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US-Israeli Symposium on C1 Chemistry :
08:00am - 09:30am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Aditya Bhan, Organizer, Univ of Minnesota; Oz M Gazit, Organizer, Technion; Prof. Dmitri Gelman, Organizer, The Hebrew University of Jerusalem; Daniel Resasco, Organizer, University of Oklahoma; Daniel Resasco, Presider, University of Oklahoma; Aditya Bhan, Presider, Univ of Minnesota
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Division/Committee: [CATL] Division of Catalysis Science & Technology

This symposium explores the topic of C1 conversion in context of the broader chemical enterprise. Presentations will feature research at the state-of-the-art in electrochemical and thermochemical upgrading of C1 species to fuels and chemicals.

Sunday
Catalytic activation of light alkanes on promoted molybdenum oxide catalysts: Coupling of catalytic rates and their mechanistic implications
08:00am - 08:30am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Catalytic conversions of light alkanes to their corresponding olefins are attractive routes for utilizing natural gas feedstocks. Starting with ethane, its reaction produces ethylene as the platform molecule for sequential synthesis of a wide variety of commodity chemicals, including polyethylene, styrene, ethylene oxide, and ethylene glycol. Its catalytic turnovers occur either without a co-oxidant via dehydrogenation or with O2 or CO2 via oxidative dehydrogenation reactions. Herein, we will unravel the mechanistic similarities and differences among the various ethane conversion reactions, on two-dimensional MoOx dispersed on Al2O3 catalysts promoted by Fe, Co, or Ni catalysts. These reactions, irrespective of the presence of or the chemical identity of the co-reactant, occur via the common step, that the initial C-H bond activation of ethane limits rates. The ethane activation cycle is catalytically coupled with the oxidant activation cycle, the latter generates reactive oxygen species that scavenge the surface carbon debris and therefore retain the catalytic reactivity and stability. We will discuss these catalytic cycles among the different ethane conversion catalysis, the key catalytic events, and their periodic reactivity trends, when incorporating the earth abundant Fe, Co, and Ni transition metal into the dispersed MoOx structures. More specifically, we will discuss how these metal cations could alter the catalytic rates of the various, concomitant catalytic cycles, interjecting deactivation, leading to the observed rates and selectivities. We attempt to provide consolidate mechanistic framework, accounting for both the rates as well as the time-dependent rate decay for ethane reactions for the series of catalyst materials.
Sunday
Multi-phase catalysts for stable methane cracking and reforming
08:30am - 09:00am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Prof. Brian A. Rosen, Presenter, Tel Aviv University
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Defective solid-catalysts and multi-phase catalysts are intriguing materials which would pave the way towards stable methane cracking and reforming. While point defects have been well studied in energy conversion ceramics by exploiting non-isovalent lattice substitutions and non-stoichiometric compounds, the impact of multidimensional defects on catalytic activity and stability is far less studied. During activation, energy conversion catalysts often go through solid-state phase transitions. These transitions can either be beneficial or detrimental to performance. We observe that extended defects critically impacts the temperature at which such phase transitions can occur, the pathway of the phase transition, and resulting catalytic activity and stability of the catalyst. Extended defects such as stacking faults in substituted lanthanum nickelates and lanthanum ferrates can be exploited to significantly extend catalyst lifetimes and lower apparent activation energy for critical reactions such as methane and carbon monoxide oxidation. Furthermore, multi-phase catalysts involving solid-liquid equilibrium are also exploited to imbue stable methane cracking with increased performance.
Sunday
Elucidating and controlling the selective electrocatalytic reduction of CO2 to C1 chemical intermediates
09:00am - 09:30am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Matthew Neurock, Presenter
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
The development of sustainable strategies to meet the world’s increasing energy demands will require the use of renewable energy sources together with carbon-neutral and energy efficient processes that can significantly reduce CO2 emissions. The sustainable catalytic conversion of CO2 to carbon monoxide as well as formic acid and their subsequent transformation to fuels and chemical intermediates offer attractive routes to carbon-neutral fuels. Nature readily carries out these reactions out with very high selectivities by co-locating the active metal centers within highly reactive reaction cavities. Recent experimental results show that the CO2 can be efficiently reduced over various late transition metals within ionic liquid as well as within alkaline media. The metal-electrolyte-solvent interface plays a critical role in enhanced the CO2 reduction and selectively forming either CO or formic acid produces.
Novel potential-dependent ab initio molecular dynamics simulations are carried out herein to help unravel the elementary steps and the mechanisms that govern these transformations and to show how changes in the solvent, electrolyte, pH and potential drive the activity as well as the selectivity in these systems. We show how changes in the potential and the reaction conditions can drive the formation of unique electrolyte, solvent, reactant environments that readily facilitate the rate controlling electron transfer reaction and selectively guide the subsequent proton addition to exclusively form CO or formic acid products. The simulations combined with experiments show that subtle changes in the electrolyte and the solvent can be used to dictate the formation of CO or formic acid with Faradaic Efficiencies of > 97 %. The simulations are used to help identify important electrolyte and metal catalysts systems as well as mixed electrolyte systems that will drive the active and selective formation to C1 products.

