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research papers
The properties of intensity data in fiber diffraction patterns are considered with the aim of developing strategies for structural studies of helical macro-molecular assemblies. A quantitative calculation is made of the number of independent intensity measurements in a fiber diffraction pattern and the number of degrees of freedom in an image of a helical object. These calculations are based on sampling theory in cylindrical coordinates. Several novel schemes for sampling intensities in a fiber diffraction pattern are demonstrated. A class of Patterson-like functions are introduced that may be useful in determining the helical symmetry of a particle from diffraction data. The use of these results in determining the significance of details of structural models based on fiber diffraction data is discussed.