Cells are lysed in a urea-containing buffer, cellular proteins are digested by proteases, and the resulting peptides are purified by reversed-phase solid-phase extraction. Phospho-peptides are then subjected to enrichment using PTMScan® IMAC Beads. Unbound peptides are removed through washing, and the captured phospho-peptides are eluted with basic pH buffer. Reversed-phase purification is performed on microtips to desalt and separate peptides from impurities prior to concentrating the enriched peptides for LC-MS/MS analysis. A detailed protocol is included with the beads.
Immobilized metal affinity chromatography, or IMAC, has been widely used to enrich proteins and peptides from biological samples by binding to clusters of negative charge. Divalent transition metal ions Co2+, Cu2+, Ni2+, and Zn2+ are often used to purify proteins rich in poly-Histidine or Cysteine as well as proteins with metal affinity. Trivalent metal ions, Fe3+, Ga3+, Al3+, as well as Ti4+ and Zr4+ are commonly used for phosphopeptide enrichment for proteomic studies (1). Iminodiacetic acid (IDA) or nitrilotriacetic acid (NTA) are used for chelating the metal ions to agarose-coated beads. In comparison studies, NTA has been shown to perform better than IDA at selectively capturing and identifying more phosphopeptides. Ga3+ and Fe3+ are comparable with respect to the number of phosphopeptides identified (2). Compared to metal oxide affinity chromatography (MOAC) using TiO2, Fe3+ IMAC performed marginally better with TiO2 having a preference for acidic phosphopeptides (pI > 4) relative to Fe3+ which preferred less acidic peptides (pI < 4) (3). The PTMScan® Fe-NTA Magnetic Beads offer an efficient tool for phosphopeptide enrichment with little or no bias for phospho-residue context. They can be employed independently or in conjunction with immunoaffinity based enrichment to complement any PhosphoScan® LC-MS/MS proteomic study.
Except as otherwise expressly agreed in a writing signed by a legally authorized representative of CST, the following terms apply to Products provided by CST, its affiliates or its distributors. Any Customer's terms and conditions that are in addition to, or different from, those contained herein, unless separately accepted in writing by a legally authorized representative of CST, are rejected and are of no force or effect.
Products are labeled with For Research Use Only or a similar labeling statement and have not been approved, cleared, or licensed by the FDA or other regulatory foreign or domestic entity, for any purpose. Customer shall not use any Product for any diagnostic or therapeutic purpose, or otherwise in any manner that conflicts with its labeling statement. Products sold or licensed by CST are provided for Customer as the end-user and solely for research and development uses. Any use of Product for diagnostic, prophylactic or therapeutic purposes, or any purchase of Product for resale (alone or as a component) or other commercial purpose, requires a separate license from CST. Customer shall (a) not sell, license, loan, donate or otherwise transfer or make available any Product to any third party, whether alone or in combination with other materials, or use the Products to manufacture any commercial products, (b) not copy, modify, reverse engineer, decompile, disassemble or otherwise attempt to discover the underlying structure or technology of the Products, or use the Products for the purpose of developing any products or services that would compete with CST products or services, (c) not alter or remove from the Products any trademarks, trade names, logos, patent or copyright notices or markings, (d) use the Products solely in accordance with CST Product Terms of Sale and any applicable documentation, and (e) comply with any license, terms of service or similar agreement with respect to any third party products or services used by Customer in connection with the Products.