Overview Topics

Diffusion of Molecules:

Molecule Type

Molecular weight

Diffusion Coefficient

Effective Diffusivity

Ref

Amyloid-Beta

3-4 kD

5 x 10 7 cm2/s = 3000 microns2 / min

1500 microns2 / min

Goodhill (97)

IL-1 beta

17 kD

3 x 10 7 cm2/s = 1800 microns2 / min

900 microns2 / min

Goodhill (97)

IL-6

26 kD

2.7 x 10 7 cm2/s = 1620 microns2 / min

810 microns2 / min

Goodhill (97); Moghe et al (95)

TGF-Beta

25 kD

 2.6 x 10 7 cm2/s =

1560 microns2 / min

780 microns2 / min

 Brown (99)

TNF-alpha

17 kD

3 x 10 7 cm2/s = 1800 microns2 / min

900 microns2 / min

 



The diffusion coefficient scales approximately as the inverse of the cube root of the molecular weight. A molecule of mw 0.3-0.5 kDa has a diffusion coefficient of approximately 10 6 cm2/s . We also use the fact that 10 7 cm2/s = 600 microns2 / min.

[1] Goodhill G J (1998) Mathematical Guidance for axons, Trends Neurosci 21, 226-231. Abstract

[2] Goodhill J G (1997) Diffusion in axon guidance, Eur J Neurosci 9: 1414-1412.Abstract



02/17/00 Update:

We have recently become aware of the correction factor that needs to be incorporated in the above calculations due to the tortuosity of the neuronal extracellular space. The effective diffusion coefficients cited above are calculated using the references provided by E. Sykova, for example:

[3] Sykova E (1997) The extracellular space in the CNS: Its regulation, volume, and geometry in normal and pathological neuronal function, The Neuroscientist 3(1): 28-41.Abstract

[4] Mazel T, Simonova Z, Sykova E (1998) Diffusion heterogeneity and anisotripy in rat hippocampus, NeuroReport 9: 1299-1304. Abstract

[5] Sykova E, T Mazel, Z Simonova (1998) Diffusion constraints and neuron-glia interaction during aging Experimental Gerontology 33 (7/8) : 837-851. Abstract

[6] Nicholson C, Sykova E (1998) Extracellular space structure revealed by diffusion analysis TINS 21 (5) : 207-215.Abstract

See also more information at the Sykova Lab Home page.


Information about molecular weights and other attributes of of cytokines were obtained from the site :

[7] Signaling Pathway mediated by IL-6 and IL-1, The Signaling PAthway Database (SPAD), Molecular Gene Technics, Kyushu University, Japan

 

 



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