Showing 31 - 40 of 59 Items
Investigating the Effects of Mixed Solvents on the Excited State Proton Transfer Mechanisms of 8-Amino-2-naphthol This record is embargoed.
- Embargo End Date: 2027-05-19
Date: 2022-01-01
Creator: Alexander Avrom Kreines
Access: Embargoed
Glycans in pathogenic bacteria - potential for targeted covalent therapeutics and imaging agents
Date: 2014-04-08
Creator: Van N. Tra, Danielle H. Dube
Access: Open access
- A substantial obstacle to the existing treatment of bacterial diseases is the lack of specific probes that can be used to diagnose and treat pathogenic bacteria in a selective manner while leaving the microbiome largely intact. To tackle this problem, there is an urgent need to develop pathogen-specific therapeutics and diagnostics. Here, we describe recent evidence that indicates distinctive glycans found exclusively on pathogenic bacteria could form the basis of targeted therapeutic and diagnostic strategies. In particular, we highlight the use of metabolic oligosaccharide engineering to covalently deliver therapeutics and imaging agents to bacterial glycans. © 2014 The Partner Organisations.
Identification, physiological actions, and distribution of TPSGFLGMRamide: A novel tachykinin-related peptide from the midgut and stomatogastric nervous system of Cancer crabs
Date: 2007-06-01
Creator: Elizabeth A. Stemmler, Braulio Peguero, Emily A. Bruns, Patsy S. Dickinson, Andrew E., Christie
Access: Open access
- In most invertebrates, multiple species-specific isoforms of tachykinin-related peptide (TRP) are common. In contrast, only a single conserved TRP isoform, APSGFLGMRamide, has been documented in decapod crustaceans, leading to the hypothesis that it is the sole TRP present in this arthropod order. Previous studies of crustacean TRPs have focused on neuronal tissue, but the recent demonstration of TRPs in midgut epithelial cells in Cancer species led us to question whether other TRPs are present in the gut, as is the case in insects. Using direct tissue matrix assisted laser desorption/ionization Fourier transform mass spectrometry, in combination with sustained off-resonance irradiation collision-induced dissociation, we found that at least one additional TRP is present in Cancer irroratus, Cancer borealis, Cancer magister, and Cancer productus. The novel TRP isoform, TPSGFLGMRamide, was present not only in the midgut, but also in the stomatogastric nervous system (STNS). In addition, we identified an unprocessed TRP precursor APSGFLGMRG, which was detected in midgut tissues only. TRP immunohistochemistry, in combination with preadsorption studies, suggests that APSGFLGMRamide and TPSGFLGMRamide are co-localized in the stomatogastric ganglion (STG), which is contained within the STNS. Exogenous application of TPSGFLGMRamide to the STG elicited a pyloric motor pattern that was identical to that elicited by APSGFLGMRamide, whereas APSGFLGMRG did not alter the pyloric motor pattern. © 2007 The Authors.
2018 Table of static dipole polarizabilities of the neutral elements in the periodic table*
Date: 2019-06-18
Creator: Peter Schwerdtfeger, Jeffrey K. Nagle
Access: Open access
- A 2018 update of the most accurate calculated and experimental static dipole polarizabilities of the neutral atoms in the Periodic Table from nuclear charge Z = 1 to 120 is given. Periodic trends are analyzed and discussed.
CrI3 revisited with a many-body ab initio theoretical approach
Date: 2021-06-01
Creator: Tom Ichibha, Allison L. Dzubak, Jaron T. Krogel, Valentino R. Cooper, Fernando A., Reboredo
Access: Open access
- CrI3 has recently been shown to exhibit low-dimensional, long-range magnetic ordering from few layers to single layers of CrI3. The properties of CrI3 bulk and few-layered systems are uniquely defined by a combination of short-range intralayer and long-range interlayer interactions, including strong correlations, exchange, and spin-orbit coupling. Unfortunately, both the long-range van der Waals interactions, which are driven by dynamic, many-body electronic correlations, and the competing strong intralayer correlations, present a formidable challenge for the local or semilocal mean-field approximations employed in workhorse electronic structure approaches like density-functional theory. In this paper we employ a sophisticated many-body approach that can simultaneously describe long- and short-range correlations. We establish that the fixed-node diffusion Monte Carlo (FNDMC) method reproduces the experimental interlayer separation distance of bulk CrI3 for the high-temperature monoclinic phase with a reliable prediction of the interlayer binding energy. We subsequently employed the FNDMC results to benchmark the accuracy of several density-functional theory exchange-correlation approximations.
