Abstract
To unravel the underlying principles of membrane adaptation in small systems like bacterial cells, robust approaches to characterize membrane fluidity are needed. Currently available relevant methods require advanced instrumentation and are not suitable for high‐throughput settings needed to elucidate the biochemical pathways involved in adaptation. We developed a fast, robust, and financially accessible quantitative method to measure the microviscosity of lipid membranes in bulk suspension using a commercially available plate reader. Our approach, which is suitable for high‐throughput screening, is based on the simultaneous measurements of absorbance and fluorescence emission of a viscosity‐sensitive fluorescent dye, 9‐(2,2‐dicyanovinyl)julolidine (DCVJ), incorporated into a lipid membrane. We validated our method using artificial membranes with various lipid compositions over a range of temperatures and observed values that were in good agreement with previously published results. Using our approach, we were able to detect a lipid phase transition in the ruminant pathogen Mycoplasma mycoides.
Highlights
Viscosity is a crucial physical property of living membranes that is tightly regulated though homeostatic adaptation to environmental and physiological challenges.[1,2,3,4,5,6,7]
Measuring viscosity is important for investigating the mechanisms involved in membrane adaptation and to constrain the range of membrane properties that can support life
We developed a method to estimate membrane viscosity by measuring the relative brightness of a viscosity-sensitive fluorescence dye using a simple plate reader capable of simultaneously measuring absorbance and fluorescence emission
Summary
Viscosity is a crucial physical property of living membranes that is tightly regulated though homeostatic adaptation to environmental and physiological challenges.[1,2,3,4,5,6,7] Measuring viscosity is important for investigating the mechanisms involved in membrane adaptation and to constrain the range of membrane properties that can support life. There are no highthroughput or broadly accessible methods to measure viscosity in bacterial cells or submicron scale synthetic membrane systems. Existing methods for measuring membrane viscosity are relatively low-throughput or require specialized instrumentation not available to many laboratories. Fluorescence correlation spectroscopy (FCS) can provide estimates of diffusivity of a molecular probe.[8,9] FCS, requires a relatively specialized microscopy setup, and measuring diffusion in [b] Dr E. Petrov+ Faculty of Physics, Ludwig Maximilian University of Munich Geschwister-Scholl-Platz 1, 80539 Munich (Germany)
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