Suppressing the background of LC-ESI-MS analysis of permethylated glycans using the active background ion reduction device.

Mass spectrometry (MS) has revolutionized analytical chemistry, enabling precise identification and quantification of chemical species, which is pivotal for biomarker discovery and understanding complex biological systems. Despite its versatility, the presence of background ions in MS analysis hinders the sensitive detection of low-abundance analytes. Therefore, studies aimed at lowering background ion levels have become increasingly important. Here, we utilized the commercially available Active Background Ion Reduction Device (ABIRD) to suppress background ions and assess its effect on the liquid chromatography-electrospray ionization (LC-ESI)-MS analyses of N-glycans on the Q Exactive HF mass spectrometer. We also investigated the effect of different solvent vapors in the ESI source on N-glycan analysis by MS. ABIRD generally had no effect on high-mannose and neutral structures but reduced the intensity of some structures that contained sialic acid, fucose, or both when methanol vapor filled the ESI source. Based on our findings on the highest number of identified N-glycans from human serum, methanol vapor in the ion source compartment may enhance N-glycan LC-ESI-MS analyses by improving the desolvation of droplets formed during the ESI process due to its high volatility. This protocol may be further validated and extended to advanced bottom-up proteomic/glycoproteomic studies for the analysis of peptide/glycopeptide ions by MS.

Differential expression of N-glycopeptides derived from serum glycoproteins in mild cognitive impairment (MCI) patients.

Mild cognitive impairment (MCI) is an early stage of memory loss that affects cognitive abilities with the aging of individuals, such as language or visual/spatial comprehension. MCI is considered a prodromal phase of more complicated neurodegenerative diseases such as Alzheimer's. Therefore, accurate diagnosis and better understanding of the disease prognosis will facilitate prevention of neurodegeneration. However, the existing diagnostic methods fail to provide precise and well-timed diagnoses, and the pathophysiology of MCI is not fully understood. Alterations of the serum N-glycoproteome expression could represent an essential contributor to the overall pathophysiology of neurodegenerative diseases and be used as a potential marker to assess MCI diagnosis using less invasive procedures. In this approach, we identified N-glycopeptides with different expressions between healthy and MCI patients from serum glycoproteins. Seven of the N-glycopeptides showed outstanding AUC values, among them the antithrombin-III Asn224 + 4-5-0-2 with an AUC value of 1.00 and a p value of 0.0004. According to proteomics and ingenuity pathway analysis (IPA), our data is in line with recent publications, and the glycoproteins carrying the identified N-sites play an important role in neurodegeneration.

O-Glycome Profiling of Breast Cancer Cell Lines to Understand Breast Cancer Brain Metastasis.

Breast cancer is the second leading cause of cancer-related death among women and a major source of brain metastases. Despite the increasing incidence of brain metastasis from breast cancer, the underlying mechanisms remain poorly understood. Altered glycosylation is known to play a role in various diseases including cancer metastasis. However, profiling studies of O-glycans and their isomers in breast cancer brain metastasis (BCBM) are scarce. This study analyzed the expression of O-glycans and their isomers in human breast cancer cell lines (MDA-MB-231, MDA-MB-361, HTB131, and HTB22), a brain cancer cell line (CRL-1620), and a brain metastatic breast cancer cell line (MDA-MB-231BR) using nanoLC-MS/MS, identifying 27 O-glycan compositions. We observed significant upregulation in the expression of HexNAc1Hex1NeuAc2 and HexNAc2Hex3, whereas the expression of HexNAc1Hex1NeuAc1 was downregulated in MDA-MB-231BR compared to other cell lines. In our isomeric analysis, we observed notable alterations in the isomeric forms of the O-glycan structure HexNAc1Hex1NeuAc1 in a comparison of different cell lines. Our analysis of O-glycans and their isomers in cancer cells demonstrated that changes in their distribution can be related to the metastatic process. We believe that our investigation will contribute to an enhanced comprehension of the significance of O-glycans and their isomers in BCBM.

Targeted Glycoproteomics Analysis Using MRM/PRM Approaches.

