Disaccharide analysis of chondroitin and heparin from farmed Atlantic salmon

Post-prin

Structural characteristic, pH and thermal stabilities of apo and holo forms of caprine and bovine lactoferrins

Apo and holo forms of lactoferrin (LF) from caprine and bovine species have been characterized and compared with regard to the structural stability determined by thermal denaturation temperature values (Tm), at pH 2.0-8.0. The bovine lactoferrin (bLF) showed highest thermal stability with a Tm of 90±1°C at pH 7.0 whereas caprine lactoferrin (cLF) showed a lower Tm value 68±1°C. The holo form was much more stable than the apo form for the bLF as compared to cLF. When pH was gradually reduced to 3.0, the Tm values of both holo bLF and holo cLF were reduced showing Tm values of 49±1 and 40±1°C, respectively. Both apo and holo forms of cLF and bLF were found to be most stable at pH 7.0. A significant loss in the iron content of both holo and apo forms of the cLF and bLF was observed when pH was decreased from 7.0 to 2.0. At the same time a gradual unfolding of the apo and holo forms of both cLF and bLF was shown by maximum exposure of hydrophobic regions at pH 3.0. This was supported with a loss in α-helix structure together with an increase in the content of unordered (aperiodic) structure, while β structure seemed unchanged at all pH values. Since LF is used today as fortifier in many products, like infant formulas and exerts many biological functions in human, the structural changes, iron binding and release affected by pH and thermal denaturation temperature are important factors to be clarified for more than the bovine species

A comparison of effects of pH on the thermal stability and conformation of caprine and bovine lactoferrin

Thermal stability and structural changes in caprine lactoferrin (cLF) and bovine lactoferrin (bLF) at pH 2.0-8.0 were measured using thermal denaturation temperature (Tm) analysis, fluorescence spectroscopy and circular dichroism (CD). Thermal stability analysis indicated a Tm of 70°C for bLF and 67°C for cLF at pH 7.0. From pH 7.0 to 3.0, a gradual reduction in the Tm of both bLF and cLF was observed and reached a value of 39°C and 30°C, respectively. At pH 2.0-3.0, a partly unfolded structure of bLF and cLF was observed with a relatively low content of α-helix structure (3% and 7%, respectively), but still rich in β-structure (54% and 57%, respectively). A higher exposure of hydrophobic surfaces at low pH for bLF compared with cLF was proved by fluorescence studies. In conclusion, the structure of cLF was more affected by pH and showed lower temperature stability than bLF