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An alpha helix (or α-helix) is a sequence of amino acids in a protein that are twisted into a coil (a helix). The alpha helix is the most common structural arrangement in the secondary structure of proteins. It is also the most extreme type of local structure, and it is the local structure that is most easily predicted from a sequence of amino ...
The beta sheet (β-sheet, also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A β-strand is a stretch of polypeptide chain typically 3 to 10 amino ...
A 310 helix is a type of secondary structure found in proteins and polypeptides. Of the numerous protein secondary structures present, the 3 10 -helix is the fourth most common type observed; following α-helices, β-sheets and reverse turns. 3 10 -helices constitute nearly 10–15% of all helices in protein secondary structures, and are ...
A machine screw. The right-handed helix (cos t, sin t, t) for 0 ≤ t ≤ 4π with arrowheads showing direction of increasing t. A helix (/ ˈhiːlɪks /; pl. helices) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis.
Ribbon diagram. Ribbon diagrams, also known as Richardson diagrams, are 3D schematic representations of protein structure and are one of the most common methods of protein depiction used today. The ribbon depicts the general course and organisation of the protein backbone in 3D and serves as a visual framework for hanging details of the entire ...
Definition. According to one definition, a turn is a structural motif where the C α atoms of two residues separated by a few (usually 1 to 5) peptide bonds are close (less than 7 Å [0.70 nm]). [1] The proximity of the terminal C α atoms often correlates with formation of an inter main chain hydrogen bond between the corresponding residues.
Protein secondary structure is the local spatial conformation of the polypeptide backbone excluding the side chains. [ 1 ] The two most common secondary structural elements are alpha helices and beta sheets, though beta turns and omega loops occur as well.
Transmembrane protein. Schematic representation of transmembrane proteins: 1) a single-pass membrane protein (α-helix) 2) a multipass membrane protein (α-helix) 3) a multipass membrane protein β-sheet. The membrane is represented in light yellow. A transmembrane protein is a type of integral membrane protein that spans the entirety of the ...