Modeling capabilities bond rotations

Significant Structure Theory and Eucken s Polymer Model. If we drop the restriction that the bulky species represent only Ice-I-like structures and reserve the term ice-like for water molecules which have merely the same spatial arrangement as ice (i.e., tetrahedrally hydrogen-bonded), we may include in this two-state theory (in which we have a bulky and a dense species) the treatment by Marchi and Eyring (107). This is a special case of the significant structure theory of liquids and introduces, as a specific element, fluidized vacancies in addition to the individual monomers (which, in turn, are assumed capable of free rotation). 

O-methylation on the basis of structural similarities between D- and L-fucose derivatives as noted in three-dimensional models. Thus, a similarity in profile and in regions of low hydrogen-bonding capability is evident between 2-O-methyl-D-fucose and L-fucose, if the latter is rotated 180° about its horizontal axis. This phenomenon is even more apparent in the binding of D-fucose derivatives to the L-fucose-binding lectin of the eel167 (see Section VI,1). 

Replacement of an amino acid by proline introduces conformational constraint by elimination of rotation about the carbon-nitrogen bond in the 5-membered ring. Proline in positions 5 and 13 is acceptable in the receptor bound conformation while in position 10 it is not.° ° Using this information, a conformation capable of receptor interaction has been proposed (O which is different from conformations proposed based on physical studies in solution. This model led to the design of analogs of the compound having Asn-5 and Thr-12 and Phe-6 and Phe-11 replaced by cystine (2 3,... 

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