Diffusion coefficient of dextran (40kDa) in Drosophila cytoplasm

Value 17.6 µm^2/s Range: ±1.8 µm^2/s
Organism Fruit fly Drosophila melanogaster
Reference Gregor T, Bialek W, de Ruyter van Steveninck RR, Tank DW, Wieschaus EF. Diffusion and scaling during early embryonic pattern formation. Proc Natl Acad Sci U S A. 2005 Dec 20 102(51):18403-7. p.18405 tables 1 & 2PubMed ID16352710
Method Fluorescent dextran injected into Drosophila embryo, confocal imaging, and fitting with 3D diffusion model
Comments P.18405 left column 2nd paragraph: "If random molecular movement is due to Brownian motion (passive diffusion), then it is governed by the Stokes–Einstein relationship: diffusion coefficients decrease inversely with increasing molecular radius. To test this relationship, [investigators] measured diffusion constants for dextran molecules of four different nominal molecular masses (Table 1)." P.18405 left column bottom paragraph: "Although Bcd is conserved across >100 million years of dipteran evolution (refs 17), the eggs of closely related species vary over at least a factor of five in length (Table 2)." P.18406 left column bottom paragraph: "Mechanisms of Scaling. How is scaling of the Bicoid gradient achieved? In the simplest model, the length constant λ =(Dτ)^0.5, where τ is the protein lifetime (see Methods). The active contribution to the effective diffusion constant D that [investigators] have identified above raises the possibility that total effective diffusive transport itself can be adjusted across species. To test this possibility, [they] injected 40-kDa dextran molecules into eggs of D. busckii, L. sericata, and Calliphora vicina. Table 2 shows a summary of [their] results: the diffusion constants in the different species vary only slightly. There is a tendency for increased diffusivity and decreased variability with increasing egg length, but the increase does not scale with egg size."(N=20). See BNID 100193
Entered by Lea Goentoro
ID 100198