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The dimeric Cu-Zn superoxide dismutase (SOD1) is a particularly interesting system for biological inorganic chemical studies because substitutions of the native Cu and/or Zn ions by a nonnative metal ion cause minimal structural changes and result in high enzymatic activity for those derivatives with Cu remaining in the Cu site. The pioneering NMR studies of the magnetically coupled derivative Cu2Co2SOD1 by Ivano Bertini and coworkers are of particular importance in this regard. In addition to Co(2+), Ni(2+) is a versatile metal ion for substitution into SOD1, showing very little disturbance of the structure in Cu2Ni2SOD1 and acting as a very good mimic of the native Cu ion in Ni2Zn2SOD1. The NMR studies presented here were inspired by and are indebted to Ivano Bertini's paramagnetic NMR pursuits of metalloproteins. We report Ni(2+) binding to apo wild-type SOD1 and a time-dependent Ni(2+) migration from the Zn site to the Cu site, and the preparation and characterization of Ni2Ni2SOD1, which shows coordination properties similar to those of Cu2Cu2SOD1, namely, an anion-binding property different from that of the wild type and a possibly broken bridging His. Mutations in the human SOD1 gene can cause familial amyotrophic lateral sclerosis (ALS), and mutant SOD1 proteins with significantly altered metal-binding behaviors are implicated in causing the disease. We conclude by discussing the effects of the ALS mutations on the remarkable stabilities and metal-binding properties of wild-type SOD1 proteins and the implications concerning the causes of SOD1-linked ALS.

Research has been conducted on the phosphate binding to ZnZn-Streptomyces dizinc aminopeptidase and its Co (super)2+ -substituted derivatives. The details of the nuclear magnetic resonance relaxation and kinetic studies of this binding are presented.

Research has been conducted on the metal-dependent peptide antibiotic. Nuclear magnetic resonance studies of the metal complex structure via paramagnetic Co(II) probe are described.

Results demonstrate use of paramagnetic metal ion cobalt(II) as an NMR probe in structural studies of the synthetic macromolecules such as dendrimers to identify metal recognition sites.

Several sharp, well resolved hyperfine shifted H NMR signals were seen in the 70 to -20 ppm chemical shift range of the hyperactive Cu(II)substituted aminopeptidase from Aeromonas proteolytica (AAP). This is due to spin-coupling of two CU(II) ions. The stronger downfield shifted signals were assigned to imidazole N-H protons of two coordinated histidine residues.

A study on the binding of various lanthanide(II) ions to anthracycline antitumor antibiotics such as daunomycin and adriamycin was conducted. The binding of the ions and the antibiotics was aided by methanol and aqueous solutions. Optical and 2D nuclear magnetic resonance techniques were utilized. Results revealed that the drug complex, which underwent slow chemical exchange with each other, dominated the metal-to-ligand binding ratio.

NMR studies of the paramagnetic Fe(II)BLM identified the ligands to the metal center in the Fe(II) adduct of bleomycin as derived from the beta-aminoalanine, the pyrimidinylpropionamide and the beta-hydroxyhistidine segments. Two-dimensional NMR techniques also allowed the identification of many of the spin networks present in the NMR spectrum of the paramagnetic Fe(II)BLM. Moreover, they clarify the assignments for the signals between -0.8 and -20 ppm. Examination of the NMR data reveals that alpha-methylvalerate and/or mannose segments do not participate in Fe(II) complexation.

Absorption and circular dichroism spectroscopic studies on Co(II)-substituted Escherichia coli ribonucleotide reductase R2 reveal that the structurally well-defined R2 metal ion binding sites constrain divalent metal ion binding to native sites. The Co-R2 complexes Co(II) centers are pentacoordinate and magnetically uncoupled. The Co(II) center characteristics resemble those of active site-bound Mn(II).

Three ligands L1, L2, and L3 with 2, 4, and 6 1,4,7,10-tetraazacyclododecane (cyclen) moieties attached to a cyclotriphosphazene core, respectively, were synthesized, and oxidation activities of their CuII complexes were investigated. Aerobic oxidation of catechol by these complexes follows an intramolecular dinuclear pathway with significant cooperativity (i.e., θ ≈ 1.5 out of a maximum of 2 for two potential substrate binding sites) and kinetic constants (i.e., kcat = 17.5 × 10-3 s-1, Km = 2.8 m m, and quite remarkable catalytic specificity kcat/ Km 12.5 m-1 s-1 per di-Cu center), while that by untethered CuII-cyclen follows a bimolecular dinuclear pathway without noticeable cooperativity ( θ = 0.96) and fourfold lower kcat, despite their similar dinuclear mechanisms. The proximity of CuII centers is suggested by EPR spectra and relaxations, showing a broad spectral component particularly in Cu6 L3. Thermodynamic parameters also indicate the significance of multi-CuII sites in the oxidative catalysis. Air is a more specific oxidation agent for the representative complex Cu2 L1, showing 3.2-fold higher catalytic specificity kcat/ Km than H2O2 toward a catechol substrate. The research provides further molecular basis for future design of O2/H2O2-specific oxidation of multi-domain Cu complexes. [ABSTRACT FROM AUTHOR]