Inexpensive synthetic-based matrix for both conventional and rapid purification of protein A- and tandem affinity purification-tagged proteins

Multiparameter screen optimizes immunoprecipitation

Immunoprecipitation (IP) coupled with mass spectrometry effectively maps protein-protein interactions when genome-wide, affinity-tagged cell collections are used. Such studies have recorded significant portions of the compositions of physiological protein complexes, providing draft 'interactomes'; yet many constituents of protein complexes still remain uncharted. This gap exists partly because high-throughput approaches cannot optimize each IP. A key challenge for IP optimization is stabilizing in vivo interactions during the transfer from cells to test tubes; failure to do so leads to the loss of genuine interactions during the IP and subsequent failure to detect. Our high-content screening method explores the relationship between in vitro chemical conditions and IP outcomes, enabling rapid empirical optimization of conditions for capturing target macromolecular assemblies.

Real-time monitoring of immunoglobulin G levels in milk using an ordered porous layer interferometric optical sensor

Immunoglobulin G (IgG) is a significant ingredient of immunological activity in milk and colostrum, the activity and content of which is easily disturbed by potentially conditional variant during sterilization. Therefore, developing robust methods for the detection of IgG levels in milk is especially important. Herein, protein A from the Staphylococcus aureus functionalized silica colloidal crystalline film (SCC@SPA) sensing unit combined with ordered porous layer interferometry (OPLI) for IgG detection in untreated bovine milk was developed. Calibration curves in milk and buffer were set up by the variations of the optical thickness (OT) of the sensing unit after the IgG association and dissociation phases. The influence of temperature on the level of IgG was evaluated. Furthermore, the identification of IgG levels with pasteurized milk and ultrahigh temperature (UHT) sterilized milk from the market randomly was successfully carried out without any sample pretreatment. More importantly, compared with other methods, this novel method has the advantages of convenient operation, low cost, and suitability for point-of-care (POC) testing.

Affinity proteomics to study endogenous protein complexes: pointers, pitfalls, preferences and perspectives

Dissecting and studying cellular systems requires the ability to specifically isolate distinct proteins along with the co-assembled constituents of their associated complexes. Affinity capture techniques leverage high affinity, high specificity reagents to target and capture proteins of interest along with specifically associated proteins from cell extracts. Affinity capture coupled to mass spectrometry (MS)-based proteomic analyses has enabled the isolation and characterization of a wide range of endogenous protein complexes. Here, we outline effective procedures for the affinity capture of protein complexes, highlighting best practices and common pitfalls.