Advancements in organic chemistry depend upon chemists' ability to interpret NMR spectra, though research demonstrates that cultivating such proficiency requires years of graduate-level study. The organic chemistry community thus needs insight into how this expertise develops to expedite learning among its newest members. This study investigated undergraduate and doctoral chemistry students' understanding and information processing during the interpretation of 1 H NMR spectra and complementary IR spectra. Eighteen undergraduate and seven doctoral chemistry students evaluated the outcome of a series of syntheses using spectra corresponding to the products. Eye movements were measured to identify differences in cognitive processes between undergraduate and doctoral participants, and interviews were conducted to elucidate the chemical assumptions that guided participants' reasoning. Results suggest five areas of understanding are necessary for interpreting spectra, and progress in understanding corresponds to increasing knowledge of experimental and implicit chemical variables. Undergraduate participants exhibited uninformed bidirectional processing of all information, whereas doctoral participants exhibited informed unidirectional processing of relevant information. These findings imply the community can support novices' development of expertise by cultivating relevant understanding and encouraging use of informed interpretation strategies, including preliminary evaluation of relevant variables, prediction of expected spectral features, and search for complementary data across spectra.
Nuclear magnetic resonance (NMR) spectra are among the most common visualizations used by chemists in both academic and industrial settings, where they serve as both representations of submicroscopic entities and tools that support social discourse. The ability to use words to communicate about features within NMR spectra is thus an essential aspect of chemists' representational competence. Collectively, these words constitute a highly specialized language specific to this technique. To adequately prepare chemists, the undergraduate curriculum must therefore cultivate students' ability to use this lexicon. We developed the NMR Lexical Representational Competence (NMR-LRC) instrument, a formative assessment to measure students' ability and perceived ability to use words to communicate the identification, analysis, and interpretation of features within 1 H NMR spectra. Following development, we administered the NMR-LRC in Spring 2020 to a total of N = 678 second-semester organic chemistry students at a large Midwestern university. We analyzed the responses using the Rasch model to collect statistical evidence of validity and reliability, and we used cluster analysis to evaluate whether the instrument could detect the Dunning−Kruger effect (i.e., students' illusions of competence). Supporting evidence of response process, content, and associative validity was also collected. The results suggest that data obtained from the NMR-LRC can be interpreted as a measure of students' lexical representational competence and associated perceived competence in 1 H NMR spectroscopy and that the NMR-LRC can detect students' illusions of such competence. Results further suggest that instructors can use the NMR-LRC to formatively assess their students' lexical ability and associated perceived ability following instruction, allowing instructors to provide feedback that promotes students' competence and perceived competence.
Ocean acidification (OA) resulting from anthropogenic CO2 emissions is impairing the reproduction of marine organisms. While parental exposure to OA can protect offspring via carryover effects, this phenomenon is poorly understood in many marine invertebrate taxa. Here, we examined how parental exposure to acidified (pH 7.40) versus ambient (pH 7.72) seawater influenced reproduction and offspring performance across six gametogenic cycles (13 weeks) in the estuarine sea anemone Nematostella vectensis. Females exhibited reproductive plasticity under acidic conditions, releasing significantly fewer but larger eggs compared to ambient females after four weeks of exposure, and larger eggs in two of the four following spawning cycles despite recovering fecundity, indicating long-term acclimatization and greater investment in eggs. Males showed no changes in fecundity under acidic conditions, but produced a greater percentage of sperm with high mitochondrial membrane potential (MMP; a proxy for elevated motility), which corresponded with higher fertilization rates relative to ambient males. Finally, parental exposure to acidic conditions did not significantly influence offspring development rates, respiration rates, or heat tolerance. Overall, this study demonstrates that parental exposure to acidic conditions impacts gamete production and physiology but not offspring performance in N. vectensis, suggesting that increased investment in individual gametes may promote fitness.
Many marine invertebrates liberate their gametes into the water column broadcast spawning, where fertilization hinges upon the successful activation of sperm motility. Here, we investigated the molecular mechanisms underpinning sperm motility in the broadcast spawning coral Astrangia poculata. We found that cytosolic alkalinization activates the pH-sensing enzyme soluble adenylyl cyclase (sAC), followed by motility, in A. poculata sperm. In addition, we show for the first time in any cnidarian that sAC activity is required to activate protein kinase A (PKA) in sperm, and that PKA activity is required for the initiation of sperm motility. Ultrastructures of A. poculata sperm displayed morphological homology to other gonochoric cnidarians, and investigation of cnidarian proteomes revealed that sAC, the central signaling node in the sperm motility pathway, demonstrates broad structural and functional conservation across a diversity of cnidarian species. Ultimately, these results suggest that the role of sAC signaling in sperm motility is conserved between sperm from gonochoric and hermaphroditic corals, which is surprising given their morphological dissimilarities. This study also offers insight into the evolution of the mechanisms controlling metazoan sperm motility.
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