Plant protein interactions studied using AFM force spectroscopy: nanomechanical and adhesion properties

Abstract

The present work was focused on the nanomechanical and adhesion properties of the napin (2S albumin) and cruciferin (12S globulin) rapeseed (Brassica napus L.) proteins, respectively, a low and high molecular weight seed protein. Using chemically modified AFM tips, force spectroscopy experiments demonstrated notable differences in the tip-protein interaction strength with regard to the nature of the protein and pH of the aqueous environment. The results clearly underline the role of residence time and electrostatic interactions in the protein-protein adhesion force. Although the nanomechanical experiments concerned more than a single molecule, unfolding length and force characteristics of the rapeseed proteins have been statistically found to be sensitive to the structural properties of the protein. This study provides insight into the characterization of rapeseed proteins and then a better knowledge of their interaction and assembling at the nanoscale range.

Atomic force microscopy of food assembly: Structural and mechanical insights at the nanoscale and potential opportunities from other fields

“…If unfolding occurs prior to unbinding, only the last or "jumpoff" peak is considered (Burgain et al, 2014b;Jin, Lafer, Peng, Smith, & Nossal, 2013). Among food proteins, the interaction between two cruciferin or napin plant proteins was measured this way (Fahs & Louarn, 2013). Protein-protein unbinding kinetics can alternatively be measured as a function of time using a constant pulling force (or force clamp).…”

“…This approach has not been used on food systems (Manibog, Yen, & Sivasankar, 2017). In other cases, the AFM tip was functionalized with methyls, hydroxyls or other groups to measure the adhesion of proteins (Fahs & Louarn, 2013), bacteria (Dorobantu, Bhattacharjee, Foght, & Gray, 2008) or Saccharomyces cerevisiae yeast (Ahimou, Denis, Touhami, & Dufrene, 2002) to hydrophilic or hydrophobic surfaces. The grafting of bacteria or cells onto AFM tips to measure their adhesion to surfaces (Beaussart et al, 2014;Friedrichs et al, 2013) or to other bacteria (Formosa-Dague et al, 2016) has also been done.…”

“…The unfolding of single proteins is a difficult experiment to implement and interpret, because of the small dimensions of proteins or of their secondary or ternary structures. After immobilization onto mica (Touhami & Dutcher, 2009) or onto gold (Fahs & Louarn, 2013), it is possible to unfold a single β-lactoglobulin, napin or cruciferin with a silicon nitride AFM tip pressed against the protein for 0.5-5 s, then retracted. It is also possible to graft the protein onto the AFM tip, to press it against gold and pull it (Fahs & Louarn, 2013).…”

“…9 C) where the last peak indicates rupture between the tip and the protein (detachment at maximal length L max ) and intermediate peaks represent unfolding of the protein's weakest structural elements, e.g., domains, loops or segments in contact with the substrate. The distance between two consecutive peaks indicates the length of the unfolded element, and not all domains may be extended if detachment occurs first (Fahs & Louarn, 2013). When β-lactoglobulin is immobilized at the surface of an oil droplet, it partially denatures to fit at the oil/water interface.…”

Biocompounds from rapeseed oil industry co‐stream as active ingredients for skin care applications

“…Rapeseed is one of the leading oilseed crops, ranking the first with respect to oil production in the EU, and third after soybean and palm worldwide [14]. Processing rapeseeds into vegetable oil generates a residue which accounts for 60 -70% of the total seed mass, reaching around 13,1 million tons of rapeseed press cake per year [15].…”