The present disclosure relates to methods of identifying the presence and/or concentration and/or amount of one or more proteins, peptides, oligopeptides, polypeptides, protein complexes, subproteomes, or proteomes of interest within a sample based on the measured label, amino acid concentration, or number of amino acids of two or more labelled amino acid types in the sample.

A sensor can include a nanostructure in a housing configured to contact a sample.

The invention relates to an activated form of procaine, and the use of the activated procaine, or salts or solvates thereof, to label amine-containing compounds. In some embodiments, the amine-containing compound is an N-glycan.

A solid phase reagent and method for simultaneously capturing and fluorescently labeling an analyte with multiple reactive sites to provide a mono-labeled analyte are disclosed. The reagent can be used in the method and comprises a plurality of analyte-reactive groups tethered to a porous solid phase, wherein each analyte-reactive group is covalently attached to a fluorescent group either directly or indirectly, wherein the distance between adjacent analyte-reactive groups is greater than the gyration radius of a captured analyte; the fluorescent group is covalently attached to a cleavable anchor group either directly or through a first spacer; and the cleavable anchor group is covalently attached to the solid phase either directly or through a second spacer, wherein the solid phase is a porous solid or a porous gel.

The present invention pertains to a method for determining the biological activity of a neurotoxin, the method comprising the steps of: (a) expressing a fusion protein comprising (i) an anchor protein, (ii) a reporter protein and (iii) a neurotoxin cleavage site intervening the anchor protein and the reporter protein, in neurotoxin-sensitive cells; (b) incubating the neurotoxin-sensitive cells of (a) with a neurotoxin and cultivating the cells under conditions which allow the neurotoxin to exert its biological activity; (c) permeabilizing the neurotoxin-sensitive cells of (b) under conditions which allow the release of the reporter protein but not the release of the anchor protein from the permeabilized neurotoxin-sensitive cells; and (d) quantifying the activity of the reporter protein released from the cells, thereby determining the biological activity of the neurotoxin. In addition, the invention relates to a fusion protein comprising (i) an anchor protein, (ii) a reporter protein, and (iii) a neurotoxin cleavage site intervening the anchor protein and the reporter protein, for determining the biological activity of a neurotoxin, in neurotoxin-sensitive cells. Further encompassed by the present invention is a kit comprising the fusion protein of the invention. Finally, the invention pertains to the use of a fusion protein of the invention for determining the biological activity of a neurotoxin, in neurotoxin-sensitive cells.

The present disclosure provides a detectable labeling reagent for coupling to a target biomolecule. The detectable labeling reagent may comprise a chemical handle configured to couple to the target biomolecule. The detectable labeling reagent may also comprise a backbone unit. The detectable labeling reagent may comprise one or more detectable moieties. The backbone unit may comprise a conformation so that, when the detectable labeling reagent is coupled to the biomolecule, the backbone unit can substantially constrain a position or an orientation of a detectable moiety of the one or more detectable moieties relative to another detectable moiety of the one or more detectable moieties that is coupled to the biomolecule.

The invention relates to an activated form of procaine, and the use of the activated procaine, or salts or solvates thereof, to label amine-containing compounds, such as N-glycans, amine-containing amino acids, amine-containing peptides, amine-containing proteins, or other amine-containing compounds in a sample. Use of activated procaine as a label allows for sensitive detection of compounds labeled with it by both fluorescence and mass spectrometry.