Methods and system for identifying and/or quantifying a protein are provided herein.

Methods for in situ detecting proximity of two targets of interest featuring an antibody conjugated with a cleavable bridge component having a detectable moiety and an antibody conjugated with a non-cleavable bridge component. The bridge components each have a chemical ligation group adapted to form a covalent bond under particular conditions and when the targets are in close proximity. Following covalent bond formation, the cleavable bridge component can be cleaved from the antibody, effectively transferring the detectable moiety to the non-cleavable bridge component. Detection of the detectable moiety is indicative of the targets being in close proximity. The methods are compatible with both chromogenic and fluorogenic detection systems. The methods may be used to perform assays wherein one or more than one proximity event is detected on the same slide.

Antibodies against citrullinated protein antigens (ACPA) have shown their relevance for the diagnosis and possibly pathogenesis in arthritis. Described are means and methods for determining antibodies against homocitrulline-containing proteins or carbamylated proteins/peptides (anti-CarP) for the classification of individuals suffering from, or at risk of suffering from, arthritis.

The present disclosure relates to a system for monitoring post-translational modification of protein using a biosensor with a gap, which performs with high reliability a diagnosis of a disease associated with a target protein for which impedance is measured, by measuring an impedance of a sample introduced into a sensor and calculating a change rate of the measured impedance, and to a method of manufacturing the biosensor used for the system.

The present invention relates to the field of proteomics and more specifically to a method for analyzing a sample possible containing peptides or modified peptides; in particular useful for biomarker discovery or validation of biomarkers. The method uses isoelectric focusing and mass spectrometry (MS) and enables identification of modified peptides with high resolution and predictability.

This disclosure provides methods, systems, and compositions of matter for studying solvent accessibility and three-dimensional structure of biological molecules. A plasma can be used to generate marker radicals, which can interact with a biological molecule and mark the solvent-accessible portions of the biological molecule.

The present disclosure relates to the technical field of comparative proteomics, in particular to a detection and quantitation method for proteomics of post-translational modifications. With this method, the protein samples to be studied and internal standards are labeled with isobaric tandem mass tags, and tandem mass spectrometry analysis is carried out for the labeled peptide mixture, wherein the internal standard is a peptide mixture rich in post-translational modifications to be detected. Through this method, the signal of peptides containing the post-translational modifications to be detected can be amplified under the situation that mass spectrometer sensitivity is unchanged, and enrichment of the post-translational modification peptides is not needed. The probability of detecting the peptides containing the post-translational modifications to be detected by mass spectrometer and being selected for subsequent MS/MS analysis is increased.

Antibodies against citrullinated protein antigens (ACPA) have shown their relevance for the diagnosis and possibly pathogenesis in arthritis. Described are means and methods for determining antibodies against homocitrulline-containing proteins or carbamylated proteins/peptides (anti-CarP) for the classification of individuals suffering from, or at risk of suffering from, arthritis.

The present invention provides improved cleavable biotin-containing isobaric tags for quantitative mass spectrometry proteomics, particularly useful in quantification of post-translational modifications (PTMs) and assessing cysteine containing proteins. The isobaric chemical tags, DiLeu-Biotin-Azide (DBA), consist of three modules: (1) a DiLeu reporter group for relative quantification using MS/MS; (2) a biotin moiety for selective enrichment via streptavidin beads; and (3) an azide functional group to enable biorthogonal click chemistry. The DBA tags could be used in a high-throughput quantitative pan-PTM analysis platform.

Methods for in situ detecting proximity of two targets of interest featuring an antibody conjugated with a cleavable bridge component having a detectable moiety and an antibody conjugated with a non-cleavable bridge component. The bridge components each have a chemical ligation group adapted to form a covalent bond under particular conditions and when the targets are in close proximity. Following covalent bond formation, the cleavable bridge component can be cleaved from the antibody, effectively transferring the detectable moiety to the non-cleavable bridge component. Detection of the detectable moiety is indicative of the targets being in close proximity. The methods are compatible with both chromogenic and fluorogenic detection systems. The methods may be used to perform assays wherein one or more than one proximity event is detected on the same slide.