Caged Molecules: Principles and Practical Considerations

Joseph P.Y. Kao1

1 University of Maryland Biotechnology Institute, Baltimore, Maryland
Publication Name:  Current Protocols in Neuroscience
Unit Number:  Unit 6.20
DOI:  10.1002/0471142301.ns0620s37
Online Posting Date:  November, 2006
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Abstract

A caged molecule is an inert but photosensitive molecule that is transformed by photolysis into a biologically active molecule at high speed (typically 1 msec). The process is referred to as photorelease. The spatial resolution of photorelease is limited by the properties of light; submicrometer resolution is potentially achievable. Therefore, focal photorelease of caged molecules enables one to control biological processes with high spatio‚Äźtemporal precision. The principles underlying caged molecules as well as practical considerations for their use are discussed in this unit.

Keywords: caged molecule; caged compound; photolysis; photorelease; uncaging; photostimulation

     
 
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Table of Contents

  • What is a Caged Molecule?
  • Why Use Caged Molecules?
  • Common Sense Considerations on the Use of Caged Molecules
  • Handling of Caged Compounds
  • Fundamental Properties of Caged Molecules that Determine Their Performance
  • Comparing the Relative Merits of Different Caged Molecules
  • Analyzing the Rate of Photorelease
  • Diffusion and Spatial Resolution of Photorelease
  • Summary
  • Literature Cited
  • Figures
  • Tables
     
 
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Materials

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Literature Cited

Literature Cited
   Adams, S.R., Kao, J.P.Y., and Tsien, R.Y. 1988. Biologically useful chelators that release Ca2+ upon illumination. J. Am. Chem. Soc. 110:3212‐3220.
   Adams, S.R., Kao, J.P.Y., and Tsien, R.Y. 1989. Biologically useful chelators that take up Ca2+ upon illumination. J. Am. Chem. Soc. 111:7957‐7968.
   Adams, S.R., Lev‐Ram, V., and Tsien, R.Y. 1997. A new caged Ca2+, azid‐1, is far more photosensitive than nitrobenzyl‐based chelators. Chem. Biol. 4:867‐878.
   Ando, H., Furuta, T., Tsien, R.Y., and Okamoto, H. 2001. Photo‐mediated gene activation using caged RNA/DNA in zebrafish embryos. Nat. Genet. 28:317‐325.
   Aarhus, R., Gee, K., and Lee, H.C. 1995. Caged cyclic ADP‐ribose. Synthesis and use. J. Biol. Chem. 270:7745‐7749.
   Arroyo, J.G., Jones, P.B., Porter, N.A., and Hatchell, D.L. 1997. In vivo photoactivation of caged‐thrombin. Thromb. Haemost. 78:791‐793.
   Atkins, P.W. 1994. The rates of chemical reactions. In Physical Chemistry. pp. 883‐884. W.H. Freeman and Company, New York.
   Barth, A. and Corrie, J.E. 2002. Characterization of a new caged proton capable of inducing large pH jumps. Biophys. J. 83:2864‐2871.
   Bayley, H., Chang, C.Y., Miller, W.T., Niblack, B., and Pan, P. 1998. Caged peptides and proteins by targeted chemical modification. Methods Enzymol. 291:117‐135.
   Bettache, N., Carter, T., Corrie, J.E., Ogden, D., and Trentham, D.R. 1996. Photolabile donors of nitric oxide: Ruthenium nitrosyl chlorides as caged nitric oxide. Methods Enzymol. 268:266‐281.
   Breitinger, H.G., Wieboldt, R., Ramesh, D., Carpenter, B.K., and Hess, G.P. 2000. Synthesis and characterization of photolabile derivatives of serotonin for chemical kinetic investigations of the serotonin 5‐HT(3) receptor. Biochemistry 39:5500‐5508.
   Cai, X., Liang, C.W., Muralidharan, S., Kao, J.P.Y., Tang, C.M., and Thompson, S.M. 2004. Unique roles of SK and Kv4.2 potassium channels in dendritic integration. Neuron 44:351‐364.
   Canepari, M., Nelson, L., Papageorgiou, G., Corrie, J.E., and Ogden, D. 2001. Photochemical and pharmacological evaluation of 7‐nitroindolinyl‐and 4‐methoxy‐7‐nitroindolinyl‐amino acids as novel, fast caged neurotransmitters. J. Neurosci. Methods 112:29‐42.
