Alcian blue 8GX is primarily used for demonstrating acid mucopolysaccharides, which it does quite selectively. In recent years there has been some difficulty obtaining the dye. Alcian Blue 8GX is also suitable for detection of glycoproteins on nitrocellulose and in PAGE gels. There are other dyes similar to alcian blue, although not necessarily belonging to the same class of dyes. Alcian green has gained some popularity, and alcian yellow has been suggested, especially in a method for demonstrating Helicobacter. They are used for acid mucopolysaccharides in the same way as alcian blue. They have no particular advantage for demonstrating mucin. According to the Merck Index the groups marked X split off during staining.