Scaling Concepts in Serpin Polymer Physics

• Main Authors: Samuele Raccosta, Fabio Librizzi, Alistair M. Jagger, Rosina Noto, Vincenzo Martorana, David A. Lomas, James A. Irving, Mauro Manno
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Materials
• Subjects: serpins; serpin polymers; atomic force microscopy; dynamic light scattering; conformational disease; polymer theory
• Online Access: https://www.mdpi.com/1996-1944/14/10/2577

<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>α</mi><mn>1</mn></msub></semantics></math></inline-formula>-Antitrypsin is a protease inhibitor belonging to the serpin family. Serpin polymerisation is at the core of a class of genetic conformational diseases called serpinopathies. These polymers are known to be unbranched, flexible, and heterogeneous in size with a beads-on-a-string appearance viewed by negative stain electron microscopy. Here, we use atomic force microscopy and time-lapse dynamic light scattering to measure polymer size and shape for wild-type (M) and Glu342→Lys (Z) <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>α</mi><mn>1</mn></msub></semantics></math></inline-formula>-antitrypsin, the most common variant that leads to severe pathological deficiency. Our data for small polymers deposited onto mica and in solution reveal a power law relation between the polymer size, namely the end-to-end distance or the hydrodynamic radius, and the polymer mass, proportional to the contour length. We use the scaling concepts of polymer physics to assess that <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>α</mi><mn>1</mn></msub></semantics></math></inline-formula>-antitrypsin polymers are random linear chains with a low persistence length.