Effect of Calcium Addition on the Thermal Denaturation of Bovine Apo-α-lactalbumin – a Preliminary Study

Bovine α-lactalbumin is known to be present in molten globule form in its apo-state (i.e., Ca depleted state). In this preliminary study, heat-induced conformational changes were analyzed using the fluorescence spectroscopy at very low pH in the absence and the presence of calcium ions. The heat treatment caused the decrease of intrinsic fluorescence, evidencing the increase of intramolecular quenching of the tryptophans. The presence of two classes of tryptophan residues (exposed and buried) was reflected also in the Stern–Volmer plot, and the KSV values were used for estimating the exposed tryptophan residues in the protein.