AqT® Fluor 750 Protein Labeling Kit (Surface Amines)

Product Description

AqT^® Fluor 750 Protein Labeling kit is a proprietary fluorescent labeling kit developed at CellMosaic^® for obtaining high quality and high loading of fluorescent labeled protein with minimal or no aggregation.

Commercial fluorescent dyes are often highly hydrophobic, so dye-labeled proteins can aggregate and exhibit fluorescence quenching at high dye loading due to fluorophore stacking, reducing signal. The AqT Fluor 750 protein Labeling Kit (Surface Amines) uses CellMosaic’s super-hydrophilic, water-soluble, charge-neutral AqT linker to improve dye-labeled protein performance by increasing solubility, reducing aggregation and nonspecific binding, and minimizing quenching; it employs a core dye with Ex/Em 750/780 nm, and the AqT spacer helps maintain protein function and produce brighter, more stable conjugates with improved signal intensity.

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

The kit is designed to label any protein with AqT Fluor 750 dye via surface amines on the protein. The user supplies the protein. The kit includes AqT Fluor 750 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 Fluor 750 acid.

This kit provides materials to label 6.67 to 20 nano-mole (nmol) of one (CM86256x1) or three  (CM86256x3) protein samples (≥20 KDa) with AqT Fluor 750 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 

• Optimized for near-infrared imaging: Features a Fluor 750 core dye (Ex 750 nm / Em 800 nm), ideal for IR-range applications.
• Advanced AqT linker technology: Utilizes CellMosaic’s proprietary, super-hydrophilic, water-soluble, charge-neutral AqT linker to minimize fluorophore stacking and protein aggregation.
• High dye loading with preserved antibody function: Typical degree of labeling (DOL) of 3–5 dyes per protein. No increase in apparent MW (hydrodynamic volume) or aggregation.
• All-inclusive kit with validated analytical method: Provides sterilized buffers and tubes, columns, and filters for fluorescent labeling. Also includes all buffers and methods 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 Fluor 750 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 Fluor 750 labeling of BSA. Using AqT® engineering, a high average degree of labeling (DOL; 5.5) 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 Fluor 750–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).