Fluorescent labeling affected the structural/conformational properties of arabinoxylans.

• Arabinoxylan was fluorescently labeled by DMSO/DBTD and reductive amination methods. • The solubility of conjugates was decreased with increasing degree of substitution. • The conjugates had a higher Mw and similar monosaccharide composition compared to AX. • The chain conformation of conjugates became more compact after labeling. Three fluorescent-labeling methods, including DMSO/DBTD, reductive amination and fluoresceinamine (FA), were applied to label arabinoxylan (AX). The conjugates were named AF, ATF and ACF, respectively. Compared to AX, the water solubility of AF significantly decreased while that of ATF significantly increased (p < 0.05); both showed decreased solubility with increasing degree of substitution (DS). However, AX was not successfully labeled by the FA method due to poor solubility. The structural and conformational properties of the AF and ATF conjugates under different DS were compared. Results showed that fluorochrome (FITC) was successfully grafted onto AX molecule by using the DMSO/DBTD and reductive amination methods. A slight increased Mw was noticed for both AF and ATF. AF existed in a more compact conformation, while the chain conformation of ATF was more elongated at a lower DS (1.15 %) and more compact at a higher DS (1.34 %). [ABSTRACT FROM AUTHOR]