Nanoparticle Interactions in Environmental Systems:
08:00am - 09:55am USA / Canada - Eastern - August 22, 2021 | Room: B402
Adeyemi Adeleye, Organizer, University of California Irvine; Arturo Keller, Organizer, University of California, Santa Barbara; Dr. Yiming Su, Presider, University of California Los Angeles; Virender Sharma, Presider, Texas AM University
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
Division/Committee: [ENVR] Division of Environmental Chemistry

This session seeks leading edge research on the interactions of nanoparticles (metallic, carbonaceous, organic, and nanoplastics) with biogenic, geogenic, and anthropogenic components in the natural environment. The interactions and processes of interest include nanoparticle transformations in different media, surface accumulation of inorganic and organic substances, transport through biological membranes, and nanoparticle-induced redox reactions. Of particular interest are studies on novel nanoparticles (e.g., nanohybrids, nanocomposites, and metal-organic frameworks) (1) used in environmentally-relevant applications (e.g., agriculture, remediation, and CO2 capture), (2) incidentally generated from manufacturing (e.g. nanoplastics produced during 3D printing), or that reach the environment due to their use in outdoor environments (e.g., coatings, and personal care products). We also seek studies that address risk of exposure to nanoparticles, by human and ecological receptors.

Sunday
Introductory Remarks
08:00am - 08:05am USA / Canada - Eastern - August 22, 2021 | Room: B402
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid

Sunday
Opportunities of nanotechnology in sustainable agricultural practices
08:05am - 08:30am USA / Canada - Eastern - August 22, 2021 | Room: B402
Dr. Yiming Su, Presenter, University of California Los Angeles; Xuefei Zhou; Yalei Zhang; Huan Meng; Tian Xia; Arturo Keller, University of California, Santa Barbara; Greg Lowry, Carnegie Mellon University; David Jassby
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
Nanotechnology has been increasingly recognized as an important approach to achieve sustainable development of agriculture, particularly in the field of fertilizers and pesticides innovation. However, to promote the practical application of nanotechnology, it is essential to evaluate the economic and environmental benefits of nanotechnology to different crops. In the present study, we carry out a cost-benefit analysis about the application of nano fertilizers and pesticides in comparison with conventional formulations, identify the potential areas for implementing nano fertilizers and pesticides, and propose future studies needed to pave the way for wide application of nanotechnology in agricultural practices.
Sunday
Withdrawn
08:30am - 08:50am USA / Canada - Eastern - August 22, 2021 | Room: B402
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid

Sunday
Biomolecular corona formation on copper oxide nanoparticles in pumpkin xylem fluid
08:50am - 09:10am USA / Canada - Eastern - August 22, 2021 | Room: B402
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
Coatings of biomolecules—biomolecular corona—acquired when nanoparticles interact with biological media, have been shown to influence the distribution, fate, and toxicity of nanoparticles in animal and bacterial systems. Mechanistic insight into the influence of biomolecular coronas on nanoparticle transport within plants is needed to understand the nanoparticle–plant interactions important for both the development of nano-enabled agriculture and to assess the impacts of inadvertent exposure to nanoparticles. We examined the interactions between copper oxide nanoparticles and pumpkin xylem fluid as a first step toward understanding biomolecular corona formation in plant vasculature systems. We find the corona formed is composed primarily of proteins, despite a higher concentration of carbohydrates in xylem fluid, and the most abundant proteins in the corona are not the most abundant ones in the xylem fluid. Additionally, the nanoparticle corona evolves over time with protein–nanoparticle interactions exhibiting long-term stability, while carbohydrate–nanoparticle interactions are mostly transient.
Sunday
Withdrawn
09:10am - 09:30am USA / Canada - Eastern - August 22, 2021 | Room: B402
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid

