Eur. Phys. J. E (2009) 29: 173-182
https://doi.org/10.1140/epje/i2009-10465-y

Regular Article

Investigating the inner structure of irregular -lactoglobulin spherulites

¹ Department of Physics, The College of Wooster, 44691, Wooster, Ohio, USA
² Department of Physics, Slippery Rock University, 16057, Slippery Rock, PA, USA
³ Department of Physics, Westminster College, 16172, New Wilmington, PA, USA
⁴ Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK

^* e-mail: kdomike@wooster.edu

Received: 10 July 2008
Revised: 31 December 2008
Accepted: 23 April 2009
Published online: 19 June 2009

Abstract

When -lactoglobulin in low p H aqueous solutions is exposed to high temperature for extended time, spherulites composed of amyloid fibrils of the -lactoglobulin protein form. Many of these spherulites have fibrils that radiate out from a centre and, under crossed polarisers, exhibit a symmetric Maltese Cross structure. However, a significant fraction (50 of the 101 observed spherulites) of -lactoglobulin spherulites formed under these conditions demonstrate various forms of irregularity in apparent structure. The irregularities of spherulites structures were qualitatively investigated by comparing optical microscopy images observed under crossed polarisers to computationally produced images of various internal structures. In this way, inner spherulite structures are inferred from microscopy images. Modelled structures that were found to produce computed images similar to some of the experimentally viewed images include fibrils curving as they radiate from a single nucleation point; multiple spherulites nucleating in close proximity to one another; and fibrils curving in opposite directions above and below a single nucleation point.