   Conrad, P.G., Givens, R.S., Weber, J.F.W., and Kandler, K. 2000. New phototriggers: Extending the p‐hydroxyphenacyl π–π* absorption range. Org. Lett. 2:1545‐1547.
   Cummings, R.T. and Krafft, G.A. 1988. Photoactivatable fluorophores. 1. Synthesis and photoactivation of o‐nitrobenzyl‐quenched fluorescent carbabmates. Tetrahedron Lett. 29:65‐68.
   Curten, B., Kullmann, P.H., Bier, M.E., Kandler, K., and Schmidt, B.F. 2005. Synthesis, photophysical, photochemical, and biological properties of caged GABA, 4‐[[(2H‐1‐benzopyran‐2‐one‐7‐amino‐4‐methoxy)carbonyl]amino]butanoic acid. Photochem. Photobiol. 81:641‐648.
   Dolphin, A.C., Wootton, J.F., Scott, R.H., and Trentham, D.R. 1988. Photoactivation of intracellular guanosine triphosphate analogues reduces the amplitude and slows the kinetics of voltage‐activated calcium channel currents in sensory neurones. Pflugers Arch. 411:628‐636.
   Duong, T.Q., Sehy, J.V., Yablonskiy, D.A., Snider, B.J., Ackerman, J.J., and Neil, J.J. 2001. Extracellular apparent diffusion in rat brain. Magn. Res. Med. 45:801‐810.
   Ellis‐Davies, G.C. and Barsotti, R.J. 2006. Tuning caged calcium: Photolabile analogues of EGTA with improved optical and chelation properties. Cell Calcium 39:75‐83.
   Ellis‐Davies, G.C. and Kaplan, J.H. 1994. Nitrophenyl‐EGTA, a photolabile chelator that selectively binds Ca2+ with high affinity and releases it rapidly upon photolysis. Proc. Natl. Acad. Sci. U.S.A. 91:187‐191.
   Endo, M., Nakayama, K., Kaida, Y., and Majima, T. 2004. Design and synthesis of photochemically controllable caspase‐3. Angew. Chem. Int. Ed. Engl. 43:5643‐5645.
   Gee, K.R., Niu, L., Schaper, K., Jayaraman, V., and Hess, G.P. 1999. Synthesis and photochemistry of a photolabile precursor of N‐methyl‐D‐aspartate (NMDA) that is photolyzed in the microsecond time region and is suitable for chemical kinetic investigations of the NMDA receptor. Biochemistry 38:3140‐3147.
   Geibel, S., Barth, A., Amslinger, S., Jung, A.H., Burzik, C., Clarke, R.J., Givens, R.S., and Fendler, K. 2000. P(3)‐[2‐(4‐Hydroxyphenyl)‐2‐oxo]ethyl ATP for the rapid activation of the Na+,K+‐ATPase. Biophys. J. 79:1346‐1357.
   Geissler, D., Antonenko, Y.N., Schmidt, R., Keller, S., Krylova, O.O., Wiesner, B., Bendig, J., Pohl, P., and Hagen, V. 2005. (Coumarin‐4‐yl)methyl esters as highly efficient, ultrafast phototriggers for protons and their application to acidifying membrane surfaces. Angew. Chem. Int. Ed. Engl. 44:1195‐1198.
   Gelperin, A., Flores, J., Raccuia‐Behling, F., and Cooke, I.R. 2000. Nitric oxide and carbon monoxide modulate oscillations of olfactory interneurons in a terrestrial mollusk. J. Neurophysiol. 83:116‐127.
   Ghosh, M., Song, X., Mouneimne, G., Sidani, M., Lawrence, D.S., and Condeelis, J.S. 2004. Cofilin promotes actin polymerization and defines the direction of cell motility. Science 304:743‐746.
   Goedhart, J. and Gadella, T.W. Jr. 2004. Photolysis of caged phosphatidic acid induces flagellar excision in Chlamydomonas. Biochemistry 43:4263‐4271.
   Grewer, C., Jager, J., Carpenter, B.K., and Hess, G.P. 2000. A new photolabile precursor of glycine with improved properties: A tool for chemical kinetic investigations of the glycine receptor. Biochemistry 39:2063‐2070.
