Acid-free paper durable acid-free paper. Archival paper is meant to be used for publications of high legal, historical, or significant value. In the USA, such paper must also be approved in accordance with the ANSI standards. The international standard for "permanent" paper is ISO 9706 and for "archival" paper, the standard is ISO 11108. Often, cotton rag paper is used for archival purposes, as it is not made from wood-based pulp. Thus, "archival paper" is sometimes broken down into two categories: Acid-free paper Acid-free paper is paper that if infused in water yields a neutral or basic pH (7 or slightly greater).
Gel electrophoresis of proteins the dye. The proteins are detected as blue bands on a clear background. When more sensitive method than staining by Coomassie is needed silver staining is usually used. Silver staining is a sensitive procedure to detect trace amounts of proteins in gels, but can also visualize nucleic acid or polysaccharides. Similarly as in nucleic acid gel electrophoresis, tracking dye is often used. Anionic dyes of a known electrophoretic mobility are usually included in the sample buffer. A very common tracking dye is Bromophenol blue. This dye is coloured at alkali and neutral pH and is a small negatively charged molecule