AAT Bioquest

Casein, TAMRA-conjugated

Proteases hydrolyze the quenching effect of the labeled TAMRA, resulting in a bright yellow-orange fluorescence proportional to protease activity.
Proteases hydrolyze the quenching effect of the labeled TAMRA, resulting in a bright yellow-orange fluorescence proportional to protease activity.
Proteases hydrolyze the quenching effect of the labeled TAMRA, resulting in a bright yellow-orange fluorescence proportional to protease activity.
Ordering information
Catalog Number
Unit Size
Add to cart
Additional ordering information
InternationalSee distributors
Bulk requestInquire
Custom sizeInquire
ShippingStandard overnight for United States, inquire for international
Request quotation
Physical properties
Molecular weightN/A
Spectral properties
Correction Factor (260 nm)0.32
Correction Factor (280 nm)0.178
Extinction coefficient (cm -1 M -1)90000
Excitation (nm)552
Emission (nm)578
Storage, safety and handling
H-phraseH303, H313, H333
Hazard symbolXN
Intended useResearch Use Only (RUO)
R-phraseR20, R21, R22
StorageFreeze (< -15 °C); Minimize light exposure


See also: Proteases
Molecular weight
Correction Factor (260 nm)
Correction Factor (280 nm)
Extinction coefficient (cm -1 M -1)
Excitation (nm)
Emission (nm)
Casein is considered to be a generic substrate for a broad spectrum of proteases. As native casein this rhodaminated casein is hydrolyzed by many proteases, and widely used for fluorometric measurement of protease activity. In the intact substrate, casein is heavily labeled with TAMRA, resulting in significant fluorescence quenching. Protease-catalyzed hydrolysis relieves its quenching effect, yielding brightly orange fluorescent dye-labeled short peptides. The increase in fluorescence intensity is directly proportional to protease activity. Compared to FITC-labeled casein, this casein substrate has pH-independent fluorescence. This feature is more convenient for the assays that require low pH. We do not recommend that this conjugate be used for fluorescence polarization assay. For fluorescence polarization we can custom-make the lightly labeled fluorescein casein conjugate.

Example protocol


Unless otherwise noted, all unused stock solutions should be divided into single-use aliquots and stored at -20 °C after preparation. Avoid repeated freeze-thaw cycles.

Casein, TAMRA-conjugated stock solution
Make a 2.5 - 5 mg/mL Casein, TAMRA-conjugated stock solution in PBS buffer.
Note     Unused stock solution can be divided into single use aliquots and stored at -20 °C, and avoid exposure to light.


Casein TAMRA-conjugated working solution (2X)
Dilute the TAMRA-conjugated stock solution into 50 - 100 mM Tris buffer (pH 7.4) at 100 - 400 μg/mL. The 2X Assay working solution is designed for detecting the activity of chymotrypsin, trypsin, thermolysin, proteinase K, protease XIV, and human leukocyte elastase. For other proteases, please refer to Table 1 for the appropriate assay buffer formula. The optimum concentration of the assay working solution should be determined experimentally for individual proteases.


Table 1. Appropriate assay buffer formula for Assay working solution.
Protease1X Assay Buffer
Cathepsin D20 mM Sodium Citrate, pH 3.0
Papain20 mM sodium acetate, 20 mM cysteine, 2 mM EDTA, pH 6.5
PAE20 mM sodium phosphate, pH 8.0
Pepsin10 mM HCl, pH 2.0
Porcine pancreas elastase10 mM Tris-HCl, pH 8.8
Subtilisin20 mM potassium phosphate buffer, pH 7.6, 150 mM NaCl
  1. Mix equal volume of the trypsin standards or samples with 2X Assay working solution.
  2. Monitor the fluorescence increase at Ex/Em = 540/590 nm. a. For kinetic reading: Immediately start measuring fluorescence intensity continuously and record data every 5 minutes for 30 minutes. b. For end-point reading: Incubate the reaction at a desired temperature for 30 to 60 minutes, protected from light. Then measure the fluorescence intensity. 


