AqT® Digoxigenin Protein Labeling Kit (Surface Amines)

Product Description

AqT^® Digoxigenin Protein Labeling kit is a proprietary digoxigenin labeling kit developed at CellMosaic^® for obtaining high quality and high loading of digoxigenin labeled protein with minimal or no aggregation.

AqueaTether® (AqT®) linkers are proprietary biomaterials developed at CellMosaic for labeling and conjugating biomolecules with highly hydrophobic small molecules, improving bioconjugate performance in downstream applications. For example, digoxigenin is poorly water-soluble and prone to aggregation; incorporation of the AqT® linker enhances its solubility, enabling labeling with minimal or no organic solvent. The linker’s hydroxyl groups form hydrogen-bond networks with surrounding water, creating a stabilizing microenvironment that reduces digoxigenin–digoxigenin interactions and prevents aggregation or precipitation over time. This allows proteins to be labeled with high levels of AqT®-digoxigenin without altering their properties, while potentially improving stability against enzymatic degradation and preserving activity. The AqT® Digoxigenin Protein Labeling Kit (Surface Amines) leverages this technology to produce high-quality, low-aggregation conjugates using a super-hydrophilic, water-soluble, charge-neutral AqT® linker that also minimizes non-specific interactions with proteins and surfaces.

For a detailed description of the AqT technologies, please see our technology section.

The kit is designed to label any protein with AqT digoxigenin via surface amines on the protein. The user supplies the protein. The kit includes AqT digoxigenin acid, which is activated within 15 minutes and then coupled directly to the protein in one step. The labeled product is subsequently purified to remove any unreacted AqT digoxigenin acid.

This kit provides materials to label 6.67 to 20 nano-mole (nmol) of one (CM86442x1) or three  (CM86442x3) protein samples (≥20 KDa) with AqT digoxigenin acid. Customer can request a recommendation for the conjugation if the protein has a special feature, a less than 6.67 nmol of protein, or less than 20KDa MW of protein or peptide to be labeled. CellMosaic provides additional accessory tools, such as buffers, standards, and reagents, for protein research. We also offer fee-based support services for customers who require assistance with final conjugate analysis by HPLC and determination of the DOL.

Requirement for Protein

1. MW: ≥ 20 KDa
2. Preferably >90% pure by gel electrophoresis
3. Total amount: 6.67-20 nmol protein content as measured by UV. 

Key Features 

• Advanced AqT linker technology: Utilizes CellMosaic’s proprietary, super-hydrophilic, water-soluble, charge-neutral AqT linker to minimize fluorophore stacking and protein aggregation.
• High digoxigenin loading: Typical degree of labeling (DOL) of 2–5 digoxigenin per protein depending on the MW and properties of the protein. No or minimal aggregation.
• All-inclusive kit with validated analytical method: Provides sterilized buffers and tubes, and filters for digoxigenin labeling. Also includes method needed for concentration measurement and loading determination.
• Fast, user-friendly workflow plus optional support: One-step labeling and purification in ~2 hours (≤1 hour hands-on), with optional post-conjugation services at CellMosaic® for analytical characterization and DOL determination.

Labeling Chemistry

Protocol

Schematic workflow diagram for preparing AqT digoxigenin labeled protein within 2 hours, starting with 20 nmol of protein. (Reagent volume will vary if the amount of protein is less than 20 nmol).

Example Data

The figures below show an example of AqT Digoxigenin labeling of BSA. Using AqT® engineering, a high average degree of labeling (DOL: 3.2) was achieved despite the extreme hydrophobicity of the dye core. The extent of labeling was assessed by reversed-phase HPLC (Figure 1). Apparent molecular weight and aggregation were evaluated by size-exclusion chromatography (SEC)-HPLC (Figure 2).

AqT digoxigenin–labeled BSA (average DOL 5.5) shows only a minimal shift in apparent molecular weight, and the conjugate retains a hydrodynamic volume similar to the native protein. Little to no additional aggregation is observed after labeling. These results confirm that AqT® labeling preserves key protein properties.

Figure 1: Overlay of reversed-phase HPLC profiles of BSA and AqT Fluor 750 labeled BSA.

Figure 2: Overlay of SEC HPLC analysis of BSA and AqT Fluor 750 labeled BSA (Insert, upper left: UV profiles of individual HPLC peaks).