Benchmarking Ab Initio Computational Methods for the Quantitative Prediction of Sunlight-Driven Pollutant Degradation in Aquatic Environments
Date: 2016-05-01
Creator: Kasidet Trerayapiwat
Access: Open access
- Understanding the changes in molecular electronic structure following the absorption of light is a fundamental challenge for the goal of predicting photochemical rates and mechanisms. Proposed here is a systematic benchmarking method to evaluate accuracy of a model to quantitatively predict photo-degradation of small organic molecules in aquatic environments. An overview of underlying com- putational theories relevant to understanding sunlight-driven electronic processes in organic pollutants is presented. To evaluate the optimum size of solvent sphere, molecular Dynamics and Time Dependent Density Functional Theory (MD-TD-DFT) calculations of an aniline molecule in di↵erent numbers of water molecules using CAM-B3LYP functional yielded excited state energy and oscillator strength values, which were compared with data from experimental absorption spectra. For the first time, a statistical method of comparing experimental and theoretical data is proposed. Underlying Gaussian functions of absorption spectra were deconvoluted and integrated to calculate experimental oscillator strengths. A Matlab code written by Soren Eustis was utilized to decluster MD-TD-DFT results. The model with 256 water molecules was decided to give the most accurate results with optimized com- putational cost and accuracy. MD-TD-DFT calculations were then performed on aniline, 3-F-aniline, 4-F-aniline, 3-Cl-aniline, 4-MeOacetophenone, and (1,3)-dimethoxybenzophenone with CAM-B3LYP, PBE0, M06-2X, LCBLYP, and BP86 functionals. BP86 functional was determined to be the best functional. Github repository: https://github.com/eustislab/MD_Scripts
Solvent Effect on Excited State Proton Transfer Mechanism of 8-Amino-2-Naphthol
Date: 2021-01-01
Creator: Gabrielle Vandendries
Access: Open access
- Photoacids, compounds that undergo excited state proton transfer (ESPT), have been utilized in different solar energy and lithographic applications.1, 2 The addition of functional groups and solvent can both change the ESPT mechanism of photoacids. In this study, the effect of solvent on the ESPT mechanism was explored using a model diprotic photoacid, 8-amino-2-naphthol (8N2OH). The photochemistry of 8N2OH in water and common nonaqueous solvents, acetonitrile, tetrahydrofuran (THF), and methanol, were studied using UV/Vis absorption, steady-state emission, and time-correlated single photon counting (TCPSC) emission spectroscopy. The results were analyzed using the Kamlet-Taft parameters. It was found that the ESPT mechanism of the cation in water is different from the mechanism in acetonitrile and THF. In water the excited cation forms the zwitterion, i.e. the OH site undergoes ESPT, while in acetonitrile and THF, the excited cation forms the neutral species, i.e. the NH3+ site undergoes ESPT. No ESPT was observed for 8N2OH in methanol. The effect of solvent mixtures on photoacidity was also investigated using acetonitrile and water mixtures. The solvent effects were more subtle; the time-resolved emission measurements showed the greatest stabilization of the excited neutral 8N2OH species at 20/80% acetonitrile-water mixtures. Finally, the ability to extend the solvent studies to ionic liquids, 1-ethyl-3-methylimidazolium (Im) trifluromethanesulfonate (OTF), was demonstrated. The combined studies reveal that solvent plays a large role in determining the ESPT mechanism and stabilization of 8N2OH.
Investigating the photoacidic properties of 8-benzylideneamino-2-naphthol This record is embargoed.
- Embargo End Date: 2027-05-19
Date: 2022-01-01
Creator: Oliver M. Nix
Access: Embargoed
Application of the Landau-Zener Model and Fermi's Golden Rule to Estimate Triplet Quantum Yield for Organic Molecules Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2014-05-01
Creator: Nathan D Ricke
Access: Access restricted to the Bowdoin Community
Phenylisocyanide Ligand Synthesis and Coordination to a Cobalt Catalyst for Dimerization of Linear Alpha Olefins Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2020-01-01
Creator: Julia Hazlitt Morris
Access: Access restricted to the Bowdoin Community