In chemistry, a contact number (CN) is a simple solvent exposure measure that measures residue burial in proteins. The definition of CN varies between authors, but is generally defined as the number of either C β {\displaystyle \beta } or C α {\displaystyle \alpha } atoms within a sphere around the C β {\displaystyle \beta } or C α {\displaystyle \alpha } atom of the residue. The radius of the sphere is typically chosen to be between 8 and 14Å.
See also Kissing number, a similar concept in mathematics
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