The glass transition and sub-Tg-relaxation in pharmaceutical powders and dried proteins by thermally stimulated current

Document Type

Article

Publication Date

1-1-2009

Abstract

The main goal of the study was to evaluate the applicability of thermally stimulated current (TSC) as a measure of molecular mobility in dried globular proteins. Three proteins, porcine somatotropin, bovine serum albumin, and immunoglobulin, as well as materials with a strong calorimetric glass transition (Tg), that is, indomethacin and poly(vinypyrrolidone) (PVP), were studied by both TSC and differential scanning calorimetry (DSC). Protein/sugar colyophilized mixtures were also studied by DSC, to estimate calorimetric T g for proteins using extrapolation procedure. In the majority of cases, TSC detected relaxation events that were not observed by DSC. For example, a sub-Tg TSC event (beta-relaxation) was observed for PVP at approximately 120°C, which was not detected by the DSC. Similarly, DSC did not detect events in any of the three proteins below the thermal denaturation temperature whereas a dipole relaxation was detected by TSC in the range of 90-140°C depending on the protein studied. The TSC signal in proteins was tentatively assigned as localized mobility of protein segments, which is different from a large-scale cooperative motions usually associated with calorimetric Tg. TSC is a promising method to study the molecular mobility in proteins and other materials with weak calorimetric Tg. © 2008 Wiley-Liss, Inc.

Identifier

58149218167 (Scopus)

Publication Title

Journal of Pharmaceutical Sciences

External Full Text Location

https://doi.org/10.1002/jps.21397

e-ISSN

15206017

ISSN

00223549

First Page

81

Last Page

93

Issue

1

Volume

98

This document is currently not available here.

Share

COinS