Open in Advanced Spectrum Viewer

Spectral properties

Correction Factor (260 nm)0.32
Correction Factor (280 nm)0.178
Extinction coefficient (cm -1 M -1)90000
Excitation (nm)552
Emission (nm)578

Product Family

NameExcitation (nm)Emission (nm)Extinction coefficient (cm -1 M -1)Quantum yieldCorrection Factor (280 nm)
Casein, FITC-conjugated491516730000.920.35



View all 3 citations: Citation Explorer
Liquid temperature measurement method in microchannels by using fluorescence polarization
Authors: Tatsumi, Kazuya and Hsu, Chi Hsuan and Suzuki, Atsushi and Nakabe, Kazuyoshi
Journal: Heat and Mass Transfer (2017): 1--10
Micro-scale temperature measurement method using fluorescence polarization
Authors: Tatsumi, K and Hsu, CH and Suzuki, A and Nakabe, K
Journal: (2016): 032097
Microscopic Fluid Temperature Measurements Using Fluorescence Polarization Method
Authors: Tatsumi, Kazuya and Tozaki, Akihisa and Nakabe, Kazuyoshi
Journal: (2011): T10167--T10167


View all 30 references: Citation Explorer
Transient kinetic experiments demonstrate the existence of a unique catalytic enzyme form in the peptide-stimulated ATPase mechanism of Escherichia coli Lon protease
Authors: Vineyard D, Zhang X, Lee I.
Journal: Biochemistry (2006): 11432
Highly stable glycosylated serine protease from the medicinal plant Euphorbia milii
Authors: Yadav SC, P and e M, Jagannadham MV.
Journal: Phytochemistry (2006): 1414
Effects of Pseudomonas fluorescens M3/6 bacterial protease on plasmin system and plasminogen activation
Authors: Frohbieter KA, Ismail B, Nielsen SS, Hayes KD.
Journal: J Dairy Sci (2005): 3392
Fibrillar amyloid beta-protein inhibits the activity of high molecular weight brain protease and trypsin
Authors: Chauhan V, Sheikh AM, Chauhan A, Spivack WD, Fenko MD, Malik MN.
Journal: J Alzheimers Dis (2005): 37
Characterization of a novel and specific inhibitor for the pro-apoptotic protease Omi/HtrA2
Authors: Cilenti L, Lee Y, Hess S, Srinivasula S, Park KM, Junqueira D, Davis H, Bonventre JV, Alnemri ES, Zervos AS.
Journal: J Biol Chem (2003): 11489
Measurement of protease activity of live Uronema marinun (Ciliata: Scuticociliatida) by fluorescence polarization
Authors: Lee EH, Kim CS, Cho JB, Ahn KJ, Kim KH.
Journal: Dis Aquat Organ (2003): 85
Mg2+-linked oligomerization modulates the catalytic activity of the Lon (La) protease from Mycobacterium smegmatis
Authors: Rudyak SG, Brenowitz M, Shrader TE.
Journal: Biochemistry (2001): 9317
Directed polar secretion of protease from single cells of Vibrio cholerae via the type II secretion pathway
Authors: Scott ME, Dossani ZY, S and kvist M., undefined
Journal: Proc Natl Acad Sci U S A (2001): 13978
Evidence for tryptophan in proximity to histidine and cysteine as essential to the active site of an alkaline protease
Authors: Tanksale AM, Vernekar JV, Ghatge MS, Deshp and e VV., undefined
Journal: Biochem Biophys Res Commun (2000): 910
Effect of psychrotrophic bacteria and of an isolated protease from Pseudomonas fluorescens M3/6 on the plasmin system of fresh milk
Authors: Fajardo-Lira C, Oria M, Hayes KD, Nielsen SS.
Journal: J Dairy Sci (2000): 2190