Alteration of infrared spectrum of serum transferrin by iron binding and lowered pH

Difference infrared spectra are reported for human serum transferrin in D₂O as a function of iron binding or increased acidity. Spectral features detected as iron is bound at high pH include difference bands that are indicative of reduced solvent exposure and binding site ligation. More extensive spectral alterations, some of which indicate titration of carboxylic acid groups, are induced in the apo protein by lowering the pH in a manner consistent with that entailed in endocytosis. © 1999 John Wiley & Sons, Inc. Biospectroscopy 5: 325–327, 1999