Sunday
Towards a general framework for quantitative assessment of the potential risks associated with soil release of reduced carbon species
09:30am - 09:50am USA / Canada - Eastern - August 22, 2021 | Room: B402
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
Some reduced carbon species enriched in aromatic functionalities can provide ecosystem services when used as soil amendments. Charcoal has been used for this purpose for millennia. Biochar (biomass intentionally pyrolyzed for soil amendment) has been recently designed to mimic charcoal’s environmental benefits. Here we consider a third family of reduced carbon species that could be used for soil amendment: engineered carbon materials produced from natural gas pyrolysis (i.e. full decomposition of methane into solid carbon and hydrogen). We term these materials generically C0. C0 can be designed to be chemically similar to charcoal or biochar, with the aim of providing similar ecosystem services (improved soil water retention, improved nutrient retention, reduced fertilizer runoff, reduced soil CH4 and N2O production, etc.). Environmental risk assessment is a crucial first step before discussion of use of these materials as soil amendment. Here we begin this process by developing a procedure to assess the release of dissolved materials from C0. We report on the amount and chemistry of dissolved organic carbon (DOC) released by C0 subjected to a range of environmental aging treatments. Specifically, we subjected C0 to 1) 10-day UVA irradiation with light intensity of 50 µW/cm2, mimicking UV-driven reactions likely to occur in natural waters, 2) H2O2 oxidation (30% and 5%), mimicking natural, long-term environmental microbial oxidation, and 3) 10 mg L-1 monochloramine (NH2Cl) oxidation, mimicking reactions that could occur were C0 materials to inadvertently enter drinking water treatment systems. DOC released from C0 was < 2 mg L-1 regardless of aging method. This is significantly lower than DOC released from wildfire-derived charcoal (up to 70 mg L-1), soft wood biochar pyrolyzed at 550 and 700 °C, and commercial biochar under the same oxidation conditions. UVA 10 days is the most oxidizing treatment for C0. UVA-aged C0 had a relatively higher O/C ratio of 0.019±0.006. However, all three aging methods were incapable of significantly oxidizing C0. Next steps involve determining the chemical nature of DOC species released.
Sunday
Concluding Remarks
09:50am - 09:55am USA / Canada - Eastern - August 22, 2021 | Room: B402
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid

US-Israeli Symposium on C1 Chemistry :
10:30am - 12:00pm USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Aditya Bhan, Organizer, Univ of Minnesota; Oz M Gazit, Organizer, Technion; Prof. Dmitri Gelman, Organizer, The Hebrew University of Jerusalem; Daniel Resasco, Organizer, University of Oklahoma; Aditya Bhan, Presider, Univ of Minnesota
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Division/Committee: [CATL] Division of Catalysis Science & Technology

This symposium explores the topic of C1 conversion in context of the broader chemical enterprise. Presentations will feature research at the state-of-the-art in electrochemical and thermochemical upgrading of C1 species to fuels and chemicals.

