Worm Breeder's Gazette 8(1): 54

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Technical Note

F. Pavalko, T. Roberts

Use of Colloidal Gold Particles in 
We have been using a simple and inexpensive procedure to produce 
colloidal gold particles of a uniform size (5 nm) which can be 
conjugated directly to proteins.  Gold particles serve as excellent 
electron dense markers for use in electron microscopy.
Preparation of Colloidal Gold Particles by 
1.  Dilute 0.1 ml of 1% gold chloride [ H(AuCl4) ] in 50 ml dH20.
2.  Make solution neutral with 0.2M K2CO3.
3.  Immediately before sonication, add 0.5 ml of 100% ethanol as a 
4.  Carry out sonication at 20 Kc and 125 W by immersing a flat-end 
probe approximately 1 cm under the surface of the gold solution.
5.  After about 2-5 min, the solution attains a pinkish color with 
maximum intensity at A = 520 nm.
Note: To prevent the solution from heating up during sonication, 
keep it cool in an ice water bath.  This helps prevent the formation 
of larger gold particles.  Store at 4 C.
Preparation of Gold Labelled 
1.  Mix 1mg of purified protein with 5ml of colloidal gold solution 
and incubate for 15 min at room temperature with mixing.
2.  Add 10mg BSA, mix, and incubate for another 5 min to prevent 
aggregation of gold-protein complexes.
3.  Add NaCl (100g/l) to make a final concentration of 10g/l.
4.  Centrifuge at 1700 g for 20 min to remove excess BSA.
5.  Centrifuge supernatant from step 4 at 60,000 g for 15 min to 
bring down gold labelled protein, leaving unlabelled protein in the 
6.  Pellet should be a loosely packed, dense red sediment and can be 
resuspended in 0.5 to 1.0 ml of desired buffer.  Use undiluted.