Luminescent/paramagnetic xanthene probes in the study of labeled biological assemblies

摘要

The techniques for specifying the angular distribution of luminescent and paramagnetic probes on biological assemblies have been combined in the investigation of probe orientation and order of labeled myosin cross-bridges muscle fibers. This combination has been accomplished on two levels involving: (i) a mathematical formalism that permits the combination of data from individual luminescent and paramagnetic probes, and (ii) the introduction of a family of specific extrinsic probes that are capable of producing an interpretable luminescent and paramagnetic signal when attached to a muscle fiber. The mathematical formalism has been applied to several probes of the myosin cross-bridge in muscle fibers to establish that the cross-bridge rotates during muscle contraction to produce muscle shortening (Burghardt & Ajtai, 1992 Biochemistry 31, 200; Ajtai et al., 1992 Biochemistry 31, 207). The luminescent/paramagnetic probes have also been employed in the investigation of order and orientation of cross-bridge in muscle fibers (Ajtai & Burghardt, 1992 Biochemistry 31, 4265). The properties of these dual nature probes invites further development of experimental techniques exploiting the high orientation sensitivity of paramagnetic probes with the ability of the probe to absorb and emit light. Flash-photolysis electron paramagnetic resonance is one such technique that may prove useful in the investigation of probe order in biological assemblies.