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The effects of structure and stereochemistry on the gas-phase ionization of /3-substituted ethanols (XCH2CH2OH), propanols (CH3CH(OH)CH2X and CH3CHXCH2OH), and cyclopentanols have been studied by ion cyclotron resonance techniques. Ionization to form XC2H4+, XC3H6+, or XC5H8+, where X = F, Cl, Br, OR, SR, SH, and NH2, occurs as the result of protonation of the alcohol and subsequent dissociation with H20 as the leaving group. Only in the case of X = F and Cl was loss of HX competitive with loss of H20. The results are qualitative but indicate that product stability is a major factor determining the mode and importance of dissociation. Neighboring group effects, alkyl substitution, and configurational effects parallel those observed in solvolytic reactions of related compounds. An attempt has been made to assign structures to ions of composition Journal of the American Chemical Society / 95:7 / April 4, 1973 * RI = relative intensities of primary fragments at KM Torr. 6 RI = relative intensities (mass corrected) of product ions at 10~4 Torr. ' Double resonance indicates precursor ion is MH+ (d/c/d£¡0" > 0) and all ions leading to MH+ (dA:/d£ion < 0). d Precursor ion is MH+. * Product ions are identified here by their mje values and composition; structure and mechanism are not implied. > MH+ -HaO {mje 47) and MH+ -HF (mje 45) account for 15 and 7% of the total ionization at 1CM Torr, 70 eV, respectively. 1 Represents (MH+ -HC1). h MH+ -H20 (mje 44) accounts for 12% of the total ionization at KM Torr, 70 eV.

Nickel cytochrome c has been synthesized by the reaction of metal-free porphyrin cytochrome c with Ni(I1) ions in 0.6 M glycylglycine and 4 M KSCN. Electronic spectra and susceptibility measurement showed the nickel to be in a high-spin octahedral configuration exemplifying the strong influence of the protein moiety as a macrocyclic ligand on the coordination chemistry of the metal ion. Nickel cytochrome c has the same electrophoretic mobility, helicity and pK values of conformational transitions as the native enzyme. At high pH, the partially denatured nickel cytochrome c becomes dimeric. Nitric oxide reacts with nickel cytochrome c to form the nitrosyl derivative with g,, = 2.187 and g , = 2.140. Reaction of NO with nickel protoporphyrin IX dimethyl ester in toluene, pyridine, or methylthioethanol produced no stable nitrosyl products, clearly demonstrating the effect of protein on metal ion ligation.Isomorphic replacement of the native metal ion in metalloproteins has been gaining acceptance as a viable and meaningful method to study functionstructure relationships of these proteins. Recently, several reports of metal-substituted cytochrome c have appeared in the literature. Co(I1) and Co(II1) cytochromes c have been synthesized [l -41 which have structures very similar to the native species. The 3d7 configuration for the reduced cobaltocytochrome c allowed EPR studies which are not possible for the diamagnetic ferrocytochrome c. It was shown that the axial ligands are His-18 and Met-80 at physiological pH and that the former is dissociated at pH below 4.0 and the latter is dissociated at pH above 12 [4]. The reactions of cobalt cytochrome c with oxidoreductases shed light on the requirements for electron transfer processes [2,3]. This synthetic procedure [1,3] has been used to prepare Zn(I1) and Sn(1V) cytochromes c [5], the fluorescent and phosphorescent properties of which have been studied.Several studies have been reported on the complexing of nickel porphyrins with nitrogenous base with conflicting conclusions. Based on magnetic data and titration ratios, some workers favored octahedral coordination [6 -103; others have described spectroscopic results supporting axial coordination Abbreviations. Ni . Gly-Gly, Ni(I1) glycylglycine; EPR, electron paramagnetic resonance; NMR, nuclear magnetic resonance; FB, Bohr magneton; CD, circular dichroism.by only one base 111 -131. Whether the polypeptide ligand would impose on NQI) ion biaxial coordination in nickel cytochrome c is one question this work aims to answer. The other objective is to discover how the ligation of Ni(I1) is modified in the protein environment. It is well known that the rate of insertion of Ni(I1) ion into water-soluble porphyrins ranks the slowest among divalent ions of first row transition elements. Therefore, a significant accomplishment of this work is the development of a procedure for the synthesis of nickel cytochrome c having native-like structure. MATERIALS AND METHODSThe synthesis of nickel cytochrome c involves the reaction of an...

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