Regulation of enzymes by naturally occurring mechanisms such as phosphorylation is fundamental to life. Small molecule control of enzymes underlies the action of many pharmaceutical drugs. Bulk thermal control of enzymatic activity enables many laboratory and industrial processes such as PCR and aspartame synthesis. Our overall goal is to establish an entirely new method for regulating enzymes. This method uses the nano- localized heat generated by metal nanoclusters such as Au102(SR)44 under radiofrequency irradiation to thermally influence the activity of a nanocluster/enzyme conjugate. The RF is chosen to interact minimally with other components of the mixture, analogous to the RF used for Wi-Fi. Thus, this nano-local thermal enzyme control does not modify the solution temperature, nor should it influence the activity of enzymes that are not directly conjugated to nanoclusters. We propose to accomplish this goal in a set of 4 specific aims.
Aim 1 tests the hypothesis that we can 'activate' thermophilic enzyme/nanocluster conjugates such as thermolysin/Au102(SR)44 at assay temperatures in which the enzyme has minimal measurable activity.
Aim 2 tests the hypothesis that we can reversibly 'deactivate' enzymes, presumably by reversible unfolding. For this hypothesis we begin by testing nanocluster conjugates to textbook enzymes such as lysozyme, RNAse A and B-galactosidase. In both Aims 1 and 2 we test the sub-hypothesis that the site of nanocluster conjugation on the enzyme influences the activity of the conjugate. A full implementation of this remote-control enzymology requires quantitative understanding of how nanoclusters heat in radiofrequencies. Such an understanding will allow accurate prediction of nanocluster temperature, which is prerequisite for understanding how locally hot an enzyme is. Currently, there are three proposed mechanisms for nanocluster heating. These are an inductive mechanism, a magnetic mechanism, and an electrophoretic mechanism. All mechanisms have different responses to the frequency of the applied radiofrequency filed.
Aim 3 is to measure the frequency response of a small number of well-defined nanoclusters and nanoparticles.
Aim 4 is to synthetically change the properties of nanoparticles in a manner that will change their thermal dissipation under different mechanisms.
Both aims 3 and 4 incorporate theoretical modeling using existing mechanisms, recognizing the possible need for combining mechanisms or developing a novel theoretical mechanism for understanding thermal dissipation. Such mechanistic understanding will not only enable a new field of remote enzyme control but may also enable other nanoparticle based hyperthermal methods such as noninvasive hyperthermal cancer therapy and a remote control molecular biophysics.

Public Health Relevance

This proposal is to develop a nanoparticle based method to control enzyme activity. Regulation of enzymes by naturally occurring mechanisms (i.e., phosphorylation) is fundamental to life. Small molecule control of enzymes underlies the action of many pharmaceutical drugs.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Enabling Bioanalytical and Imaging Technologies Study Section (EBIT)
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Flicker, Paula F
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Colorado State University-Fort Collins
Schools of Arts and Sciences
Fort Collins
United States
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Collins, Christian B; Tofanelli, Marcus A; Noblitt, Scott D et al. (2018) Electrophoretic Mechanism of Au25(SR)18 Heating in Radiofrequency Fields. J Phys Chem Lett 9:1516-1521
Collins, C B; Tofanelli, M A; Crook, M F et al. (2017) Practical Stability of Au25(SR)18-1/0/+1. RSC Adv 7:45061-45065
Tofanelli, Marcus A; Salorinne, Kirsi; Ni, Thomas W et al. (2016) Jahn-Teller effects in Au25(SR)18. Chem Sci 7:1882-1890
Tofanelli, Marcus A; Ni, Thomas W; Phillips, Billy D et al. (2016) Crystal Structure of the PdAu24(SR)18(0) Superatom. Inorg Chem 55:999-1001