Reversible oxygenation of oxygen transport proteins

A lecture demonstration illustrating changes in the visible spectra of oxygen transport proteins upon reversihle oxygen binding is reported. The coloration upon exposure to oxygen is dramatic. Deoxyhemoglobin changes from purple to red, deoxyhemocyanin is transformed from colorless to blue, while colorless deoxyhemerythrin turns red. This demonstration illustrates an interesting example of a chemically reversible reaction and is used in the discussion of basic thermodynamic properties. A comparison of the physical characteristics of these oxveen storaee and transn.o rt ~ro- A teins is provided to illustrate the stru&ral diversity associated with these proteins having a similar biological role

Ni(II) (dioxo[16]aneN5)-Induced Methane Formation from Methyl Coenzyme M

The nickel tetrapyrrole containing factor, F430, is implicated in the final methane evolution step in methanogenic ba~terial-~ and has attracted considerable a t t e n t i ~ n . ~T- ~he essential role of F430 in methane formation was demonstrated by Ankel-Fuchs and Thauer, who reported the in vitro catalysis of H3CSCH2CH2S03-, methyl coenzyme M (methyl-CoM), to methane and CoM by purified methyl-CoM reductase under reducing condit i o n ~ .S~in ce F,,o exists in both the Ni(1) (or Ni(II1)) and the Ni(I1) states in Methanobacterium thermoautotrophicum,loi,t ll is of interest to examine the role of the nickel ion oxidation stateI2.l3 in methyl-CoM catalysis. We have found both the mono- and the divalent oxidation states of the water-soluble Ni(dioxo[ 161- aneNS), NiL, complexI4 catalyze methyl-CoM to methane and CoM