Compositions and methods for analyzing disulfide bonds are provided. An exemplary method includes preparing peptide standards having no disulfide bonds, scrambled disulfide bond peptide standards, and native disulfide bond peptide standards according to the sequence of the region of the protein drug product that includes the disulfide bond, digesting a sample of protein drug product into peptides, separating the protein drug product peptides, analyzing the protein drug product peptides and the peptide standards, identifying scrambled and native disulfide bond peptides by retention time, and quantifying the level of scrambled disulfide bond peptides.

Provided are methods of detecting the presence or amount of a vitamin D metabolite in a sample using mass spectrometry. The methods generally directed to ionizing a vitamin D metabolite in a sample and detecting the amount of the ion to determine the presence or amount of the vitamin D metabolite in the sample. Also provided are methods to detect the presence or amount of two or more vitamin D metabolites in a single assay.

Provided are methods of detecting the presence or amount of a vitamin D metabolite in a sample using mass spectrometry. The methods generally directed to ionizing a vitamin D metabolite in a sample and detecting the amount of the ion to determine the presence or amount of the vitamin D metabolite in the sample. Also provided are methods to detect the presence or amount of two or more vitamin D metabolites in a single assay.

The present invention provides a method for quantifying a monoclonal (M-) protein in a sample of a subject, the method comprising the steps of:—subjecting a serum sample of a subject to serum protein electrophoresis (SPE) in a gel, preferably serum protein electrophoresis in an agarose gel, to separate serum proteins into different serum protein fractions, optionally followed by immunofixation electrophoresis (IFE) and further optionally involving immunostaining of the gel;—excising from said gel a gel part comprising, or suspected of comprising, a M-protein;—performing an enzymatic digestion of proteins present in said gel part in order to provide a peptide digest comprising at least one M-protein peptide;—subjecting said peptide digest comprising said at least one M-protein peptide to liquid chromatography-mass spectrometry (LC-MS) to determine a quantity of said at least one M-protein peptide, thereby quantifying said M-protein in said sample.

The present invention relates to the field of protein characterization, and in particular to methods for identifying critical quality attributes of therapeutic proteins expressed in host cells by implementing a workflow including using a competitive binding assay with insufficient antigen followed by SCX-MS.

The present invention relates to the field of protein characterization, and in particular to methods for identifying critical quality attributes of therapeutic proteins expressed in host cells by implementing a workflow including using a competitive binding assay with insufficient antigen followed by SCX-MS.

Methods, devices, and systems for improving the quality of electrospray ionization mass spectrometer (ESI-MS) data are described, as are methods, devices, and systems for achieving improved correlation between chemical separation data and mass spectrometry data.

Methods, devices, and systems for improving the quality of electrospray ionization mass spectrometer (ESI-MS) data are described, as are methods, devices, and systems for achieving improved correlation between chemical separation data and mass spectrometry data.

A process for decreasing contamination of a commercial refining process by vanadyl porphyrins and/or nickel porphyrins by allowing rapid screening of porphyrins directly from asphaltenes isolated from crude oil without enrichment by use of positive-ion electrospray ionization mass spectrometry (ESI MS). Sodium formate is utilized as a ESI spray modifier. The vanadyl porphyrins are detected predominantly as sodiated species, while nickel porphyrins are observed as both sodiated species and molecular ions. Crude oil feedstocks exceeding a defined threshold concentration of vanadyl porphyrins and/or nickel porphyrins are rejected or diluted prior to utilization as refinery feedstock. Certain embodiments additionally quantitate both deoxophylloerythroetioporphyrins and etioporphyrin content (and their ratio) to predict crude oil thermal maturity.

A method of performing mass spectrometry includes accumulating, over an accumulation time, ions produced from components eluting from a chromatography column and transferring the accumulated ions to a mass analyzer. During an acquisition, a mass spectrum of detected ions derived from the transferred ions is acquired. An elution profile is obtained from a series of acquired mass spectra including the acquired mass spectrum and a plurality of previously-acquired mass spectra. The elution profile includes a plurality of detection points representing intensity of the detected ions as a function of time. A current signal state of the elution profile is classified based on a subset of detection points included in the plurality of detection points. The accumulation time for a next acquisition of a mass spectrum is set based on the classified current signal state of the elution profile.