A multiplexed immunocapture liquid chromatography tandem mass spectrometry assay for the simultaneous measurement of myostatin and GDF-11 in rat serum using an automated sample preparation platform

Bioorthogonal Chemistry: Enzyme Immune and Protein Capture for Enhanced LC-MS Bioanalysis

Immunocapture liquid chromatography-mass spectrometry (IC-LC-MS) bioanalysis has become an indispensable technique across various scientific disciplines, ranging from drug discovery to clinical diagnostics. While traditional immunocapture techniques have proven to be effective, they often encounter limitations in sensitivity, specificity, and compatibility with MS analysis. Chemoenzymatic immunocapture and protein capture (IPC) offers a promising solution, combining the high specificity of antibodies or proteins with the versatility of enzymatic and chemical modifications. This Review explores the foundational principles of chemoenzymatic IPC and examines various modification strategies including bioorthogonal click-chemistry, enzymatic-tagging, and HaloTag/CLIP-tag. Recent advancements in chemoenzymatic IPC techniques have significantly expanded their applicability to a diverse range of biomolecules including small molecules, peptides, RNAs, and proteins. This Review focuses on improvements in analytical performance achieved through these innovative approaches. Moreover, we discuss the broad applications of chemoenzymatic immunocapture in drug discovery, clinical diagnostics, and environmental analysis and explore its potential for future advancements in bioanalysis. We propose a novel solid-phase chemoenzymatic IPC assay (SCEIA) that effectively utilizes bioorthogonal click chemistry and chemoenzymatic approaches for efficient IPC and target analyte release. In summary, chemoenzymatic IPC represents a transformative paradigm shift in IC-LC-MS bioanalysis. By overcoming the limitations of traditional IPC techniques, this approach paves the way for more robust, sensitive, and versatile analytical workflows.

Simultaneous quantification of the 22-kDa isoforms of human growth hormone 1 and 2 in human plasma by multiplexed immunocapture and LC-MS/MS

An LC-MS/MS method is presented for the simultaneous quantification of two structurally closely related protein biomarker isoforms, the 22-kDa isoforms of human growth hormone 1 and human growth hormone 2, in human plasma. It is based on multiplexed immunocapture using two monoclonal antibodies immobilized on magnetic beads, tryptic digestion and quantification of two specific signature peptides plus an additional peptide for estimation of total growth hormone related concentrations. A full validation according to international guidelines was performed across the clinically relevant concentration ranges of 0.5 to 50 ng/mL for growth hormone 1, and 2 to 50 ng/mL for growth hormone 2 and demonstrated satisfactory method performance in terms of accuracy, precision, stability and absence of interference. The method's applicability for routine analysis and its ability to effectively distinguish between GH1 and GH2 was demonstrated by the analysis of plasma samples from pregnant individuals to study the changes in growth hormone levels during pregnancy.

Low-density lipoproteins, resveratrol and quercetin as alternative additives to improve boar semen cooling

Low-density lipoproteins (LDL), quercetin (Q) and resveratrol (R) have been used for sperm preservation to improve sperm quality in different species. To evaluate the effects of LDL, Q and R during the cooling of boar semen. Fifteen boar semen samples were diluted in a BTS extender supplemented with the treatments: LDL at 6%, Q at 10 μM (Q10), 30 μM (Q30) and 50 μM (Q50), or R at 10 μM (R10), 30 μM (R30) and 50 μM. A control without supplementation was included. The semen was stored by cooling at 16°C for 96 h. Every 24 h, sperm motility and kinetics were evaluated using a computer-assisted sperm analyzer (IVOS). At 24 and 96 h of cooling, functional membrane integrity and mitochondrial membrane potential (ΔΨM) of sperm were evaluated by the hypoosmotic swelling test (HOST) an flow cytometry with JC-1 probe, respectively, LDL improved progressive motility of sperm during cooling. Likewise, LDL increased average path velocity (VAP) and straight-line velocity (VSL) and/or curvilinear velocity (VCL) during the first 48 h of cooling. The use of Q between 10 and 30 μM caused a reduction in total motility, progressive motility and amplitude of the lateral head displacement during the entire cooling period, as well as a decrease in VAP, VSL and VCL at 96 h of cooling. LDL, Q10, Q30 and Q50 modulated mitochondrial activity by reducing high-ΔΨM sperm at 0 and 96 h of cooling. During the cooling of the boar semen prior to artificial insemination, the parameters of sperm quality that could influence fertility decrease; however, the inclusion of antioxidants and additives that protect the plasma membrane, such as LDL, could mitigate the damaging effects on spermatozoa. It is concluded that LDL can improve the motility and kinetics of boar semen during cooling while it could modulating the sperm's mitochondrial activity. On the contrary, Q could alter the motility and kinetics of boar sperm during the cooling period.