   Guerrero, L., Smart, O.S., Woolley, G.A., and Allemann, R.K. 2005. Photocontrol of DNA binding specificity of a miniature engrailed homeodomain. J. Am. Chem. Soc. 127:15624‐15629.
   Hagen, V., Dzeja, C., Frings, S., Bendig, J., Krause, E., and Kaupp, U.B. 1996. Caged compounds of hydrolysis‐resistant analogues of cAMP and cGMP: Synthesis and application to cyclic nucleotide‐gated channels. Biochemistry 35:7762‐7771.
   Hagen, V., Dzeja, C., Bendig, J., Baeger, I., and Kaupp, U.B. 1998. Novel caged compounds of hydrolysis‐resistant 8‐Br‐cAMP and 8‐Br‐cGMP: Photolabile NPE esters. J. Photochem. Photobiol. B 42:71‐78.
   Hagen, V., Frings, S., Wiesner, B., Helm, S., Kaupp, U.B., and Bendig, J. 2003. [7‐(Dialkylamino)coumarin‐4‐yl]methyl‐caged compounds as ultrafast and effective long‐wavelength phototriggers of 8‐bromo‐substituted cyclic nucleotides. Chembiochem 4:434‐442.
   Harootunian, A.T., Kao, J.P., Paranjape, S., Adams, S.R., Potter, B.V., and Tsien, R.Y. 1991. Cytosolic Ca2+ oscillations in REF52 fibroblasts: Ca2+‐stimulated IP3 production or voltage‐dependent Ca2+ channels as key positive feedback elements. Cell Calcium 12:153‐164.
   Heinbockel, T., Brager, D.H., Reich, C.G., Zhao, J., Muralidharan, S., Alger, B.E., and Kao, J.P. 2005. Endocannabinoid signaling dynamics probed with optical tools. J. Neurosci. 25:9449‐9459.
   Hiraoka, T. and Hamachi, I. 2003. Caged RNase: Photoactivation of the enzyme from perfect off‐state by site‐specific incorporation of 2‐nitrobenzyl moiety. Bioorg. Med. Chem. Lett. 13:13‐15.
   Homsher, E. and Millar, N.C. 1990. Caged compounds and striated muscle contraction. Annu. Rev. Physiol. 52:875‐896.
   Huang, X.P., Sreekumar, R., Patel, J.R., and Walker, J.W. 1996. Response of cardiac myocytes to a ramp increase of diacylglycerol generated by photolysis of a novel caged diacylglycerol. Biophys. J. 70:2448‐2457.
   Huang, Y.H., Sinha, S.R., Fedoryak, O.D., Ellis‐Davies, G.C., and Bergles, D.E. 2005a. Synthesis and characterization of 4‐methoxy‐7‐nitroindolinyl‐D‐aspartate, a caged compound for selective activation of glutamate transporters and N‐methyl‐D‐aspartate receptors in brain tissue. Biochemistry 44:3316‐3326.
   Huang, Y.H., Muralidharan, S., Sinha, S.R., Kao, J.P., and Bergles, D.E. 2005b. Ncm‐D‐aspartate: A novel caged D‐aspartate suitable for activation of glutamate transporters and N‐methyl‐D‐aspartate (NMDA) receptors in brain tissue. Neuropharmacology 49:831‐842.
   Humphrey, D., Rajfur, Z., Vazquez, M.E., Scheswohl, D., Schaller, M.D., Jacobson, K., and Imperiali, B. 2005. In situ photoactivation of a caged phosphotyrosine peptide derived from focal adhesion kinase temporarily halts lamellar extension of single migrating tumor cells. J. Biol. Chem. 280:22091‐22101.
   Ishihara, A., Gee, K., Schwartz, S., Jacobson, K., and Lee, J. 1997. Photoactivation of caged compounds in single living cells: An application to the study of cell locomotion. Biotechniques 23:268‐274.
   Janko, K. and Reichert, J. 1987. Proton concentration jumps and generation of transmembrane pH‐gradients by photolysis of 4‐formyl‐6‐methoxy‐3‐nitrophenoxyacetic acid. Biochim. Biophys. Acta 905:409‐416.
   Kantevari, S., Hoang, C.J., Ogrodnik, J., Egger, M., Niggli, E., and Ellis‐Davies, G.C. 2006. Synthesis and two‐photon photolysis of 6‐(ortho‐nitroveratryl)‐caged IP3 in living cells. Chembiochem 7:174‐180.
