First profiling in hydrophilic interaction liquid chromatography of intact human chorionic gonadotropin isoforms

Exploring the Chemical Space of Protein Glycosylation in Noncovalent Protein Complexes: An Expedition along Different Structural Levels of Human Chorionic Gonadotropin by Employing Mass Spectrometry

Modern analytical approaches employing high-resolution mass spectrometry (MS) facilitate the generation of a vast amount of structural data of highly complex glycoproteins. Nevertheless, systematic interpretation of this data at different structural levels remains an analytical challenge. The glycoprotein utilized as a model system in this study, human chorionic gonadotropin (hCG), exists as a heterodimer composed of two heavily glycosylated subunits. In order to unravel the multitude of glycoforms of recombinant hCG (drug product Ovitrelle), we combine established techniques, such as released glycan and glycopeptide analysis, with novel approaches employing high-performance liquid chromatography-mass spectrometry (HPLC-MS) to characterize protein subunits and native MS to analyze the noncovalent hCG complex. Starting from the deconvoluted mass spectrum of dimeric hCG comprising about 50 signals, it was possible to explore the chemical space of hCG glycoforms and elucidate the complexity that hides behind just 50 signals. Systematic, stepwise integration of data obtained at the levels of released glycans, glycopeptides, and subunits using a computational annotation tool allowed us to reveal 1031 underlying glycoforms. Additionally, critical quality attributes such as sialylation and core fucosylation were compared for two batches of Ovitrelle to assess the potential product variability.

Analysis of Serum Paraoxonase 1 Using Mass Spectrometry and Lectin Immunoassay in Patients With Alpha-Fetoprotein Negative Hepatocellular Carcinoma

The diagnosis of AFP (alpha-fetoprotein)-negative HCC (hepatocellular carcinoma) mostly relies on imaging and pathological examinations, and it lacks valuable and practical markers. Protein N-glycosylation is a crucial post-translation modifying process related to many biological functions in an organism. Alteration of N-glycosylation correlates with inflammatory diseases and infectious diseases including hepatocellular carcinoma. Here, serum N-linked intact glycopeptides with molecular weight (MW) of 40–55 kDa were analyzed in a discovery set (n = 40) including AFP-negative HCC and liver cirrhosis (LC) patients using label-free quantification methodology. Quantitative lens culinaris agglutin (LCA) ELISA was further used to confirm the difference of glycosylation on serum PON1 in liver diseases (n = 56). Then, the alteration of site-specific intact N-glycopeptides of PON1 was comprehensively assessed by using Immunoprecipitation (IP) and mass spectrometry based ¹⁶O/¹⁸O C-terminal labeling quantification method to distinguish AFP-negative HCC from LC patients in a validation set (n = 64). Totally 195 glycopeptides were identified using a dedicated search engine pGlyco. Among them, glycopeptides from APOH, HPT/HPTR, and PON1 were significantly changed in AFP-negative HCC as compared to LC. In addition, the reactivity of PON1 with LCA in HCC patients with negative AFP was significantly elevated than that in cirrhosis patients. The two glycopeptides HAN²⁵³WTLTPLK (H5N4S2) and (H5N4S1) corresponding to PON1 were significantly increased in AFP-negative HCC patients, as compared with LC patients. Variations in PON1 glycosylation may be associated with AFP-negative HCC and might be helpful to serve as potential glycomic-based biomarkers to distinguish AFP-negative HCC from cirrhosis.

Analysis of seized peptide and protein-based doping agents using four complimentary methods: Liquid chromatography coupled with time of flight mass spectrometry, liquid chromatography-ultraviolet, Bradford, and immunoassays

Analysis and identification of seized doping-related products are important tasks for customs or forensic laboratories in order to prevent potentially dangerous and illegal compounds to go into circulation. At the Section of Forensic Chemistry in Copenhagen, we have a workflow consisting of four complimentary validated methods to identify common doping-related substances: liquid chromatography-ultraviolet (LC-UV), LC coupled with time of flight mass spectrometry (LC-TOF-MS), the colorimetric Bradford assay, and an immunoassay. The Bradford assay screens for peptide or proteins in the sample, and the immunoassay confirmed human chorionic gonadotropin (hCG). LC-UV was carried out with a C4 protein column for identification of peptides and proteins from a standard reference library, based on retention times and ratios between peak areas at 220, 254, and 280 nm. LC-TOF-MS was performed using a C18 column, and identification was based on comparison of the retention time and the accurate mass with those of reference standards. In 2019, we received 36 samples for peptide/protein analysis, all of which were tested using the LC-UV, LC-TOF-MS, and colorimetric method, and samples suspected of containing hCG were confirmed with an immunoassay. We found a total of 15 samples containing an illegal doping substance, 12 samples containing substances not prohibited by the Danish Doping List, and nine samples containing no peptides or proteins. In conclusion, the four complimentary methods constitute a suitable approach for identifying common peptide/protein doping substances in the day-to-day routine of a forensic laboratory, with limited sample preparation and interpretation of data.