MS-target analyses are frequently utilized to analyze and validate structural changes of biomolecules across diverse fields of study such as proteomics, glycoproteomics, glycomics, lipidomics, and metabolomics. Targeted studies are commonly conducted using multiple reaction monitoring (MRM) and parallel reaction monitoring (PRM) techniques. A reliable glycoproteomics analysis in intricate biological matrices is possible with these techniques, which streamline the analytical workflow, lower background interference, and enhance selectivity and specificity.

Targeted Analysis of Permethylated N-Glycans Using MRM/PRM Approaches.

Targeted mass spectrometric analysis is widely employed across various omics fields as a validation strategy due to its high sensitivity and accuracy. The approach has been successfully employed for the structural analysis of proteins, glycans, lipids, and metabolites. Multiple reaction monitoring (MRM) and parallel reaction monitoring (PRM) have been the methods of choice for targeted structural studies of biomolecules. These target analyses simplify the analytical workflow, reduce background interference, and increase selectivity/specificity, allowing for a reliable quantification of permethylated N-glycans in complex biological matrices.

O-Glycoproteomics Sample Preparation and Analysis Using NanoHPLC and Tandem MS.

Glycosylation refers to the biological processes that covalently attach carbohydrates to the peptide backbone after the synthesis of proteins. As one of the most common post-translational modifications (PTMs), glycosylation can greatly affect proteins' features and functions. Moreover, aberrant glycosylation has been linked to various diseases. There are two major types of glycosylation, known as N-linked and O-linked glycosylation. Here, we focus on O-linked glycosylation and thoroughly describe a bottom-up strategy to perform O-linked glycoproteomics studies. The experimental section involves enzymatic digestions using trypsin and O-glycoprotease at 37 °C. The prepared samples containing O-glycopeptides are analyzed using nanoHPLC coupled with tandem mass spectrometry (MS) for accurate identification and quantification.

Metabolomic Changes in Rat Serum after Chronic Exposure to Glyphosate-Based Herbicide.

Glyphosate-based herbicides (GBHs) have gained extensive popularity in recent decades. For many years, glyphosate has been regarded as harmless or minimally toxic to mammals due to the absence of its primary target, the shikimic acid pathway in humans. Nonetheless, mounting evidence suggests that glyphosate may cause adverse health effects in humans via other mechanisms. In this study, we described the metabolomic changes in the serum of experimental rats exposed to chronic GBH using the highly sensitive LC-MS/MS technique. We investigated the possible relationship between chronic exposure to GBH and neurological disorders. Our findings suggest that chronic exposure to GBH can alter spatial learning memory and the expression of some important metabolites that are linked to neurophysiological disorders in young rats, with the female rats showing higher susceptibility compared to the males. This indicates that female rats are more likely to show early symptoms of the disorder on exposure to chronic GBH compared to male rats. We observed that four important metabolites (paraxanthine, epinephrine, L-(+)-arginine, and D-arginine) showed significant changes and involvement in neurological changes as suggested by ingenuity pathway analysis. In conclusion, our results indicate that chronic exposure to GBH can increase the risk of developing neurological disorders.

Variations in O-Glycosylation Patterns Influence Viral Pathogenicity, Infectivity, and Transmissibility in SARS-CoV-2 Variants.

The highly glycosylated S protein plays a vital role in host cell invasion, making it the principal target for vaccine development. Differences in mutations observed on the spike (S) protein of SARS-CoV-2 variants may result in distinct glycosylation patterns, thus influencing immunological evasion, infectivity, and transmissibility. The glycans can mask key epitopes on the S1 protein and alter its structural conformation, allowing the virus to escape the immune system. Therefore, we comprehensively characterize O-glycosylation in eleven variants of SARS-CoV-2 S1 subunits to understand the differences observed in the biology of the variants. In-depth characterization was performed with a double digestion strategy and an efficient LC-MS/MS approach. We observed that O-glycosylation is highly conserved across all variants in the region between the NTD and RBD, whereas other domains and regions exhibit variation in O-glycosylation. Notably, omicron has the highest number of O-glycosylation sites on the S1 subunit. Also, omicron has the highest level of sialylation in the RBD and RBM functional motifs. Our findings may shed light on how differences in O-glycosylation impact viral pathogenicity in variants of SARS-CoV-2 and facilitate the development of a robust vaccine with high protective efficacy against the variants of concern.

