Thermodynamic Analysis of Proteins Adsorbed on Silica Particles: Electrostatic Effects

✍ Scribed by Helén Larsericsdotter; Sven Oscarsson; Jos Buijs

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 70 KB
• Volume: 237
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.2001.7485

✦ Synopsis

Electrostatic effects on protein adsorption were investigated using differential scanning calorimetry (DSC) and adsorption isotherms. The thermal denaturation of lysozyme, ribonuclease A (RNase), and α-lactalbumin in solution and adsorbed onto silica nanoparticles was examined at three concentrations of cations: 10 and 100 mM of sodium and 100 mM of sodium to which 10 mM of calcium was added. The parameters investigated were the denaturation enthalpy ( H), the temperature at which the denaturation transition was half-completed (T m ), and the temperature range of the denaturation transition.

For lysozyme and RNase, adsorption isotherms depend strongly on the ionic strength. At low ionic strength both proteins have a high affinity for the silica particles and adsorption is accompanied by a 15-25% reduction in H and a 3-6 • C decrease in T m , indicating that the adsorbed state of the proteins is destabilized. Also, an increase in the width of the denaturation transition is observed, signifying a larger conformational heterogeneity of the surface bound proteins. At higher ionic strengths, both with and without the addition of calcium, no significant adsorption-induced alteration in H was observed for all three proteins. The addition of calcium, however, decreases the width of the denaturation transition for lysozyme and RNase in the adsorbed state.