Sunday
Effect of surface phase oxides on Ni catalyzed methane dry reforming
10:30am - 11:00am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Anup Tathod; Jin Wang; Oz M Gazit, Presenter, Technion
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Under reducing conditions, a strongly interacting reducible support can hinder the sintering of a nickel (Ni) nano-particle but, may also lead to severely reduced catalyst activity due to overcoating of the Ni by the support (i.e. SMSI). In contrast, Ni supported on a weakly interacting non-reducible support will have lower thermal stability but, can show higher activity. We find that the level of these metal support interactions (MSI) can be balanced using a mediating layer of surface phase thin oxides (SPO) in the form of MgAl mixed oxide nano-platelets (MO). We show that this approach can be practically implemented to balance between the benefits of the strong MSI of the SPO and the weak MSI of the underlying support (SiO2, ZrO2). Testing this approach for methane dry reforming (MDR) we found that the presence of 0.5-2.5 %wt Ni on the SPO, which is dispersed on an underlying ZrO2 surface, enhances the catalytic activity by ~15 fold, as compared to Ni supported on bulk MO. To better understand and control the nature of these interaction we performed extensive HAADF-STEM-EDS and XPS analyses. Planer model catalysts are analyzed using atomic force microscopy (AFM) to study the effect of the underlying support on the Ni and on the exposed surface of the SPO. Obtained information related to surface adhesion, surface potential and surface friction forces of the MO-NSs are correlated to catalyst performance and the mechanism by which the Ni is promoted by the presence of the SPO.
Sunday
Mechanism and surface species for formic acid decomposition on dispersed copper nanoparticles
11:00am - 11:30am USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Mechanistic details of HCOOH dehydrogenation routes on Cu nanoparticles are relevant to C1 chemistries that involve formate-type species as intermediates or spectators, such as water-gas shift and methanol synthesis. It has been widely accepted that HCOOH decomposes unimolecularly on transition metal surfaces via bidentate formate (*HCOO*) intermediate, with its C-H activation kinetically limiting the overall rates. Although such route is relevant during temperature-programmed surface reactions (TPSR) of pre-adsorbed *HCOO* species, bimolecular routes may be prevalent at catalytic conditions when HCOOH(g) coexists with *HCOO*. This study seeks to clarify and update our understanding of HCOOH dehydrogenation routes on Cu nanoparticles by combining kinetic, isotopic, and spectroscopic experiments with density functional theory (DFT) calculations.

At practical conditions (0.1-3.5 kPa HCOOH; 473-503 K), Cu surfaces are covered with *HCOO* species, which reach their saturation at 0.25 monolayer (ML) (*HCOO*/Cusurface=0.25) because of strong repulsion among bound *HCOO* species. HCOOH(g) binds molecularly at the interstices (denoted as ' sites; HCOOH') within such saturated *HCOO* adlayers; such interstices become saturated with HCOOH' upon formation of another 0.25 ML adlayer, with HCOOH' species forming strong H-bonds with vicinal *HCOO*. Measured rates reflect the bimolecular decomposition of the HCOOH'-*HCOO* complex, in which either HCOOH' or *HCOO* can lead to the formation of the CO2 product, while the other one re-forms the *HCOO* adlayer. These two bimolecular routes cannot be distinguished from kinetic data, isotopic effects, or infrared spectra or accessible to TPSR studies. DFT-derived barriers are slightly larger for the route that forms CO2 from HCOOH' than for the one forming CO2 from *HCOO* (ΔHact = 83 vs. 68 kJ mol-1).

These bimolecular routes are consistent with all experimental and theoretical data. This work, in turn, provides a compelling example of how repulsive interactions among bound species restricts their coverages to < 1 ML, thus allowing residual interstices in such “passivated” surfaces to bind intermediates less strongly, thus allowing them to react or to increase the reactivity of the bound species in the more refractory template.

Sunday
Multifunctional pincer complexes possessing a secondary coordination sphere as catalysts for CO2 hydrogenation
11:30am - 12:00pm USA / Canada - Eastern - August 22, 2021 | Room: B216 - B217
Prof. Dmitri Gelman, Presenter, The Hebrew University of Jerusalem
Division: [CATL] Division of Catalysis Science & Technology
Session Type: Oral - Hybrid
Burning fossil fuels worldwide has led to an increasing CO2 concentration in the atmosphere to such a large extent that global climate change caused by greenhouse gases has become a major ecological challenge. At present, its amount can be reduced by either capture and storage or by chemical conversion and utilization. There is no doubt that carbon dioxide storage is a cheaper solution and that it is useful for reducing CO2 emissions quickly. Unfortunately, it does not solve the accumulation problem in the long term, whereas converting CO2 into carbon-containing value-added products and feedstock does.
The catalytic conversion of CO2/H2/CO to methanol is already being performed on an industrial scale. Other products, such as formic acid and its derivatives, can be synthesized by carbon dioxide hydrogenation. However, despite this progress, we are still far from the point where carbon dioxide becomes a concrete player in the sustainable chemistry/energy market. Significant steps should be taken toward developing more efficient catalysts for CO2 conversion processes, as well as developing new reaction schemes that allow for more efficient utilization of carbon dioxide in fine and bulk synthesis.
The talk is devoted to designing ligand-metal cooperative catalytic systems for the dehydrogenation of formic acid and hydrogenation of CO2. Our studies revolve around a family of 3-dimensional PC(sp3)P pincer complexes developed by our group. The synthetic approach leading to all these examples is straightforward and represents a modular and divergent approach to a variety of 3-dimensional platforms equipped with custom-tailored primary and secondary coordination spheres. In particular, we address the cooperative activation and functionalization of carbon dioxide by bifunctional catalysts possessing transition metals in the primary coordination sphere and a pendant Lewis acidic functionality in the secondary sphere.

