Developing Expertise in 1H NMR Spectral Interpretation.

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 1H 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.

Variations in Fusion Pore Formation in Cholesterol-Treated Platelets.

Exocytosis is a highly regulated intercellular communication process involving various membrane proteins, lipids, and cytoskeleton restructuring. These components help control granule fusion with the cell membrane, creating a pore through which granular contents are released into the extracellular environment. Platelets are an ideal model system for studying exocytosis due to their lack of a nucleus, resulting in decreased membrane regulation in response to cellular changes. In addition, platelets contain fewer granules than most other exocytosing cells, allowing straightforward measurement of individual granule release with carbon-fiber microelectrode amperometry. This technique monitors the concentration of serotonin, an electroactive molecule found in the dense-body granules of platelets, released as a function of time, with 50 µs time resolution, revealing biophysical characteristics of the fundamental exocytotic process. Variations in fusion pore formation and closure cause deviations from the classic current versus time spike profile and may influence diffusion of serotonin molecules from the site of granule fusion. Physiologically, the delivery of smaller packets of chemical messengers or the prolonged delivery of chemical messengers may represent how cells/organisms tune biological response. The goals of this work are twofold: 1) to categorize secretion features that deviate from the traditional mode of secretion and 2) to examine how changing the cholesterol composition of the platelet membrane results in changes in the pore formation process. Results herein indicate that the expected traditional mode of release is actually in the minority of granule content release events. In addition, results indicate that as the cholesterol content of the plasma membrane is increased, pore opening is less continuous.

Super-resolution imaging for monitoring cytoskeleton dynamics.

The cytoskeleton is a key cellular structure that is important in the control of cellular movement, structure, and sensing. To successfully image the individual cytoskeleton components, high resolution and super-resolution fluorescence imaging methods are needed. This review covers the three basic cytoskeletal elements and the relative benefits and drawbacks of fixed versus live cell imaging before moving on to recent studies using high resolution and super-resolution techniques. The techniques covered include the near-diffraction limited imaging methods of confocal microscopy and TIRF microscopy and the super-resolution fluorescence imaging methods of STORM, PALM, and STED.

Cytoskeleton dynamics in drug-treated platelets.

Platelet activation is a key process in blood clot formation. During activation, platelets go through both chemical and physical changes, including secretion of chemical messengers and cellular shape change. Platelet shape change is mediated by the two major cytoskeletal elements in platelets, the actin matrix and microtubule ring. Most studies to date have evaluated these structures qualitatively, whereas this paper aims to provide a quantitative method of examining changes in these structures by fluorescently labeling the element of interest and performing single cell image analysis. The method described herein tracks the diameter of the microtubule ring and the circumference of the actin matrix as they change over time. Platelets were incubated with a series of drugs that interact with tubulin or actin, and the platelets were observed for variation in shape change dynamics throughout the activation process. Differences in shape change mechanics due to drug incubation were observable in each case.

Generation of singlet oxygen from fragmentation of monoactivated 1,1-dihydroperoxides.

The first singlet excited state of molecular oxygen ((1)O(2)) is an important oxidant in chemistry, biology, and medicine. (1)O(2) is most often generated through photosensitized excitation of ground-state oxygen. (1)O(2) can also be generated chemically through the decomposition of hydrogen peroxide and other peroxides. However, most of these "dark oxygenations" require water-rich media associated with short (1)O(2) lifetimes, and there is a need for oxygenations able to be conducted in organic solvents. We now report that monoactivated derivatives of 1,1-dihydroperoxides undergo a previously unobserved fragmentation to generate high yields of singlet molecular oxygen ((1)O(2)). The fragmentations, which can be conducted in a variety of organic solvents, require a geminal relationship between a peroxyanion and a peroxide activated toward heterolytic cleavage. The reaction is general for a range of skeletal frameworks and activating groups and, via in situ activation, can be applied directly to 1,1-dihydroperoxides. Our investigation suggests the fragmentation involves rate-limiting formation of a peroxyanion that decomposes via a Grob-like process.

Postsecondary Faculty Attitudes and Beliefs about Writing-Based Pedagogies in the STEM Classroom.

Writing is an important skill for communicating knowledge in science, technology, engineering, and mathematics (STEM) and an aid to developing students' communication skills, content knowledge, and disciplinary thinking. Despite the importance of writing, its incorporation into the undergraduate STEM curriculum is uneven. Research indicates that understanding faculty beliefs is important when trying to propagate evidence-based instructional practices, yet faculty beliefs about writing pedagogies are not yet broadly characterized for STEM teaching at the undergraduate level. Based on a nationwide cross-disciplinary survey at research-intensive institutions, this work aims to understand the extent to which writing is assigned in undergraduate STEM courses and the factors that influence faculty members' beliefs about, and reported use of, writing-based pedagogies. Faculty attitudes about the effectiveness of writing practices did not differ between faculty who assign and do not assign writing; rather, beliefs about the influence of social factors and contextually imposed instructional constraints informed their decisions to use or not use writing. Our findings indicate that strategies to increase the use of writing need to specifically target the factors that influence faculty decisions to assign or not assign writing. It is not faculty beliefs about effectiveness, but rather faculty beliefs about behavioral control and constraints at the departmental level that need to be targeted.

Identifying and Remediating Student Misconceptions in Introductory Biology via Writing-to-Learn Assignments and Peer Review.

Student misconceptions are an obstacle in science, technology, engineering, and mathematics courses and unless remediated may continue causing difficulties in learning as students advance in their studies. Writing-to-learn assignments (WTL) are characterized by their ability to promote in-depth conceptual learning by allowing students to explore their understanding of a topic. This study sought to determine whether and what types of misconceptions are elicited by WTL assignments and how the process of peer review and revision leads to remediation or propagation of misconceptions. We examined four WTL assignments in an introductory biology course in which students first wrote about content by applying it to a realistic scenario, then participated in a peer-review process before revising their work. Misconceptions were identified in all four assignments, with the greatest number pertaining to protein structure and function. Additionally, in certain contexts, students used scientific terminology incorrectly. Analysis of the drafts and peer-review comments generated six profiles by which misconceptions were addressed through the peer-review process. The prevalent mode of remediation arose through directed peer-review comments followed by correction during revision. It was also observed that additional misconceptions were elicited as students revised their writing in response to general peer-review suggestions.