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Biomolecule displacement by Brownian step
- Gmachowski, Lech
- Colloids and surfaces 2019 v.568 pp. 99-104
- colloids, diffusivity, models
- Interactions in biological membranes cause the molecular mobility to behave specifically. The random walk of a molecule at short times is not described by the Einstein relation since the character of motion evolves from ballistic to diffusive. This phenomenon is detected because of the long length of the Brownian step which can be comparable to the size of the membrane confined domain and hence has a great influence on the diffusion coefficient in restricted areas and subsequent subdiffusive behavior in longer times. The experimental values of Brownian step length are analyzed. A model is formulated connecting the step length with the real-to-thermal speed ratio of the diffusing tagged molecule. A method is derived to estimate the diffusing biomolecule Brownian step length on the base of the measured diffusion coefficient divided by the thermal speed of tagged molecule. The method seems to be reasonable in a wide interval of diffusion coefficient.