The gold conjugates are made to the highest standards and specifications, yielding excellent results when correctly used. All gold conjugates are supplied in one of the two buffers listed below. Buffer constituents dictate the shelf life and storage conditions for the individual conjugates.
Gold conjugates for electron microscopy (EM) are supplied in the following buffer: 20mM Tris (tris-hydroxymethyl-aminomethane); 20mM sodium azide; 154mM NaCl; 1% BSA; 20% glycerol; pH 8.2.
Recipe to make 100ml: 0.242g (20mM) Tris + 0.9g (154mM) NaCl + ultrapure water to make 100ml. Adjust pH from 7.2 to 8.2 with 1N HCl or 1N NaOH.
Storage: Stable for 1 year at 4°C; stability for 2+ years at –20°C. The conjugates demonstrate remarkable stability at ambient temperatures for up to 7 days. Repeat freezing and thawing is not recommended.
Gold conjugates for lateral flow applications are supplied in the following buffer: 2mM sodium tetraborate at pH 8.2 containing 0.095% sodium azide.
Storage: Stable for 1-2 years at 4-8°C. DO NOT FREEZE. The conjugates demonstrate remarkable stability at ambient temperatures for up to 7 days.
Each gold conjugate has a technical data sheet which indicates the following information: 1) Number of particles counted; 2) Mean particle diameter; 3) Coefficient of variation given as a percent; 4) Percent of single particles; 5) Percent of particles larger than triplets; and 6) Minimum detectable protein. The coefficient of variation is an important parameter in describing the relative distribution of gold particle sizes around the mean for a given batch. The coefficient of variation equals the standard deviation divided by the mean.
Normal Gaussian distributions work as follows: ±1 standard deviation describes 68% of the area under the curve; ± 2 standard deviations describe 95% of the area under the curve; ± 3 standard deviations describe 99.73% of the area under the curve. As an example, you have purchased a gold conjugate - Goat anti-Rabbit IgG (H+L), 10nm - having a mean particle diameter of 9.8nm with a coefficient of variation of 4.1%. First, the standard deviation needs to be determined. In this case it is 0.402nm (4.1% x mean particle diameter). Statistically, 68% of the particles will be from 9.40 to 10.20nm, 95% from 9.00 to 10.60nm and 99.73% from 8.60 to 11.00nm. A reliable size characterization has been determined for the batch.
Link to mean recommended working dilutions and technical information.