   Kao, J.P.Y. and Keitz, P.F. 1997. Photosensitive organic compounds that release carbon monoxide upon illumination. U.S. Patent No. 5,670,664. Published September 23, 1997.
   Kaplan, J.H. and Ellis‐Davies, G.C. 1988. Photolabile chelators for the rapid photorelease of divalent cations. Proc. Natl. Acad. Sci. U.S.A. 85:6571‐6575.
   Kaplan, J.H., Forbush, B. III, and Hoffman, J.F. 1978. Rapid photolytic release of adenosine 5′‐triphosphate from a protected analogue: Utilization by the Na:K pump of human red blood cell ghosts. Biochemistry 17:1929‐1935.
   Karpen, J.W., Zimmerman, A.L., Stryer, L., and Baylor, D.A. 1988. Gating kinetics of the cyclic‐GMP‐activated channel of retinal rods: Flash photolysis and voltage‐jump studies. Proc. Natl. Acad. Sci. U.S.A. 85:1287‐1291.
   Khan, S., Castellano, F., Spudich, J.L., McCray, J.A., Goody, R.S., Reid, G.P., and Trentham, D.R. 1993. Excitatory signaling in bacterial probed by caged chemoeffectors. Biophys. J. 65:2368‐2382.
   Krafft, G.A., Sutton, W.R., and Cummings, R.T. 1988. Photoactivatable fluorophores. 3. Synthesis and photoactivation of fluorogenic difunctionalized fluoresceins. J. Am. Chem. Soc. 110:301‐303.
   Lee, H.C., Aarhus, R., Gee, K.R., and Kestner, T. 1997. Caged nicotinic acid adenine dinucleotide phosphate. Synthesis and use. J. Biol. Chem. 272:4172‐4178.
   Li, W., Llopis, J., Whitney, M., Zlokarnik, G., and Tsien, R.Y. 1998. Cell‐permeant caged InsP3 ester shows that Ca2+ spike frequency can optimize gene expression. Nature 392:936‐941.
   Loudwig, S., Nicolet, Y., Masson, P., Fontecilla‐Camps, J.C., Bon, S., Nachon, F., and Goeldner, M. 2003. Photoreversible inhibition of cholinesterases: Catalytic serine‐labeled caged butyrylcholinesterase. Chembiochem 4:762‐767.
   Lougheed, T., Borisenko, V., Hennig, T., Ruck‐Braun, K., and Woolley, G.A. 2004. Photomodulation of ionic current through hemithioindigo‐modified gramicidin channels. Org. Biomol. Chem. 2:2798‐2801.
   Makings, L.R. and Tsien, R.Y. 1994. Caged nitric oxide. Stable organic molecules from which nitric oxide can be photoreleased. J. Biol. Chem. 269:6282‐6285.
   Marriott, G. 1994. Caged protein conjugates and light‐directed generation of protein activity: Preparation, photoactivation, and spectroscopic characterization of caged G‐actin conjugates. Biochemistry 33:9092‐9097.
   Marriott, G. and Heidecker, M. 1996. Light‐directed generation of the actin‐activated ATPase activity of caged heavy meromyosin. Biochemistry 35:3170‐3174.
   Mendel, D., Ellman, J.A., and Schultz, P.G. 1991. Construction of a light‐activated protein by unnatural amino acid mutagenesis. J. Am. Chem. Soc. 113:2758‐2760.
   Milburn, T., Matsubara, N., Billington, A.P., Udgaonkar, J.B., Walker, J.W., Carpenter, B.K., Webb, W.W., Marque, J., Denk, W., McCray, J.A. and Hess, G.P. 1989. Synthesis, photochemistry, and biological activity of a caged photolabile acetylcholine receptor ligand. Biochemistry 28:49‐55.
   Miller, J.C., Silverman, S.K., England, P.M., Dougherty, D.A., and Lester, H.A. 1998. Flash decaging of tyrosine sidechains in an ion channel. Neuron 20:619‐624.
   Mitchison, T.J. 1989. Polewards microtubule flux in the mitotic spindle: Evidence from the photoactivation of fluorescence. J. Cell Biol. 109:637‐652.
