12/4/96

Two recent postings have implied colloidal gold probes have a relatively

short half life. Could people comment on how long their probes are stable

and how they store them. TIA

Thomas E. Phillips, Ph.D.

Associate Professor of Biological Sciences

Director, Molecular Cytology Core Facility

3 Tucker Hall

University of Missouri

Columbia, MO 65211

(573)-882-4712 (voice)

(573)-882-0123 (fax)

tphillips@biosci.mbp.missouri.edu

Shelf life depends on the protein conjugated to the gold and the batch. We

use IgG conjugates for 6 months or more storing them at 4 C. I have used

protein A conjugates that were a year and a half old. Other times they have

gone bad much more quickly. It is always best to have a positive control

for activity of the gold if it has been several weeks since the last use.

If the gold is in a glycerol solution it can be frozen to extend its useful

life.

G.W. Erdos, Ph.D. Phone: 352-392-1295

Scientific Director,

ICBR Electron Microscopy Core Lab

218 Carr Hall Fax: 352-846-0251

University of Florida E-mail: gwe@biotech.ufl.edu

Gainesville, FL 32611 http://www.biotech.ufl.edu/~emcl/

Three months tops for me, stored in the original container at 4C,

regardless of supplier. Definitely weaker after 6 weeks. (I've tried

Amersham, E-Y Labs, Chemicon, Biocell--Chemicon gets my vote for the best

buy.)

kennedy@nsi.edu

Grace Kennedy

Hey folks --

We use gold probes from Jackson exclusivly. Stored at 4C, we get

excellent results for at least one year -- I have one batch of anti-HRP

gold that is three years old and still works fine (by eye). I have not

done a quantitative analysis on decrease in labeling over time. We also

see a batch-to-batch variation in shelf life.

Greg Martin

Dept. of Cell Biology and Anatomy

Johns Hopkins School of Medicine

gmartin@welchlink.welch.jhu.edu

Tom -

At Goldmark we sell the gold conjugates and stains produced by

BBInternational known as British BioCell International in Europe and the

rest of the world. The standard gold probe formulation for electron

microscopy, light microscopy, and blotting grades is made up in glycerol.

These can be frozen and essentially the shelf life is indefinite. Some have

lasted for 5 to 6 years. A non-glycerol formulation is also available and

usually provides a life of 12 - 18 months, but the latter number is about

the maximum in my experience.

Our colloidal 1nm gold probes, however, are not freezable and usually

provide a 12 month life.

Hope this helps.

Don Cox

Donald P. Cox, Ph.D., M.B.A.

GOLDMARK BIOLOGICALS/D.P. COX ASSOCIATES

437 Lock Street, Phillipsburg, NJ 08865-2764

(908) 859-2631 - - (908) 859-2875-FAX

E-Mail: goldmrkr@fast.net/goldmarker@aol.com

Web Page: http://members.aol.com/goldmarker

~~~"Goldmarking is everlasting probing!"~~~

I buy all my conjugate antibodies by Aurion ( sold by EMS in the USA)

and I am really satisfied with. Aurion is a small compagny managed by

Dr. Jan Leunissen. Many of you may know him through the books that he

has written on Immunogold, and the courses that he teaches on the

subject.Aurion Immunogold reagents have a guaranteed shelf life of 18

months from the date of the quality control analysis.

Jan Leunissen, Ph.D.

AURION ImmunoGold Reagents & Accessories

Costerweg 5, 6702 AA Wageningen

The Netherlands

phone (31)-317-497676

fax (31)-317-415955

There has been much talk about "shelf life" of colloidal gold probes but little

explanation of how this is evaluated.

We use protein A, and other protein-gold congujates for many different

applications. For us, shelf life is determined by the final labeling efficiency

i.e. is the signal the same as when we first made/purchased the probe?

As far as I know there are no published stereological studies on the labeling

efficiency of gold probes over time. However, from experience I know that if we

try to label biotinylated cells with streptavidin-gold that is more than 5 days

old, we get no signal.

(Commercial produces of this probe need not worry because most applications

involve detection of biotinylated antibodies followed by silver intensification,

both producing colossal amplifications of the signal.)

In contrast, although I have been told on numerous occasions that protein A-gold

has a shelf life of between 3 months to a year, I have used probes that are more

than 6 years old and seen qualitative results similar to those produced using

fresh probes. Unfortunately, other protein A-gold preparations have not aged so

well.

For us there seem to have been little difference between storing the probes

frozen in glycerol or in a 'fridge in the presence of azide. However (more

dogma) I have been advised that freezing in glycerol will produce small

aggregates of 2-3 particles. Again this is not something we have noticed.

From what is published it seems fair to conclude that the stability of a

particular probe depends on the protein used to stabilize the colloid and on the

amount of protein used. If these variables can be compared and correlated with

labeling efficiency then it is worth sharing this data.

Posting opinions only serves to add further support to dogma.

Best regards,

Paul Webster, Ph.D

Center for Cell Imaging

Yale School of Medicine

http://info.med.yale.edu/cellimg

paul.webster@Yale.edu

[Return to Tips & Tricks Menu]