Fluorescence spectroscopy and molecular modeling investigations on the thermally induced structural changes of bovine β-lactoglobulin

• Published in: Innovative food science & emerging technologies 2012-07, Vol.15, p.50-56
• Main Authors: Stănciuc, Nicoleta, Aprodu, Iuliana, Râpeanu, Gabriela, Bahrim, Gabriela
• Format: Article
• Language: English
• Subjects: Conformational changes; Fluorescence spectroscopy; Molecular modeling; β-lactoglobulin
• ISSN: 1466-8564; 1878-5522
• DOI: 10.1016/j.ifset.2012.03.001

The heat-induced conformational and structural changes in β-lactoglobulin were analyzed using the fluorescence techniques and the molecular modeling approach. The experimental results confirm a two-state model for heat-induced changes of β-lactoglobulin at pH 6.5. The heat treatment at temperatures higher than 70°C caused an increase in both intrinsic and ANS fluorescence intensity. The addition of quenching agents was employed to discriminate the fluorescence contributions of the two tryptophan residues of β-lactoglobulin (Trp19 and Trp61). The addition of acrylamide and KI causes an increase of the quenching constants associated with Trp19. This effect is observed at all temperatures studied, but the effect is stronger at temperatures higher than 70°C. The heat-induced changes in the secondary and tertiary structure were outlined after running molecular dynamics simulations at different temperatures and neutral pH, therefore supporting the experimental observations. In the food industry, one of the major concerns of whey processors is to produce whey protein products (such as whey protein concentrates or isolates as well as fractions enriched in β-lactoglobulin or α-lactalbumin) with specific functionalities. In this sense, the potential use of β-lactoglobulin as a supplement for special food products has encouraged the study of its physico-chemical and biological properties. ► Conformational changes of β-lactoglobulin were checked at different temperatures. ► The heat-induced denaturation of β-lactoglobulin at pH 6.5 was a two-state model. ► Heating over 70°C caused an increase in intrinsic and ANS fluorescence intensity. ► The conformational changes involved mainly the strands and 310 helices. ► The KSV values indicate significant increase in the accessibility of Trp19.