Advances in Renewable Materials:
10:30am - 12:30pm USA / Canada - Eastern - August 22, 2021 | Room: B406b - B407
Glenn Larkin, Organizer, Michigan Technological University; Falk Wolfgang Liebner, Organizer, Boku University Vienna; Amir Sheikhi, Organizer, Penn State University; Glenn Larkin, Presider, Michigan Technological University; Amir Sheikhi, Presider, Penn State University
Division: [CELL] Division of Cellulose and Renewable Materials
Session Type: Oral - Hybrid
Division/Committee: [CELL] Division of Cellulose and Renewable Materials

General Oral Session for the Division of Cellulose and Renewable Materials

Sunday
Introductory Remarks
10:30am - 10:35am USA / Canada - Eastern - August 22, 2021 | Room: B406b - B407
Division: [CELL] Division of Cellulose and Renewable Materials
Session Type: Oral - Hybrid

Sunday
Towards a new understanding of the retro-aldol reaction for oxidative conversion of lignin to aromatic aldehydes and acids
10:35am - 11:00am USA / Canada - Eastern - August 22, 2021 | Room: B406b - B407
Division: [CELL] Division of Cellulose and Renewable Materials
Session Type: Oral - Hybrid
Lignin is the most abundant natural bio-polymer after cellulose and accounts for 30% of non-fossil carbon on earth. The retro-aldol reaction is one of the key steps involved in the oxidative conversion of lignin to aromatic aldehydes and acids. In principle, the retro-aldol reaction can proceed in the absence of oxygen. In this work, a new approach based on the influence of oxygen on the oxidation of lignin was investigated. The effect of reaction chemistry, time, temperature, and lignin feedstock play a key role on the yield of aromatic aldehydes and acids. At 140°C, oxidation of softwood Lignoboost kraft lignin for 40 minutes results in combined maximum yield of 5.17% w/w of vanillin and vanillic acid. In comparison, using the new approach in which oxygen was charged for only 20 minutes during the 40 minute reaction improved this yield considerably to 6.95%. Further, yield improvement was obtained when applying this approach to different lignin feedstocks. Oxidation also increased the carboxyl content of lignin from 0.49 mmol/g to 1.41 mmol/g which represents consequential improvement. The current study provides further evidence showing that the oxidation reaction is a crucial pathway for lignin valorization.
Sunday
Photocatalytic rejuvenation enabled self-sanitizing, reusable, and biodegradable masks against COVID-19
11:00am - 11:25am USA / Canada - Eastern - August 22, 2021 | Room: B406b - B407
Hongli Zhu, Presenter
Division: [CELL] Division of Cellulose and Renewable Materials
Session Type: Oral - Hybrid
Personal protective equipment (PPE) has been highly recommended by the U.S. Centers for Disease Control and Prevention (CDC) for self-protection under the disastrous SARS-CoV-2 (COVID-19) pandemic. Nevertheless, the massive utilization of PPE, especially the N95 respirators and sing-use masks, encounters significant challenges in recycling and sterilizing the used masks. To tackle the environmental pollution of currently used masks made of synthetic plastic, in this work, we designed a reusable, biodegradable, and antibacterial mask. The mask was prepared by electrospinning of polyvinyl alcohol (PVA), poly(ethylene oxide) (PEO), and cellulose nanofiber (CNF), and with subsequent esterification and then deposition of nitrogen-doped TiO2 (N-TiO2) and TiO2 mixture. The fabricated mask containing photocatalytic N-TiO2/ TiO2 can reach 100% bacteria disinfection under either light source (200-2500 nm, 106 Wm-2) as 0.1 sun simulation or natural sunlight for only 10 min. Thus, the used mask can be rejuvenated through light irradiation and reused, which represents one of the handiest technologies for handling used masks. Furthermore, the intermolecular interactions between PVA, PEO and CNF enhanced electrospinnability and the mechanical performance of the resultant mask. The obtained masks possess superior mechanical strength (10-fold elastic modulus and 2-fold tensile strength higher than a commercial single use mask). The comprised electrospun nanofibers with porous structures in between as well as strong electrostatic attraction enabled breathability (83.4 L min-1 of air flow rate) and superior particle filterability (98.7 %). The prepared mask also had excellent cycling performance, wearability, and stable filtration efficiency even after 120 min wearing. Therefore, this novel mask could be a great alternative to current masks to addressing the urgent need for sustainable, reusable, environmentally friendly, and efficient personal protection designs under the ongoing COVID-19 contagion.
Sunday
Withdrawn
11:25am - 11:50am USA / Canada - Eastern - August 22, 2021 | Room: B406b - B407
Division: [CELL] Division of Cellulose and Renewable Materials
Session Type: Oral - Hybrid

