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In chemistry, pyramidal inversion (also umbrella inversion) is a fluxional process in compounds with a pyramidal molecule, such as ammonia (NH 3) "turns inside out". [1] [2] It is a rapid oscillation of the atom and substituents, the molecule or ion passing through a planar transition state. [3]
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.
The methylene bridge (methanediyl group) In organic chemistry, a methylene bridge, methylene spacer, or methanediyl group is any part of a molecule with formula −CH 2 −; namely, a carbon atom bound to two hydrogen atoms and connected by single bonds to two other distinct atoms in the rest of the molecule.
As stated above, a chair flip is a ring inversion specifically of cyclohexane (and its derivatives) from one chair conformer to another, often to reduce steric strain.The term, "flip" is misleading, because the direction of each carbon remains the same; what changes is the orientation.
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.
The main chain–main chain hydrogen bond is replaced by a side chain–main chain hydrogen bond. 3D computer superimposition shows that, in proteins, they occur [12] as one of the same four types that beta turns do, except that their relative frequency of occurrence differs: type II’ is the most common, followed by types I, II and I’.
In chemistry, a disulfide (or disulphide in British English) is a compound containing a R−S−S−R′ functional group or the S 2− 2 anion.The linkage is also called an SS-bond or sometimes a disulfide bridge and usually derived from two thiol groups.
A bridge can be categorized by what it is designed to carry, such as trains, pedestrian or road traffic (road bridge), a pipeline (Pipe bridge) or waterway for water transport or barge traffic. An aqueduct is a bridge that carries water, resembling a viaduct, which is a bridge that connects points of equal height.