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Silver staining detects proteins after electrophoretic separation on polyacrylamide gels. Its main positive features are its excellent sensitivity (in the low nanogram range) and the use of very simple and cheap equipment and chemicals. The sequential phases of silver staining are protein fixation, then sensitization, then silver impregnation, and finally image development. Several variants of silver staining are described here, which can be completed in a time range from 2 h to 1 day after the end of the electrophoretic separation. Once completed, the stain is stable for several weeks.

Microtubule-binding proteins are conveniently divided into two large groups: MAPs (microtubule-associated proteins), which can stabilize, anchor, and/or nucleate microtubules, and motors, which use the energy of ATP hydrolysis for a variety of functions, including microtubule network organization and cargo transportation along microtubules. Here, we describe the use of Taxol-stabilized microtubules for purification of MAPs, motors, and their complexes from Xenopus egg extracts. Isolated proteins are analysed using sodium dodecyl sulfate gel electrophoresis and identified by various mass spectrometry and database mining technologies. Found proteins can be grouped into three classes: (1) known MAPs and motors; (2) proteins previously reported as associated with the microtubule cytoskeleton, but without a clearly defined cytoskeletal function; (3) proteins not yet described as having microtubule localization. Sequence-similarity methods employed for protein identification allow efficient identification of MAPs and motors from species with yet unsequenced genomes.

Because of the outstanding separating capabilities of two-dimensional electrophoresis for complete proteins, it would be advantageous to be able to apply it to all types of proteins. Unfortunately, severe solubility problems hamper the analysis of many classes of proteins, but especially membrane proteins. These problems arise mainly in the extraction and isoelectric focusing steps, and solutions are sought to improve protein solubility under the conditions prevailing during isoelectric focusing. These solutions deal mainly with chaotropes and new detergents, which are both able to enhance protein solubility. The input of these compounds in proteomics analysis of membrane proteins is discussed, as well as future directions.