Physical Sciences and Mathematics Commons^™

Hydrogen-Bonding-Directed Ordered Assembly Of Carboxylated Poly(3-Alkylthiophene)S, David W. Bilger, Jose A. Figueroa, Neil D. Redeker, Amrita Sarkar, Morgan Stefik, Shanjuu Zhang

Faculty Publications

Hydrogen-bonding-induced ordered assembly of poly(3-alkylthiophene)s derivatives bearing carboxylic acid groups has been investigated from diluted and concentrated solutions to solid films using ultraviolet–visible absorption spectroscopy, polarized optical microscopy, and four-point probe conductivity measurements. In dilute solutions, the polymer undergoes a spontaneous structural transition from disordered coil-like to ordered rodlike conformations, which is evidenced by time-dependent chromism. Many factors such as alkyl-chain length, types of solvents, and temperature are studied to understand the assembly behavior. Transition kinetics of the assembly process reveals a universal second-order rate law, indicating an intermolecular origin due to hydrogen bonding. When more concentrated, hydrogen bonding drives …

Blockade Of Cb1 Cannabinoid Receptor Alters Gut Microbiota And Attenuates Inflammation And Diet-Induced Obesity, Pegah Mehrpouya-Bahrami, Kumaraswamy Naidu Chitrala, Mitra S. Ganewatta, Chuanbing Tang, E Angela Murphy, Reilly Enos, Kandy T. Velazquez, Jamie Mccellan, Mitzi Nagarkatti, Prakash Nagarkatti

Faculty Publications

Obesity is characterized by chronic low-grade, systemic inflammation, altered gut microbiota, and gut barrier disruption. Additionally, obesity is associated with increased activity of endocannabinoid system (eCB). However, the clear connection between gut microbiota and the eCB system in the regulation of energy homeostasis and adipose tissue inflammation and metabolism, remains to be established. We investigated the effect of treatment of mice with a cannabinoid receptor 1 (CB1) antagonist on Diet-Induced Obesity (DIO), specifically whether such a treatment that blocks endocannabinoid activity can induce changes in gut microbiota and anti-inflammatory state in adipose tissue. Blockade of CB1 attenuated DIO, inflammatory cytokines …

A Colorimetric Competitive Displacement Assay For The Evaluation Of Catalytic Peptides, Anneliese Gest, Erika M. Aguiluz, Malik T. Mays, Xinyu Liu, Eliza K. Neidhart, Leah S. Witus

Faculty Publications

No abstract provided.

Single-Reference Coupled Cluster Theory For Multi-Reference Problems, Johannes T. Margraf, Ajith Perera, Jesse J. Lutz, Rodney J. Bartlett

Faculty Publications

Coupled cluster (CC) theory is widely accepted as the most accurate and generally applicable approach in quantum chemistry. CC calculations are usually performed with single Slater-determinant references, e.g., canonical Hartree-Fock (HF) wavefunctions, though any single determinant can be used. This is an attractive feature because typical CC calculations are straightforward to apply, as there is no potentially ambiguous user input required. On the other hand, there can be concern that CC approximations give unreliable results when the reference determinant provides a poor description of the system of interest, i.e., when the HF or any other single determinant ground state has …

Spin-Imbalance In A 2d Fermi-Hubbard System, Peter Brown, Debayan Mitra, Elmer Guardado-Sanchez, Peter Schauß, Stanimir Kondov, Ehsan Khatami, Thereza Paiva, Nandini Trivedi, David Huse, Waseem Bakr

Faculty Publications

The interplay of strong interactions and magnetic fields gives rise to unusual forms of superconductivity and magnetism in quantum many-body systems. Here, we present an experimental study of the two-dimensional Fermi-Hubbard model—a paradigm for strongly correlated fermions on a lattice—in the presence of a Zeeman field and varying doping. Using site-resolved measurements, we revealed anisotropic antiferromagnetic correlations, a precursor to long-range canted order. We observed nonmonotonic behavior of the local polarization with doping for strong interactions, which we attribute to the evolution from an antiferromagnetic insulator to a metallic phase. Our results pave the way to experimentally mapping the low-temperature …

