1.Imidazole, imidazolate, and hydroxide complexes of (protoporphyrin IX)iron(III) and its dimethyl ester as model systems for ferric hemoproteins: electron paramagnetic resonance and electronic spectral study.
Yoshimura T, Ozaki T. Arch Biochem Biophys. 1984 May 1;230(2):466-82.
The EPR and electronic spectral changes upon titration of systems consisting of (protoporphyrin IX)iron(III) chloride (Fe(PPIX)Cl) or its dimethyl ester (Fe-(PPIXDME)Cl) and imidazole derivatives with tetrabutylammonium hydroxide solution have been measured at 77 and 298 degrees K in various solvents. The EPR and electronic spectra of the melt of Fe(PPIXDME)Cl in imidazole derivatives have been also measured. The imidazole derivatives studied here were imidazole and 4-methyl-, 4-phenyl-, 2-methyl-, 2,4-dimethyl-, 1-methyl-, and 1-acetylimidazole. The spectral changes upon addition of hydroxide were markedly different between the systems containing NH imidazoles (BH), with a dissociable proton, and those containing NR imidazoles (BR), without it. In the former systems, five spectral species were successively formed at 77 degrees K and were assigned to following complexes: [Fe(P)(BH)2]+, Fe(P)(BH)(B), [Fe(P)(B)2]-, Fe(P)(BH)(OH), and [Fe(P)(B)(OH)]-, where P is PPIX or PPIXDME.
2.Chemical synthesis of urotensin II, a somatostatin like peptide in the caudal neurosecretory system of fishes.
Clark BR, Dattilo J, Pearson D. Int J Pept Protein Res. 1982 May;19(5):448-53.
In the goby, Gillichthys mirabilis, urotensin II (a bioactive neuropeptide present in the urophysis of teleost fish) has the dodecapeptide sequence, H2N-AGTADC-FWKYCV-OH, which is homologous with mammalian somatostatin at positions 1, 2 and 7-9. The Merrifield solid phase synthesis of Gillichthys urotensin II (UII) was accomplished by stepwise assembly from the carboxy terminus using N-alpha-tert, butyloxycarbonyl (Boc) amino acids containing benzyl-derived groups for protection of side-chain functionalities, Coupling of amino acids to the growing peptide was mediated by diisopropylcarbodiimide (DIC) in the presence of 1-hydroxybenzotriazole (HOBt). Residual alpha-amino groups remaining after coupling were blocked by acetylation with 1-acetylimidazole. Crude, synthetic UII was extracted from the HF-treated, protected peptide-resin product, reduced with dithiothreitol (DTT), reoxidized at high dilution with O2, and separated into its components using a single, preparative, reverse-phase HPLC step.
3.Supramolecular allosteric cofacial porphyrin complexes.
Oliveri CG1, Gianneschi NC, Nguyen ST, Mirkin CA, Stern CL, Wawrzak Z, Pink M. J Am Chem Soc. 2006 Dec 20;128(50):16286-96.
Nature routinely uses cooperative interactions to regulate cellular activity. For years, chemists have designed synthetic systems that aim toward harnessing the reactivity common to natural biological systems. By learning how to control these interactions in situ, one begins to allow for the preparation of man-made biomimetic systems that can efficiently mimic the interactions found in Nature. To this end, we have designed a synthetic protocol for the preparation of flexible metal-directed supramolecular cofacial porphyrin complexes which are readily obtained in greater than 90% yield through the use of new hemilabile porphyrin ligands with bifunctional ether-phosphine or thioether-phosphine substituents at the 5 and 15 positions on the porphyrin ring. The resulting architectures contain two hemilabile ligand-metal domains (RhI or CuI sites) and two cofacially aligned porphyrins (ZnII sites), offering orthogonal functionalities and allowing these multimetallic complexes to exist in two states, "condensed" or "open".
