Lyophilized globular proteins under rapid heating: High thermal stability and properties of the resulting material

Abstract

A notable feature of globular proteins is their relatively poor thermostability. Water, while being important in maintaining the native protein structure, participates in many thermal degradation processes either directly (hydrolysis, deamidation) or indirectly by enhancing the mobility of protein molecules. It has been long known that reducing hydration enhances the thermal stability of proteins. However, the temperature stability of essentially dry proteins is unexplored because the traditional means of heating cause the charring of proteins. Fast Scanning Calorimetry (FSC) is a technique that allows rapid heating and cooling of micrometer-size samples. It was previously used to determine the melting point of silk fibroin. Here we demonstrate that under rapid heating, the dried powders of globular proteins remain stable up to ca. 200 °C. Further heating produces a glass-like material without charring. The glass transition temperature of the produced material is above 200 °C. The results may be of potential interest for additive manufacturing of biocompatible products.