Taming Charge Transport In Semiconducting Polymers With Branched Alkyl Side Chains, Bob C. Schroeder, Tadanori Kurosawa, Tianren Fu, Yu-Cheng Chiu, Jaewan Mun, Ging-Ji Nathan Wang, Xiaodan Gu, Leo Shaw, James Kneller, Theo Kreouzis, Michael F. Toney, Zhenan Bao

Faculty Publications

The solid-state packing and polymer orientation relative to the substrate are key properties to control in order to achieve high charge carrier mobilities in organic field effect transistors (OFET). Intuitively, shorter side chains are expected to yield higher charge carrier mobilities because of a denser solid state packing motif and a higher ratio of charge transport moieties. However our findings suggest that the polymer chain orientation plays a crucial role in high-performing diketopyrrolopyrrole-based polymers. By synthesizing a series of DPP-based polymers with different branched alkyl side chain lengths, it is shown that the polymer orientation depends on the branched alkyl …

Fatty Acid Concentration And Phase Transitions Modulate Aβ Aggregation Pathways, Pratip Rana, Dexter Dean, Edward Steen, Ashwin Vaidya, Vijayaraghavan Rangachari, Preetam Ghosh

Faculty Publications

Aggregation of amyloid β (Aβ) peptides is a significant event that underpins Alzheimer disease (AD) pathology. Aβ aggregates, especially the low-molecular weight oligomers, are the primary toxic agents in AD and hence, there is increasing interest in understanding their formation and behavior. Aggregation is a nucleation-dependent process in which the pre-nucleation events are dominated by Aβ homotypic interactions. Dynamic flux and stochasticity during pre-nucleation renders the reactions susceptible to perturbations by other molecules. In this context, we investigate the heterotypic interactions between Aβ and fatty acids (FAs) by two independent tool-sets such as …

Preferential Binding Effects On Protein Structure And Dynamics Revealed By Coarse-Grained Monte Carlo Simulation, Ras B. Pandey, D.L. Jacobs, Barry L. Farmer

Faculty Publications

The effect of preferential binding of solute molecules within an aqueous solution on the structure and dynamics of the histone H3.1 protein is examined by a coarse-grained Monte Carlo simulation. The knowledge-based residue-residue and hydropathy-index-based residue-solvent interactions are used as input to analyze a number of local and global physical quantities as a function of the residue-solvent interaction strength (f). Results from simulations that treat the aqueous solution as a homogeneous effective solvent medium are compared to when positional fluctuations of the solute molecules are explicitly considered. While the radius of gyration (R_g) of the …

Phospholipase Dζ Enhances Diacylglycerol Flux Into Triacylglycerol, Wenyu Yang, Geliang Wang, Jia Li, Philip D. Bates, Xuemin Wang, Doug K. Allen

Faculty Publications

Plant seeds are the primary source of triacylglycerols (TAG) for food, feed, fuel, and industrial applications. As TAG is produced from diacylglycerol (DAG), successful engineering strategies to enhance TAG levels have focused on the conversion of DAG to TAG. However, the production of TAG can be limited by flux through the enzymatic reactions that supply DAG. In this study, two Arabidopsis phospholipase D_ζ genes (AtPLD_ζ1 and AtPLD_ζ2) were coexpressed in Camelina sativa to test whether the conversion of phosphatidylcholine to DAG impacts TAG levels in seeds. The resulting transgenic plants produced 2% to 3% more TAG …

Functional Photosystem I Maintains Proper Energy Balance During Nitrogen Depletion In Chlamydomonas Reinhardtii, Promoting Triacylglycerol Accumulation, Mahmoud Gargouri, Philip D. Bates, Jeong-Jin Park, Helmut Kirchhoff, David R. Gang

