The pentaammineruthenium(III)histidine complex in ribonuclease A: Application to the assignment of histidine proton resonances

Nonrandom structure in thermally unfolded ribonuclease A

“…The synthesis, isolation, and characterization of the derivative of RNAase A in which a single (NH3)5Runl complex is formed with the N-3 nitrogen of histidine-105 has been described. [5][6][7] As expected from model compound data,8 this complex is extremely stable at moderate temperatures (0-50 °C) from pH 1 to 8. It decomposes at temperatures greater than 60 °C or at pH values above pH 11.15 The samples were prepared for NMR study by two cycles of a process in which they were heated at 40 °C in 99.7% 2H20 (Merck Sharp and Dohme Isotopes) at pH* 2 (uncorrected meter reading) for 15 min and then lyophilized.…”

“…Recently, the application of a paramagnetic probe that forms tight complexes with histidine residues, (NH3)5Rum, to RNAase A5,6 enabled us to obtain a derivative labeled at histidine-105. 7 By examining the proton NMR spectrum of the thermally unfolded form of this derivative, we can now complete the assignment of the histidine C-2 resonances in thermally unfolded RNAase A and thereby obtain more information on the structure of this form.…”

A totally synthetic (nonporphyrin) iron(II) dioxygen carrier that is fully functional under ambient conditions

“…Like their congeners, these iron(II) complexes are high spin (Table I), and the C1PF6 salts are uni-univalent electrolytes in acetonitrile (X 125-150 ™1 mol™1 cm2 at 1 mM). It is therefore concluded that (9) As indicated, the unhindered lacunar cobalt complexes show 2 values as large as those of FeMb. Since FeMb has a 2 = 102 times that of CoMb, we could anticipate K02 = 102 torr™1 for the lacunar iron complex.…”

“…Underhill and Ahmad have found a new type of highly conducting planar platinum complex, Li0 75 [Pt(C4N2S2)2] •2 20, where the conduction pathway is considered to be formed by intermolecular contacts of the sulfur atoms of the ligands.14,15 The (8) Kobayashi, H.; Kobayashi, A.; Saito, G.; Inokuchi, H., to be submitted for publication. (9) Thorup, N.; Rindorf, G.; Soling, H. Phys. Scr., in press.…”