Abstract
Nonlinear dielectric spectroscopy (NDS) is a non-invasive probe of cellular metabolic activity with potential application in the development of whole-cell biosensors. However, the mechanism of NDS interaction with metabolic membrane proteins is poorly understood, partly due to the inherent complexity of single cell organisms. Here we use the light-activated electron transport chain of spinach thylakoid membrane as a model system to study how NDS interacts with metabolic activity. We find protein modification, as opposed to membrane pump activity, to be the dominant source of NDS signal change in this system. Potential mechanisms for such protein modifications include reactive oxygen species generation and light-activated phosphorylation.
Highlights
IntroductionThe most commonly studied biosensors typically use purified enzymes and antibodies for detection
The most commonly studied biosensors typically use purified enzymes and antibodies for detection.While displaying a high degree of specificity, these assays have some drawbacks including unwantedBiosensors 2011, 1 sensitivity to experimental conditions, lengthy preparation time and high cost
The proton motive force and electron transport chain (ETC) can both be influenced by various inhibitors or uncouplers as well as chemicals which enhance the production of reactive oxygen species (ROS)
Summary
The most commonly studied biosensors typically use purified enzymes and antibodies for detection. Thylakoid membranes are similar to mitochondria and bacteria since all three use electron transport processes to generate a proton motive force [15] (essentially a voltage and/or proton gradient), but are much less complex. Another advantage of the thylakoid membrane system is the ETC is driven by photosynthesis and can be activated by light. The proton motive force and ETC can both be influenced by various inhibitors or uncouplers as well as chemicals which enhance the production of reactive oxygen species (ROS) These properties of the thylakoid membrane suspension allow a more detailed study of the mechanisms of metabolism that contributes to the nonlinear dielectric response
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