Rid 10a series

Purity and molecular weight of polysaccharide were assessed by high performance gel permeation chromatography (HPGPC) [54 (link)]. The assay was performed on an Agilent 1260 Infinity HPLC instrument fitted with a Shodex OHpak SB-804 HQ column (8.0 mm × 300 mm, Tokyo, Japan) and elution with 0.2 mol/L Na₂SO₄ at a flow rate of 0.5 mL/min. The signals were measured using a refractive index detector (Agilent RID-10A Series). The molecular weight was estimated by reference to a calibration curve made by pullulan standards; molecular weights of pullulan standards were 5.9, 9.6, 21.1, 47.1, 107, 200, 344, and 708 kDa, respectively.

For Fourier transform infrared spectroscopy (FT-IR) (Thermo Fisher Nicolet iS50, Waltham, MA, USA) analysis, the sample (2 mg) was first mixed with the dried KBr (w/w = 1:100), and then pressed into a flake for measurement. The spectrum was recorded in the range of 500–4000 cm⁻¹ at a resolution of 2 cm⁻¹. The molecular weight of the isolated chrysolaminarin was measured by high-performance gel permeation chromatography (HPGPC) (Agilent 1260, Santa Clara, CA, USA) equipped with a TSK-G3000 PW_XL column (7.5 mm × 300 mm) and a refractive index detector (Agilent RID-10A Series) [20 (link)]. The molecular weight was estimated by reference to a calibration curve made with T-series Dextran standards (1–670 kDa). The monosaccharide composition was determined using gas chromatography–mass spectrometry (GC–MS) as described by Xia et al. [15 (link)]. Identification of the derivatized monosaccharide was carried out according to the retention time and mass fragmentation patterns of the standards. For nuclear magnetic resonance (NMR) analysis (Bruker Advance III 500, Karlsruhe, Germany), the sample (10 mg) was dissolved in D₂O (deuterium oxide) in an NMR tube, and the ¹H (500 MHz) and ¹³C (125 MHz) spectra were recorded at 30 °C.