Calorimetric and Raman investigation of cow’s milk lactoferrin

• Published in: Journal of thermal analysis and calorimetry Vol. 103; no. 1; pp. 41 - 47
• Main Authors: Iafisco, Michele, Foltran, Ismaela, Di Foggia, Michele, Bonora, Sergio, Roveri, Norberto
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Dordrecht Springer Netherlands 01.01.2011; Springer
• Subjects: Analysis; Analytical Chemistry; Biological and medical sciences; Calorimetry; Chemistry; Chemistry and Materials Science; Denaturation; Differential scanning calorimetry; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; Inorganic Chemistry; Investigations; Iron; Lactoferrins; Measurement Science and Instrumentation; Methods of analysis, processing and quality control, regulation, standards; Milk; Milk and cheese industries. Ice creams; Physical Chemistry; Physiological aspects; Polymer Sciences; Protein binding; Proteins; Raman spectroscopy; Differential scanning calorimetry; Lactoferrin; Protein denaturation; Raman spectroscopy; Protein biophysics; Ferroprotein; Denaturation; Cow milk; Raman spectrometry; Thermal analysis; Biophysics; Protein
• ISSN: 1388-6150; 1572-8943
• DOI: 10.1007/s10973-010-1084-2

Lactoferrin (LF), a non-heme iron-binding protein of blood plasma and milk with antioxidant, cariostatic, anticarcinogenic, and anti-inflammatory properties, has been studied by differential scanning calorimetry (DSC) and Raman spectroscopy over a wide pH range (4.0–9.0). Using these two techniques, the modifications in the quantity of iron bounded in the cow’s milk LF and in the secondary structures, as a function of pH and heating, have been evaluated. DSC curves showed higher value of denaturation temperatures and enthalpy changes when LF was saturated with iron (holo-form) than when it was in its unsaturated form (apo-form). The denaturation curves of the protein solutions at pH ≥ 5.5 confirming that LF is a mix of apo- and holo-forms; on the contrary at pH 4.0, the holo-form is practically absent. Spectroscopic investigation showed that, as a function of pH, the content of α-helix increases up to pH 7.4, followed by a small decrease by further pH increase. The β-sheet percentage exhibits the opposite behavior, while the random-coil and turn structures do not change noticeably. In contrast, after heat-induced denaturation, strong variations were observed in the secondary structure, with an evident increase of β-sheet and decrease of the α-helix percentage. Finally, both thermal and spectroscopic analysis pointed out that the structure of cow’s milk LF is strictly sensible to pH variation and it has the highest thermal stability at physiological pH.