Hi Patricia,

perhaps these papers are helpful to you:

http://www.pnas.org/content/90/9/3835.full.pdf

and

http://geo1.tcu.edu/annunziata/2005_lang_01.pdf

In addition to that - have a look on this page: http://www.life.illinois.edu/crofts/bioph354/diffusion1.html

Perhaps you could just assume the diffusion coefficient as something like 10^-6 cm^2 s^-1?

I hope this helps.

Best regards,

Alex

Hi,

No idea what are you talking about,  but just a BCC mail to EVERYone on the attached list might help! 

Also a lot more research groups are out there as you may contact members directly.

Regards,

SM

http://www.inrf.uci.edu/mf3/academicPartners.htm

http://en.wikipedia.org/wiki/List_of_microfluidics_research_groups#North_America

Dear Patricia,

Salam,

I think Dr Mehdi Hedayati may could help you in this case. He is the head of biochemistry laboratory at Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences. He is a knowledgeable scientist in the field of biochemistry. You can find him in ResearchGate. No hesitate to contact me if I could help you more.

Hi Patricia,

If the proteins/macromolecules are suspended in a liquid, you can find the bulk diffusion coefficient using dynamic light scattering (DLS).

Navid 

Hi dear, I hope you are fine.

I have no specialty in this matter. But maybe this article will help you:

https://www.researchgate.net/publication/23436148_Diffusion_coefficient_measurements_in_microfluidic_devices

Also, I found a book chapter about it but it is not free:

http://link.springer.com/chapter/10.1007%2F978-94-011-5286-0_46

Take care

Article Diffusion coefficient measurements in microfluidic devices

Hello,

if the concentration of ur protein /macromolecule is large enough, then you can use gradient field NMR, there is an experiment called DOSY, if u have a Bruker NMR equipped with a gradeint probe it's done easily, a probe with z-gradient is more than enough. however, if the concentration is very low, or the structure is very complicated to code/decode certain peaks u can go to DLS, but I've never used it for macromolecules before and it is not sensitive to ur molecules (it measure whatever particles u have in fluid and for complex samples u can't differentiate between them)

Hi Patricia,

A common way to measure diffusion coefficient of macromolecules using microfluidics systems is: label your macromolecule with a fluorescent probe. In this context, proteins can be labeled with FITC, which is fluorescent in green.

Then you can use your microfluidic system to generate a gradient and study by fluorescence microscopy how your molecule diffuses. Normally, you can generate a gradient using parallel flow of one control liquid and other liquid containing your fluorescent macromolecule. Using hydrogels you can also determine the diffusion coefficient, but in this case it would be the diffusion coefficient in the hydrogel.

In this paper they calculate the diffusion coefficient for two chemokines within a collagen hydrogel using microfluidics systems.

http://www.ncbi.nlm.nih.gov/pubmed/21422278 

Hi,

An alternative to Jose's suggestion is calculating the diffusion coefficient using particle tracking methods. The paper below describes a tracking method applicable to nanoparticles:

Marki etal 2014. Biomech Model Mechanobiol, doi 10.1007/s10237-013-0499-7

Dynamic Light Scattering (DLS) you can use

The problem is I want to design the length of my channels in the microfluidic based on the diffusion coefficient of the proteins .... So I was wondering whether there is other way (instead of calculating the variable in a microfluidic) to calculated these variables before developing the test

Hi Patricia,

perhaps these papers are helpful to you:

http://www.pnas.org/content/90/9/3835.full.pdf

and

http://geo1.tcu.edu/annunziata/2005_lang_01.pdf

In addition to that - have a look on this page: http://www.life.illinois.edu/crofts/bioph354/diffusion1.html

Perhaps you could just assume the diffusion coefficient as something like 10^-6 cm^2 s^-1?

I hope this helps.

Best regards,

Alex

Dear Alex

Tanx for the useful links .... I was wondering does the 10^-6 cm^2 s^-1 depends on the size of the protein ???!!!

Hi Patricia,

yes, the diffusion coefficient depends on the size and on the shape of the protein.This nice table which gives you an overview:

http://www.math.utah.edu/~keener/classes/math5120/homework/homework1.pdf

Best regards, Alex

Hii,,,,

I think you want to design a Micromixer. In that case, you can use the diffusion coefficient of 10^-6 cm^2 s^-1 (typical value of protein in aqueous solution).

IS there any reference based on which I could put the 10^-6 cm^2 s^-1 in my calculations?

Please, find the following Reference paper published in Lab on a Chip:

I. Glasgow and N. Aubry, Enhancement of Microfluidic mixing using time pulsing, Lab chip,2003,3,114-120.

You could perform single molecule mobility observations using particle tracking procedures, or perform Fluorescence Correlation Spectroscopy analysis; bot things you can do in situ, and account for microchannel wall-protein interactions,  microchannel confinement on lateral mobility. 

Hello Denis,

Can you please specifically give the reference link for  Eq. 

Mw (kDa) = 1.68 * Rh (nm)^2.3398 (sphere)?  Thanks  a lot.