Collaborative Research: Molecular Determinants of Power Inputs and Outputs of Synchronous Flight Muscle in Vivo

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Project Title: Collaborative Research: Molecular Determinants of Power Inputs and Outputs of Synchronous Flight Muscle In Vivo Principal Investigators: Irving, Thomas C, and Thomas L. Daniel NSF Project Numbers: IOS 1022058 and 1022471 All moving animals, from humans to flying insects, operate with muscles that not only cyclically generate force, they do so while generating significant heat. This research project is aimed at understanding the molecular basis and physiological consequences of temperature dependent force generation in muscle. As with many other biological rate processes, the speed and power output of muscle is strongly influenced by temperature. Surprisingly, heat generation by the muscles that power flight in Hawkmoths show a large temperature gradient, with more superficial muscles operating at cooler temperatures than deeper, more insulated, muscles. This temperature gradient has profound functional consequences and is likely a general result for many moving creatures. The researchers will examine the notion that thermal gradients lead to functional gradients. Thus, deeper warmer, muscle subunits may serve as power generators driving locomotion whereas cooler subunits may act as elastic energy storage systems. All of this function operates with protein motors that will be examined from the molecular level to the fully intact muscle in a moving animal. A mix of high-speed x-ray imaging methods and whole muscle force and energy measurement methods will be used to tackle this problem. The combination of heat generation by the volume of muscle in humans and other animals, combined with processes that dissipate heat suggests that temperature gradients may be more common than historically assumed. Thus it is likely a general phenomenon that the temperature dependent function of muscle will vary spatially within a single muscle group. In addition, the flight muscle of Manduca sexta will provide a new model system for understanding muscle function in animals in general. A result of this project will be development and refinement of x-ray diffraction methods to probing muscle function in vivo.