What Is the AF680 Antibody Labeling Kit?

The AF680 Antibody Labeling Kit (SKU: A1491940, Aladdin Scientific) provides researchers with a streamlined solution for covalently conjugating immunoglobulins to AF680, a bright and photostable near-infrared (near-IR) fluorescent dye with excitation and emission maxima in the ~679/702 nm range. Near-IR fluorophores such as AF680 offer several practical advantages over visible-range dyes: autofluorescence from biological samples is substantially reduced in the near-IR window, signal-to-noise ratios are improved, and compatibility with red laser–equipped instruments is broad.

The kit format eliminates the need for researchers to source and titrate reactive dye separately, providing pre-optimized reagent ratios, purification components, and reaction buffers in a single package. This makes it particularly convenient for core facilities, translational research groups, and any laboratory that needs to label custom or proprietary antibodies without committing to large-scale conjugation chemistry.

Labeling Principle and Workflow

AF680 dye molecules are functionalized with amine-reactive groups (typically NHS esters) that form stable amide bonds with primary amines (lysine residues and the N-terminus) on the antibody surface. This chemistry is well-established and proceeds under mild aqueous conditions, preserving antibody antigen-binding activity when the degree of labeling (DOL) is appropriately controlled.

A typical workflow using the AF680 Antibody Labeling Kit involves the following general steps:

1. Antibody preparation: The antibody is buffer-exchanged into a reaction-compatible buffer (e.g., sodium bicarbonate or phosphate buffer, pH 8.0–9.0) to ensure efficient NHS-ester reactivity. Removal of primary amine–containing excipients such as Tris or glycine is critical.
2. Conjugation reaction: The antibody is mixed with the kit-supplied reactive AF680 reagent at the recommended molar ratio and incubated for the specified time at room temperature or 4 °C.
3. Purification: Unreacted free dye is removed using the included spin-column or size-exclusion resin, yielding a purified AF680–antibody conjugate ready for use.
4. Quality assessment: The degree of labeling is calculated by measuring absorbance at 280 nm (protein) and at the dye's absorption maximum (~679 nm). A DOL of 2–5 dye molecules per antibody is typically considered optimal for most flow cytometry and imaging applications.

Please refer to the kit insert supplied with product A1491940 for exact reagent volumes, incubation times, and spin-column protocols, as these may be updated by the manufacturer.

Applications and Instrument Compatibility

AF680-labeled antibodies are widely used across several research platforms:

• Flow cytometry: AF680 is excited efficiently by the 633 nm or 647 nm red laser lines present on most modern flow cytometers. Its emission (~702 nm) falls in a spectral region with minimal overlap with many common fluorophores such as PE, FITC, and APC, making it well suited for multicolor panels. It is detected in channels often designated APC-R700 or equivalent near-IR channels.
• Fluorescence microscopy and imaging: The near-IR emission of AF680 reduces tissue autofluorescence background, enabling cleaner imaging of targets in complex biological specimens including tissue sections and whole-mount preparations. It is compatible with standard confocal, widefield, and near-IR-optimized imaging systems.
• Immunoassays: AF680 conjugates can be used in dot blots, in-cell Westerns, and near-IR Western blot detection systems (e.g., LI-COR Odyssey-compatible formats), offering high sensitivity and quantitative linear range.
• In vivo / ex vivo imaging: The near-IR spectral window provides reduced tissue absorption and scattering, making AF680 conjugates applicable for small-animal optical imaging studies, though researchers should consult instrument and regulatory requirements for their specific use case.

Tips for Optimal Labeling Results

Achieving high-quality AF680 conjugates requires attention to several practical considerations:

• Antibody purity and concentration: Use antibodies that are >90% pure (ideally affinity-purified) and free of carrier proteins such as BSA or gelatin, which compete for dye reactive sites. Antibody concentration should be in the range recommended by the kit (typically 1–10 mg/mL).
• Buffer compatibility: Avoid primary amine–containing buffers (Tris-HCl, glycine, ethanolamine). If the antibody is stored in such buffers, perform buffer exchange using the supplied desalting column or dialysis prior to labeling.
• Degree of labeling (DOL) control: Over-labeling (DOL >6–8) can quench fluorescence and impair antigen binding. Under-labeling reduces detection sensitivity. Follow the kit's recommended dye:antibody molar ratio and adjust for antibody molecular weight if conjugating non-IgG formats.
• Light protection: AF680 is photosensitive. Conduct all labeling steps under subdued light and store the final conjugate protected from light at 2–8 °C.
• Functional validation: After conjugation, validate the labeled antibody by flow cytometry or ELISA against a known positive control to confirm retained binding activity and appropriate signal intensity before use in experiments.

Ordering and Storage Information

The AF680 Antibody Labeling Kit is available from Aladdin Scientific under SKU A1491940. Researchers should confirm current pack size, pricing, and availability through the Aladdin Scientific website or by contacting the sales team directly.

Storage: Store the kit at 2–8 °C, protected from light. Do not freeze reactive dye components unless explicitly specified in the kit insert, as freeze-thaw cycles can hydrolyze NHS ester groups and reduce labeling efficiency. Check the kit insert for component-specific storage conditions and expiration information.

Shipping: The kit is typically shipped with cold packs. Upon receipt, inspect all components, record the lot number, and store immediately under recommended conditions.

For technical support, custom conjugation inquiries, or bulk pricing, contact Aladdin Scientific's technical support team.