A continuous wave laser T-jump apparatus and its application to chemical reactions in hemoglobin single crystals.
A laser temperature jump apparatus is constructed where the T-jump is achieved
by means of the direct absorption of continuous laser radiation of low
intensity by a solid sample. The final temperature in the irradiated volume
element is reached when the absorbed radiation power equals the dissipation
of heat by heat conduction. The time range from the beginning of irradiation
to the stationary state depends on the geometry of the irradiated volume
element and is less than 10 ms. The heating laser beam is simultaneously
used to detect the relaxation to the new chemical equilibrium in the sample.
Relaxation processes with relaxation rates between 10(2) s-1 and less than
10(-3) s-1 on samples with volumes less than 10(-3) mm3 may be investigated
using this T-jump method. One application of this method is the determination
of reaction rates of ligand reactions in hemoglobin single crystals. Rate
constants obtained for the reaction of thiocyanate with crystallized horse
methemoglobin are presented.