   Mitchison, T.J., Swain, K.E., Theriot, J.A., Gee, K., and Mallavarapu, A. 1998. Caged fluorescent probes. Methods Enzymol. 291:63‐78.
   Muralidharan, S. and Nerbonne, J.M. 1995. Photolabile “caged” adrenergic receptor agonists and related model compounds. J. Photochem. Photobiol. B 27:123‐137.
   Muralidharan, S., Maher, G.M., Boyle, W.A., and Nerbonne, J.M. 1993. “Caged” phenylephrine: Development and application to probe the mechanism of alpha‐receptor‐mediated vasoconstriction. Proc. Natl. Acad. Sci. U.S.A. 90:5199‐5203.
   Nakayama, K., Endo, M., and Majima, T. 2005. A hydrophilic azobenzene‐bearing amino acid for photochemical control of a restriction enzyme BamHI. Bioconjug. Chem. 16:1360‐1366.
   Nerbonne, J.M., Richard, S., Nargeot, J., and Lester, H.A. 1984. New photoactivatable cyclic nucleotides produce intracellular jumps in cyclic AMP and cyclic GMP concentrations. Nature 310:74‐76.
   Nguyen, A., Rothman, D.M., Stehn, J., Imperiali, B., and Yaffe, M.B. 2004. Caged phosphopeptides reveal a temporal role for 14‐3‐3 in G1 arrest and S‐phase checkpoint function. Nat. Biotechnol. 22:993‐1000.
   Nichols, C.G., Niggli, E., and Lederer, W.J. 1990. Modulation of ATP‐sensitive potassium channel activity by flash‐photolysis of “caged‐ATP” in rat heart cells. Pflugers Arch. 415:510‐512.
   Ottl, J., Gabriel, D., and Marriott, G. 1998. Preparation and photoactivation of caged fluorophores and caged proteins using a new class of heterobifunctional, photocleavable cross‐linking reagents. Bioconjug. Chem. 9:143‐151.
   Pan, P. and Bayley, H. 1997. Caged cysteine and thiophosphoryl peptides. FEBS Lett. 405:81‐85.
   Peng, L. and Goeldner, M. 1998. Photoregulation of cholinesterase activities with caged cholinergic ligands. Methods Enzymol. 291:265‐278.
   Philipson, K.D., Gallivan, J.P., Brandt, G.S., Dougherty, D.A., and Lester, H.A. 2001. Incorporation of caged cysteine and caged tyrosine into a transmembrane segment of the nicotinic ACh receptor. Am. J. Physiol. Cell Physiol. 281:C195‐C206.
   Pirrung, M.C., Drabik, S.J., Ahamed, J., and Ali, H. 2000. Caged chemotactic peptides. Bioconjug. Chem. 11:679‐681.
   Qiao, L., Kozikowski, A.P., Olivera, A., and Spiegel, S. 1998. Synthesis and evaluation of a photolyzable derivative of sphingosine 1‐phosphate—caged SPP. Bioorg. Med. Chem. Lett. 8:711‐714.
   Rossi, F.M. and Kao, J.P. 1997. Nmoc‐DBHQ, a new caged molecule for modulating sarcoplasmic/endoplasmic reticulum Ca2+ ATPase activity with light flashes. J. Biol. Chem. 272:3266‐3271.
   Roy, P., Rajfur, Z., Jones, D., Marriott, G., Loew, L., and Jacobson, K. 2001. Local photorelease of caged thymosin β4 in locomoting keratocytes causes cell turning. J. Cell Biol. 153:1035‐1048.
   Ruane, P.H., Bushan, K.M., Pavlos, C.M., D'Sa, R.A., and Toscano, J.P. 2002. Controlled photochemical release of nitric oxide from O2‐benzyl‐substituted diazeniumdiolates. J. Am. Chem. Soc. 124:9806‐9811.
   Scott, R.H., Pollock, J., Ayar, A., Thatcher, N.M., and Zehavi, U. 2000. Synthesis and use of caged sphingolipids. Methods Enzymol. 312:387‐400.
   Tatsu, Y., Shigeri, Y., Ishida, A., Kameshita, I., Fujisawa, H., and Yumoto, N. 1999. Synthesis of caged peptides using caged lysine: Application to the synthesis of caged AIP, a highly specific inhibitor of calmodulin‐dependent protein kinase II. Bioorg. Med. Chem. Lett. 9:1093‐1096.
