Monomeric green fluorescent protein as a protein standard for small angle scattering

Protein small angle scattering (SAS) has become increasing important in structural biochemistry, due to the increased performance and specification of new instruments and advances in the software and hardware used to analyse the data. Whilst all of this is encouraging, there is a lack of standardised experimental methodology within the community. Although a number of protein standards are currently used in SAS experiments to allow accurate molecular weight determination, each has specific advantages and disadvantages. We therefore propose the use of a mutated monomeric enhanced green fluorescent protein, as a protein standard, abbreviated to m-eGFP. It has a number of advantages over the currently used protein standards, for example it is cheap and easy to produce. It can be expressed in large amounts (>40 mg/L) in both hydrogenated and deuterated form. The mutation means it is highly monodisperse and GFP being a beta-barrel structure is thermodynamically stable over a number of days, giving highly reproducible results. We therefore believe m-eGFP is a good protein standard for small angle scattering (SAS).