Size and shape of the repetitive domain of high molecular weight wheat gluten proteins. 1. Small angle neutron scattering

The solution structure of the central repetitive domain of high molecular weight (HMW) wheat gluten proteins has been investigated for a range of concentrations and temperatures using mainly small-angle neutron scattering. A representative part of the repetitive domain (dBl) was studied as well as an "oligomer" basically consisting of four dBl units, which has a length similar to the complete central domain. The scattering data over the entire angular range of both proteins are in quantitative agreement with a structural model based on a worm-like chain, a model frequently used in polymer theory. This model describes the "supersecondary, structure" of dBl and dB4 as a semiflexible cylinder with a length of about 235 and 900 Angstrom, respectively, and a cross-sectional diameter of about 15 Angstrom. The flexibility of both proteins is characterized by a persistence length of about 13 Angstrom. Their structures are thus quantitatively identical, which implies that the central HMW domain can be elongated while retaining its structural characteristics. It seems conceivable that the flexible cylinder results from a helical structure, which resembles the beta-spiral observed in earlier studies on gluten proteins and elastin. However, compared to the previously, proposed structure of a (stiff) rod, our experiments clearly indicate flexibility of the cylinder. (C) 2003 Wiley Periodicals, Inc.