   Theriot, J.A. and Mitchison, T.J. 1991. Actin microfilament dynamics in locomoting cells. Nature 352:126‐131.
   Thuring, J.W., Li, H., and Porter, N.A. 2002. Comparative study of the active site caging of serine proteases: Thrombin and factor Xa. Biochemistry 41:2002‐2013.
   Walker, J.W., McCray, J.A., and Hess, G.P. 1986. Photolabile protecting groups for an acetylcholine receptor ligand. Synthesis and photochemistry of a new class of o‐nitrobenzyl derivatives and their effects on receptor function. Biochemistry 25:1799‐1805.
   Walker, J.W., Somlyo, A.V., Goldman, Y.E., Somlyo, A.P., and Trentham, D.R. 1987. Kinetics of smooth and skeletal muscle activation by laser pulse photolysis of caged inositol 1,4,5‐trisphosphate. Nature 327:249‐252.
   Walker, J.W., Gordon, P.R., McCray, J.A., and Trentham, D.R. 1988. Photolabile 1‐(2‐nitrophenyl)ethyl phosphate esters of adenine nucleotide analogues. Synthesis and mechanism of photolysis. J. Am. Chem. Soc. 110:7170‐7177.
   Walker, J.W., Feeney, J., and Trentham, D.R. 1989a. Photolabile precursors of inositol phosphates. Preparation and properties of 1‐(2‐nitrophenyl)ethyl esters of myo‐inositol 1,4,5‐trisphosphate. Biochemistry 28:3272‐3280.
   Walker, J.W., Reid, G.P., and Trentham, D.R. 1989b. Synthesis and properties of caged nucleotides. Methods Enzymol. 172:288‐301.
   Walker, J.W., Gilbert, S.H., Drummond, R.M., Yamada, M., Sreekumar, R., Carraway, R.E., Ikebe, M., and Fay, F.S. 1998. Signaling pathways underlying eosinophil cell motility revealed by using caged peptides. Proc. Natl. Acad. Sci. U.S.A. 95:1568‐1573.
   Walseth, T.F., Aarhus, R., Gurnack, M.E., Wong, L., Breitinger, H.G., Gee, K.R., and Lee, H.C. 1997. Preparation of cyclic ADP‐ribose antagonists and caged cyclic ADP‐ribose. Methods Enzymol. 280:294‐305.
   Wang, Q., Scheigetz, J., Roy, B., Ramachandran, C., and Gresser, M.J. 2002. Novel caged fluorescein diphosphates as photoactivatable substrates for protein tyrosine phosphatases. Biochim. Biophys. Acta 1601:19‐28.
   Wilcox, M., Viola, R.W., Johnson, K.W., Billington, A.P., Carpenter, B.K., McCray, J.A., Guzikowski, A.P., and Hess, G.P. 1990. Synthesis of photolabile “precursors” of amino acid neurotransmitters. J. Org. Chem. 55:1585‐1589.
   Williger, B.T., Reich, R., Neeman, M., Bercovici, T., and Liscovitch, M. 1995. Release of gelatinase A (matrix metalloproteinase 2) induced by photolysis of caged phosphatidic acid in HT 1080 metastatic fibrosarcoma cells. J. Biol. Chem. 270:29656‐29659.
   Wu, N., Deiters, A., Cropp, T.A., King, D., and Schultz, P.G. 2004. A genetically encoded photocaged amino acid. J. Am. Chem. Soc. 126:14306‐14307.
   Yu, H.S., Saw, J.H., Hou, S., Larsen, R.W., Watts, K.J., Johnson, M.S., Zimmer, M.A., Ordal, G.W., Taylor, B.L., and Alam, M. 2002. Aerotactic responses in bacteria to photoreleased oxygen. FEMS Microbiol. Lett. 217:237‐242.
   Zhao, J., Gover, T.D., Muralidharan, S., Auston, D.A., Weinreich, D., and Kao, J.P. 2006. Caged vanilloid ligands for activation of TRPV1 receptors by 1‐ and 2‐photon excitation. Biochemistry 45:4915‐4926.
   Zou, K., Cheley, S., Givens, R.S., and Bayley, H. 2002. Catalytic subunit of protein kinase A caged at the activating phosphothreonine. J. Am. Chem. Soc. 124:8220‐8229.
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