antibody gold labeling - (Apr/17/2008 )

Hi, Does anyone have a protocol for gold labeling of antibodies. I have some antibodies that i would like to label with gold for a visual assay.

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Adjust the pH of the gold above the pI of the ab (say 8.5). Make sure the ab is in solution. You then have to do a protein isotherm vary mass of ab per ml of Au. The concentration of the Au and size (diameter) will determine the mass of ab to protect (coat) the gold particles. Ab should be low M buffer (lit says 2 mM borate...but you can go higher; low M will cause ab to fall out of solution).

After reaction (15 min...but it is immediate) add small vol of 10% NaCl or 10% CaCl to each tube. Where there is NO color change is the optimal for 'protection'.


in summary 1ml au particles (ph adjusted) ~~ 50 - 100 ul ab (low M buffer) 15 min; 100 ul salt solution.

You can repeat the step to optimize pH and repeat with ab mass.

NOTE: use glass tubes; proteins stick to plastic. Also, you can reduce mass of ab used by postcoating with another less expensive protein

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Cheers. would this be the same for Fab fragments? or is it more tricky.

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Use same procedure for F(ab')2 or any other proteins. Abs usually fall into about 20+ mg/ ml 20nM dia particles.
Good luck!

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