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Rapid relaxation of single frog skeletal muscle fibres following laser flash photolysis of the caged calcium chelator, diazo‐2
Author(s) -
Mulligan I.P.,
Ashley C.C.
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)81090-7
Subject(s) - flash photolysis , diazo , calcium , chemistry , biophysics , chelation , flash (photography) , photodissociation , relaxation (psychology) , skeletal muscle , photochemistry , anatomy , biology , kinetics , inorganic chemistry , optics , organic chemistry , neuroscience , physics , quantum mechanics , reaction rate constant
Diazo‐2 is a calcium chelator based on BAPTA [(1989) J. Biol. Chem., in press], whose electron withdrawing diazoacetyl group may be rapidly (2000 s −1 ) converted photochemically to an electron donating carboxymethyl group by exposure to near ultraviolet light, producing an increase in its calcium affinity ( K d changes from 2.2μM to 0.073 μM) without steric modification of the metal binding site. Photolysis of a 2 mM solution of this compound with a brief flash of light from a frequency‐doubled ruby laser (347 nm) caused single skinned muscle fibres from the semitendinosus muscle of the frog Rana temporaria to relax with a mean half‐time of 60.4±5 ms (range 30–100 ms, n = 15) at 12°C, which is faster than the relaxation observed in intact muscles (half‐time 133 ms at 14°C [(1986) J. Mol. Biol. 188, 325–342]) and similar to the rate of the fast phase of tension decay in intact single fibres (20 s −1 at 1O°C [(1982) J. Physiol. 329, 1–20]).