Custom Labeling and Custom Synthesis

Looking for something special?

Our researchers will be happy to discuss your requirements for a custom synthesis. Let us know your needs by using our custom synthesis form, email us at, or give us a call at 631-205-9490 (US toll-free: 877-447-6266).


General Information

We are currently able to offer custom labeling with Nanogold® or colloidal gold-labeled antibodies. Nanogold® labeling is restricted to the preparation of labeled Fab; fragments from F(ab')2 fragments, or the labeling of IgG molecules. While we will be glad to consider other requests, our time and resource to undertake such syntheses are limited. Please be advised also that new syntheses frequently require much more work than anticipated, and if a similar procedure has not been demonstrated before, may be better handled as a contract research project or collaboration.

Before requesting a custom synthesis quotation, we recommend that you consider our labeling reagents, which you may use to label a wide variety of molecules. Monomaleimido-Nanogold® reacts slectively with thiols (such as cysteines); Mono-Sulfo-NHS-Nanogold® labels primary alihatic amines (N-terminal or lysine residues) while Monoamino-Nanogold®M can be used with a variety of homo- or heterobifunctional cross-linkers, or directly to label RNA or glycoproteins.




Because the gold cluster labels developed by Nanoprobes, Inc. are attached by covalent cross-linking, they may be used to label almost any molecule with a suitably reactive functionality. We have already conjugated our probes to proteins, lectins, peptides, lipids, biotin and cytoskeletally active probes such as modified phalloidins. Although we are currently only able to complete custom syntheses of Nanogold® or colloidal gold-labeled antibodies, we are pleased to advise on the use of our labeling reagents to label other molecules.

Please let us know your needs; you can use our online custom synthesis form, or drop us a line by phone, fax or email. Since our researchers are not necessarily familiar with your particular probe or application, we can often provide quotations and suggestions much more quickly if you provide some key information.

The following data are particularly useful:

  1. Molecular weight: All our labeling reactions use specific molar ratios of gold to probe. We need the molecular weight to calculate how much gold labeling reeagent we will need, how much of the probe we will need to use for labeling, and also which product isolation protocol to use.
  2. Optical density or UV/visible absorption data: The extinction coefficients of undecagold, Nanogold® and FluoroNanogold at specific wavelengths have been accurately determined, and these values allow us to determine how successfully your probe has been labeled. If you supply or refer us to specific values for your probe, we can provide you with the exact ratio of gold cluster label to probe in the product.
  3. Molecular structure and functional groups: Ideally, targeted biomolecules should be labeled at a unique reactive group, remote from the substrate binding region, and we try to identify suitable sites for labeling, such as a unique thiol or a terminal primary amine. Some idea of the overall structure of your molecule and which regions are thought to bind to the target would be very helpful in selecting a labeling site. Thiols, primary amines, carboxylates and aldehydes may all be labeled. Labeling through hydroxyls or cis-1,2-dihydroxy groups is also possible; other groups may require extensive synthetic modification which will increase the cost and synthesis time considerably.
  4. References for labeling with other tags: We can often obtain a good idea about which labeling approaches might work from related literature articles. A paper which describes a successful labeling with a fluorophore, for example, is a good starting point for evaluating potential gold-labeling strategies, because our gold labels are conjugated using similar cross-linking reactions and have similar site requirements. Data on properties such as solubility and compatibility with various solvents is also useful, because small molecules can sometimes alter the solubility properties of gold clusters significantly. Knowing an alternative solvent beforehand saves time spent solubility testing later.

Terms and Conditions for custom labeling and custom synthesis.


To inquire about a custom synthesis

Our researchers will be happy to discuss your requirements for a custom synthesis. Let us know your needs by using our custom synthesis form, email us at, or give us a call at 631-205-9490 (US toll-free: 877-447-6266).


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