Showing 21 - 30 of 67 Items
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.
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
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.
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
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
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
Exploring Solution-Based Co-Crystal Growth of Curcumin as an Approach for Alzheimer’s Therapeutics Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Nadia E. Puente
Access: Access restricted to the Bowdoin Community
Dismantling the bacterial glycocalyx: Chemical tools to probe, perturb, and image bacterial glycans
Date: 2021-07-15
Creator: Phuong Luong, Danielle H. Dube
Access: Open access
- The bacterial glycocalyx is a quintessential drug target comprised of structurally distinct glycans. Bacterial glycans bear unusual monosaccharide building blocks whose proper construction is critical for bacterial fitness, survival, and colonization in the human host. Despite their appeal as therapeutic targets, bacterial glycans are difficult to study due to the presence of rare bacterial monosaccharides that are linked and modified in atypical manners. Their structural complexity ultimately hampers their analytical characterization. This review highlights recent advances in bacterial chemical glycobiology and focuses on the development of chemical tools to probe, perturb, and image bacterial glycans and their biosynthesis. Current technologies have enabled the study of bacterial glycosylation machinery even in the absence of detailed structural information.
A semester-long project-oriented biochemistry laboratory based on Helicobacter pylori urease
Date: 2015-09-01
Creator: Kate R. Farnham, Danielle H. Dube
Access: Open access
- Here we present the development of a 13 week project-oriented biochemistry laboratory designed to introduce students to foundational biochemical techniques and then enable students to perform original research projects once they have mastered these techniques. In particular, we describe a semester-long laboratory that focuses on a biomedically relevant enzyme-Helicobacter pylori (Hp) urease-the activity of which is absolutely required for the gastric pathogen Hp to colonize the human stomach. Over the course of the semester, students undertake a biochemical purification of Hp urease, assess the success of their purification, and investigate the activity of their purified enzyme. In the final weeks of the semester, students design and implement their own experiments to study Hp urease. This laboratory provides students with an understanding of the importance of biochemistry in human health while empowering them to engage in an active area of research.
Limitations and potential of commercially available rhodamine WT as a groundwater tracer
Date: 2001-06-09
Creator: D. J. Sutton, Z. J. Kabala, A. Francisco, D. Vasudevan
Access: Open access
- We conducted chemical characterization, batch, column, and modeling studies to elucidate the sorption and transport of rhodamine WT (RWT) in the subsurface. The sand-pack material from the Lizzie field site near Greenville, North Carolina, served as our porous media. Our study confirms earlier results that RWT consists of two isomers with different sorption properties. It also shows that the two isomers have distinct emission spectra and are equally distributed in the RWT solution. The presence of the two isomers with different sorption properties and distinct emission spectra introduces an error in measuring the RWT concentration with fluorometers during porous media tracer studies. The two isomers become chromatographically separated during transport and thus arrive in a different concentration ratio than that of the RWT solutions used for fluorometer calibration and test injection. We found that this groundwater tracer chromatographic error could be as high as 7.8%. We fit six different reactive-solute transport models of varying complexity to our four column experiments. A two-solute, two-site sorption transport model that accounts for nonequilibrium sorption accurately describes the breakthrough curves of the shorter-timescale column experiments. However, possibly due to the groundwater tracer chromatographic error we discovered, this model, or a similar one that accounts for a Freundlich isotherm for one of the solutes, fails to describe the RWT transport in the longer-timescale column experiments. The presence of the two RWT isomers may complicate the interpretation of field tracer tests because a shoulder, or any two peaks in a breakthrough curve, could result from either aquifer heterogeneity or the different arrival times of the two isomers. In cases where isomer 2 sorbs to such an extent that its breakthrough is not recorded during a test, only isomer 1 is measured, and therefore only 50% of the injected mass is recorded. Isomer 1 of RWT can be accurately modeled with a one-solute, two-site, nonequilibrium sorption model. This conclusion and the results from our batch studies suggest that RWT isomer 1 is an effective groundwater tracer but that the presence of isomer 2 hampers its effectiveness.