Dean, W. F.; Nawara, T. J.; Albert, R. M.; Mattheyses, A.

Most essential cellular functions are performed by proteins assembled into larger complexes. Fluorescence Polarization Microscopy (FPM) is a powerful technique that goes beyond traditional imaging methods by allowing researchers to measure not only the localization of proteins within cells, but also their orientation or alignment within complexes or cellular structures. FPM can be easily integrated into standard widefield microscopes with the addition of a polarization modulator. However, the extensive image processing and analysis required to interpret the data have limited its widespread adoption. To overcome these challenges and enhance accessibility, we introduce OOPS (Object-Oriented Polarization Software), a MATLAB-based analysis tool tailored for FPM data. This work highlights the distinctive features of our software, which empower researchers to efficiently manage large datasets; detect and analyze individual structures; conduct population assessments based on morphology, intensity, and polarization-specific parameters; and create publication-quality visualizations, all within a user-friendly graphical interface. Importantly, OOPS is adaptable to various sample types, labeling techniques, and imaging setups, facilitating in-depth analysis of diverse polarization-sensitive samples. Here, we demonstrate the power and versatility of our approach by applying OOPS to FPM images of both punctate and filamentous structures. OOPS is freely available under the GNU GPL 3.0 license and can be downloaded at https://github.com/Mattheyses-Lab/OOPS.