The synthesis and self-assembly behavior of biohybrid ABC triblock copolymers consisting of a synthetic diblock, polystyrene-b-polyethylene glycol (PSm-b-PEG113), where m is varied, and a hemeprotein, myoglobin (Mb) or horse radish peroxidase (HRP), is described. The synthetic diblock copolymer is first functionalized with the heme cofactor and subsequently reconstituted with the apoprotein or the apoenzyme to yield the protein-containing ABC triblock copolymer. The obtained amphiphilic block copolymers self-assemble in aqueous solution into a large variety of aggregate structures. Depending on the protein and the polystyrene block length, micellar rods, vesicles, toroids, figure eight structures, octopus structures, and spheres with a lamellar surface are formed.

Self-Assembled Architectures from Biohybrid Triblock Copolymers

The nature of the singlet and triplet excited states of a series of meso-to-meso ethyne-linked bis(porphyrin) compounds was probed by electronic absorption, polarized pump−probe fluorescence, electron paramagnetic resonance (EPR), electroabsorption (Stark), and transient triplet−triplet absorption spectroscopic methods. Pump−probe fluorescence anisotropy experiments show that the presence of meso-ethynyl substituents drives a reorientation of orthogonal x- and y-polarized singlet excited states in the macrocycle frame of reference with respect to that evinced for conventional free-base porphyrin chromophores. Analogous experiments in conjugated bis(porphyrin) species bis[(5,5‘,-10,20-bis[3‘ ‘,5‘ ‘-(di-tert -butyl)phenyl]porphinato)zinc(II)]ethyne, 5-[10,20-bis[3‘ ‘,5‘ ‘-(di-tert-butyl)phenyl]porphinato)zinc(II)]-5‘-[10‘,20‘-bis[3‘ ‘,5‘ ‘-(di-tert-butyl)phenyl]porphyryl]ethyne, and bis[5,5‘,-10,20-bis[3‘ ‘,5‘ ‘-(di-tert-butyl)phenyl]porphyryl]ethyne demonstrate substantial energetic splittings of the x- an...

Singlet and Triplet Excited States of Emissive Conjugated (Bis)porphyrin Compounds Probed by Optical and EPR Spectroscopic Methods

Photoinitiation of relaxation of two peptides (labeled 1 and 2) and spectroscopic studies of the ensuing dynamics have led to new information about peptide conformational dynamics. Following photolysis of the aryl disulfide chromophore that constrains a peptide to be distorted from its equilibrium form, the S−S bond is broken in <200 fs, and the liberated thiyl radicals either undergo geminate recombination or diffuse apart to allow the peptides to change conformation. From anisotropy measurements, overall peptide rotation is on the time scale of 600 ps. At an even earlier time (ca. 100 ps), transient IR measurements show a bleaching of the amide I‘ region, arising from a vibrational Stark effect produced upon ring opening of peptide 2. We did not detect any significant shift in the amide I‘ region up to 2 ns, suggesting no significant helix formation in this time domain. Thiyl radicals arising from peptide 2 recombine with a power law rate over the time range from picoseconds to microseconds signaling an...

Peptide Conformational Dynamics and Vibrational Stark Effects Following Photoinitiated Disulfide Cleavage

Using femtosecond absorption spectroscopy, the photodissociation dynamics of HgI2 in solution were investigated. Upon photolysis, the HgI fragment is formed in a coherent superposition of its vibrational states. Solvent dependence of the wave packet motion is evidenced by the different results for ethanol and DMSO and between solution and gas phase.

Wave packet dynamics of the HgI2 photodissociation reaction in solution

Optical and proton nuclear magnetic resonance (NMR) studies were carried out to assess the structure of the polypeptide chain and metal ligation in zinc-substituted horse heart cytochrome c (Zn Cyt c). The 1D- and 2D-NMR (COSY, TOCSY, and NOESY) spectra allowed the assignment of proton resonances in 67 amino acid residues. These residues arose from all structural elements of the protein, alpha-helices, beta-turns, and segments of the protein with no defined secondary structure. Small deviations of the chemical shifts of Zn Cyt c proton resonances from native Fe(II) Cyt c of less than 0.1 ppm are due to not fully matching solvent conditions. Differences in the chemical shifts between the two proteins in the range 0.10-0.20 ppm are not clustered and are observed not only in the vicinity of the Zn porphyrin but also on distant surface locations of the cytochrome. The resonance positions of the bridge protons, from the thioether bonds of the porphyrin with Cys 14 and Cys 17, were conserved in Zn Cyt c. Similarly, the Met 80 and His 18 protons had chemical shifts supporting the proposal that His 18 and Met 80, as for Fe(II) Cyt c, may provide the axial ligation in the Zn protein and that zinc may be in an unusual hexacoordinated geometry. Chemical shifts from proton resonances of alternative axial ligands of misfolded cytochrome like His 33, Lys 79, and Phe 82 were found to be the same as in the Fe(II) protein, excluding the possibility of their axial ligation to Zn. The His 18-Zn-Met 80 ligation was also consistent with data from absorption and luminescence studies. We conclude that Zn Cyt c is an adequate structural model for Fe(II) Cyt c as both share the same overall structure, including axial ligands, environment in the porphyrin vicinity, and the same binding interface with redox partners.

Structure of zinc-substituted cytochrome c: nuclear magnetic resonance and optical spectroscopic studies.

Reactions of excited triplet states of metal substituted myoglobin with dioxygen and quinone.

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Reactions of excited triplet states of metal substituted myoglobin with dioxygen and quinone.