Hydrophilic Interaction Liquid Chromatography (HILIC): Latest Applications in the Pharmaceutical Researches

Background:

Significant advances have been occurred in analytical research since the 1970s by Liquid Chromatography (LC) as the separation method. Reverse Phase Liquid Chromatography (RPLC) method, using hydrophobic stationary phases and polar mobile phases, is the most commonly used chromatographic method. However, it is difficult to analyze some polar compounds with this method. Another separation method is the Normal Phase Liquid Chromatography (NPLC), which involves polar stationary phases with organic eluents. NPLC presents low-efficiency separations and asymmetric chromatographic peak shapes when analyzing polar compounds. Hydrophilic Interaction Liquid Chromatography (HILIC) is an interesting and promising alternative method for the analysis of polar compounds. HILIC is defined as a separation method that combines stationary phases used in the NPLC method and mobile phases used in the RPLC method. HILIC can be successfully applied to all types of liquid chromatographic separations such as pharmaceutical compounds, small molecules, metabolites, drugs of abuse, carbohydrates, toxins, oligosaccharides, peptides, amino acids and proteins.

Objective:

This paper provides a general overview of the recent application of HILIC in the pharmaceutical research in the different sample matrices such as pharmaceutical dosage form, plasma, serum, environmental samples, animal origin samples, plant origin samples, etc. Also, this review focuses on the most recent and selected papers in the drug research from 2009 to the submission date in 2020, dealing with the analysis of different components using HILIC.

Results and Conclusion:

The literature survey showed that HILIC applications are increasing every year in pharmaceutical research. It was found that HILIC allows simultaneous analysis of many compounds using different detectors.

Identification and semi-relative quantification of intact glycoforms of human chorionic gonadotropin alpha and beta subunits by nano liquid chromatography-Orbitrap mass spectrometry

The human chorionic gonadotropin (hCG) protein belongs to a family of glycoprotein hormones called gonadotropins. It is a heterodimer made of two non-covalently linked subunits. The α-subunit structure, hCGα, has 2 N-glycosylation sites, while the beta subunit, hCGβ, has 2 N- and 4 O-glycosylation sites. This leads to numerous glycoforms. A method based on the analysis of hCG glycoforms at the intact level by nano-reversed phase liquid chromatography coupled to high resolution mass spectrometry (nanoLC-HRMS) with an Orbitrap analyzer was previously developed using a recombinant hCG-based drug, Ovitrelle®, as standard. It allowed the detection of about 30 hCGα glycoforms, but didn't allow the detection of hCGβ glycoforms. This method was thus here significantly modified (addition of a pre-concentration step of the sample to increase the sample volume from 70 nl to 1 µl, optimization of the gradient slope and the nature and content of the acidic additive in the mobile phase). It led to an improvement of the separation of hCGα and hCGβ glycoforms, which allowed for the first time the detection of 33 hCGβ glycoforms at intact level. In addition, a higher number of hCGα glycoforms (42 in total, i.e. a 40% increase) was detected. The figures of merit of this new method were next assessed. The relative standard deviations (RSDs) of the retention time ranged between 0.02 and 0.95% (n = 3), with an average value of 0.36% for the alpha glycoforms and between 0.01 and 1.08% (n = 3) with an average value of 0.23% for the beta glycoforms. The RSDs of the relative peak area measured on the extracted ion chromatogram of each glycoform were below 20% (n = 3), with an average value of 9.8%, thus allowing semi-relative quantification. Therefore, this method has a high potential for rapid quality control aiming for the detection and comparison of glycoforms present in glycoprotein-based pharmaceutical preparations.

Multi-dimensional LC-MS: the next generation characterization of antibody-based therapeutics by unified online bottom-up, middle-up and intact approaches

This review presents an overview of current analytical trends in antibody characterization by multidimensional LC-MS approaches.