An Infrared Spectroscopic Study of the Hydrogen-Deuterium Exchange of Bovine Submaxillary Mucin

An infrared spectroscopic method was used to study the hydrogen-deuterium exchange of a glycoprotein, bovine submaxillary mucin (BSM), dissolved in D2O. The pH-dependence of the rate and extent of the H—D exchange of BSM was determined. The rate constant of the exchange decreased as pH increased from 3.7 to 5.3 and remained constant at a minimum value, (0.82 ± 0.09) X 10−2 min−1, from pH 5.3 to 7.2. The extent of the exchange decreased with increasing pH in the pH range 3.7 to 5.3 and levelled off from pH 5.3 to 7.2. It is suggested that these results are due to a pH-dependent conformational change.