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Photoreactive Amino Acids

Diazirine-based amino acid analogs for real-time crosslinking of protein interactions in living cells.

Pierce Photoreactive Amino Acids

Thermo Scientific Pierce Photoreactive Amino Acids are analogs of L-Leucine and L-Methionine that can be incorporated into proteins during synthesis and then light-activated to covalently crosslink interacting proteins in cells.

Thermo Scientific L-Photo-Leucine and L-Photo-Methionine are analogs of L-Leucine and L-Methionine amino acids that can be endogenously incorporated into the primary sequence of proteins during synthesis and then ultraviolet light (UV)-activated to covalently crosslink proteins within protein-protein interaction domains in their native environment within live cells. The powerful method enables both stable and transient protein interactions in cells to be studied and characterized without the use of completely foreign chemical crosslinkers and associated reagent solvents during the interaction experiment that can adversely aspects of the cell biology being studied.


  • In vivo labeling – incorporate photo-reactive group into proteins using normal cellular machinery of live cells
  • In vivo crosslinking – find interacting proteins in the native cellular environment
  • Increased specificity – crosslink interacting proteins correctly positioned at their interfaces within protein interaction domains
  • Efficient recovery – 90% protein recovery in cell lysates after crosslinking
  • Compatible – crosslink proteins expressed in a wide variety of cell lines, including HeLa, 293T, COS7, U2OS, A549, A431, HepG2, NIH 3T3 and C6
  • Easy to use – reagents are photo-stable under normal laboratory lighting, eliminating the need to work in the dark

Product Details:

L-2-amino-5,5'-azi-hexanoic acid; L-Photo-Methionine
Chemical structures of photoreactive amino acids.

Procedure summary for protein interaction experiment using photo-reactive amino acids.
Protocol summary for protein interaction experiments with Photo-activated Amino Acids.

When used in combination with specially formulated limiting media that is devoid of leucine and methionine, the photo-activatable derivatives are treated like naturally occurring amino acids by the protein synthesis machinery within the cell. As a result, they can be substituted for leucine or methionine in the primary sequence of proteins during catabolism and growth. Photo-Leucine and Photo-Methionine derivatives contain diazirine rings that activate when exposed to UV light to become reactive intermediates that form covalent bonds with nearby protein side chains and backbones. Naturally associating binding partners within the cell can be instantly trapped by photoactivation of the diazirine-containing proteins in the cultured cells. Crosslinked protein complexes can be detected by decreased mobility on SDS-PAGE followed by Western blot detection, size exclusion chromatography, sucrose density gradient sedimentation or mass spectrometry.

UV light source compatibility with the photo-reactive amino acids.
UV Lamp Bulb Wavelength
and Power
UVA Output
at 1 cm
Photo AA
UVP-3UV 365nm, 8 W 2800µW/cm2 4 min 16 min
Stratalinker 2400 365nm, 15 W 3000µW/cm2 3 min 12 min
Spectroline XX-15A 365nm, 15 W 3500µW/cm2 2 min 8 min
UVP UVGL-58 365nm, 6 W 2300µW/cm2 5 min 20 min
UVP UVMLS-38 365nm, 8 W 2800μW/cm2 4 min 16 min


Western blotting results of photoreactive amino acid protein interaction experiments. Photo-reactive amino acid crosslinking and formaldehyde crosslinking are complementary techniques for protein interaction analysis. HeLa cells were mocktreated (Lane 1), treated with 1% formaldehyde for 10 minutes (Lane 2), or treated with Photo-Methionine and Photo-Leucine followed by UV treatment (Lane 3). Cells were lysed and 10µg of each was analyzed by SDS-PAGE and Western blotting with antibodies against HSP90, STAT3, Ku70 and Ku86. Lower panels are beta-actin (upper band) and GAPDH (lower band), which were blotted as loading controls.


  1. Bomgarden R.D., et al. (2007). In vivo crosslinking strategies to identify and characterize transcription factor protein complexes.[abstract] In: Proceedings of the 100th Annual Meeting of the American Association for Cancer Research; 2007 Apr 14-18; Los Angeles, CA. Philadelphia (PA): AACR; 2007. p 141. Abstract nr 1192.
  2. Jumper C. C. and Schriemer D. C. (2011) Mass spectrometry of laser-initiated carbene reactions for protein topographic analysis. Anal Chem. 83, 2913-2920.PMID: 21425771
  3. Zhao W. Q. et al. (2010) Inhibition of calcineurin-mediated endocytosis and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors prevents amyloid beta oligomer-induced synaptic disruption. J Biol Chem. 285, 7619-7632. PMID: 20032460
  4. Weaver M. S. et al. (2008) The copper binding domain of SPARC mediates cell survival in vitro via interaction with integrin beta1 and activation of integrin-linked kinase. J Biol Chem. 283, 22826-22837. PMID: 18503049
  5. Suchanek, M., et al. (2005). Photo-leucine and photo-methionine allow identification of protein-protein interactions. Nat. Methods 2(4):261-267.
  6. Vila-Perello, M., et al. (2007). Covalent capture of phospho-dependent protein oligomerization by site-specific incorporation of a diazirine photo-cross-linker. J. Am. Chem. Soc., 129(26):8068 -8069.


Photoreactive Amino Acid FAQ

Related Products:

Formaldehyde, methanol-free
Label Transfer Reagents
UV Lamps for Photo-Crosslinkers

Ordering Information
Product # Description Pkg. Size Instructions MSDS CofA Price
22610 L-Photo-Leucine
Formulation: L-2-amino-4,4'-azi-pentanoic acid; solid
Sufficient For: 175mL of typical 1X (4mM) reaction solution, or approx. 50 uses at 2mg reagent per use
100mg Product Instructions for product #22610 L-Photo-Leucine MSDS for product #22610 L-Photo-Leucine Certificate of Analysis for product #22610 L-Photo-Leucine $336.00

Now available on lifetechnologies.com
22615 L-Photo-Methionine
Formulation: L-2-amino-5,5'-azi-hexanoic acid; solid
Sufficient For: 318mL of typical 1X (2mM) reaction solution, or approx. 50 uses at 2mg reagent per use
100mg Product Instructions for product #22615 L-Photo-Methionine MSDS for product #22615 L-Photo-Methionine Certificate of Analysis for product #22615 L-Photo-Methionine $336.00

Now available on lifetechnologies.com
30030 Dulbecco's Modified Eagle's Limiting Medium (DMEM-LM)
Formulation: Sterile filtered DMEM (-)L-leucine, (-)L-methionine with 4.5g/L glucose, 4.0mM L-glutamine, sodium pyruvate and phenol red
Sufficient For: One experiment with Part No. 22610, 22615

Also recommended: Dialyzed Fetal Bovine Serum (Part No. 89986)
500mL Product Instructions for product #30030 Dulbecco's Modified Eagle's Limiting Medium (DMEM-LM) MSDS for product #30030 Dulbecco's Modified Eagle's Limiting Medium (DMEM-LM) Certificate of Analysis for product #30030 Dulbecco's Modified Eagle's Limiting Medium (DMEM-LM) $38.00

Now available on lifetechnologies.com

Instructions | MSDS | CofA
Product Instructions | MSDS | CofA  

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