Individual macromolecule motion in a crowded living cell

Area of Science:

• Biophysics
• Biochemistry
• Cellular Biology

Background:

• Single-molecule studies in dilute solutions are well-described by mass action law and dynamic equilibria.
• Living cells exhibit anomalous diffusion, a phenomenon not accounted for by traditional models.
• Crowded cellular environments pose challenges for accurate biophysical and biochemical analysis.

Purpose of the Study:

• To highlight the limitations of normal diffusion models in cellular environments.
• To emphasize the necessity of anomalous diffusion models for accurate single-molecule analysis in cells.
• To discuss current challenges in applying single-molecule techniques within living cells.

Main Methods:

• Analysis of fluorescence correlation spectroscopy (FCS) and dual color fluorescence cross-correlation spectroscopy (FCCS) data.
• Application of equations based on anomalous subdiffusion.
• Comparison with traditional normal diffusion models.

Main Results:

• Normal diffusion models applied to cellular data yield artifacts in fitted parameters and interpretations.
• Equations based on anomalous subdiffusion provide accurate analysis of FCS and FCCS data in crowded cells.
• Normal diffusion equations are invalid and lead to misinterpretations in living cells.

Conclusions:

• Anomalous diffusion models are crucial for accurate single-molecule biophysics and biochemistry in cellular systems.
• The use of normal diffusion models in living cells leads to significant errors.
• Further research is needed to overcome obstacles hindering single-molecule applications in cellular environments.