helix

mathematics

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structure of proteins

  • Linus Pauling
    In Linus Pauling: Elucidation of molecular structures

    …configuration, later called the alpha helix. The most significant aspect of Pauling’s structure was its determination of the number of amino acids per turn of the helix. During this same period he became interested in deoxyribonucleic acid (DNA), and early in 1953 he and protein crystallographer Robert Corey published their…

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work of Pappus

  • In Pappus of Alexandria

    …properties of several varieties of spirals and other curved lines and demonstrates how they can be used to solve another classical problem, the division of an angle into an arbitrary number of equal parts. Book 5, in the course of a treatment of polygons and polyhedra, describes Archimedes’ discovery of…

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surface, In geometry, a two-dimensional collection of points (flat surface), a three-dimensional collection of points whose cross section is a curve (curved surface), or the boundary of any three-dimensional solid. In general, a surface is a continuous boundary dividing a three-dimensional space into two regions. For example, the surface of a sphere separates the interior from the exterior; a horizontal plane separates the half-plane above it from the half-plane below. Surfaces are often called by the names of the regions they enclose, but a surface is essentially two-dimensional and has an area, while the region it encloses is three-dimensional and has a volume. The attributes of surfaces, and in particular the idea of curvature, are investigated in differential geometry.

This article was most recently revised and updated by William L. Hosch.
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