Congratulations to Beryl Zhang ’18 who presented her poster, on Enzymatic hydrogel thickness measurements by AFM, at the at the Mid-Michigan Symposium for Undergraduate Research Experiences (Mid-SURE). Beryl helped Alex getting our new AFM-SECM system off the ground, measuring the thickness of hydrogels made using the slide coating technique. This approach will be used for electrochemical microscopy studies of single and multi-enzyme cascades.
Congrats to former group member Josh Gallaway who is starting a new tenure-track position in the Dept. of Chemical Engineering at Northeastern University. Josh’s research in our group was on redox complexes for mediating enzymatic reactions, but his recent studies have combined spectroscopic and electrochemical techniques to understand battery chemistry, especially zinc alkaline batteries. We can’t wait to see what Josh does at NEU!
Former postdoc Cenk Gumeci and Duyen Do have published new work on electrospun nanofiber-based bioelectrodes in Electrocatalysis. Electrospinning allows for the control of fiber diameter and density, and allow for very thin and highly efficient biocatalytic films. Current density reaching 10 mA cm−2 was observed for glucose oxidation, rivaling that of commercial carbon nanomaterials. This work was featured as cover art for the July 2017 issue.
- C. Gumeci, D. Do and S. C. Barton, “Electrospun Carbon Nanofibers as Supports for Bioelectrodes”, Electrocatalysis, 8, 321–328 (2017). link
A new paper by Erica Earl is available now in Physical Chemistry Chemical Physics (PCCP). In this paper, Erica uses a continuum model to demonstrate the effectiveness of channeling strategies in reaction cascades. She studied proximity, physisorption, and electrostatic interactions, three modes discussed in a recent review paper by our collaborators and us. The paper clearly demonstrates the effectiveness of electrostatic interactions for channelling of intermediates between active sites.
The continuum approach is useful for studying long-range interactions, but interactions specific to molecular structure must be assessed using molecular-scale modeling such as molecular dynamics. Our collaborative MD study, recently published in ACS Catalysis, complements this paper well.
Electrostatic interactions are capable of channeling reaction intermediates in catalytic
cascades, but simulations predict this is true only for sufficiently high kinetic rates.
- E. Earl and S. Calabrese Barton, “Simulation of intermediate transport in nanoscale scaffolds for multistep catalytic reactions”, Phys. Chem. Chem. Phys., 19, 15463–15470 (2017). doi:10.1039/C7CP00239D
Current Ph.D. student Yuanchao Liu has published new work on molecular dynamics (MD) simulation of electrostatic channeling in ACS Catalysis, collaborating with Dr. David P. Hickey of the Minteer group and Sigman group at the University of Utah. This is the first study of an artificial cascade using electrostatic channeling. In this work, we utilize MD simulations to describe the transport of anionic intermediates on a theoretical cationic peptide bridge, and identify rules for molecular-level design of electrostatic channeling.
MD simulations demonstrate design rules for designing electrostatic complexes (see videos after the break), and using MD studies as a foundational blueprint, our partners synthesized an enzyme complex using a poly(lysine) peptide chain as a cationic bridge between glucose-6-phosphate dehydrogenase and hexokinase (image below). Stopped-flow lag time experiments demonstrate the ability of the artificially linked enzyme complex to facilitate electrostatic substrate channeling.
Charged intermediate molecules (e.g., glucose 6-phosphate) are able to be adsorbed and hop on the peptide surface with oppositely charged amino acid side chains. When such peptides were used to covalently conjugate two enzymes without naturally channeling effect (Hexokinase and Glucose 6-phosphate dehydrogenase), the overall kinetics of the cascade was greatly improved.
- Y. Liu, D. P. Hickey, J.-Y. Guo, E. Earl, S. Abdellaoui, R. D. Milton, M. S. Sigman, S. D. Minteer and S. Calabrese Barton, “Substrate Channeling in an Artificial Metabolon: A Molecular Dynamics Blueprint for an Experimental Peptide Bridge”, ACS Catalysis, 7, 2486–2493 (2017). doi: 10.1021/acscatal.6b03440
This Fall, we’ll be presenting our work at PRiME 2016 in October and the AIChE National Meeting in November. Here are the details:
Erica defended her MS Thesis this Friday and is heading to Ann Arbor to work for Detroit Edison. Look for a paper based on Erica’s work soon. Congratulations!
Update: Due to weather the meeting is rescheduled to Thursday, March 3, 2016.
On Thursday February 25, Dr. Calabrese Barton will present an invited seminar at the ECS Detroit Local Section Meeting. The talk, entitled “Low-Cost Oxygen Reduction Catalysts Prepared from Transition Metals by High Pressure Pyrolysis” will follow a reception at 5:30 and dinner at 6:30 on the campus of Lawrence Institute of Technology in Southfield, MI. A seminar flyer and directions to Lawrence Tech can be found here.
The nonlinear relationship between oxygen concentration and current density prompted Nate to apply a Langmuir isotherm to his analysis. [ref]
Congratulations to Nate Leonard for winning the 2014 Norman Hackerman Young Author Award
from the Electrochemical Society. Nate was honored for his paper “Analysis of Adsorption Effects on a Metal-Nitrogen-Carbon Catalyst Using a Rotating Ring-Disk Study
” published in the Journal of the Electrochemical Society. Nate made an excellent contribution to our ability to model ORR kinetics on non-PGM catalysts by including Langmuir adsorption effects in the analysis of his ring-disk data.
Nate will receive his award at the Fall 2015 meeting of the ECS in Phoenix this October. He joins a long line of illustrious awardees, including academic “ancestors” Alan West and John Newman. We are particularly pleased that Nate’s award-winning paper appeared in a JES Focus issue honoring Adam Heller for his lifelong contributions to Electrochemistry.
Nate summarizes his fuel cell design work conducted using his non-PGM cathode model
Congratulations to Nate Leonard, who on Tuesday defended his dissertation titled “Non-Precious Metal Catalysis for Proton-Exchange Membrane Fuel Cells”. Nate has done an excellent job on materials characterization and modeling, with two papers published, and one more on the way. Great job, Nate!