| Summary: | The met and deoxy forms of sperm whale myoglobin (Mb) can be unfolded by guanidine hydrochloride (GuHCl). Electronic absorption and circular dichroism spectroscopic measurements show that folded deoxyMb is more stable than the folded met protein. Laser excitation of NADH generates species that rapidly reduce unfolded metMb, triggering the formation of folded deoxyMb in less than 10 ms (pH 7.0, 2.5 to 3 M GuHCl, 20 °C). At comparable reaction driving forces (∼10 kJ/mol), deoxyMb folds much faster than reduced cytochrome c. © 1998 American Chemical Society. Received: November 17, 1997; In Final Form: April 1, 1998. Publication Date (Web): May 23, 1998. P.W.-S. thanks the Swedish Technical Research Council for a postdoctoral fellowship and Ivan Dmochowski for assistance with the diode array measurements. This work was supported by the National Science Foundation (H.B.G., J.R.W.), the Nobel Institute for Chemistry (B.G.M.), and the Arnold and Mabel Beckman Foundation.
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