Stability characteristics of deuterated myoglobin

• Published in: Biopolymers
• Main Authors: Appel, Pearl, Brown, W. Duane
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1971
• Subjects: Sperm whale
• Online Access: http://dx.doi.org/10.1002/bip.360101122; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fbip.360101122; https://onlinelibrary.wiley.com/doi/pdf/10.1002/bip.360101122

Abstract Purified sperm whale myoglobin was deuterated by being exposed to pD 3.5 in D 2 O buffer for 1 hr, then raised to pD 10.6 for an additional hour, and finally brought to neutrality in a D 2 O environment. Control myoglobin was similarly treated in H 2 O. The specific rotation at 233 mμ and/or the absorbance in the Soret region were used to follow the helix‐coil transition of myoglobin subjected to denaturation by acid, alkali, urea and guanidine. Deuterated and control myoglobin had similar 50% transition points in the four denaturing media studied (acid: pH 4.4, pD 4.9; alkali: pH 9.4, pD 10.0; urea, 7.2 M guanidine, 2.5 M ). The shift toward the alkaline side of 0.5 or 0.6 units of the transition induced by either acid or alkaline denaturation reflects only the weakened acidity of ionizable groups in deuterium systems. Deuterated myoglobin in 3.25 M guanidine had a 20% faster denaturation rate than that of control. Acid, urea, and guanidine denaturation curves showed fairly steep transitions, taken as indicative of a one‐step process involving only two states (native and denatured molecules). Supporting this conclusion was the fact that plots of absorption and polarimetry measurements of the helix‐coil transition induced by either acid or guanidine could be superimposed.