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chemistry

Understanding the role of charge on particle transport within semidilute and concentrated biopolymer solutions and tau protein condensates.

Abstract: Biological polymer networks such as mucus, extracellular matrix, nuclear pore complex, and bacterial biofilms, play a critical role in governing the transport of nutrients, biomolecules and particles within cells and tissues. The interactions between particle and polymer chains are responsible for effective selective filtering of particles within these macromolecular networks. This selective filtering is not dictated by steric alone but must use additional interactions such electrostatics, hydrophobic and hydrodynamic effects to control particle transport within biogels. Depending on chemical composition and desired function, biogels use selective filtering to allow some particles to permeate while preventing others from penetrating the biogel. The mechanisms underlying selective filtering are still not well understood yet have important ramifications for a variety of biomedical applications. Controlling these non-steric interactions are critical to understanding molecular transport in vivo as well as for engineering optimized gel-penetrating therapeutics. Fluorescence correlation spectroscopy (FCS) is an ideal tool to study particle transport properties within uncharged and charged polymer solutions. In this dissertation, our research focuses primarily on the role of electrostatics on the particle diffusion behavior within polymer solutions in the semi-dilute and concentrated regimes.

Using a series of charged dye molecules, with similar size and core chemistry but varying net molecular charge, we systematically investigated their diffusion behavior in polymer solutions and networks made up of polysaccharide and proteins. Specifically, we studied in Chapter 3 the probe diffusion in semidilute and concentrated dextran solutions. The hindered diffusion observed in attractive gels is dependent on the probe net charge and shows a dependence on the solution ionic strength. Using a biotinylated probe, we also show evidence of an additional non-electrostatic interaction between the biotin molecule and the dextran polymer chains. In contrast, comparisons to a highly charged, water soluble polyvinylamine (PVAm) semidilute solution shows that all probes, regardless of charge, were highly hindered and a weaker dependence on solution ionic strength was observed. In Chapter 4, we characterized the transport properties of our probe molecules within pure and mixed charge solutions of amino(+)-dextran and carboxymethyl(-)-dextran. We show that these mixed charge polymer solutions still have the potential to be efficient filters for interacting particles even with comparably few attractive interaction sites. By chemical modification of the amino dextran, we also compare these results to those obtained in polyampholytic solutions. Lastly, we investigate the transport properties of both probes and a much larger bovine serum albumin (BSA) protein molecule within liquid-liquid phase separated (LLPS) tau protein in chapter 5. Tau is an intrinsically disordered protein with both positive and negatively charged amino acids. We show that despite having a high local protein concentration, tau droplets are relatively low density and comparable to semi-dilute polymer solutions. Both probe molecules and BSA are observed by FCS to be recruited within the liquid droplet resulting in ~10x fold increase in particle concentration inside the tau droplet compared to outside. Probe transport within the phase separated tau is sensitive to probe net charge and solution ionic strength. Lastly, we show that BSA transport inside the tau droplet can be fairly well described by using Stokes-Einstein adjusted for the experimentally determined microviscosity within the tau droplet.

 

Keywords: diffusion, biological gels, fluorescence correlation spectroscopy, electrostatic, interaction filtering.

 

Join the seminar at https://uky.zoom.us/j/9237836600

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Chemistry Graduation Celebration

The Department of Chemistry hosts a Graduation Celebration and Awards Ceremony to recognize the outstanding acheivements of our students on an annual basis. This year's event will be streamed via Facebook. Please join us by clicking here!

We are delighted to recognize the following graduates of our PhD, Masters, and Undergraduate programs:

Doctor of Philosophy
Thilini Abeywansha
Qianxiang Ai
Harsha Attanayake
Alex Boehm
Xu Fu
Robby Pace
Alexandra Riddle
Josiah Roberts
Melonie Thomas
Md Aslam Uddin
Namal Wanninayake
Master of Science
Dallas Bell
Heather Everson
Nathaniel George
Thilini Malsha Suduwella
Taylor Varner
Bachelor of Arts
Mary Ball
Matthew Burton
Brandon Cooke
Noah Franklin
Sarah Hodges
Emma Johnson
Danine Lindley
Michael Martin
Maggie McGoldrick
Claire Scott
Lauren Seeger
Sydney Sheldon
Nicholas Strobl
Hanna Suarez*
Phillip Woolery
* Denotes Chemistry Department Honors
Bachelor of Science
Elizabeth Ashley
Jessica Bennion
Bailey Chandler
Courtney Clifford
Gabrielle Evers
Matthew Farmer
Camryn Kennemore
Turner Lee
Alexsandr Lukyanchuk*
Lexius Lynch
Cameron McNeill
Richard Murt
Taylor Nelson
Danielle Peterson
William Sanders
Amanda Shaw
Dakota Smith
James Spagnola
Alyssa Vance
Tyler Vogel*
Madison Webb*
* Denotes Chemistry Department Honors

