteriorates with the hyperglycemia of diabetes.  This talk will briefly explore these two mechanisms. After a general overview of BBB and insulin transport, mechanisms by which hyperglycemia through oxidative stress results in pericyte death and BBB disruption will be discussed.  I will then discuss CNS insulin resistance and therapeutic approaches to overcoming it.

SomaLogic has developed a novel class of chemically-modified aptamers, called SOMAmer Reagents™.   Aptamers are short ssDNA molecules, which are identified through an in vitro evolution process called SELEX, that bind protein targets with affinities approaching that of antibodies.   Modification of canonical ssDNA aptamers with amino acid side chains or aromatic rings further enhances their protein binding capability by allowing evolution of stabilizing hydrophobic-hydrophobic interactions not possible for the natural CAGT bases.   Examples of the synthetic chemistry and biomedical applications of SOMAmer reagents will be presented.

Abstract: Although the conversion of oleaginous biomass to the fatty acid methyl esters (FAMEs) that constitute biodiesel is a mature technology, feedstock availability issues as well as challenges stemming from the high oxygen content of FAMEs have limited the widespread application of biodiesel. Consequently, attention has shifted to processes capable of catalytically deoxygenating oleaginous biomass to afford fuel-like hydrocarbons. Deoxygenation via decarboxylation/decarbonylation (deCO_x) represents a promising alternative to the hydrodeoxygenation (HDO) processes typically employed to achieve this transformation, as deCO_x does not necessitate the high pressures of hydrogen and the problematic sulfided catalysts required by HDO.

To date, the majority of deCO_x reports involve Pd or Pt catalysts, the cost of which may be prohibitive. However, Ni-based catalysts have been shown to be capable of affording comparable results to precious metal-based formulations [1]. Recently, we have observed that the promotion of Ni with other earth-abundant metals – such as Cu – leads to considerable improvements in activity, selectivity and resistance to coking [2]. Results of Temperature Programmed Reduction (TPR) and X-ray Photoelectron Spectroscopy (XPS) measurements suggest that these improvements can be attributed to the ability of the aforementioned metal promoters to improve the reducibility of Ni. This results in an increased amount of Ni⁰, which is believed to be the active phase in the deCO_x reaction.

Ni catalysts promoted in this manner afford remarkable results in the conversion of a wide variety of ­model, waste and/or highly unsaturated lipids – including tristearin, triolein, yellow grease, brown grease, hemp seed oil and algal FAMEs – to fuel-like hydrocarbons [3-6]. Indeed, using a fixed-bed reactor operated using industrially-relevant reaction conditions, close to quantitative yields of diesel-like hydrocarbons are obtained. In addition, as shown in Figure 1, a catalyst employed has displayed remarkable stability and recyclability in a run comprising two 100 h time on stream cycles [5].  

Mentoring has been identified as an effective tool not only for attracting and retaining students from groups traditionally underrepresented in STEM disciplines, but also for improving their academic performance. However, additional benefits could be obtained by housing mentoring initiatives in research centers as opposed to in traditional academic departments. Therefore, a mentoring initiative based at the ����vlog�ٷ���� Center for Applied Energy Research is striving to test this hypothesis [7]. Recently, providing the participating students access to international research opportunities has become a focus of this mentoring program.

References

[1] T. Morgan, D. Grubb, E. Santillan-Jimenez, M. Crocker. Top. Catal., 2010, 53, 820.

[2] R. Loe, E. Santillan-Jimenez, A.F. Lee, M. Crocker, et al. Appl. Catal. B: Environ., 2016, 191, 147.

[3] E. Santillan-Jimenez, R. Pace, T. Morgan, C. McKelphin, M. Crocker, et al. Fuel, 2016, 180, 668.

[4] E. Santillan-Jimenez, R. Loe, M. Garrett, T. Morgan, M. Crocker. Catal. Today, 2018, 302, 261.

[5] R. Loe, M. Maier, M. Abdallah, R. Pace, E. Santillan-Jimenez, M. Crocker, et al. Catalysts, 2019, 9, 123.

[6] R. Loe, K. Huff, M. Walli, R. Pace, Y. Song, E. Santillan-Jimenez, M. Crocker, et al. Catalysts (IN PRESS).

[7] E. Santillan-Jimenez, W. Henderson. 124^th American Society for Engineering Education Annual Conference Proceedings, 2017, Conference Paper ID #17681.

