A selenium atom is very dense and in X-ray diffraction studies these dense atoms are used as points of reference to overcome crystal phasing problems. Historically, selenium has been incorporated into protein crystals either by leaching selenium into previously formed crystals or by using proteins selenated via expression in selenomethionine media. Replacing your current detergent that previously produced poor X-ray diffraction results with selenium-based equivalent will create reference points and help to resolve your protein. In addition, recent membrane protein studies have suggested that detergents can bind at putative lipid binding sites on membrane proteins.