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Visualization of Single and Aggregated Hulless Oat (Avena nuda L.) (1→3),(1→4)-β-d-Glucan Molecules by Atomic Force Microscopy and Confocal Scanning Laser Microscopy
journal contribution
posted on 2006-02-08, 00:00 authored by Jia Wu, Yun Zhang, Lan Wang, Bijun Xie, Haibo Wang, Shaoping DengSurfactants were used to disperse oat β-glucan. Atomic force microscopy (AFM) images of the resulting
samples revealed a distribution of extended chainlike molecules and allowed, for the first time, direct
visualization of single oat β-glucan molecules with cross-sectional heights of about 0.44 nm. The
number-average contour length (Ln) and root-mean-square end-to-end distance (〈Ree2〉1/2) measured
from the AFM images were 938 and 912 nm, respectively. The calculated persistence length (Lp)
was 526 nm. The weight-average molecular weight (Mw) calculated from single β-glucan molecules
was 4.43 × 105. Samples without surfactant showed a strong tendency to form aggregates. The
sample concentration, reserving time, and calcofluor as well as freezing could affect the formation of
aggregates. These aggregates were visualized by both AFM and confocal scanning laser microscopy.
The shape of the aggregates changed from small dots with diameters of approximately 20−50 nm to
microfibrils over 3 μm long with the increasing of the concentration of oat β-glucan from 10 to 100
μg/mL. The particle size distribution obtained by a laser particle size analyzer was 926 nm, which
confirmed the size of oat β-glucan molecules obtained from AFM images.
Keywords: Oat; β-glucan; atomic force microscope; confocal scanning laser microscopy; sodium
dodecyl sulfate; particle size