Virus-like particles are unique platforms well suited for the construction of nanomaterials with broad-range applications. The research presented here describes the development of a modular approach for the covalent attachment of protein domains to the exterior of the versatile bacteriophage P22 virus-like particle (VLP) via a sortase-mediated ligation strategy. The bacteriophage P22 coat protein was genetically engineered to incorporate an LPETG amino acid sequence on the C-terminus, providing the peptide recognition sequence utilized by the sortase enzyme to catalyze peptide bond formation between the LPETG-tagged protein and a protein containing a polyglycine sequence on the N-terminus. Here we evaluate attachment of green fluorescent protein (GFP) and the head domain of the influenza hemagglutinin (HA) protein by genetically producing polyglycine tagged proteins. Attachment of both proteins to the exterior of the P22 VLP was found to be highly efficient as judged by SDS-PAGE densitometry. These results enlarge the tool kit for modifying the P22 VLP system and provide new insights for other VLPs that have an externally displayed C-terminus that can use the described strategy for the modular modification of their external surface for various applications.

Observation is at the heart of the Scientific Method, but students receive very little direct help in science curricula to assess or build this important power. We have addressed this problem with the development of a "Chemistry Toy". ChemToy1 is a dynamic, colorful, and interesting chemical apparatus that students take home with them to engage in chemical observation over a 1 day to 4 week period. The Toy undergoes many different kinds of chemical and physical changes during this time in terms of dynamics−kinetics, a rainbow of colors, surface tension, fluorescence, and states of matter. Students are first attracted by the fun of it, but they are soon drawn to explore a deeper world of chemical observation, which includes about 50 fundamental observations. Somewhat different results are obtained when the Toy is handled in various ways; thus, a degree of serendipity enters into the results that any particular student might obtain. Instructors can determine the fraction of total possible observations achieved by each student as a means to measure observational power. Science majors achieve only 36.1 ± 14.3% of possible observations on first encounter. Use of the Toy later in the semester or in another semester helps build stronger observational skills. Although Chemistry majors may benefit the most from ChemToy1, instructors and students of other disciplines may find it useful as well. In summary, instructors now have a robust tool that can be used to help students quantify and improve observational power.