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MpUL-multi: Software for Calculation of Amyloid Fibril Mass per Unit Length from TB-TEM Images
Matthew G Iadanza1, Matthew P Jackson1, Sheena E Radford1
1Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT. UK.
Abstract:
Structure determination for amyloid fibrils presents many challenges due to the high variability exhibited by fibrils and heterogeneous morphologies present, even in single samples. Mass per unit length (MPL) estimates can be used to differentiate amyloid fibril morphologies and provide orthogonal evidence for helical symmetry parameters determined by other methods. In addition, MPL data can provide insight on the arrangement of subunits in a fibril, especially for more complex fibrils assembled with multiple parallel copies of the asymmetric unit or multiple twisted protofilaments. By detecting only scattered electrons, which serve as a relative measure of total scattering, and therefore protein mass, dark field imaging gives an approximation of the total mass of protein present in any given length of fibril. When compared with a standard of known MPL, such as Tobacco Mosaic Virus (TMV), MPL of the fibrils in question can be determined. The program suite MpUL-multi was written for rapid semi-automated processing of TB-TEM dark field data acquired using this method. A graphical user interface allows for simple designation of fibrils and standards. A second program averages intensities from multiple TMV molecules for accurate standard determination, makes multiple measurements along a given fibril, and calculates the MPL.
Insights
Mass per unit length (MPL) analysis of amyloid fibrils using dark field imaging helps differentiate their structures. A new software tool, MpUL-multi, automates this process for faster, more accurate fibril characterization.
Area of Science:
- Structural biology
- Biophysics
- Materials science
Background:
- Amyloid fibril structure determination is challenging due to high variability and heterogeneous morphologies.
- Mass per unit length (MPL) offers a method to differentiate fibril morphologies and understand subunit arrangement.
- Dark field imaging detects scattered electrons, approximating protein mass along the fibril length.
Purpose of the Study:
- To present a novel semi-automated software suite, MpUL-multi, for processing dark field transmission electron microscopy (TB-TEM) data.
- To enable accurate determination of amyloid fibril Mass per unit length (MPL) using a standardized method.
- To provide a tool for differentiating fibril morphologies and characterizing complex fibril structures.
Main Methods:
- Utilized dark field transmission electron microscopy (TB-TEM) to acquire scattering electron data.
- Employed Tobacco Mosaic Virus (TMV) as a standard with a known Mass per unit length (MPL).
- Developed the MpUL-multi program suite with a graphical user interface for semi-automated data processing and analysis.
Main Results:
- The MpUL-multi software facilitates rapid, semi-automated processing of TB-TEM dark field data.
- Accurate standard determination by averaging intensities from multiple Tobacco Mosaic Virus (TMV) molecules.
- The method allows for multiple measurements along fibrils to calculate Mass per unit length (MPL) and differentiate morphologies.
Conclusions:
- Mass per unit length (MPL) estimation via dark field imaging provides valuable orthogonal data for amyloid fibril structure determination.
- The MpUL-multi software streamlines the analysis of TB-TEM data, improving efficiency and accuracy.
- This approach aids in understanding the assembly of complex amyloid fibrils and their structural diversity.
