Submicron hybrid particles will be developed. Each particle will have a silica core and covalently attached polypeptide shell. The shell confers the interesting chemical properties; it can be tailored to respond to temperature, even in an organic solvent where powerful ionic forces are absent, or to pH in aqueous environments where those forces predominate. The size, surface density and surface thickness of the particles will be controlled, enabling a study of how these parameters affect conformational transitions. The limits of making the particles by an "attach to" mechanism (fully formed polymers are connected to the silica cores) will be explored. The particles feature a number of useful physical functions. Either core or shell may bear fluorescent moieties to facilitate visualization of magnetic alignment, equilibrium structures or phase separation. The polypeptides comprising the shell are capable of forming liquid crystals when not tethered to a core, raising the possibility that "local liquid crystals" will form where particles covered with these molecules touch, elevating the local concentration of mesogens. This will be explored by chaining together superparamagnetic variants of the particles using an applied magnetic field. While held in these chains, reactions on the particles or their precursor cores will be explored, possibly leading to particles wearing a polypeptide belt or to poly(colloids) that may be able to undergo muscle-like expansions and contractions, even in an organic solvent.
Polypeptide-coated particles provide an excellent platform for applied discovery because they merge the characteristics of proteins' chemical versatility, ability to recognize markers for disease, switchable size and shape with ease of manipulation using gravitational or magnetic fields. The particles look a bit like porcupines, with "prickles" coating a central core. It is hoped that variants built with magnetic inclusions can be connected, leading to artificial "cilia" that respond to stimuli such as acidity or temperature. Related materials in the future are anticipated to have optoelectronic uses, such as light harvesting or sensing of amino acids related to disease. Researchers associated with the project team will train for a long career, emphasizing technical skills, critical thinking, ethical awareness and communication. Team members are expected to be factual advocates for their craft and for science in general. An important venue for such expression will be the Chemical Education Foundation's You Be the Chemist Challenge competition, a "quiz bow" for middle school students. Graduate student and postdoctoral team members will assist with the competition and/or training of students. Selected young scholars who perform well in the competition will actively participate in the proposed research, erasing the major deficiency of a structured question-and-answer competition, i.e. that it provides no practical training. The Chemical Education Foundation attempts to follow the careers of its young challengers, which provides at no cost to NSF a way to track the efficacy of competition-based science training. It is hoped that additional middle school students will be engaged in active learning, using a technical hobby as a starting point.
This project was designed to combine the features of polymers and particles. The polymers (in our case, polypeptides related to proteins) confer chemical properties, such as ability to purify pharmaceuticals by "recognizing" the shape of the desired product. Unfortunately, it is still difficult to manipulate the polymers. So we connected the polymers to larger particles that are easy to control and move using applied magnetic or gravitational fields. In this way, the polymers can be put where they do the most good, and they can be captured and used again. For example, the hybrid polymer-particle assembly can hold an enzyme that is useful in the perfume industry. Rather than use and lose that enzyme, it can be recaptured because it is bound to the particle. Technology such as this was prefaced by some important discoveries about the polymers and particle constituents. For example, it was shown that the core particle (made of silica, like very fine sand) could be prepared in very uniform sizes, even better than standards from the best sources. Because the new materials are extremely uniform in size, we can look for small structural variations in the silica. This is of interest because silica itself has some cargo-carrying capacity (e.g., encapsulation of proteins for pharmaceutical purposes). The research was conducted by a postdoctoral associate, graduate students, undergraduate students and even a high school student. Four graduate students completed their PhD studies with full or partial support from the award. One found a job at a major chemical and specialties manufacturer in Minnesota, while three others pursued postdoctoral work. One obtained an International NSF Fellowship, which he spent in China; he is now seeking an initial academic appointment in the US. Another current postdoc, who is aiming for an industrial slot after completing her studies, also formed an LLC to assist scientific writers. Still another hopes for an academic career in the US. Former undergraduate students are either in medical school or in graduate school (Physics). Our high school student received a full scholarship to study chemical engineering as a pre-med student. All members of the team were engaged in outreach activities. The most significant is service to the Chemical Educational Foundation, an industry-supported non-profit that promotes science understanding in middle schools. Its You Be the Chemist competition now reaches >25000 students in 30 states, on the way to all 50. Other activities include judging science fairs and hands-on demos at science expositions. Some team members have held positions in a university student association devoted to promoting polymers and biopolymers.
