Rosalind Franklin and Raymond Gosling: Obtained the X-ray crystallography pattern of DNA in 1952.
James Watson and Francis Crick: Noted the simplicity and symmetry of the DNA pattern.
Morris Wilkins: Worked with Franklin to derive basic dimensions of DNA structure.
B-Form X-ray Pattern:
The pattern is distinctive due to the X shape, indicating a helix structure.
Consistency: The regularity of the pattern suggests consistent dimensions for the helix, such as its diameter.
Dimension Derivations from the X-ray Pattern:
Spot Distance: Closer spots on the X-ray pattern indicate larger actual distances in the DNA structure.
Horizontal Bars: Correspond to helical turns.
Vertical Distance Between Bars (34 Å): Measures the height of one helical turn.
Distance from Middle to Top of Pattern (3.4 Å): Corresponds to the distance between two stacked base pairs.
Helical Repeat: With the height of one helical repeat being 34 Å and the distance between base pairs being 3.4 Å, there are 10 nucleotides per helical repeat.
Helical Pitch: The degree of rise can be calculated from the angle the X makes with the horizontal axis.
Interpretations by Rosalind Franklin:
Phosphate Groups: Deduced to be on the outside of the helix.
Basic Dimensions and Structure: Franklin's measurements provided key dimensions for the DNA structure.