Nanogold® Labeling Reagents
Nanogold® is a better gold label. The 1.4 nm Nanogold® particle is a gold compound: it is not just adsorbed to proteins, like colloidal gold, but covalently reacts at specific sites under mild buffer conditions. This gives a well defined product that can be purified chromatographically.
Nanogold® brings the versatility of fluorescent conjugation to gold labeling. It may be used to label any molecule with a suitable reactive group: oligonucleotides, lipids, peptides, proteins, enzyme inhibitors and others, unlike colloidal gold which may be adsorbed only to antibodies and a limited range of proteins and peptides. Nanogold® is small and highly uniform in size, in sharp contrast to small colloidal gold preparations (most commonly used "1 nm" golds actually range from 1 to 3 nm). Nanogold® is available both as a labeling reagent for labeling your own biomolecules and in a range of antibody IgG, Fab' and streptavidin conjugates.
Although 1.4 nm Nanogold® is smaller than most other EM probes, it can easily be enhanced with silver (LI Silver or HQ Silver) by brief exposure (1 - 5 min.) to produce highly visible grains 2-20 nm in size (depending on development time). Further development (8-25 min.) gives a black signal easily seen in the light microscope and on immunoblots, polyacrylamide gels and Western blots.
Nanogold® labeling reagents are now available in three different packages: 30 nmol for larger labeling experiments, 5 X 6 nmol for several smaller labeling experiments, or in single 6 nmol vials so you can try these reagents on a smaller scale for a low price.
Features of Nanogold®
- Unparalleled penetration of conjugates up to 40 µm.
- Higher density of immunolabeling than with larger gold probes.
- Can be conjugated to any molecule with a suitable reactive group. Available with different reactivities.
- Extremely uniform 1.4 nm gold particle.
- Label at specific sites which do not obstruct native reactivity.
- Close to stoichiometric labeling.
- Reacts under mild, neutral conditions.
- Conjugates are easily isolated by gel filtration.
- Conjugates are stable to a wide range of pH and ionic strengths.
- High stability: conjugates show unchanged reactivity after storage for a year.
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 Monomaleimido Nanogold®
Prepare the smallest gold immunoprobe with your own primary antibody for unsurpassed resolution, penetration and localization, or label a variety of other biological molecules.
Monomaleimido Nanogold® may be used to covalently label Fab', IgG, proteins or peptides containing cysteine, and other molecules with sulfhydryls -- Use our unique gold labeling reagents just as you would use fluorescent labeling reagents.
Easy to use: Simply mix redissolved Monomaleimido Nanogold® with the target molecule for 1-16 hours, then chromatographically purify the product by gel filtration, ion exchange chromatography or hydrophobic interaction chromatography. The maleimide on the 1.4 nm Nanogold® specifically reacts with a free sulfhydryl under mild conditions to produce a stable covalent bond.
Applications:
- Create your own small gold probes by linking Nanogold® to your primary antibody Fab' fragments. [References]
- Label 5'-thiolated oligonucleotides directly with Nanogold® (see Alivisatos, A. P., et al.; Nature, 382, 609 (1996)). [References]
- Label other proteins directly for high resolution site specific identification.
- Label peptides containing cysteine (see Gregori, L., et al.; J. Biol. Chem., 272, 258-262 (1997)). [Other references]
A similar product based on the smaller 11 gold atom cluster, undecagold, is also available (Monomaleimido-Undecagold).
Mono-Sulfo-NHS-Nanogold®
Mono-Sulfo-NHS-Nanogold® is the 1.4 nm Nanogold® compound with a single reactive group, a sulfo-N-hydroxysuccinimide ester (sulfo-NHS) that reacts with primary amines under mild conditions (pH 7.5 to 8.2).
The result is stable, covalent attachment of the Nanogold® to a protein, lipid, peptide, modified oligonucleotide or other amine-containing molecule to give a unique gold probe without the problems associated with colloidal gold (aggregation, poor stability, and low penetration).
Nanogold® is readily enhanced with a silver developer (LI Silver or HQ Silver) so that the small gold particles are easily visualized by EM or light microscopy, or by eye on blots and gels.
Mono-Sulfo-NHS-Nanogold® is easy to use: The dry labeling reagent is dissolved in a small amount of DMSO or isopropanol, reconstituted with water and mixed with the molecule to be labeled. Reaction is complete in a few hours, and the labeled conjugate is purified chromatographically by gel filtration.
Applications:
- Label proteins which do not contain a cysteine.
- Label peptides at the N-terminal (see Segond von Banchet, G., and Heppelman, B.: J. Histochem. Cytochem., 43, 821 (1995)).
- Use Fv antibody fragments to prepare the smallest antibody probes (see Ribrioux, S., et al.: J. Histochem. Cytochem., 44, 207-213 (1996)).
- Label small molecules as inhibitors or substrate analogs.
- Label amino-substituted lipids for insertion into liposomes.
A similar product based on the smaller 11 gold atom cluster, undecagold, is also available (Mono-Sulfo-NHS-Undecagold).
Monoamino Nanogold®
Nanogold® is also available with a primary amine attached for other crosslinking reactions.
Covalent attachment to the carbohydrate moiety of a glycoprotein may be effected by periodate oxidation of the carbohydrate followed by reaction with Monoamino Nanogold® and reduction of the resulting Schiff base linkages (see: Shah, N., et al.: Endocrinology, 136, 2825-2835 (1995)).
A similar product based on the smaller 11 gold atom cluster, undecagold, is also available (Mono-Sulfo-NHS-Undecagold).
Charged Nanogold®
Positively and negatively charged Nanogold® may be used as ionic labels.
The positive Nanogold® has multiple amines on its surface, whereas negative Nanogold® has multiple carboxyl groups.
Application:
- Tracing the yeast endocytic pathway (see: Prescianotto-Baschong, C., and Riezman, H.: Mol. Cell Biol., 9, 173-189 (1998)). [Other references]
Similar products based on the smaller 11 gold atom cluster, undecagold, are also available (Charged Undecagold).
Non-Functionalized Nanogold®
Non-fuctionalized Nanogold® is an inert, stable form of the Nanogold® particle with no reactive chemical functionalities or specific affinity properties.
Applications:
- As a size standard for calibration in high-resolution electron microscopy.
- Sizing pores (see: Schwartz, M. P., and Matouschek, A.: The dimensions of the protein import channels in the outer and inner mitochondrial membranes. Proc. Natl. Acad. Sci. USA, 96, 13086-13090 (1999)). [Complete references]
- For tracing contiguous interior spaces in cells and tissues.
A similar product based on the smaller 11 gold atom cluster, undecagold, is also available (Non-Functional Undecagold).
Custom Labeling
Nanoprobes will perform custom conjugation of Nanogold®, FluoroNanogold, undecagold or colloidal gold to primary antibodies, peptides, small molecules, or other molecules if feasible. This includes the purification and characterization of conjugates. Call 877-447-6266 (US toll-free number) or (631) 205-9490, use the custom synthesis quotation form, or e-mail us at [email protected] to discuss your project and obtain a quote.
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