Crystallography 101. Welcome to BR's Macromolecular Crystallography Website on ruppweb.org. Lectures. The Interactive Structure Factor Tutorial. Welcome to the structure factor tutorial! The aim of this tutorial is to learn about structure factors, phases, symmetry, and the relationship between the structure factors and the electron density map. The tutorial uses an interactive tool, the `structure factor applet'. The structure factor applet has four windows. Top left is the control window, in which you can select reflections and set their values by entering values in the text boxes.
Magnitudes and phases are encoded as colours using the same scheme as the Book of Fourier. Bugs and fixesMost browsers with reliable Java implementations work fine, but if you have problems, please tell me. The Structure Factor Applet may be installed locally and/or customised for teaching topics not covered here, with certain conditions. Back to my YSBL page. Chemistry | 5.069 Crystal Structure Analysis, Spring 2010 | Syllabus. Crystallographic Tutorials. (IUCr) International Union of Crystallography. Site Information. Kevin Cowtan's Book of Fourier, University of York, UK. It is possible to reconstruct an image from the Fourier magnitudes alone if we have a similar image to provide phase information.
For example, suppose we are trying to reconstruct the image of a cat, and have the fourier magnitudes for it. Since for this experiment we only have the magnitudes of the transform it is represented in monochrome, and we cannot reconstruct the image. In addition to these magnitudes, we have an image which we know is similar to the missing cat. This image is of a Manx (tailless) cat. One simple method to try and restore the image of the cat is to simply calculate an image using the known Fourier magnitudes from the cat transform with the phases from the manx cat: Despite the fact that the phases contain more structural information about the image than the magnitudes, the missing tail is restored at about half of its original weight. This suggests a simple way to restore the tail at full weight: apply double the correction to the magnitudes.