Showing 31 - 40 of 59 Items

Date: 2020-12-01

Creator: Andrew E. Christie, Cindy D. Rivera, Catherine M. Call, Patsy S. Dickinson, Elizabeth A., Stemmler, J. Joe Hull

Access: Open access

Over the past decade, in silico genome and transcriptome mining has led to the identification of many new crustacean peptide families, including the agatoxin-like peptides (ALPs), a group named for their structural similarity to agatoxin, a spider venom component. Here, analysis of publicly accessible transcriptomes was used to expand our understanding of crustacean ALPs. Specifically, transcriptome mining was used to investigate the phylogenetic/structural conservation, tissue localization, and putative functions of ALPs in decapod species. Transcripts encoding putative ALP precursors were identified from one or more members of the Penaeoidea (penaeid shrimp), Sergestoidea (sergestid shrimps), Caridea (caridean shrimp), Astacidea (clawed lobsters and freshwater crayfish), Achelata (spiny/slipper lobsters), and Brachyura (true crabs), suggesting a broad, and perhaps ubiquitous, conservation of ALPs in decapods. Comparison of the predicted mature structures of decapod ALPs revealed high levels of amino acid conservation, including eight identically conserved cysteine residues that presumably allow for the formation of four identically positioned disulfide bridges. All decapod ALPs are predicted to have amidated carboxyl-terminals. Two isoforms of ALP appear to be present in most decapod species, one 44 amino acids long and the other 42 amino acids in length, both likely generated by alternative splicing of a single gene. In carideans, a gene or terminal exon duplication appears to have occurred, with alternative splicing producing four ALPs, two 44 and two 42 amino acid isoforms. The identification of ALP precursor-encoding transcripts in nervous system-specific transcriptomes (e.g., Homarus americanus brain, eyestalk ganglia, and cardiac ganglion assemblies, finding confirmed using RT-PCR) suggests that members of this peptide family may serve as locally-released and/or hormonally-delivered neuromodulators in decapods. Their detection in testis- and hepatopancreas-specific transcriptomes suggests that members of the ALP family may also play roles in male reproduction and innate immunity/detoxification.

Date: 2019-10-01

Creator: Patsy S. Dickinson, Heidi M. Samuel, Elizabeth A. Stemmler, Andrew E. Christie

Access: Open access

The SIFamides are a broadly conserved arthropod peptide family characterized by the C-terminal motif –SIFamide. In decapod crustaceans, two isoforms of SIFamide are known, GYRKPPFNGSIFamide (Gly1-SIFamide), which is nearly ubiquitously conserved in the order, and VYRKPPFNGSIFamide (Val1-SIFamide), known only from members of the astacidean genus Homarus. While much work has focused on the identification of SIFamide isoforms in decapods, there are few direct demonstrations of physiological function for members of the peptide family in this taxon. Here, we assessed the effects of Gly1- and Val1-SIFamide on the cardiac neuromuscular system of two closely related species of Cancer crab, Cancer borealis and Cancer irroratus. In each species, both peptides were cardioactive, with identical, dose-dependent effects elicited by both isoforms in a given species. Threshold concentrations for bioactivity are in the range typically associated with hormonal delivery, i.e., 10−9 to 10−8 M. Interestingly, and quite surprisingly, while the predicted effects of SIFamide on cardiac output are similar in both C. borealis and C. irroratus, frequency effects predominate in C. borealis, while amplitude effects predominate in C. irroratus. These findings suggest that, while SIFamide is likely to increase cardiac output in both crabs, the mechanism through which this is achieved is different in the two species. Immunohistochemical/mass spectrometric data suggest that SIFamide is delivered to the heart hormonally rather than locally, with the source of hormonal release being midgut epithelial endocrine cells in both Cancer species. If so, midgut-derived SIFamide may function as a regulator of cardiac output during the process of digestion.

Date: 2007-05-15

Creator: Elizabeth A. Stemmler, Emily A. Bruns, Noah P. Gardner, Patsy S. Dickinson, Andrew E., Christie

Access: Open access

In invertebrates, peptides possessing the carboxy (C)-terminal motif -RXRFamide have been proposed as the homologs of vertebrate neuropeptide Y (NPY). Using matrix assisted laser desorption/ionization mass spectrometry, in combination with sustained off-resonance irradiation collision-induced dissociation and chemical and enzymatic reactions, we have identified the peptide pEGFYSQRYamide from the neuroendocrine pericardial organ (PO) of the crab Pugettia producta. This peptide is likely the same as that previously reported, but misidentified, as PAFYSQRYamide in several earlier reports (e.g. [Li, L., Kelley, W.P., Billimoria, C.P., Christie, A.E., Pulver, S.R., Sweedler, J.V., Marder, E. 2003. Mass spectrometric investigation of the neuropeptide complement and release in the pericardial organs of the crab, Cancer borealis. J. Neurochem. 87, 642-656; Fu, Q., Kutz, K.K., Schmidt, J.J., Hsu, Y.W., Messinger, D.I., Cain, S.D., de la Iglesia, H.O., Christie, A.E., Li, L. 2005. Hormone complement of the Cancer productus sinus gland and pericardial organ: an anatomical and mass spectrometric investigation. J. Comp. Neurol. 493, 607-626.]). The -QRYamide motif contained in pEGFYSQRYamide is identical to that present in many vertebrate members of the NPY superfamily. Mass spectrometric analysis conducted on the POs of several other decapods showed that pEGFYSQRYamide is present in three other brachyurans (Cancer borealis, Cancer irroratus and Cancer productus) as well as in one species from another decapod infraorder (Lithodes maja, an anomuran). Thus, our findings show that at least some invertebrates possess NPY-like peptides in addition to those exhibiting an -RXRFamide C-terminus, and raise the question as to whether the invertebrate -QRYamides are functionally and/or evolutionarily related to the NPY superfamily. © 2007 Elsevier Inc. All rights reserved.

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.

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.

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.

Date: 2022-01-01

Creator: William J. Rackear

Access: Access restricted to the Bowdoin Community

Date: 2020-01-01

Creator: Thomas Regan

Access: Access restricted to the Bowdoin Community

Date: 2023-01-01

Creator: Seamus Frey

Access: Access restricted to the Bowdoin Community

• Embargo End Date: 2027-05-16

Date: 2024-01-01

Creator: Morgan Adams

Access: Embargoed