Eastern blotting

The eastern blot is a biochemical technique used to analyze protein post translational modifications (PTM) such as lipids, phosphomoieties and glycoconjugates. It is most often used to detect carbohydrate epitopes. Thus, eastern blotting can be considered an extension of the biochemical technique of western blotting. Multiple techniques have been described by the term eastern blotting, most use proteins blotted from SDS-PAGE gel on to a PVDF or nitrocellulose membrane. Transferred proteins are analyzed for post-translational modifications using probes that may detect lipids, carbohydrate, phosphorylation or any other protein modification. Eastern blotting should be used to refer to methods that detect their targets through specific interaction of the PTM and the probe, distinguishing them from a standard far-western blot. In principle, eastern blotting is similar to lectin blotting (i.e. detection of carbohydrate epitopes on proteins or lipids).

Definition of the term eastern blotting is somewhat confused due to multiple sets of authors dubbing a new method as eastern blotting, or a derivative thereof. All of the definitions are a derivative of the technique of western blotting developed by Towbin in 1979. The current definitions are summarized below in order of the first use of the name; however, all are based on some earlier works. In some cases, the technique had been in practice for some time before the introduction of the term.

There is clearly no single accepted definition of the term. A recent highlight article has interviewed Ed Southern, originator of the Southern blot, regarding a re-christening of eastern blotting from Tanaka et al. The article likens the eastern blot to "fairies, unicorns, and a free lunch" and states that eastern blots "don't exist." The eastern blot is mentioned in an immunology textbook which compares the common blotting methods (Southern, northern, and western), and states that "the eastern blot, however, exists only in test questions."

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