Conformational States of Sunflower (Helianthus annuus) Helianthinin:  Effect of Heat and pH

Abstract

The structure and solubility of helianthinin, the most abundant protein of sunflower seeds, was investigated as a function of pH and temperature. Dissociation of the 11S form (hexamer) into the 7S form (trimer) gradually increased with increasing pH from 5.8 to 9.0. High ionic strength (I = 250 mM) stabilizes the 11S form at pH > 7.0. Heating and low pH resulted in dissociation into the monomeric constituents (2-3S). Next, the 7S and 11S forms of helianthinin were isolated and shown to differ in their secondary and tertiary structure, and to have denaturation temperatures (T(d)) of 65 and 90 degrees C, respectively. Furthermore, the existence of two populations of the monomeric form of helianthinin with denaturation temperatures of 65 and 90 degrees C was described. This leads to the hypothesis that helianthinin can adopt two different conformational states: one with T(d) = 65 degrees C and a second with T(d) = 90 degrees C.

Purification and biochemical characterization of 11S globulin from chan (Hyptis suaveolens L. Poit) seeds

“…Furthermore, under fixed storage conditions, the time seems to be an important factor. About 50% of sunflower 11S globulin at pH 7.0 and ionic strength of 30 mM, dissociates into the 7S form after five days of storage without subsequent re-association into 11S form (González-Pérez et al, 2004).…”

A new way of valorizing biomaterials: The use of sunflower protein for α-tocopherol microencapsulation

“…Protein powder was mixed with deionized water (3% w/w), and the mixture pH was adjusted to 1.0-13.0 with 4 M NaOH or 4 M HCl. Protein solution was stirred for 1 h at room temperature, and at 70°C, chosen to ensure higher solubility without protein denaturation, because the major SP globulin fraction (11S of helianthinin) still resists thermal denaturation at 90°C (Gonzalez-Perez et al, 2004). After stirring, the suspensions were centrifuged at 10,000 rpm for 15 min (Sigma Laborzentrifugen, Osterode, Germany).…”

Functional properties of proteins isolated from industrially produced sunflower meal

“…Without addition of NaCl, the alteration was more prominent at pH 2 where approximately 3 fold increase of the foam capacity was observed. According to González-Pérez et al (2004), the smaller foam volume of sunflower proteins in neutral or alkaline media is due to the relatively large molecules and stable conformation of helianthinin which impair their absorption at system interfaces. In acidic medium (pH < 3), globulins dissociate to monomers which increases the volume of the foam.…”

“…The extraction/precipitation of proteins with alcoholic or aqueous solutions is less toxic and more advantageous when used in the food industry but may also lead to altered functionality of the protein isolates (Moure, Sineiro, Dominguez, & Parajo, 2006). Most published studies on sunflower meal proteins have been performed under mild laboratory conditions where no change of the native structure and functions of the proteins occurred (Pawar, Patil, Sakhale, & Agarkar, 2001;González-Pérez et al, 2004;Pickardt et al, 2009). However, sunflower proteins obtained from industrially produced meal may have different functional characteristics due to the impact of the technological parameters of oil production and sunflower seed pre-treatment.…”