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PerKit™ Protein Small Molecule Acid Conjugation Kit

  • Protein small molecule acid conjugation kit
In stock, usually ships within 24 hrs
Calculated at checkout
Describe your small molecule:

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This is a personalized conjugation kit (PerKit™) to work with any protein with a MW over 20 KDa and for protein labeling of a small molecule containing carboxylic acid (-COOH) functional groups. Using the kit components, the customer converts the carboxylic acid to an activated N-hydroxysuccinimide (NHS) ester, followed by reaction with the surface amino groups of the protein to form a stable amide bond. The final product is desalted to remove any unreacted small molecule acid. 

This kit provides materials to label one protein. Scale of the reaction: 50 nmol (2 mg total for a 40KDa protein)

Shipping policy: heat-sensitive, choose overnight (ships Mon.-Thur.) or 2-day delivery (ships Mon.-Wed.) at checkout.

Requirement for Small Molecule

  • Preferably > 90% pure
  • Absence of primary or secondary amine (-NH2) groups
  • Preferably contains only one non-hindered aliphatic carboxylic acid (-COOH)
  • For molecule containing aromatic carboxylic acid, hindered aliphatic carboxylic acid, or hydroxyl (-OH) groups, please consult CellMosaic first before placing the order.

Key Features of this PerKit™

  • Offers a simple and easy way to label protein with any small molecule containing carboxylic acid
  • Fast and easy preparation: 4 h preparation and <30 minutes hands-on time
  • All reagents and supplies included for preparation and purification
  • Over 90% pure conjugated products by SEC
  • Options to choose tailored services at CellMosaic prior to and after conjugation

Prior to conjugation: you can upload your small molecule information when you place your order. CellMosaic will general a PerKit™ sheet containing calculation, chemical structure, MW of your final conjugate, and recommendations for the conjugation if your molecule has special features. 

After conjugation: you can choose to send your sample to CellMosaic for HPLC analysis.




Labeling Chemistry



Typical Kit Performance Data

SM acid information: 6-carboxyfluorescein (20 µmol)

Protein information: Bovine Serum Albumin (BSA) (50 nmol)

Kit Lot number: 5506.S51207

Figure 1: Size-exclusion HPLC analysis of the purified fluorescein labeled BSA from Step D6 using various amounts of Fluorescein NHS ester. 

Fluorescein labeling of protein


Figure 2: UV/Vis spectrum of the purified fluorescein labeled BSA from Step D6 using various amounts of Fluorescein NHS ester. 

CM52408 example fluorescein labeling of protein

Table 1: Summary results of the purity and the average DOL of the fluorescein labeled BSA from Step D6 (Note: Fluorescein is a very hydrophobic compound. A lower DOL was obtained.)

Sample NHS ester solution from Step B7 (µl) SEC HPLC Rt (min) 220 nm ΔRt % of small molecule after purification Calc. DOL based on UV/Vis
BSA N/A 16.616 N/A N/A N/A
R1 7.5 16.538 0.078 0 1
R2 15 16.466 0.150 0 1.8
R3 30 16.337 0.279 1.3 2.7
R4 60 16.218 0.398 2.2 3.3





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