Abstract:

The interface between two fluids is not only important for defining reactivity of dislike materials, but is also applicable for the preparation of stable higher order structures. Recently, the Pentzer lab developed 2D carbon-based nanosheets that assemble at different fluid-fluid interfaces including oil-water, oil-oil, and ionic liquid-water and demonstrated the use of these Pickering emulsions as templates for the preparation of higher order hybrid structures. Graphene oxide (GO) and its functionalized analogues are used as the 2D particle surfactant, and are especially attractive given they have properties distinct and complimentary to the more commonly studied spherical and rod-like counterparts, and because these nanosheets are multifunctional (e.g., antimicrobial, good gas barriers, precursor to electrically conductive nanosheets, etc.).  Recent advances from the Pentzer lab will be reported, including preparation of Janus nanosheets, water-sensitive reactions in oil-in-oil emulsions, GO capsules filled with ionic liquid for supercapacitor electrodes, GO capsules for compartmentalization of phase change materials, and GO coatings for 3D printable polymers to prepare conductive structures. This work makes use of fundamental organic chemistry reactions and thus gives access to unique structures and assemblies of interest for a broad range of applications in a scalable fashion.

Abstract:

Dye-sensitized solar cells have received considerable attention since the advent of mesoporous TiO₂ thin films described by Grätzel and O’Regan [1].  The UNC-Energy Frontier Research Center (EFRC) is interested in these materials for the application in dye-sensitized photoelectrosynthesis cells (DSPECs) that produce fuels that can be used when the sun has set [2]. Recently a kinetic pathway for an unwanted charge recombination reaction between the electrons injected into TiO₂ and an oxidized dye was identified. [2,3] This was accomplished by the rational design of molecules where the distance and driving force were held near parity and only a bridge unit was varied between a xylyl- and a phenyl- thiophene bridge. Spectroscopic analysis revealed that electronic coupling through the phenyl bridge was a factor of ten greater than through the xylyl bridge and this lowered the free energy for electron transfer. [3,4] Dye-sensitization was also utilized to generate a high valent metal oxo species implicated in water oxidation [5] and I-I bonds in terionic iodide complexes.[6]  Background on dye-sensitization and solar energy conversion will be provided that gives context for these most recent advances and suggests new directions for future research and applications.

References:

[1] “A Low- Cost, High Efficiency Solar Cell Based on the Dye- Sensitized Colloidal TiO₂ �󾱱�����” O’Regan, B.; Grätzel, M. Nature 1991, 353, 737.

[2] “Finding the Way to Solar Fuels with Dye Sensitized Photoelectrosynthesis Cells” Brennaman, M.K.; Gish, M.K.; Alibabaei, L.; Dares, C.J.; Dillon, R.J.; Ashford, D.L.; House, R.L.; Meyer, G.J.; Papanikolas, J.M.; Meyer, T.J. J. Am. Chem. Soc. 2016, 138, 13085-13102.

[3] “A Kinetic Pathway for Interfacial Electron Transfer from a Semiconductor to a Molecule” Hu. K.; Blair, A.D.; Piechota, E.J.; Schauer, P.A.; Sampaio, R.N.; Parlane, F.; Meyer, G.J.; Berlinguette, C.P. Nature Chem. 2016, 8, 853-859.

[4] “Kinetics Teach That Equilibrium Constants Shift Toward Unity with Increased Electronic Coupling” Sampaio, R.N.; Piechota, E.J.; Troian-Gautier, L.; Maurer, A.B.; Berlinguette, C.P., Meyer, G.J. Proc. Nat. Acad. Sci. USA 2018, 115, 7248-7253. 

[5] “A High Valent Metal Oxo Species Produced by Photoinduced One Electron, Two Proton Transfer Reactivity” Hu, K.; Sampaio, R.N.; Tamaki, Y.; Marquard, S.; Meyer, T.J.; Meyer, G.J. Inorg. Chem. 2018, 57, 486-494.

[6] “A Ter-Ionic Complex that Forms a Bond Upon Visible Light Absorption” Wehlin, S.A.M.; Troian-Gautier, L.; Sampaio, R.N.; Marcélis, L.; Meyer, G.J. J. Am. Chem. Soc. 2018, 140, 7799–7802.