We provide a direct measure of the change in effective dielectric constant within a protein matrix after a photoinduced electron transfer (ET) reaction. A linked donor-bridge-acceptor molecule, PZn-Ph-NDI, consisting of a (porphinato)Zn donor (PZn), a phenyl bridge (Ph), and a naphthalene diimide acceptor (NDI), is shown to be a ‘meter’ to indicate protein dielectric environment. We calibrated PZn-Ph-NDI ET dynamics as a function of solvent dielectric, and computationally de novo designed a protein SCPZnI3 to bind PZn-Ph-NDI in its interior. Mapping the protein ET dynamics onto the calibrated ET catalogue shows that SCPZnI3 undergoes a switch in the effective dielectric constant following photoinduced ET, from εS ~8 to ~3.

High and unique gas and hydrocarbon adsorption in a highly stable guest-free microporous metal-organic framework constructed on rigid aliphatic ligands, H(2)bodc and ted, is reported in this work.

Functionalization of nanoparticles with biopolymers has yielded a wide range of structured and responsive hybrid materials. DNA provides the ability to program length and recognition using complementary oligonucleotide sequences. Nature more often leverages the versatility of proteins, however, where structure, assembly, and recognition are more subtle to engineer. Herein, a protein was computationally designed to present multiple Zn coordination sites and cooperatively self-associate to form an antiparallel helical homodimer. Each subunit was unstructured in the absence of Zn or when the cation was sequestered with a chelating agent. When bound to the surface of gold nanoparticles via cysteine, the protein provided a reversible molecular linkage between particles. Nanoparticle association and changes in interparticle separation were monitored by redshifts in the surface plasmon resonance (SPR) band and by transmission electron microscopy (TEM). Titrations with Zn revealed sigmoidal transitions at submicromolar concentrations. The metal-ion concentration required to trigger association varied with the loading of the proteins on the nanoparticles, the solution ionic strength, and the cation employed. Specifying the number of helical (heptad) repeat units conferred control over protein length and nanoparticle separation. Two different length proteins were designed via extension of the helical structure. TEM and extinction measurements revealed distributions of nanoparticle separations consistent with the expected protein structures. Nanoparticle association, interparticle separation, and SPR properties can be tuned using computationally designed proteins, where protein structure, folding, length, and response to molecular species such as Zn can be engineered.

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