Molecular Biology

Protein Interactions

Sigma® has prepared product lists for commonly used protocols from Cold Spring Harbor Protocols.

  View the protocol on

Selected Protocol from "Protein-Protein Interactions: A Molecular Cloning Manual, 2nd Edition,", Erica A. Golemis and Peter D. Adams.

View the protocol "Protein Interactions Captured by Chemical Cross-linking: One-Step Cross-linking with Formaldehyde" at

Owen W. Nadeau and Gerald M. Carlson

This protocol describes a method for chemical cross-linking of proteins using formaldehyde. With the exception of zero-length cross-linkers, formaldehyde has the shortest cross-linking span (~2-3 Å) of any cross-linking reagent, thus making it an ideal tool for detecting specific protein-protein interactions with great confidence. Despite its simple chemical structure (CH2O), formaldehyde’s single carbonyl group functions essentially as a homobifunctional reagent and is capable of conjugating targets through two different chemical pathways. In Mannich-type reactions, which typically require elevated temperatures (37 °C or above) for a period of 2-24 hours for acceptable yields, formaldehyde condenses with amines (1°, 2°, or salts of ammonia) and compounds with active hydrogens to form stable cross-links. Formaldehyde also reacts with amines to form highly reactive immonium cations that are reactive toward protein-containing nucleophiles, including sulfhydryls, amines, phenols, and imidazoles. The latter reaction is more rapid than the former and is generally the more predominant in typical protein cross-linking reactions at ambient temperatures.

Buy this book, Z719145

Products Available for this Protocol

Protocol Material Description Product #  Product Name Add to Cart
SDS L4390 Sodium dodecyl sulfate, for molecular biology, ≥98.5% (GC)
Paraformaldehyde 158127 Paraformaldehyde, powder, 95%
HEPES H4034 HEPES, Biotechnology Performance Certified, ≥99.5% (titration), cell culture tested
EDTA E5134 Ethylenediaminetetraacetic acid disodium salt dihydrate, for molecular biology, ≥99%

back to top
View all available product lists for Cold Spring Harbor Laboratory Protocols

Product Association Disclaimer: The Sigma-Aldrich products listed for this specific protocol were selected either to match or to supplement the products listed within the actual protocol. The products/reagents from Sigma-Aldrich have been qualified for usage, but may not have been validated for this specific application. Please refer to the detailed product description on the usage of specific products of interest.