Comparison of capillary electrophoresis and capillary liquid chromatography coupled to mass spectrometry for the analysis of transthyretin in human serum

The Human Proteoform Atlas: a FAIR community resource for experimentally derived proteoforms

The Human Proteoform Atlas (HPfA) is a web-based repository of experimentally verified human proteoforms on-line at http://human-proteoform-atlas.org and is a direct descendant of the Consortium of Top-Down Proteomics' (CTDP) Proteoform Atlas. Proteoforms are the specific forms of protein molecules expressed by our cells and include the unique combination of post-translational modifications (PTMs), alternative splicing and other sources of variation deriving from a specific gene. The HPfA uses a FAIR system to assign persistent identifiers to proteoforms which allows for redundancy calling and tracking from prior and future studies in the growing community of proteoform biology and measurement. The HPfA is organized around open ontologies and enables flexible classification of proteoforms. To achieve this, a public registry of experimentally verified proteoforms was also created. Submission of new proteoforms can be processed through email vianrtdphelp@northwestern.edu, and future iterations of these proteoform atlases will help to organize and assign function to proteoforms, their PTMs and their complexes in the years ahead.

Neurodegenerative Proteinopathies in the Proteoform Spectrum-Tools and Challenges

Proteinopathy refers to a group of disorders defined by depositions of amyloids within living tissue. Neurodegenerative proteinopathies, including Alzheimer's disease, Parkinson's disease, Creutzfeldt-Jakob disease, and others, constitute a large fraction of these disorders. Amyloids are highly insoluble, ordered, stable, beta-sheet rich proteins. The emerging theory about the pathophysiology of neurodegenerative proteinopathies suggests that the primary amyloid-forming proteins, also known as the prion-like proteins, may exist as multiple proteoforms that contribute differentially towards the disease prognosis. It is therefore necessary to resolve these disorders on the level of proteoforms rather than the proteome. The transient and hydrophobic nature of amyloid-forming proteins and the minor post-translational alterations that lead to the formation of proteoforms require the use of highly sensitive and specialized techniques. Several conventional techniques, like gel electrophoresis and conventional mass spectrometry, have been modified to accommodate the proteoform theory and prion-like proteins. Several new ones, like imaging mass spectrometry, have also emerged. This review aims to discuss the proteoform theory of neurodegenerative disorders along with the utility of these proteomic techniques for the study of highly insoluble proteins and their associated proteoforms.

Prealbumin: The clinical utility and analytical methodologies

Prealbumin is a small protein which has been widely evaluated as a nutritional and a prognostic marker. The small size and concentration of prealbumin in blood proposes challenges on measuring it with high sensitivity and specificity. Over the years, a number of analytical methodologies have been developed, which may help establish prealbumin as a useful biomarker in routine clinical practice. The aim of the short review was to explore the current literature on the clinical utility of prealbumin and the advances made in the analytical methodologies of prealbumin. We searched MEDLINE, EMBASE and the Cochrane Library for articles published between January 1980 and July 2019, with the general search terms of 'prealbumin', 'prognostic marker', 'nutritional marker', 'analytical methodologies' and 'malnutrition'. Additionally, we selected relevant articles and comprehensive overviews from reference lists of identified studies. The routine use of prealbumin in clinical practice remains debatable; however; it can complement clinical history, anthropometric assessment and physical examination to assess malnutrition with more certainty. Consensus on the clinical applications of prealbumin in the management of malnutrition is warranted.

Polymeric monolithic microcartridges with gold nanoparticles for the analysis of protein biomarkers by on-line solid-phase extraction capillary electrophoresis-mass spectrometry

In this study, polymeric monoliths with gold nanoparticles (AuNP@monolith) were investigated as microcartridges for the analysis of protein biomarkers by on-line solid-phase extraction capillary electrophoresis-mass spectrometry (SPE-CE-MS). "Plug-and-play" microcartridges (7 mm) were prepared from a glycidyl methacrylate (GMA)-based monolithic capillary column (5 cm x 250 µm i.d.), which was modified with ammonia and subsequently functionalized with gold nanoparticles (AuNPs). The performance of these novel microcartridges was evaluated with human transthyretin (TTR), which is a protein related to different types of familial amyloidotic polyneuropathies (FAP). Protein retention depended on the isoelectric point of the protein (TTR pI~5.4) and elution was achieved with a basic phosphate solution. Under the optimized conditions, limits of detection (LODs) for TTR by AuNP@monolith-SPE-CE-MS were 50 times lower than by CE-MS (5 vs 250 mg•L^-1, with an ion trap (IT) mass spectrometer). The sensitivity enhancement was similar compared to SPE-CE-MS using immunoaffinity (IA) microcartridges with intact antibodies against TTR. Linearity, repeatability in migration times and peak areas, reusability, reproducibility and application to serum samples were also evaluated.

On-Line Immunoaffinity Solid-Phase Extraction Capillary Electrophoresis-Mass Spectrometry for the Analysis of Serum Transthyretin

The analysis of low abundant proteins in biological fluids by capillary electrophoresis (CE) is particularly problematic due to the typically poor concentration limits of detection of microscale separation techniques. Another important issue is sample matrix complexity that requires an appropriate cleanup. Here, we describe an on-line immunoaffinity solid-phase extraction capillary electrophoresis-mass spectrometry (IA-SPE-CE-MS) method for the immunoextraction, preconcentration, separation, detection, and characterization of serum transthyretin (TTR). TTR is a protein biomarker related to diverse types of amyloidosis, such as familial amyloidotic polyneuropathy type I (FAP-I), which is the most common hereditary systemic amyloidosis.