ISSN:
1432-1017
Keywords:
UV damage
;
sodium channels
;
axon
;
UV absorption
;
polarization
;
tryptophan
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract UV irradiation of squid giant azons at wavelengths of 280 or 290 nm produces nearly the same rate of irreversible decrease of sodium currents. The rate of photodeactivation is unaffected by extensive removal of axoplasm with pronase, and it is independent of temperature in the range 5° to 20°C. The photochemical effect appears to be all or nothing. It does not alter the time course and the voltage dependence for activation and inactivation of the residual currents. Similar deactivation rates were produced by irradiations of the same intensity, but linearly polarized either parallel or perpendicular to the axon. The efficiency of the deactivation process is close to that expected if it was caused by the photooxidation of a single tryptophan residue per sodium channel. Owing to the geometry of the preparation the lack of polarization asymmetry suggests that this residue assumes nearly random (or pseudo-random) orientation in the three-dimensional structure of the sodium channel corresponding to the closed state.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00255516
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