Sunday
Free-radical polymerization of bio-based monomers
11:50am - 12:15pm USA / Canada - Eastern - August 22, 2021 | Room: B406b - B407
Maryam Mousa, Presenter; Eva Malmstrom, KTH Royal Institute of Technology; Anna Larsson Kron; Helena Bergenudd
Division: [CELL] Division of Cellulose and Renewable Materials
Session Type: Oral - Hybrid
The demand to produce materials from non-fossil based sources, i.e. bio-based raw materials, is increasing due to environmental concerns and limited resources. Bio-based building blocks result in new materials with sometimes unprecedented properties rendering them an interesting subject to study.
Two of these building blocks are the itaconic acid-derived α-methylene-γ-butyrolactone and the structurally similar α-methylene-γ-valerolactone which can be synthesized from the bio-based levulinic acid. Itaconic acid is a promising platform chemical that is produced by the fermentation of carbohydrates and it was listed by the U.S. Department of Energy as one of the top-value added chemicals from biomass. In this study, we report the free-radical polymerization of these two lactones into homopolymers or together with fossil-based (meth)acrylate monomers, methyl acrylate and methyl methacrylate in different ratios. 2,2′-Azobisisobutyronitrile or lauroyl peroxide were used as initiators to investigate their effect on the polymerization behaviors. Polymerizations were monitored by monomer conversion, and the final polymers were characterized with respect to molecular weight, composition, glass transition temperature and thermal degradation. The incorporation of the monomers in the copolymers was significantly affected by the differences in reactivity ratios, sometimes to such an extent that the polymers exhibited a substantial compositional drift as corroborated by assessed thermal properties.
Increased thermal stability and tailored Tg’s were achieved by copolymerizing the lactones and the (meth)acrylates in different ratios, making the lactones interesting building blocks for synthesis of bio-based or partially bio-based materials.

Sunday
Panel Discussion
12:15pm - 12:30pm USA / Canada - Eastern - August 22, 2021 | Room: B406b - B407
Division: [CELL] Division of Cellulose and Renewable Materials
Session Type: Oral - Hybrid