Undergraduate Scholarships (Fall 2021-Spring 2022)
Thomas B. Nantz Scholarship Linda Omali
Paul G. Sears Chemistry Scholarship Anna Fatta
Paul G. Sears Chemistry Scholarship Andrew Smith
Robert M. Boyer Memorial Scholarship Alexandria Sims
David W. and Eloise C. Young Scholarship Angelina Kue
David W. and Eloise C. Young Scholarship Ashley Bates
Robert Singleton Hart 1907 Scholarship Darcy Adreon
Paul L. Corio Scholarship Jessica Ray
Dr. Hume and Ellen Towle Bedford Scholarship Samantha Hillman
ACS-Hach Land Grant Scholarship Randall Sampson
Fellowships
Stephen H. Cook Memorial Fellowship (Summer 2021) Amanda Medina
Murrill Graduate Fellowship (Fall 2020) Rebekah Duke
Murrill Graduate Fellowship (Fall 2020) Mary Wheeler
Murrill Graduate Fellowship (Spring 2021) Moses Ogbaje

 

Graduate Awards (Fall 2020-Spring 2021)
100% Plus Setareh Saryazdi
Outstanding Graduate Research Mohamed Nishya Raseek
Outstanding Graduate Research Raphael Ryan
Outstanding TA Shashika Bandara
Outstanding TA Manisha De Alwis Goonatilleke
Outstanding General Chemistry TA Kathryn Pitton
Outstanding General Chemistry TA Md Abu Monsur Dinar
Undergradute Awards (Fall 2020-Spring 2021)
General Chemistry Excellence Award (Fall 2020 - CHE105) Abby Roetker
General Chemistry Excellence Award (Fall 2020 - CHE107) Jason Wang
General Chemistry Excellence Award (Spring 2021 - CHE105) Brysen Honeycutt
General Chemistry Excellence Award (Spring 2021 - CHE107) Abby Roetker
Freshman Chemistry Award Sophia Li
Hammond Leadership Award Hunter Mulloy
Willard R. Meredith Memorial Award Matthew Farmer
Nancy J. Stafford Award Bailey Chandler
Hammond Undergraduate Service Award Darcy Adreon
Hammond Undergraduate Service Award Mirindi Kabangu
100% Plus Sam Chasen

 

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Jacobs Science Building, Room 121
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Reaction Profiling in Unlimited Detail: Applications of Online HPLC

Abstract: Process analytical technology (PAT) plays an essential role in understanding and optimization chemical manufacturing routes by furnishing data-dense reaction profiles. However, each PAT tool presents certain limitations with respect to chemical component resolution, reaction compatibility or useful operational domain. High-pressure liquid chromatography (HPLC) represents one of the most versatile analytical tools available for providing detailed reaction progress analysis. Yet this technology introduces a new set of challenges relating to sample acquisition and preparation, especially when trying to utilize HPLC as a real time analytical technology.

Our lab has developed a comprehensive set of automated tools, which allow nearly any chemical process to be visualized in real time by HPLC. This includes reactions performed under inert atmosphere, systems with heterogenous reagents, and complex competition reactions with many components. The combination of excellent resolving power of UHPLC, coupled to the high dynamic range of standard UV/Vis and MSD detectors has allowed this tool to be broadly deployed. This has allowed complex reactions to be visualized in exceptional details with unprecedented ease. This presentation will discuss several case studies to demonstrate the flexibility and fidelity of this new online HPLC technology. Examples will include studying reaction mechanisms, measuring crystallization processes and deployment as an in-process control for reaction automation.

