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Research has been conducted on the intrastrand cross-linking of actin filaments by N-(4-azido-2-nitrophenyl) putrescine. Results indicate that this cross-linking inhibits force generation with myosin.

A novel heterobifunctional photo-cross-linking reagent, N-(4-azido-2-nitrophenyl)-putrescine, was synthesized and covalently bound to Gln-41 of rabbit skeletal muscle actin. The G-actin was polymerized and the resulting F-actin was intermolecularly cross-linked by irradiation with ultraviolet light. Experimental results showed that the reagent is capable of cross-linking Gln-41 to Cys-374 on two adjacent monomers of the skeletal muscle actin.

The structural and functional properties of the intrastrand actin filaments of the heterobifunctional photo-cross-linking reagent, N-(4-azido-2-nitrophenyl)-putrescine, between Gln-41 and Cys-374 on adjacent monomers were investigated. Extensive cross-linking of F-actin results in its loss of ability to activate myosin ATPase at 60 degrees Celsius. Results also showed the uncoupling between force generation and other events in actomyosin interactions and demonstrated the important role of actin filament structure and function in the contractile process.

Actin filaments partially cross-linked with the heterobifunctional photo-cross-linking reagent, N-(4-azido-2-nitrophenyl)-putrescine, between Gln-41 and Cys-374 on adjacent monomers in the long-pitch helix were described. The filaments were depolymerized and fractionated into pools of longitudinal cross-linked dimers, trimers and higher-order oligomers. Experimental results showed the importance of lateral actin-actin interaction for the activation of myosin ATPase and the polymerization of actin by myosin subfragment.

Gel filtration technique was used to purify actin dimer cross-linked along the pitch of the F-actin helix by N-(4-azido)-2-nitrophenyl (ANP). The results provide insights into more active participation of actin via myosin-induced conformational changes during the force generating cross-bridge cycle.