Application and use of differential scanning calorimetry in studies of thermal fluctuation associated with amyloid fibril formation

The aggregation of proteins into amyloid fibrils is a topic that has attracted great interest because the process is associated with the pathology of numerous human diseases. Despite considerable progress in the elucidation of the structure of amyloid fibrils and the kinetic mechanism of their formation, knowledge on the thermodynamic aspects underlying the formation and stability of amyloid fibrils is limited. In this review, we summarize recent calorimetric studies of amyloid fibril formation, with the goal of obtaining a better understanding of the causal factors that thermally induce proteins to aggregate into amyloid fibrils. Calorimetric data show that differential scanning calorimetry is a useful technique to study the causative factors that thermally trigger the conversion to the amyloid structure and highlight the physics related to the thermal fluctuation of proteins during this conversion.     

Detection of immunologically related Kunitz and Bowman-Birk proteinase inhibitors expressed during potato tuber development

Antiserum against a potato Kunitz-type proteinase inhibitor (PKPI) expressed in Escherichia coli was produced. In immunoblotting assays of proteins from potato tubers cultured in vitro, three proteins reacted to the antiserum, two of 20 kDa and one of 10 kDa. Their N-termini were sequenced. While the 20 kDa proteins showed 59 and 90% identity to PKPI, the 10 kDa one had 65% identity to soybean C-II proteinase inhibitor. Characterization of the temporal expression of these proteins showed that both could be detected from 10 days after induction of tuberization (DAI) in vitro, but the times when maximum amounts of PKPI and 10 kDa protein could be detected were different, corresponding to 22 and 32 DAI, respectively. The amounts of these proteins decreased in the following stages, and no positive reaction of the antiserum with mature tuber proteins could be found. The 20 kDa proteins were also detected in early stages of development of potato tubers grown in the field, indicating that these proteins are expressed during normal tuber development, and differ from the PKPIs reported previously.