Oxidative ligation

Fig. 6. Electrospray mass spectrum of an acetonitrile solution of [(salen)Mn]C104,p-CN-iV,iV-dimethylaniline N-oxide, and iodosobenzene, showing the formation of N-oxide ligated man-ganese(III) and oxomanganese species...

The reaction between rhodium trichloride and nitric oxide forms another ternary nitrosyl whose formulation is unknown.1294 However, nitric oxide ligates rhodium(II) acetate (equation 293).1295 The ternary complexes have been used to prepare other complexes, but these derivatives are commonly prepared from more accessible starting materials. 

The high-frequency shifted His imidazole ring NH proton signals in a variety of oxidation/ligation states of Mb are compared in Fig. 16. Observations of... 

In Table 14.3, six types of chemical reactions are listed. In metabolic pathways, these reactions would be catalyzed by enzymes. Enzymes are given functional names. For example, isomerization is catalyzed by an isomerase. What would be the enzyme name, ending in -ase for the following oxidation, ligation, group transfer, hydrolytic. 

Oxidative addition of polar electrophiles, such MeX or HX (X= halide, sulfonate, or related stable anion) need not occur to a 16-electron metal center if a cationic metal center is generated with an uncoordinated anion. In this "oxidative ligation" mentioned previously and shown in Figure 6.1, the electrons of the Me-X or H-X bond do not add to the electron count of the metal because they are contained in the free anion of the product. 

The automated method differs from the ICSH method chiefly in that oxidation and ligation of heme iron occur after the hemes have been released from globin. Therefore, ferricyanide and cyanide need not diffuse into the hemoglobin and methemoglobin, respectively. Because diffusion is rate-limiting in this reaction sequence, the overall reaction time is reduced from approximately three minutes for the manual method to 3 —15 seconds for the automated method. Reaction sequences in the Coulter S + II and the Technicon H 1 and H 2 are similar. Moreover, similar reactions are used in the other Coulter systems and in the TOA and Unipath instmments. 

A relationship between the redox state of an iron—sulfur center and the conformation of the host protein was furthermore established in an X-ray crystal study on center P in Azotobacter vinelandii nitroge-nase (270). In this enzyme, the two-electron oxidation of center P was found to be accompanied by a significant displacement of about 1 A of two iron atoms. In both cases, this displacement was associated with an additional ligation provided by a serine residue and the amide nitrogen of a cysteine residue, respectively. Since these two residues are protonable, it has been suggested that this structural change might help to synchronize the transfer of electrons and protons to the Fe-Mo cofactor of the enzyme (270). 

Doublestrand break repair Ionizing radiation, chemotherapy, oxidative free radicals Synapsis, unwinding, alignment, ligation... 

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