Flip-flop disorder

Hydrogen Bond Flip-Flop Disorder Conformational and Configurational... 

In biological structures, the conformational flip-flop disorder will occur in the carbohydrates, the cyclodextrins, in water, or generally, in all systems where hydroxyl groups are involved. 

From Flip-Flop Disorder to Ordered Homodromic Arrangements at Low Tbmperature... 

The cooperative effect determines the formation of extended O-H - O patterns. The conclusions that can be drawn from a comparison of the crystal structures of / -cyclodextrin 11H20 above and below the transition temperature (—46°C) are twofold. First, the flip-flop disorder is dynamic. Second, on reducing... 

When this type of disorder occurs in long cooperative chains or in cyclic systems of hydrogen bonds, it has been described as a. flip-flop mechanism [118], because it must proceed from bond to bond like a domino effect and involves only two well-defined states. 

The net result is the same two different states with nearly identical geometry and, presumably, nearly identical energy. This is favorable for entropical reasons and we expect considerable entropic stabilization of the disordered flip-flop hydrogen bonds. 

Do the flip-flop hydrogen bonds represent dynamical or statical disorder ... 

Fig. 18.15. a Stereo view of y8-cyclodextrin 11H20 at 120 K, with water molecules W1 to W14. Only one 0(2) -0(3 ) flip flop has remained which is part of the flip-flop quadrilateral marked by a solid square, b View of the homodromic cycle formed in the cavity of jff-cyclodextrin at 120 K. At room temperature, these five water molecules are statistically disordered over eight sites... 

Saenger W, Betzel Ch, Hingerty BE, Brown GM (1982) Flip-flop hydrogen bonding in a partially disordered system. Nature (Lond) 296 581-583... 

The lipids in a lipid bilayer may translocate across the bilayer from one monolayer to the apposed monolayer. This transmembrane translocation process, which is also known as flip-flop, is slow for lipids with large polar head groups such as glyc-erolipids and sphingophospholipids but can be fast in the case of lipids with very small polar moieties such as cholesterol. Typical first-order rate constants for transmembrane translocation of a phospholipid-like molecule in liquid-disordered phase bilayers prepared from l-palmitoyl-2-oleoylphosphatidylcholine (POPC) are s and may be about 10-fold slower in... 

Assuming that the orientation of an asymmetric molecule can be represented by a vector or a spin, the flip-flop orientational disorder within the different... 

W. Saenger, Ch. Betzel, B. Hingerty, and G. M. Brown, Flip-Flop Hydrogen Bonding in a Partially Disordered System, Nature (London) 296, 581-583 (1982). 

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