The formation of highly ordered fibrils for the human
islet amyloid polypeptide (hIAPP) is considered as one of the precipitating factors of
type 2 diabetes mellitus. In this study, an emerging new approach microscale thermophoresis and conventional ThT fluorescence assay were utilized to investigate the aggregation behavior of hIAPP(11-20), giving a new insight of the
solvent effect on the aggregation of hIAPP(11-20). hIAPP(11-20) displayed different aggregation behaviors in various
buffers, revealing that hIAPP(11-20) not only self-aggregates but also binds to
solvent components. hIAPP(11-20) had a higher binding affinity for Tris than other selected
buffers because multiple hydrogen bonds form, resulting in weaker self-aggregation of hIAPP(11-20) at the early stage of aggregation and prolonging the fibril formation process. hIAPP(11-20) displayed similar self-aggregation in both
HEPES and pure water. Negatively charged
phosphate ions in the PBS
solution 'neutralize' the charges carried by hIAPP(11-20) itself to some extent, causing rapid aggregation of hIAPP(11-20), and leading to a shorter fibrillation process of hIAPP(11-20). These results revealed that
solvents contribute to the aggregation of hIAPP(11-20) and demonstrated the affect of
solvents on the activity of biomolecules. Additionally, as a new technique, microscale thermophoresis offers a powerful and promising approach to study the early stages of aggregation of
peptides or
proteins.