Proximity labeling for investigating protein-protein interactions

The study of protein complexes and protein-protein interactions is of great importance due to their fundamental roles in cellular function. Proximity labeling, often coupled with mass spectrometry, has become a powerful and versatile tool for studying protein-protein interactions by enriching and identifying proteins in the vicinity of a specified protein-of-interest. Here, we describe and compare traditional approaches to investigate protein-protein interactions to current day state-of-the-art proximity labeling methods. We focus on the wide array of proximity labeling strategies and underscore studies using diverse model systems to address numerous biological questions. In addition, we highlight current advances in mass spectrometry-based technology that exhibit promise in improving the depth and breadth of the data acquired in proximity labeling experiments. In all, we show the diversity of proximity labeling strategies and emphasize the broad range of applications and biological inquiries that can be addressed using this technology.

Strategies for mass spectrometry-based phosphoproteomics using isobaric tagging

INTRODUCTION

Protein phosphorylation is a primary mechanism of signal transduction in cellular systems. Isobaric tagging can be used to investigate alterations in phosphorylation events in sample multiplexing experiments where quantification extends across all conditions. As such, innovations in tandem mass tag methods can facilitate the expansion of the depth and breadth of phosphoproteomic analyses.

AREAS COVERED

This review discusses the current state of tandem mass tag-centric phosphoproteomics and highlights advances in reagent chemistry, instrumentation, data acquisition, and data analysis. We stress that approaches for phosphoproteomic investigations require high-specificity enrichment, sensitive detection, and accurate phosphorylation site localization.

EXPERT OPINION

Tandem mass tag-centric phosphoproteomics will continue to be an important conduit for our understanding of signal transduction in living organisms. We anticipate that progress in phosphopeptide enrichment methodologies, enhancements in instrumentation and data acquisition technologies, and further refinements in analytical strategies will be key to the discovery of biologically relevant findings from phosphoproteomics studies.

Advances in quantitative high-throughput phosphoproteomics with sample multiplexing

Eukaryotic protein phosphorylation modulates nearly every major biological process. Phosphorylation regulates protein activity, mediates cellular signal transduction, and manipulates cellular structure. Consequently, the dysregulation of kinase and phosphatase pathways has been linked to a multitude of diseases. Mass spectrometry-based proteomic techniques are increasingly used for the global interrogation of perturbations in phosphorylation-based cellular signaling. Strategies for studying phosphoproteomes require high-specificity enrichment, sensitive detection, and accurate localization of phosphorylation sites with advanced LC-MS/MS techniques and downstream informatics. Sample multiplexing with isobaric tags has also been integral to recent advancements in throughput and sensitivity for phosphoproteomic studies. Each of these facets of phosphoproteomics analysis present distinct challenges and thus opportunities for improvement and innovation. Here, we review current methodologies, explore persistent challenges, and discuss the outlook for isobaric tag-based quantitative phosphoproteomic analysis.

Improved ultra-high performance liquid chromatographic method for simultaneous determination of five gout-related metabolites in human serum

Creatinine and purines are gout-related metabolites commonly quantified by liquid chromatography coupled with ultraviolet and mass spectrometry. However, the high cost of liquid chromatography coupled with mass spectrometry hindered its extensive use in ordinary hospitals and clinical laboratories. Using the traditional liquid chromatography method, the full separation of these metabolites in complex biological samples is still not achieved. In this study, an improved ultra-high-performance liquid chromatography with ultraviolet spectroscopy method was reported for quantitative determination of five gout-related metabolites (i.e., creatinine, uric acid, hypoxanthine, xanthine, and inosine) in human serum within 10 min. A UHPLC system equipped with a hydrophilic C18 column was used to improve separation, shorten analysis time, and increase analysis throughput. The performance of the method was validated by evaluating linearity (squared correlation coefficient > 0.9991), recovery (92.8-100.0%, with relative standard deviation < 4.7%), accuracy (relative errors < 14.6%), precision (0.2-4.1% for intraday and 2.1-7.3% for interday) and stability (-14.1 to 8.3% in autosampler for 12 h and -13.3 to 2.2% for freeze-thaw cycles). This method was successfully applied to quantify gout-related metabolites in serum samples of healthy controls and gout patients, which was expected to be used in the clinical investigation of gout at different stages.

