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Deep Proteome Profiling by Isobaric Labeling, Extensive Liquid Chromatography, Mass Spectrometry, and Software-assisted Quantification
Published on: November 15, 2017
Increasing the Throughput and Reproducibility of Activity-Based Proteome Profiling Studies with Hyperplexing and
Hanna G Budayeva1, Taylur P Ma1, Shuai Wang2
1Department of Microchemistry, Proteomics and Lipidomics, Genentech, Inc., South San Francisco, California 94080, United States.
This paper introduces a new software tool called inSeqAPI that allows researchers to create custom data collection methods for mass spectrometry. Using this tool, the authors developed a technique called PairQuant, which significantly increases the number of proteins identified in complex experiments. By combining different labeling strategies, PairQuant enables the analysis of 36 experimental conditions simultaneously. This approach improves the detection of specific protein sites that could be targeted by new drugs, particularly within the cell nucleus. The study demonstrates that these custom algorithms can match or exceed the performance of standard commercial software while providing greater flexibility for complex proteomic research.
Area of Science:
- Proteomics and Activity-Based Proteome Profiling (ABPP) methodology
- Analytical chemistry and mass spectrometry instrumentation
Background:
Current mass spectrometry workflows often struggle to balance high throughput with deep proteome coverage in complex biological samples. Researchers frequently face limitations when attempting to analyze large numbers of experimental conditions simultaneously. This uncertainty drove the development of advanced intelligent data acquisition strategies. Prior research has shown that real-time database searching can enhance the identification of peptides labeled with isobaric tags. However, existing vendor-provided software often lacks the flexibility required for custom experimental designs. No prior work had resolved the need for a programmable interface to build bespoke acquisition algorithms. This gap motivated the creation of a new application programming interface for instrument control. The field requires more adaptable tools to improve the reproducibility and efficiency of large-scale proteomic investigations.
Purpose Of The Study:
The study aims to increase the throughput and reproducibility of proteomic profiling experiments through intelligent data acquisition strategies. Researchers sought to address the limitations of existing vendor-provided software in handling complex, hyperplexed samples. They recognized the need for a more flexible platform to construct novel data acquisition algorithms. This motivation led to the development of an instrument application programming interface. The authors intended to demonstrate that custom algorithms could match the performance of standard methods while enabling more complex experimental designs. They specifically focused on improving the quantification of cysteine sites within the proteome. By integrating protein-level and peptide-level labeling, they aimed to expand the number of conditions analyzed in a single sample. The project ultimately sought to facilitate the identification of druggable sites on critical nuclear proteins.
Main Methods:
The review approach involved developing a programmable instrument interface to control data acquisition parameters directly. Researchers designed the software to enable the creation of custom algorithms for complex proteomic workflows. They utilized biotinylated cysteine peptides to assess the efficacy of their real-time search implementation. The team compared the performance of their custom interface against established vendor-provided acquisition methods. For the hyperplexing experiments, they integrated protein-level isotopic labeling with peptide-level isobaric tagging. This combined labeling strategy allowed for the simultaneous processing of 36 distinct experimental conditions. The investigators applied these techniques to analyze ligandable cysteine sites within the nucleus. They evaluated the success of the acquisition strategy by calculating the percentage of peptide pair coverage and the total number of quantified sites.
Main Results:
The PairQuant method achieved approximately 98% coverage of both peptide pair partners during hyperplexed experiments. This approach yielded a 40% improvement in the number of quantified cysteine sites compared to non-real-time acquisition strategies. The authors observed that their real-time search method within the custom interface performed similarly to equivalent commercial vendor methods. By applying this technique to nuclear proteins, they identified additional druggable sites on transcription regulators. These sites were specifically located on protein- and DNA-interaction domains. The researchers also successfully mapped sites on nuclear ubiquitin ligases using the hyperplexed workflow. These results confirm that programmable acquisition enhances the depth of proteome coverage in complex samples. The data demonstrate that the new software effectively supports high-throughput and reproducible proteomic profiling studies.
Conclusions:
The authors demonstrate that their custom application programming interface provides a robust framework for designing novel mass spectrometry acquisition strategies. Their findings indicate that this software performs comparably to established commercial methods while offering increased experimental flexibility. The implementation of the hyperplexing approach allows for the simultaneous analysis of 36 distinct conditions. This strategy achieves high coverage of peptide pairs, ensuring reliable data across complex samples. The researchers report a significant increase in the quantification of cysteine sites compared to standard acquisition techniques. These improvements facilitate the discovery of potential drug targets on transcription regulators and nuclear ubiquitin ligases. The study highlights the utility of programmable data acquisition for expanding the scope of proteomic profiling. Future applications of this tool may enhance the depth and consistency of large-scale biological datasets.
Frequently Asked Questions
The researchers propose PairQuant, a method utilizing protein-level isotopic labeling and peptide-level Tandem Mass Tag (TMT) labeling. This approach enables the analysis of 36 conditions in one sample, achieving approximately 98% coverage of peptide pairs and a 40% increase in quantified cysteine sites versus non-real-time search methods.
The authors developed inSeqAPI, an instrument application programming interface. This tool allows users to construct novel data acquisition algorithms, providing greater flexibility than standard vendor-provided software for complex experiments like Activity-Based Proteome Profiling.
Real-time database search methods are necessary to improve the depth of proteome coverage. By performing gas-phase purification during the acquisition process, these strategies filter out noise, allowing the instrument to focus on high-quality peptide signals.
The study utilizes biotinylated cysteine peptides to validate the performance of the new interface. These peptides serve as a benchmark to compare the custom acquisition method against existing commercial standards.
The researchers measured the number of quantified cysteine sites and the percentage of peptide pair coverage. They observed a 40% improvement in site quantification and 98% coverage of partners using their hyperplexed approach.
The authors propose that their method facilitates the identification of additional druggable sites on protein- and DNA-interaction domains. This implication suggests that programmable acquisition can uncover targets on transcription regulators and nuclear ubiquitin ligases.

