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Does the "C3 effect" offset the Δ}2 effect, as regards the solution flexibility of aldoses?



Mallory J. Morris, Andre Striegel


The solution flexibility of carbohydrates in general, and of monosaccharides in particular, influences a variety of molecular recognition and regulatory processes, from the cryoprotectant ability of glycoproteins to the relative ease with which certain sugars penetrate phospholipid membranes. For aldoses and other monosaccharides, this flexibility is dictated by the orientations of the various hydroxyl (OH) groups present as, depending on the number and position of axial OH groups, a variety of structures can coexist in solutions at equilibrium. In 1950, as part of his pioneering studies on the shape of pyranoside rings, Reeves described the delta 2 effect, the greater destabilization of the pyranose ring conformation when the OH group on carbon 2 (C2) is in the axial position. It was later proposed by Angyal that the delta 2 effect could be cancelled by the presence of an axial OH on C3, termed here the "C3 effect." Employing size-exclusion chromatography, an entropically-controlled separation technique, we have investigated whether or not the C3 and delta 2 effects indeed do compensate for one another with respect to their influence on the solution flexibility of select aldohexoses and aldopentoses. As will be seen, while qualitatively and semi-quantitatively this mutual cancellation of effects does occur in aldohexoses, it does not appear to do so in aldopentoses. An explanation for the latter appears to lie in the variety of anomers and conformers present in equilibrium solutions of those aldopentoses studied.


Solution conformational entropy, size-exclusion chromatography, aldohexoses, aldopentoses, {&#916;}2 effect, “C<sub>3</sub> effect.”


Morris, M. and Striegel, A. (2014), Does the &#147;C<sub>3</sub> effect&#148; offset the {&#916;}2 effect, as regards the solution flexibility of aldoses?, Biopolymers, [online], (Accessed April 13, 2024)
Created April 20, 2014, Updated October 12, 2021