High-throughput characterization of increasingly complex and heterogeneous protein structures (including both primary and higher order structures) is now required in a variety of fields ranging from personalized medicine (biomarkers) to industrial-scale production of recombinant proteins (for both product quality control and feedback adaptive process control). However, extensive structural characterization usually involves several multi-step processes that are both time- and labor-consuming, and frequently cannot be implemented in a high-throughput format. Additional complication arises from the presence of multiple protein sub-populations in the analytical/clinical/production sample, which may exhibit altered functional or biophysical properties despite having very similar structural characteristics (e.g, small soluble aggregates, aberrant glycoforms, disulfide- scrambled species, etc.). The proposed research aims at developing a robust and versatile analytical technology using the novel cross-path reactive chromatography (XP-RC) platform with on-line detection by electrospray ionization mass spectrometry (ESI MS) augmented by protein ion manipulation in the gas phase (including both conventional top-down MS/MS and the limited charge reduction technique developed in our laboratory). XP-RC allows protein chemical modifications (such as disulfide reduction, covalent labeling, H/D exchange, etc.) to be combined in-line with the separation step and enables real-time MS measurements that are not adversely affected by components incompatible with the ESI process. This is achieved by utilizing the unique elution characteristics (retention) of proteins and small-molecule reagents in non-denaturing chromatographic media (size exclusion or ion exchange); during their retention the proteins can be exposed to various reagents to induce the desired modification(s) in a highly controlled fashion. Our preliminary data provide strong evidence that multiple reactions can be carried out inside a single column in a sequential manner by exposing the protein to multiple reagent plugs as it moves through the column prior to MS detection/characterization of the modified protein. The initial efforts will be focused on implementing differential in-line reduction of disulfide bonds followed by free thiol capping with isotopically labeled reagents for high-throughput disulfide mapping and glycoform profiling (Aim 1). These efforts will be then extended to enable selective reduction of inter-chain disulfides while preserving the non-covalent interactions and internal disulfides in complex protein systems to enable identification of binding partners within such systems; MS/MS detection will allow binding interfaces within such selectively preserved complexes to be localized (Aim 2). An alternative approach will utilize in-line chemical labeling as a means of localizing the binding interfaces. Lastly, the XP-RC/MS platform will be used to implement dilution-free H/D exchange characterization of protein complexes and small soluble aggregates in the top-down fashion (Aim 3).

Public Health Relevance

Reliable characterization of both covalent structure and conformation of complex heterogeneous proteins is required in a variety of fields ranging from personalized medicine to industrial-scale production of recombinant proteins. Extensive characterization involves multi-step processes that are both time- and labor-consuming and are usually a poor fit for a high-throughput format. The proposed research will make a critical contribution towards streamlining protein analysis at a variety of levels by developing a versatile platform that is based on cross-path reactive chromatography (where protein modifications are carried out in-line) with real time detection by mass spectrometry.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Enabling Bioanalytical and Imaging Technologies Study Section (EBIT)
Program Officer
Krepkiy, Dmitriy
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Massachusetts Amherst
Schools of Arts and Sciences
United States
Zip Code