N-Glycome Profile of the Spike Protein S1: Systemic and Comparative Analysis from Eleven Variants of SARS-CoV-2.

The SARS-CoV-2 virus rapidly spread worldwide, threatening public health. Since it emerged, the scientific community has been engaged in the development of effective therapeutics and vaccines. The subunit S1 in the spike protein of SARS-CoV-2 mediates the viral entry into the host and is therefore one of the major research targets. The S1 protein is extensively glycosylated, and there is compelling evidence that glycans protect the virus' active site from the human defense system. Therefore, investigation of the S1 protein glycome alterations in the different virus variants will provide a view of the glycan evolution and its relationship with the virus pathogenesis. In this study, we explored the N-glycosylation expression of the S1 protein for eleven SARS-CoV-2 variants: five variants of concern (VOC), including alpha, beta, gamma, delta, and omicron, and six variants of interest (VOI), including epsilon, eta, iota, lambda, kappa, and mu. The results showed significant differences in the N-glycome abundance of all variants. The N-glycome of the VOC showed a large increase in the abundance of sialofucosylated glycans, with the greatest abundance in the omicron variant. In contrast, the results showed a large abundance of fucosylated glycans for most of the VOI. Two glycan compositions, GlcNAc4,Hex5,Fuc,NeuAc (4-5-1-1) and GlcNAc6,Hex8,Fuc,NeuAc (6-8-1-1), were the most abundant structures across all variants. We believe that our data will contribute to understanding the S1 protein's structural differences between SARS-CoV-2 mutations.

Isomeric separation of native N-glycans using nano zwitterionic- hydrophilic interaction liquid chromatography column.

Changes in the expression of glycan isomers have been implicated in the development and progression of several diseases. However, the analysis of structurally diverse isomeric N-glycans by LC-MS/MS is still a major analytical challenge, particularly due to their large number of possible isomeric conformations. Common approaches derivatized the N-glycans to increase their hydrophobicity and to gain better detection in the MS system. Unfortunately, glycan derivatization is time-consuming and, in many cases, adds complexity because of the multiple reaction and cleaning steps, incomplete chemical labeling, possible degradation, and unwanted side reactions. Thus, analysis of native glycans, especially for samples with low abundance by LC-MS/MS, is desirable. Normal phase chromatography, which employs HILIC stationary phase, has been commonly employed for the identification and separation of labeled glycans. In this study, we focused on achieving efficient isomeric separation of native N-glycans using a nano ZIC-HILIC column commonly employed to separate labeled glycans and glycopeptides. Underivatized sialylated and oligomannose N-glycans derived from bovine fetuin and Ribonuclease B were initially utilized to optimize chromatographic conditions, including column temperature, pH of mobile phases, and gradient elution time. The optimized condition was then applied for the isomeric separation of native N-glycans derived from alpha-1 acid glycoprotein, as well as from biological samples. Finally, we confirmed the stability and reproducibility of the ZIC-HILIC column by performing run-to-run comparisons of the full width at half height (FWHM) and retention time on different N-glycans. The variability in FWHM was less than 0.5 min, while that of retention time was less than 1.0 min with %RSD less than 1.0%.

Fighting COVID-19 at the Expense of Malaria in Africa: The Consequences and Policy Options.

Malaria remains a major global health burden, killing hundreds of thousands annually, especially in sub-Saharan Africa. In December 2019, a novel illness termed COVID-19, caused by SARS-CoV-2, was reported in China. This disease soon spread around the world and was declared a pandemic by the WHO on March 11, 2020. Considering that the malaria burden is high in many low-income tropical countries with little capacity to fund malaria control and eradication programs, the fight against malaria in these regions is likely to be hindered by COVID-19. Indeed, access to health care has generally been limited during the pandemic, whereas malaria interventions, such as seasonal malaria chemoprevention, and distribution of long-lasting insecticide-treated bed nets, have been suspended because of lockdowns. Likewise, the repurposing of antimalarials for the treatment of COVID-19 and a shift in focus from the production of malaria rapid diagnostic tests to COVID-19 rapid diagnostic tests are causes for concern in malaria-endemic regions. COVID-19 has disproportionately affected developed countries, threatening their capacity to aid in malaria control efforts. Here, we address impacts of the COVID-19 pandemic on the management and control of malaria in Africa.