Computational Studies of Transmembrane Receptors, Channels, & Transporters:
10:30am - 12:30pm USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 07
Oliver Beckstein, Organizer; Jana Shen, Organizer, University of Maryland, Baltimore; Oliver Beckstein, Presider
Division: [COMP] Division of Computers in Chemistry
Session Type: Oral - Virtual
Division/Committee: [COMP] Division of Computers in Chemistry
Sunday
The force awakens: The interplay between the membrane topology and mechanosensitive Piezo channel
10:30am - 10:52am USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 07
Yun Lyna Luo, Presenter, Western University of Health Sciences; Wenjuan Jiang; Yi Chun Lin; Wesley Botello-Smith
Division: [COMP] Division of Computers in Chemistry
Session Type: Oral - Virtual
Mechanotransduction, the ability of organisms to sense and respond to mechanical stimuli, play central roles in a large variety of physiological and pathological processes. In vertebrates, this task is mainly performed by two cation-selective mechanosensitive channels called PIEZO1 and PIEZO2. PIEZO channels share the same inverted-dome structure, which curved the cell membrane, imposing a large membrane footprint that extends far beyond the channel boundary. Using multiscale simulations, we show that, due to the intrinsic bending rigidity of the membrane, the deformation energy of the membrane footprint applies work to flatten the PIEZO dome. The open state PIEZO1 model generated by membrane flattening revealed the presence of intracellular and extracellular fenestrations acting as cation-selective sites. We propose that the overlap of Piezo channel footprints may act as a cooperative mechanism to regulate channel activity.
Sunday
Simulations of calcium-activated potassium channel activity and modulation from the membrane
10:52am - 11:14am USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 07
Emelie Flood; Crina Nimigean; Prof Toby W Allen, Presenter, RMIT University
Division: [COMP] Division of Computers in Chemistry
Session Type: Oral - Virtual
Big potassium conductance (BK) channels exist in every cell in the body and are important for regulating neuronal firing, vascular smooth muscle tone, circadian rhythms and neurotransmitter release. Here we have used atomistic molecular dynamics simulations based on high-resolution cryo-EM structures to describe the activation cycle of the BK homologue channel, MthK, from Methanobacterium thermoautotrophicum. These structures have resolved previous uncertainty in the closed state of MthK and BK channels, now seen with a narrow intracellular gate that is expected to sterically block ions and other molecules. Our simulations reveal extensive membrane interactions involving the calcium-binding domain and C-linkers that communicate change to the pore domain, as well as lipid-facing fenestrations that connect the pore to the membrane interface, offering a potential pathway for drugs into the closed channel. Our free energy calculations show that these fenestrations provide a preferred pathway for channel blockers, including hydrophobic ions such as tetrapentylammonium, with high calculated on-rates to explain experimental measurements. Our simulations have also described high-affinity N-terminal pore block, known as ball-and-chain N-type inactivation. We show that the N-termini are dynamic in the open state and can bind strongly to lipids, potentially helping explain lipid-composition dependent inactivation. Overall these simulations shed light on the activity and modulation of potassium channels by membrane-active molecules.
Sunday
Kinetic ratchet effect as a non-equilibrium design principle for selective channels
11:14am - 11:24am USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 07
Chase Slowey, Presenter
Division: [COMP] Division of Computers in Chemistry
Session Type: Oral - Virtual
In living cells, ion channels passively allow for ions to flow through as the concentration gradient relaxes to thermal equilibrium. Most ion channels are selective, only allowing one type of ion to go through while blocking another. One salient example is KcsA, which allows for larger K+ ions through but blocks the smaller Na+ ions. This counter-intuitive selectivity has been explained by two distinct theories that both focus on equilibrium properties: particle-channel affinity and particle-solvent affinity. However, ion channels operate far from equilibrium. By constructing minimal kinetic models of channels, we discover a ubiquitous kinetic ratchet effect as a non-equilibrium mechanism to explain such selectivity. We find that a multi-site channel kinetically couples the competing flows of two types of particles, where one particle's flow could suppress or even invert the flow of another type. At the inversion point (transition between the ratchet and dud modes), the channel achieves infinite selectivity. We have applied our theory to obtain general design principles of artificial selective channels.
Sunday
Conduction strategies in potassium channels is a family business
11:24am - 11:46am USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 07
Division: [COMP] Division of Computers in Chemistry
Session Type: Oral - Virtual
Potassium channels are the most widely distributed type of ion channels, found in virtually all living organisms where they control a large variety of cellullar functions by facilitating selective K+ transport in and out of the cell. The molecular determinants responsible for this functional diversity are still poorly understood. More than 20 years after the first release of the atomic structure of a potassium channel, the mechanism of K+ conduction is still a matter of intense debate. An implicit assumption of previous work is that the mechanism of K+ conduction is a common feature of this extensive family of membrane proteins. This oversimplification is to some extent a consequence of experimental and computational limitations. However, structural biology and computer simulation have evolved rapidly and we are in a position where we can take advantage of the progress made. An indepth investigation of conduction mechanisms in potassium channels will be presented using ~100 microseconds of classical MD trajectories which allowed estimation of Markov State Models of permeation events. A rigorous quantitative comparison between conduction strategies in two prototype families of K+ channels will be described, where the main difference is the the sequence of the selectivity filter; conduction through a symmetric and canonical vs a highly asymmetric and noncanonical selectivity filters has been explored. All in all, ion conduction is found to be a property that depends on the family considered which represents a paradigm shift.
Sunday
The molecular dynamics of potassium channel gating
11:46am - 12:08pm USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 07
Bert L de Groot, Presenter
Division: [COMP] Division of Computers in Chemistry
Session Type: Oral - Virtual
Ion channels facilitate the passive, selective permeation of ions such as sodium, potassium and chloride across biological membranes and as
such are essential for cellular electrical signalling. Molecular dynamics simulations are used to study ion permeation across potassium channels at the atomic level. Together with crystallographic analyses and electrophysiological experiments these provide insight into the mechanisms of permeation of potassium, as well as the complex and subtle conformational changes involved in the gating of these channels.

