The Yariv reagent: Behaviour in different solvents and interaction with a gum arabic arabinogalactanprotein

• β-d-Glc Yariv reagent aggregates, up to 300 units, in D2O.
• Aggregates of approx. 150 bind AGP, while aggregates of approx. 100 do not bind AGP.
• Aggregates are caused by both H-bonds and hydrophobic interactions.
• AGPs appear to need at least 5–7 (1 → 3)-β-linked galactose units to make aggregates with the Yariv reagent.

The β-d-Glc Yariv reagent is frequently used to isolate and to study the structure of arabinogalactan-proteins with the arabinogalactan type II structure. The present paper describes the aggregation features of the Yariv reagent in water, salt solutions and in organic solvents as determined by NMR, absorption spectroscopy and light scattering experiments. The results indicate that in water the Yariv reagent forms aggregates of up to 300 units and in 1% aqueous NaCl the degree of aggregation is approx. 150. The aggregates are formed both by H-bonds and hydrophobic interactions, the former appearing to be of most importance in water.The interaction between the Yariv reagent and an AGP fraction from gum arabic, showed a degree of aggregation of the Yariv reagent when using 1% NaCl to be of approx. 150 units, whereas disruption of the aggregate took place in 10% NaCl with an aggregation number of approx. 100.Partial acid hydrolysis of an AGP from gum Arabic (Acacia Senegal) and analyses of the linkage types remaining indicated that a certain length of (1 → 3)-β-linked galactose units was necessary for binding between the Yariv reagent and the AGP. This is in accordance to what also was recently observed by Kitazawa et al. (2013).