Plasma growth differentiation factors 8 and 11 levels in cats with congestive heart failure secondary to hypertrophic cardiomyopathy

OBJECTIVES

Growth differentiation factor (GDF) 11 has been shown to reduce cardiac hypertrophy in mice. Low levels of GDF-11 are associated with cardiac hypertrophy in humans. The authors hypothesized that plasma GDF-11 level is decreased in cats with hypertrophic cardiomyopathy (HCM). Given the close homology between GDF-11 and myostatin/GDF-8, GDF-8 levels were also assessed.

ANIMALS

Thirty-seven client-owned cats were enrolled, including cats with normal cardiac structure (n = 16), cats with HCM or hypertrophic obstructive cardiomyopathy (HOCM; n = 14), and cats with HCM and congestive heart failure (CHF; n = 7).

METHODS

Plasma samples were analyzed for GDF-8 and GDF-11 using liquid chromatography tandem-mass spectrometry. Levels of GDF-8 and GDF-11 were compared between cats with normal cardiac structure, HCM or HOCM, and CHF.

RESULTS

No differences in GDF-11 concentrations were found between cats with normal cardiac structure and cats with HCM/HOCM, with or without history of CHF. Decreased GDF-8 concentrations were detected in cats with CHF compared to cats with HCM/HOCM without history of CHF (p=0.031) and cats with normal cardiac structure (p=0.027). Growth differentiation factor 8 was higher in cats with HOCM compared to those with CHF (p=0.002). No statistical difference was noted in GDF-8 level as a function of age, weight, or body condition score.

CONCLUSIONS

Plasma GDF-11 was not different between cats with HCM/HOCM and cats with normal cardiac structure regardless of age. Plasma GDF-8 was decreased in cats with CHF compared to cats with normal cardiac structure and cats with asymptomatic HCM/HOCM, suggesting a possible role in CHF development.

A sensitive antibody-free 2D-LC–MS/MS assay for the quantitation of myostatin in the serum of different species

Aim: Myostatin (MSTN) is an attractive therapeutic target for the treatment of muscle degeneration-related diseases and is being evaluated as a target engagement biomarker. Methods: A sensitive 2D-LC–MS/MS assay was developed to quantify MSTN in different animal species. Sample preparation involved SDS denaturation of serum proteins followed by tryptic digestion and peptide enrichment by SPE. Results: The assay was validated with LLOQ of 2.5 ng/ml in rat and monkey serum. The precision was within 13.7%, and the bias was within ±12.6% for all quality control samples in authentic matrices. Conclusion: This new assay was successfully applied to measure MSTN in mouse, rat, monkey and human serum. The total MSTN in rat and monkey serum was elevated following administration of an MSTN inhibitor.

ADME Considerations and Bioanalytical Strategies for Pharmacokinetic Assessments of Antibody-Drug Conjugates

Antibody-drug conjugates (ADCs) are a unique class of biotherapeutics of inherent heterogeneity and correspondingly complex absorption, distribution, metabolism, and excretion (ADME) properties. Herein, we consider the contribution of various components of ADCs such as various classes of warheads, linkers, and conjugation strategies on ADME of ADCs. Understanding the metabolism and disposition of ADCs and interpreting exposure-efficacy and exposure-safety relationships of ADCs in the context of their various catabolites is critical for design and subsequent development of a clinically successful ADCs. Sophisticated bioanalytical assays are required for the assessments of intact ADC, total antibody, released warhead and relevant metabolites. Both ligand-binding assays (LBA) and hybrid LBA-liquid chromatography coupled with tandem mass spectrometry (LBA-LC-MS/MS) methods have been employed to assess pharmacokinetics (PK) of ADCs. Future advances in bioanalytical techniques will need to address the rising complexity of this biotherapeutic modality as more innovative conjugation strategies, antibody scaffolds and novel classes of warheads are employed for the next generation of ADCs. This review reflects our considerations on ADME of ADCs and provides a perspective on the current bioanalytical strategies for pharmacokinetic assessments of ADCs.

Critical considerations for immunocapture enrichment LC–MS bioanalysis of protein therapeutics and biomarkers

In recent years, immunocapture enrichment coupled with LC–MS technology has seen more applications for the measurement of low abundant protein therapeutics and biomarkers in biological matrices. In this article, several critical considerations for the application of immunocapture enrichment to LC–MS bioanalysis of protein therapeutics and biomarkers, including reagent selection, reagent characterization, designing of capture format, etc. are discussed. All these considerations are critical in developing reliable and robust bioanalytical assays with high assay specificity and sensitivity. Successful examples using the immunocapture LC–MS approach in the quantification of biotherapeutic and low abundant protein biomarkers will also be discussed.