Abstract

Interactions of biomolecules at interfaces are important for a variety of physiological processes. Among these, interactions of lectins with monosaccharides have been investigated extensively in the past, while polysaccharide-lectin interactions have scarcely been investigated. Here, we explore the adsorption of galactomannans (GM) extracted from Prosopis affinis on cellulose thin films determined by a combination of multi-parameter surface plasmon resonance spectroscopy (MP-SPR) and atomic force microscopy (AFM). The galactomannan adsorbs spontaneously on the cellulose surfaces forming monolayer type coverage (0.60 ± 0.20 mg·m−2). The interaction of a lectin, Concavalin A (ConA), with these GM rendered cellulose surfaces using MP-SPR has been investigated and the dissociation constant KD (2.1 ± 0.8 × 10−8 M) was determined in a range from 3.4 to 27.3 nM. The experiments revealed that the galactose side chains as well as the mannose reducing end of the GM are weakly interacting with the active sites of the lectins, whereas these interactions are potentially amplified by hydrophobic effects between the non-ionic GM and the lectins, thereby leading to an irreversible adsorption.

Highlights

  • Hemicelluloses are important constituents of plant cell walls and feature rich structural diversity.For instance, xylans are prominent examples in soft and hard wood [1,2,3,4,5] while other hemicelluloses such as galactomannans (GM) mainly occur in the endosperm [3,5,6]

  • The adsorption of the GM was studied in situ by multi-parameter surface plasmon resonance spectroscopy (MP-SPR) spectroscopy and revealed irreversible adsorption on the cellulose thin films

  • Concavalin A (ConA) was adsorbed at different concentrations and the dissociation constant KD was determined

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Summary

Introduction

Hemicelluloses are important constituents of plant cell walls and feature rich structural diversity. Xylans are prominent examples in soft and hard wood [1,2,3,4,5] while other hemicelluloses such as galactomannans (GM) mainly occur in the endosperm [3,5,6]. The structure of GM is composed of a β-1,4-D-mannopyranosyl backbone with α-D-galactopyranosyl residues attached to C6 of the mannosyl units [7]. The main structural motifs of GMs are classified according to the ratio between the galactose and the mannose units, usually referred to as M/G. Available GM such as locust bean gum and guar gum feature M/G ratios of 3.5:1 and 1.5:1, respectively [10,11,12]. The galactose side chains impede interactions between mannose backbones and significantly reduce the degree

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