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Zoom
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Supramolecular Influences on Luminescence: From Coordination Complexes to Porous Solids

Abstract:

Imparting supramolecular interactions on transition metal systems such as Iridium complexes (with various N^C ligands), can have a profound impact on their luminescence properties. These types of complexes are under intensive investigation due to their excellent performance when used as emitters in phosphorescent organic light emitting diodes (PhOLEDs).1 The ideal interactions for holding supramolecular systems together are hydrogen bonds, as they combine relatively strong intermolecular attractions with excellent reversibility. In using DNA base-pair-like interactions in super strong hydrogen bonding arrays to drive assembly,2 we can influence chromaticity efficiently.3,4 Beyond molecular systems, we can also apply these principles in extended solid-state systems whose porosities are such that small molecule uptake can influence the inherent physical (and photophysical) properties of the host materials.5 In this lecture, a broad view of our research program will be presented, spanning molecular systems to solid-state materials, and how we can make use of inherent luminescence properties for chromaticity modulation, small molecule sensing, and diagnostics.6,7

References:

  1. A.F. Henwood, E. Zysman-Colman, Chem. Commun. 2017, 53, 807.
  2. B.A. Blight, C.A. Hunter, D.A. Leigh, H. McNab, P.I.T. Thomson, Nature Chemistry, 2011, 3, 246.
  3. B. Balónová, D.  Rota Martir, E.R. Clark, H.J. Shepherd, E. Zysman-Colman, B.A. Blight, Inorganic Chemistry, 2018, 57, 8581.
  4. B. Balónová, H.J.  Shepherd, C.J. Serpell, B.A. Blight, Supramolecular Chemistry, 2019, DOI: 10.1080/10610278.2019.1649674
  5. R.J. Marshall, Y. Kalinovskyy; S.L. Griffin, C. Wilson, B.A. Blight, R.S. Forgan, J. Am. Chem. Soc.2017139, 6253.
  6. S.J. Thomas, B. Balónová, J. Cinatl M.N. Wass, C.J. Serpell, B.A. Blight, M. Michaelis, ChemMedChem202015(4), 349.
  7. C.S. Jennings, J.S. Rossman, B.A. Hourihan, R.J. Marshall, R.S. Forgan, B.A. Blight, Soft Matter, 2021, In Press. DOI: 10.1039/D0SM02188A

 

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News from a Chemistry Alumni: Michael Goodman

Alum Michael Goodman graduated with a PhD in Chemistry from Vanderbilt University in 2018. Prior, he graduated from the University of Kentucky, College of Arts & Sciences with a Chemistry BS in 2011 and completed a post-doc at University of California, Davis.

This interview is part of a series conducted by the department called, “UK Chemistry Alumni: Where Are They Now?” This interview was coordinated by Dr. Arthur Cammers.


 

Using Electricity to Efficiently Drive the Synthesis of Chemicals and Materials

Joel Rosenthal


Department of Chemistry and Biochemistry,

University of Delaware, Newark, DE, 19716

 

Abstract: Development of new electrosynthetic tools and methods has attracted much interest
in recent years as a means to prepare chemicals and materials that are either
inaccessible or whose preparation is inefficient using traditional thermal chemistries. In
addition to opening up routes to new compounds and materials, implementation of
electrosynthetic strategies can enable reduced waste streams and more streamlined
synthetic routes, while circumventing the use of expensive, acutely toxic, and highly
reactive reagents. Driving synthetic chemistry with electric current as opposed to heat
also represents a direct way to power chemical processes using renewable energy (such
as electricity from wind or sunlight), and therefore provides an opportunity for more
sustainable chemical syntheses and renewable energy storage.
Our lab has developed efficient electrosynthetic routes to prepare commodity
chemicals and fuels, fine chemicals, and new inorganic materials. In this presentation, we
will provide an overview of our efforts in each of these areas, which include 1) controlling
the electrochemical reduction of carbon dioxide to switch between the formation of either
formic acid or carbon monoxide depending on the electrolysis conditions; 2) the
electrosynthesis of α,β-ynones en route to polyphenols that show anti-cancer and anti-
HIV activity; and 3) the electrochemical synthesis of new classes of metal-organic
frameworks and other porous materials that are based upon non-traditional metal ions
and organic linkers. Throughout the presentation, we will show how the ability to drive
challenging transformations that require the activation of strong bonds or access to highly
reactive chemical intermediates is greatly facilitated through an electrochemical
approach. We will also demonstrate how controlling the chemical dynamics and
environments at working electrode interfaces can be leveraged to promote interesting
energy conversion processes, solar fuel generation, and porous material construction.
Implications for the future development of efficient electrosynthetic strategies and
platforms will also be discussed.

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Zoom
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