Faculty Publications

Background

Nutrient deprivation causes significant stress to the unicellular microalga, Chlamydomonas reinhardtii, which responds by significantly altering its metabolic program. Following N deprivation, the accumulation of starch and triacylglycerols (TAGs) is significantly altered following massive reprogramming of cellular metabolism. One protein that was found to change dramatically and early to this stress was TAB2, a photosystem I (PSI) translation initiation factor, whose transcript and protein levels increased significantly after only 30 min of N deprivation. A detailed physiological and omics-based analysis of an insertional mutant of Chlamydomonas with reduced TAB2 function was conducted to determine what role the functional …

Hierarchical Corannulene-Based Materials: Energy Transfer And Solid-State Photophysics, Allison M. Rice, W. Brett Fellows, Ekaterina A. Dolgopolova, Andrew B. Greytak, Aaron K. Vannucci, Mark D. Smith, Stavros G. Karakalos, Jeanette A. Krause, Stanislav M. Avdoshenko, Alexey A. Popov, Natalia B. Shustova Prof. Dr.

Faculty Publications

We report the first example of a donor–acceptor corannulene-containing hybrid material with rapid ligand-to-ligand energy transfer (ET). Additionally, we provide the first time-resolved photoluminescence (PL) data for any corannulene-based compounds in the solid state. Comprehensive analysis of PL data in combination with theoretical calculations of donor–acceptor exciton coupling was employed to estimate ET rate and efficiency in the prepared material. The ligand-to-ligand ET rate calculated using two models is comparable with that observed in fullerene-containing materials, which are generally considered for molecular electronics development. Thus, the presented studies not only demonstrate the possibility of merging the intrinsic properties of π-bowls, …

Effects Of Molecular Structure And Packing Order On The Stretchability Of Semicrystalline Conjugated Poly(Tetrathienoacene-Diketopyrrolopyrrole) Polymers, Chien Lu, Wen-Ya Lee, Xiaodon Gu, Jie Xu, Ho-Hsiu Chou, Hongping Yan, Yu-Cheng Chiu, Mingqian He, James R. Matthews, Weijun Niu, Jeffery B.-H. Tok, Michael F. Toney, Wen-Chang Chen, Zhenan Bao

Faculty Publications

The design of polymer semiconductors possessing high charge transport performance, coupled with good ductility, remains a challenge. Understanding the distribution and behavior of both crystalline domains and amorphous regions in conjugated polymer films, upon an applied stress, shall provide general guiding principles to design stretchable organic semiconductors. Structure–property relationships (especially in both side chain and backbone engineering) are investigated for a series of poly(tetrathienoacene-diketopyrrolopyrrole) polymers. It is observed that the fused thiophene diketopyrrolopyrrole-based polymer, when incorporated with branched side chains and an additional thiophene spacer in the backbone, exhibits improved mechanical endurance and, in addition, does not show crack propagation …

Thermal Conductivity Performance Of Polypropylene Composites Filled With Polydopamine-Functionalized Hexagonal Boron Nitride, Lin Chen, Hong-Fei Xu, Shao-Jian He, Yi-Hang Du, Nan-Jie Yu, Jun Lin, Sergei I. Nazarenko

Faculty Publications

Mussel-inspired approach was attempted to non-covalently functionalize the surfaces of boron nitride (BN) with self-polymerized dopamine coatings in order to reduce the interfacial thermal barrier and enhance the thermal conductivity of BN-containing composites. Compared to the polypropylene (PP) composites filled with pristine BN at the same filler content, thermal conductivity was much higher for those filled with both functionalized BN (f-BN) and maleic anhydride grafted PP (PP-g-ma) due to the improved filler dispersion and better interfacial filler-matrix compatibility, which facilitated the development of more thermal paths. Theoretical models were also applied to predict the composite thermal conductivity in which the …