Crystal structure of the ferritin from the hyperthermophilic archaeal anaerobe Pyrococcus furiosus

The crystal structure of the ferritin from the archaeon, hyperthermophile and anaerobe Pyrococcus furiosus (PfFtn) is presented. While many ferritin structures from bacteria to mammals have been reported, until now only one was available from archaea, the ferritin from Archaeoglobus fulgidus (AfFtn). The PfFtn 24-mer exhibits the 432 point-group symmetry that is characteristic of most ferritins, which suggests that the 23 symmetry found in the previously reported AfFtn is not a common feature of archaeal ferritins. Consequently, the four large pores that were found in AfFtn are not present in PfFtn. The structure has been solved by molecular replacement and refined at 2.75-Å resolution to R = 0.195 and Rfree = 0.247. The ferroxidase center of the aerobically crystallized ferritin contains one iron at site A and shows sites B and C only upon iron or zinc soaking. Electron paramagnetic resonance studies suggest this iron depletion of the native ferroxidase center to be a result of a complexation of iron by the crystallization salt. The extreme thermostability of PfFtn is compared with that of eight structurally similar ferritins and is proposed to originate mostly from the observed high number of intrasubunit hydrogen bonds. A preservation of the monomer fold, rather than the 24-mer assembly, appears to be the most important factor that protects the ferritin from inactivation by heat

Characterization of a Dimeric Copper(II) Complex of a Dissymmetric Schiff Base and Its Ligand Adducts

The synthesis and characterization of a binuclear copper(II) complex of a Schiff base derived from salicylaldehyde and (1S,25)-(+)D-1-phenyl-2-amino-1,3-propanediol are described. A distorted square-planar configuration about the copper centers is proposed on the basis of its spectral properties and its reduced magnetic moment in solution. The complex reacts in solution with a series of ligands to form bis(ligand) adducts in which the dimeric unit remains intact. The bis(imidazole) adduct exhibits catalase activity, and in the presence of hydrogen peroxide a band near 440 nm is observed that is most probably a 022−–Cu(II) charge-transfer transition

Density Functional Theory Study of Vibrational Spectra: Part 5. Structure, Dipole Moment, and Vibrational Assignment of Azulene

Density functional theory (DFT) calculations (using Becke\u27s exchange in conjunction with Lee-Yang-Parr\u27s correlation functional (BLYP) and Becke\u27s three-parameter hybrid DFT/HF method using Lee-Yang-Parr\u27s correlation functional (B3LYP)) have been carried out to investigate the structure, dipole moment, and vibrational spectrum of azulene. Structural parameters obtained by both BLYP/6-31G* and B3LYP/6-31G* geometry optimization are in good agreement with available experimental data and show clearly the aromatic nature (bond equalization), a property the Hartree-Fock theory fails to describe correctly. The BLYP/6-31G* and B3LYP/6-31G* dipole moments are within experimental uncertainty and are in good agreement with results obtained from the much more expensive MP2 and MR-SDCI calculations. Most of the BLYP/6-31G* vibrational frequencies are in excellent agreement with available experimental assignments. On the basis of the calculated results, assignments of some missing frequencies in the experimental studies are proposed