Influence of glycosidic linkage on solution conformational entropy of oligosaccharides: Malto‐ vs. isomalto‐ and cello‐ vs. laminarioligosaccharides

Abstract

Carbohydrate flexibility can influence a variety of recognition, processing, and end-use properties, at both the polymeric and oligomeric levels. The influence of glycosidic linkage, in particular, on carbohydrate flexibility is manifested in properties such as bacterial selectivity, solution viscosity, and the ability to regulate the spread of disease. Here, we apply size-exclusion chromatography, an entropically controlled technique, to determine the solution conformational entropy (ΔS) of various oligosaccharide series. The aim of the present study is to highlight how, for a given anomeric configuration, glycosidic linkage affects ΔS, and to do so quantitatively as a function of degree of polymerization (DP). To this end, we compare ΔS values for DP 1-7 for malto- and isomaltooligosaccharides, and for DP 1-5 for cello- and laminarioligosaccharides. To do so, we realize previously unattainable separations of disaccharides via a strict size-exclusion mechanism. Also given here are the requirements for extending our method to other oligomers, as well as to biopolymers

Influence of molecular configuration and conformation on the electromigration of oligosaccharides in narrow bore capillaries

“…The resulting migration time versus DP plot exhibited a curve shaped increase for both oligosaccharide ladders in the low DP range. This curvature, reflecting the relative changes in hydrodynamic radius with increasing DP, was in accordance with previously reported results based on SEC [25]. Maltooligosaccharides from 1 to 7 SUs showed an average increase of 1 min per ⌬GU, changing to a linear increase of approximately 0.70 min per ⌬GU after around 7-8 GUs.…”

Does the “C3 effect” offset the Δ2 effect, as regards the solution flexibility of aldoses?

“…The particular experimental method employed is size-exclusion chromatography (SEC), 12 an entropicallycontrolled separation technique, which has previously been applied successfully to determining the solution conformational entropy of a variety of mono-, di-, and oligosaccharides. [13][14][15][16][17][18] As will be seen for aldohexoses, while the D2 effect is greater than the C 3 effect (in semiquantitative agreement with Reeves's original results), in aqueous solution at quasiphysiological conditions to a large extent these effects do compensate for one another with respect to their influence on solution conformational entropy. Results for the aldopentoses studied are less straightforward, their interpretation requiring consideration of the variety of conformers and anomers, and the equilibrium amongst these, that result from the need to minimize the intramolecular strain that is created as a result of the select placement of axial OH groups.…”

“…As described by Angyal as early as 1968, “It is thought that axial hydroxyl groups on each of C 2 and C 3 would cancel each other's effect.” Here, we systematically investigate how the C 3 and Δ2 effects affect the solution conformational entropy −Δ S (for an explanation of the use of the minus sign, see Calculation of the solution conformational entropy −Δ S ) of equilibrium solutions of aldopentoses and aldohexoses. The particular experimental method employed is size‐exclusion chromatography (SEC), an entropically‐controlled separation technique, which has previously been applied successfully to determining the solution conformational entropy of a variety of mono‐, di‐, and oligosaccharides . As will be seen for aldohexoses, while the Δ2 effect is greater than the C 3 effect (in semiquantitative agreement with Reeves's original results), in aqueous solution at quasi‐physiological conditions to a large extent these effects do compensate for one another with respect to their influence on solution conformational entropy.…”

“…Calculation of the standard conformational entropy difference between the mobile and stationary phases for the monosaccharides in solution was based on the retention times of peak maxima ( V R ), as measured by SEC, as well as the solute distribution coefficient ( K SEC ). These two parameters are related via: where V 0 is the void volume of the columns and V i is the total column volume. The internal pore volume of the system is defined as the difference between V i and V 0 .…”

“…Calculation of the standard conformational entropy difference between the mobile and stationary phases for the monosaccharides in solution was based on the retention times of peak maxima (V R ), as measured by SEC, as well as the solute distribution coefficient (K SEC ). These two parameters are related via [12][13][14][15][16][17][18] :…”