UV versus 2-photon uncaging.
At the last Annual Meeting of the Society for Neuroscience there was a “MINI-symposium” entitled: “Flashy science: controlling neural function with light.” A report of the talks has been published in J. Neurosci. (2005) 25: 10358-10365 (DOI:10.1523/JNEUROSCI.3515-05.2005). Scott Thompson is the communicating author of this report and writes about his own work (Science (2001) 293: 2272–2275) on UV uncaging of CNB-glu or Nmoc-glu in comparison to the work we have done using 2-photon uncaging of MNI-glu (Nature Neuroscience (2001) 4: 1086-1092). Thompson says that the Mill Hill group lead by David Ogden found that the 2-photon cross-section of MNI-glu is “low (Kiskin et al., 2002), so that it requires high intensities or extend illumination (Carter and Sabatini, 2004) to achieve millimolar concentrations . The power levels necessary can induce photodamage (Kiskin et al., 2002).”
There are several serious errors of fact in these statements.
Firstly, The Mill Hill group did not measure the 2-photon cross-section of MNI-glu in the 2002 paper (they did not even use MNI-glu in their work), we did in our 2001 paper.
Secondly, the duration of uncaging by Carter & Sabatini was 200-500 microseconds, most would not characterise this period as “extended”, though it is 10-times longer than UV uncaging used by Thompson.
Thirdly, the photodamage that the Mill Hill group found from 2-photon excitation came about at 640 nm not 720 nm-there is a huge difference in photoxicity between these two wavelengths, so Thompson is tarring us with brush that does not apply. Equally significantly, the toxicity found by the Mill Hill group was using 500-1000 uncaging events at a single point at power levels greater than 7 mW-a power dosage we do not even come close to in our work.
Thus, Thompson’s comparison of his own UV uncaging with our 2-photon work is disingenuous.
Carter AG, Sabatini BL (2004) State-dependent calcium signaling in dendritic spines of striatal medium spiny neurons. Neuron 44: 483–493.
Kiskin NI, Chillingworth R, McCray JA, Piston D, Ogden D (2002) The efficiency of two-photon photolysis of a “caged” fluorophore, o-1-(2nitrophenyl)ethylpyranine, in relation to photodamage of synaptic terminals. Eur Biophys J 30: 588–604.
At the last Annual Meeting of the Society for Neuroscience there was a “MINI-symposium” entitled: “Flashy science: controlling neural function with light.” A report of the talks has been published in J. Neurosci. (2005) 25: 10358-10365 (DOI:10.1523/JNEUROSCI.3515-05.2005). Scott Thompson is the communicating author of this report and writes about his own work (Science (2001) 293: 2272–2275) on UV uncaging of CNB-glu or Nmoc-glu in comparison to the work we have done using 2-photon uncaging of MNI-glu (Nature Neuroscience (2001) 4: 1086-1092). Thompson says that the Mill Hill group lead by David Ogden found that the 2-photon cross-section of MNI-glu is “low (Kiskin et al., 2002), so that it requires high intensities or extend illumination (Carter and Sabatini, 2004) to achieve millimolar concentrations . The power levels necessary can induce photodamage (Kiskin et al., 2002).”
There are several serious errors of fact in these statements.
Firstly, The Mill Hill group did not measure the 2-photon cross-section of MNI-glu in the 2002 paper (they did not even use MNI-glu in their work), we did in our 2001 paper.
Secondly, the duration of uncaging by Carter & Sabatini was 200-500 microseconds, most would not characterise this period as “extended”, though it is 10-times longer than UV uncaging used by Thompson.
Thirdly, the photodamage that the Mill Hill group found from 2-photon excitation came about at 640 nm not 720 nm-there is a huge difference in photoxicity between these two wavelengths, so Thompson is tarring us with brush that does not apply. Equally significantly, the toxicity found by the Mill Hill group was using 500-1000 uncaging events at a single point at power levels greater than 7 mW-a power dosage we do not even come close to in our work.
Thus, Thompson’s comparison of his own UV uncaging with our 2-photon work is disingenuous.
Carter AG, Sabatini BL (2004) State-dependent calcium signaling in dendritic spines of striatal medium spiny neurons. Neuron 44: 483–493.
Kiskin NI, Chillingworth R, McCray JA, Piston D, Ogden D (2002) The efficiency of two-photon photolysis of a “caged” fluorophore, o-1-(2nitrophenyl)ethylpyranine, in relation to photodamage of synaptic terminals. Eur Biophys J 30: 588–604.
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