The developing urea class of H-bond donors facilitates the solvent-free ROP of lactones at ambient and elevated temperatures, displaying enhanced rates and control versus other known organocatalysts for ROP under solvent-free conditions. The ROPs retain the characteristics of living polymerizations despite solidifying prior to full conversion, and copolymers can be accessed in a variety of architectures. One-pot block copolymerizations of lactide and valerolactone, which had previously been inaccessible in solution phase organocatalytic ROP, can be achieved under these reaction conditions, and one-pot triblock copolymers are also synthesized. For the ROP of lactide, however, thioureas remain the more effective H-bond donating class. For all (thio)­urea catalysts under solvent-free conditions and in solution, the more active catalysts are generally more controlled. A rationale for these observations is proposed. The triclocarban (TCC) plus base systems are particularly attractive in the context of solvent-free ROP due to their commercial availability which could facilitate the adoption of these catalysts.

A combined experimental and computational investigation revealed a hydrophobicity trend for oxygen-containing functional groups commonly encountered in monomers and polymers. Based on solvatochromatic dye experiments, HPLC retention times, and theoretical LogP values, the arrangement of the three oxygen atoms in carbonates results in more hydrophobicity than other permutations like anhydrides. Another trend emerged for functional groups with two oxygen atoms (acetals > esters). Overall, when comparing aliphatic polymers with similarly sized monomers, hydrophobicity decreased as follows: carbonates > acetals > esters > anhydrides. These trends have important implications for degradation, conductivity, and many other applications.

Growth in the biomedical and biotechnology sectors requires a highly trained and highly skilled workforce to answer the next great scientific questions. Undergraduate laboratory courses incorporating hands-on training based in authentic research position soon-to-be graduates to learn in environments that mirror those of academic, industrial, and government laboratories. Mass spectrometry is one of the most broadly applied analyses carried out in the biomedical and pharmaceutical sciences, and thus, it is essential that upper-division students gain hands-on experience in techniques and analytical workflows in mass spectrometry. Our precourse assessments identified weaknesses in student experience and knowledge in the fundamentals of mass spectrometry, supporting that it was a necessary area for improvement. We incorporated a laboratory experiment focused on tandem mass spectrometry and database searching into a preexisting mini-semester project devoted to identifying metabolites from medicinal plants. Implementation of the experiment allowed students to make more confident metabolite identifications, introduced them to a cutting-edge database analysis platform (GNPS: Global Natural Products Social Molecular Networking), and increased student experience and knowledge of mass spectrometry in addition to the principle of dereplication of samples derived from nature.

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Infections caused by the bacterium Staphylococcus aureus continue to pose threats to human health and put a financial burden on the healthcare system. The overuse of antibiotics has contributed to mutations leading to the emergence of methicillin-resistant Staphylococcus aureus, and there is a critical need for the discovery and development of new antibiotics to evade drug resistant bacteria. Medicinal plants have shown promise as sources of new small molecule therapeutics with potential uses against pathogenic infections. The Principal Rhode Island Secondary Metabolite (PRISM) library is a botanical extract library generated from specimens in the URI Heber W. Youngken Jr. Medicinal Garden by upper-division undergraduate students. PRISM extracts were screened for activity against strains of methicillin-susceptible S. aureus (MSSA). An extract generated from the tulip tree (Liriodendron tulipifera) demonstrated growth inhibition against MSSA, and a bioassay-guided approach identified a sesquiterpene lactone, laurenobiolide, as the active constituent. Intriguingly, its isomers tulipinolide and epi-tulipinolide lacked potent activity against MSSA. Laurenobiolide also proved to be more potent against MSSA than the structurally similar sesquiterpene lactones constunolide and dehydrocostus lactone. Laurenobioloide was most abundant in the twig bark of the tulip tree, supporting the historical and cultural usage of twig bark in poultices and teas.