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This work reports the first example of a single-chain protein computationally designed to contain four α-helical segments and fold to form a four-helix bundle encapsulating a supramolecular abiological chromophore that possesses exceptional nonlinear optical properties. The 109-residue protein, designated SCRPZ-1, binds and disperses an insoluble hyperpolarizable chromophore, ruthenium(II) [5-(4'-ethynyl-(2,2';6',2″-terpyridinyl))-10,20-bis(phenyl)porphinato]zinc(II)-(2,2';6',2″-terpyridine)(2+) (RuPZn) in aqueous buffer solution at a 1:1 stoichiometry. A 1:1 binding stoichiometry of the holoprotein is supported by electronic absorption and circular dichroism spectra, as well as equilibrium analytical ultracentrifugation and size exclusion chromatography. SCRPZ-1 readily dimerizes at micromolar concentrations, and an empirical redesign of the protein exterior produced a stable monomeric protein, SCRPZ-2, that also displayed a 1:1 protein:cofactor stoichiometry. For both proteins in aqueous buffer, the encapsulated cofactor displays photophysical properties resembling those exhibited by the dilute RuPZn cofactor in organic solvent: femtosecond, nanosecond, and microsecond time scale pump-probe transient absorption spectroscopic data evince intensely absorbing holoprotein excited states having large spectral bandwidth that penetrate deep in the near-infrared energy regime; the holoprotein electronically excited triplet state exhibits a microsecond time scale lifetime characteristic of the RuPZn chromophore. Hyper-Rayleigh light scattering measurements carried out at an incident irradiation wavelength of 1340 nm for these holoproteins demonstrate an exceptional dynamic hyperpolarizabilty (β1340 = 3100 × 10(-30) esu). X-ray reflectivity measurements establish that this de novo-designed hyperpolarizable protein can be covalently attached with high surface density to a silicon surface without loss of the cofactor, indicating that these assemblies provide a new approach to bioinspired materials that have unique electro-optic functionality.

Electronics made from biological materials are desirable for use in medical devices, biosensors, and soft robotics because they have properties inaccessible to current inorganic technologies. Here, a series of cationic peptides were developed to self‐assemble with the anionic porphyrin meso‐tetra(4‐sulfonatophenyl)porphine (TPPS4) into supramolecular light‐harvesting wires known as J‐aggregates were developed. In addition to quantifying the binding events between each peptide and TPPS4, we found co‐incubation with mixed peptides allowed TPPS4 to bridge two different peptides at their terminal porphyrin‐binding regions. The J‐aggregates formed on macroscopic scale in near quantitative yield within ~3 h and readily interconverted with the soluble monomers upon cycling the pH; to our knowledge, this is the first report of a peptide‐porphyrin system with such properties. This work has practical and conceptual relevance to the development of new bioelectronic materials. [ABSTRACT FROM AUTHOR]

Time-resolved infrared flash photolytic techniques are employed to initiate and observe the efficient dissociation of CO from a synthetic heme-CO/copper complex, in CH(sub 3)CN and acetone at room temperature. It is demonstrated that this CO photodissociation can be mimicked by ligating it to copper and then binding it to the heme.

The observation and fast time-scale kinetic determination of a primary dioxygen-copper interaction have been investigated in a study. A novel copper 'flash-and-trap' experiment typically used for hemes is performed, leading to the accurate determination of the second-order rate constant for (ligand)Cu/O2 reaction, a value that exceeds that for synthetic and natural hemes.

A membrane protein PRIME (PoRphyrins In MEmbrane) that closely positions two non-natural iron diphenylporphyrins ([Fe.sup.III]DPP's) is designed to provide a multicentered pathway for transmembrane electron transfer. UV-vis absorbance, CD spectroscopy, analytical ultracentrifugation, redox potentiometry, and EPR demonstrated that PRIME binds the cofactor with high affinity and specificity in the expected geometry.

The article explains the development of an amphiphilic four-helix bundle peptide that can be used for incorporating the ' push-pull' chromophore RuPZn compounds into the densely packed monolayer ensembles. A complete characterization of the macroscopic nonlinear optical properties of the peptide-chromophore complexes is also presented.

A study is conducted to measure the macroscopic nonlinear optical response of the 'push-pull' chromophore RuPZn incorporated into a single monolayer of the amphiphilic 4-helix bundle peptide (AP0) covalently attached to a solid substrate at high in-plane density. The microscopic hyperpolarizability of the RuPZn chromophore which is preserved upon incorporation into the peptide monolayer indicated that the first-order molecular hyperpolarizability is not substantially affected by the chromophore-chromophore interaction in the densely packed ensemble.

The first example of a computationally de novo designed protein is described that binds an emissive abiological chromophore, in which a sophisticated level of cofactor discrimination is pre-engineered. The elements of design in the heterotetrameric, [C.sub.2]-symmetric bundle protein have shown that interactions within the tetra-[alpha]-helical bundle are such that only the heterotetramer is stable in solution and the corresponding homomeric bundles have presented unfavorable ligand-binding environments, thus precluding protein structural rearrangements leading to binding of (porphinato)iron cofactors.