Sunday
Small molecule permeation through a wide-pore channel via applied voltage and Markovian milestoning
12:08pm - 12:18pm USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 07
Yi Chun Lin, Presenter; Wenjuan Jiang; Yun Lyna Luo, Western University of Health Sciences
Division: [COMP] Division of Computers in Chemistry
Session Type: Oral - Virtual
Computational methods play key roles to study the mechanism of ion channel with a charged molecular. Connexin ion channel can form gap junction which is located in between two adjacent cells to help permeation of ions or small molecules. The diseases can be caused by mutation of connexin include heart disease, nervous system disease, skin disease and cancers. In order to understand the permeation of a negatively charged second messenger cyclic AMP (cAMP) and a positively charged dye molecule ethidium through connexin26, we first conducted molecular dynamics (MD) simulation of Cx26 hemichannel under the positive and negative voltage. Under those two voltage environments, the location of the binding sites and energy barrier of the ligands inside connexin channel were obtained. Next, we sampled the permeation of a single charged molecule and potassium ion in Cx26 with zero voltage. With zero voltage simulation, it could provide the intrinsic free energy profile for a charged molecule permeating through the Cx26 ion channel. Markovian milestone sampling method was used to obtain the free energy and kinetics of the permeation process, and compared with the results from voltage simulation.
Sunday
Insights into the effect of hydration on enantiomeric selectivity and drug resistance using grand canonical Monte Carlo simulations
12:18pm - 12:28pm USA / Canada - Eastern - August 22, 2021 | Room: Zoom Room 07
Division: [COMP] Division of Computers in Chemistry
Session Type: Oral - Virtual
The matrix 2 (M2) protein is a multifunctional protein found within the influenza A virus, and considered an attractive drug target. The transmembrane domain of the M2 protein acts as a proton channel and contains the binding site of adamantyl-amine drugs, such as amantadine and rimantadine. Whilst clinical use of these drugs has been discontinued, owing to widespread resistance, their study remains useful for the design of the next generation of antiviral compounds. Of special interest is the network of water molecules which facilitate proton transport and also appear to stabilise the binding of these drugs to the hydrophobic channel.

Grand canonical Monte Carlo (GCMC) is a simulation technique which allows kinetic barriers that inhibit the sampling of buried water molecules to be bypassed, by alchemically inserting and deleting waters from the system, according to a specified chemical potential. Additionally, carrying out a GCMC titration of the system (by simulating at a range of chemical potential values) allows the binding free energy of the water network to be rigorously calculated, accounting for cooperative binding effects. GCMC moves are carried out alongside molecular dynamics sampling (GCMC/MD) in this work, using the Python module, grand.

We apply GCMC/MD titration calculations to determine the binding free energies of water networks in M2-drug complexes. First, we study the potential enantiomeric selectivity of the chiral drug rimantadine, when bound to the wild type (WT) structure of M2. Second, we perform a similar analysis for amantadine with both the wild type and a resistant mutant, and compare and contrast these results with a recently developed inhibitor which can inhibit both forms of the protein. The results obtained provide insights into the mechanisms of drug binding to the M2 protein, and how drug resistance is achieved.