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Lignin, a complex and abundant biopolymer, is a major constituent of plant cell walls. Due to its chemical and structural complexity, lignin degradation is a challenging task for both natural and engineered systems. Therefore, investigation of lignin degradation using so called “model compounds” has been the focus of many research efforts in recent years. This study addresses the utility of guaiacylglycerol-β-guaiacyl ether (Gβ2) as a model compound for evaluating the β-O-4 bond cleavage under diverse thermal and aqueous medium conditions. Experimental conditions included varied pH (3–10), microbial biodegradation, subcritical water environment (150–250 °C), and mild pyrolysis (150–250 °C). A high-performance liquid chromatography with high-resolution mass spectrometry was employed for accurate detection and quantification of both Gβ2 and its degradation/modification products in an aqueous environment. Pyrolysis experiments were performed using gas chromatography-mass spectrometry analysis with a pyrolyzer. The results showed that Gβ2 remained stable under exposure to moderate pH and several bacterial strains, which were successfully used previously for biodegradation of other recalcitrant pollutants. We report, for the first time, differing Gβ2 breakdown pathways for subcritical water treatment vs. pyrolysis under an inert atmosphere. The scientific novelty lies in the presentation of differences in the degradation pathways of Gβ2 during subcritical water treatment compared to pyrolysis in an inert atmosphere, with water playing a key role. The observed differences are ascribed to the suppression of homolytic reactions by water as a solvent. 

The Undergraduate Scholarships with Mathematics and Science Training, Exploration, and Research Program (US MASTER) is a STEM scholarship program funded by the United States National Science Foundation. It was implemented at an upper-Midwest institution to target and provide structured support to low-income, academically talented undergraduates in biology, chemistry, geography and geographic information science (GISc), environmental sciences, and physics and astrophysics. In addition to providing financial support, the program features an integrated approach to mentorship and advising consisting of an ongoing seminar course in which students engage in collaborative projects, research experiences with a faculty mentor, and targeted academic advising. As part of our assessment efforts, we interviewed student participants regarding their experiences. A consistent theme emerged regarding mentorship: in addition to providing access to professional socialization experiences and the facilitation of competency and performance, students reported that it was the ability to form close relationships based on personal authenticity and feelings of psychological safety and trust that provided the best scaffolding for success in a challenging STEM environment. 

Science identity is composed of three key components, including competence (possessing scientific knowledge), performance (the capacity to use scientific tools and language in appropriate settings), and recognition (earning validation from others in the field) (Carlone & Johnson, 2007). The significance of a strong science identity is in shaping a student’s future behavior, such as intent to graduate and pursue a STEM career (Chang et al., 2011; Chemers et al., 2011), which is particularly important for those with notable retention challenges within STEM like women, underrepresented minorities, first generation, and rural students (President’s Council of Advisors on Science and Technology, 2012). The work of building students’ science identity and encouraging their development as emerging scholars and scientists relies on both classroom experiences and the form and quality of mentoring relationships with faculty (Kendricks et al., 2013). This study considers how students see their own science identity development, and which supports they believe most central to science identity. 

Temperature-dependent sex determination (TSD) is a well-known characteristic of many reptilian species. However, the molecular processes linking ambient temperature to determination of gonad fate remain hazy. Here, we test the hypothesis that Wnt expression and signaling differ between female- and male-producing temperatures in the snapping turtle Chelydra serpentina. Canonical Wnt signaling involves secretion of glycoproteins called WNTs, which bind to and activate membrane bound receptors that trigger β-catenin stabilization and translocation to the nucleus where β-catenin interacts with TCF/LEF transcription factors to regulate expression of Wnt targets. Non-canonical Wnt signaling occurs via 2 pathways that are independent of β-catenin: one involves intracellular calcium release (the Wnt/Ca²⁺ pathway), while the other involves activation of RAC1, JNK, and RHOA (the Wnt/planar cell polarity pathway). We screened 20 Wnt genes for differential expression between female- and male-producing temperatures during sex determination in the snapping turtle. Exposure of embryos to the female-producing temperature decreased expression of 7 Wnt genes but increased expression of 2 Wnt genes and Rspo1 relative to embryos at the male-producing temperature. Temperature also regulated expression of putative Wnt target genes in vivo and a canonical Wnt reporter (6x TCF/LEF sites drive H2B-GFP expression) in embryonic gonadal cells in vitro. Results indicate that Wnt signaling was higher at the female- than at the male-producing temperature. Evolutionary analyses of all 20 Wnt genes revealed that thermosensitive Wnts, as opposed to insensitive Wnts, were less likely to show evidence of positive selection and experienced stronger purifying selection within TSD species.