TY - JOUR
T1 - Factors affecting the formation of insulin amyloid spherulites
AU - Smith, M I.
AU - Foderà, Vito
AU - Sharp, James S
AU - Roberts, Clive J
AU - Donald, Athene M
N1 - Copyright © 2011 Elsevier B.V. All rights reserved.
PY - 2012/1/1
Y1 - 2012/1/1
N2 - Thermally induced amyloid aggregation of bovine insulin can produce a number of distinct aggregate morphologies. In this work amyloid spherulites were analysed using cross polarized optical microscopy and light scattering. A new semi-quantitative methodology to estimate the balance of spherulites and free fibrils is reported and, from this analysis, the effects of pH, temperature, salt, and protein concentration on spherulite formation were quantitatively determined for the first time. The number and size of spherulites measured with polarized light microscopy were related to changes in the colloidal stability of the solution and fibril nucleation times (measured by static light scattering). Importantly, changes in pH between 1.75 and 2 were found to result in a dramatic decrease in the spherulite radii, which were related to differences in the conformational stability of the protein. Moreover, estimates of the final spherulite volume fraction clearly indicate that amyloid spherulite formation is the dominant pathway for insulin aggregation in HCl solutions at low pH and protein concentrations below ~5 mg ml(-1), with the balance shifting towards fibrils as the concentration increases.
AB - Thermally induced amyloid aggregation of bovine insulin can produce a number of distinct aggregate morphologies. In this work amyloid spherulites were analysed using cross polarized optical microscopy and light scattering. A new semi-quantitative methodology to estimate the balance of spherulites and free fibrils is reported and, from this analysis, the effects of pH, temperature, salt, and protein concentration on spherulite formation were quantitatively determined for the first time. The number and size of spherulites measured with polarized light microscopy were related to changes in the colloidal stability of the solution and fibril nucleation times (measured by static light scattering). Importantly, changes in pH between 1.75 and 2 were found to result in a dramatic decrease in the spherulite radii, which were related to differences in the conformational stability of the protein. Moreover, estimates of the final spherulite volume fraction clearly indicate that amyloid spherulite formation is the dominant pathway for insulin aggregation in HCl solutions at low pH and protein concentrations below ~5 mg ml(-1), with the balance shifting towards fibrils as the concentration increases.
U2 - 10.1016/j.colsurfb.2011.09.018
DO - 10.1016/j.colsurfb.2011.09.018
M3 - Journal article
C2 - 21982213
SN - 0927-7765
VL - 89
SP - 216
EP - 222
JO - Colloids and Surfaces B: Biointerfaces
JF - Colloids and Surfaces B: Biointerfaces
ER -