King's College London
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On the Veldt: The British Army in South Africa 1899-1902

Discovering the structure of actin

colour drawing showing actin as a chain of greenish spheres with bands running along in brown labelled Tropomyosin containing a few spheres labelled TroponinDiagram showing location of actin (1960s) During the 1960s, Hanson applied herself to discovering the actual structure of actin and thus obtain a clearer picture of how contraction occurs.

She and Lowy used the negative staining technique and the magnesium precipitation process to produce paracrystals of actin.

These revealed its essential helical structure and identified the vital role of tropomysin in the regulation of contraction. The results were also consistent with x-ray diffraction pictures.

This insight was an important component in the theory of cross bridges between the myosin and actin that provide the force for movement when the chemical energy conserved in ATP is converted into useful mechanical energy - a hypothesis developed out of the electron microscopy of Hugh and Andrew Huxley in the late 1950s.

Her work also helped explain the role of calcium uptake in muscle contraction.

Hanson's discovery at this time demonstrated how muscle protein fibres work at the molecular level to produce a more comprehensive and complete picture of muscle function and fully explain the microscope observations that underlay the sliding filament hypothesis.

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