Deamidation is usually viewed as a post-translational modification that sets an expiration date on proteins. Among apoptosis regulators of the Bcl-2 family, Bcl-xL shows a unique eligibility to be either singly or doubly deamidated. The inventors therefore analysed Bcl-xL deamidation state in platelets from mice models where platelets lifespan was manipulated. In parallel, the inventors compared human platelets obtained at steady state from healthy controls, to platelets newly synthesized after recovery from acute thrombocytopenia: they found that while expression levels of Asn52 monodeamidated Bcl-xL remains unchanged, Asn52Asn66 doubly-deamidated Bcl-xL is virtually absent in young platelets and accumulates in old platelets. Therefor the Asn52Asn66 doubly-deamidated Bcl-xL could be used as a reliable biomarker for determining the age of platelets.

Provided herein are epitopes and mimotopes thereof useful in the diagnosis and treatment of type 1 diabetes (T1D), as well as antibodies recognizing such epitopes, and diagnostics, therapeutics, kits, and methods of use thereof.

Disclosed is a deamidation rate measurement kit, which includes a stock solution of the compound Boc-Asn-Gly-OEt in deionized/distilled water, and a stock solution of the compound Boc-Asp-Gly-OEt in deionized/distilled water.

The invention provides the use of non-polyaminated lipocalin-2 and/or polyaminated lipocalin-2 as biomarkers for cardiometabolic disease as well as antibodies, assays and devices related to these biomarkers.

The application discloses compositions, methods, systems, and apparatuses for rapid sequence analysis of proteins, including location of post-translational modifications and disulfide bonds. Limited digestion of fully denatured antibody occurs in seconds by flowing sample in 8M urea at constant pressure through a micro column reactor containing immobilized aspergillopepsin I, resulting in a product mixture containing 3-10 kDa peptides, which is then fractionated by capillary column chromatography and analyzed by both electron transfer dissociation (ETD) and collision activated dissociation mass spectrometry. This method provides 95% sequence coverage of a mAb and detects numerous post-translational modifications. For disulfide bond location, native mAb is subjected to longer digestion times. Release of disulfide containing peptides from accessible regions of the folded protein occurs with short digestion times. The identity of peptides connected by a disulfide bond is determined using ETD and ion-ion proton transfer chemistry.

The present invention relates to a method for analysing protein variants of a recombinant protein of interest, such as antibodies or Fc-fusion proteins, in a liquid sample of a mammal. Specifically the method comprises a step of affinity purifying the recombinant protein of interest from the sample together with an internal standard, and analyzing the protein variants using an analytic separating method such as HPLC, capillary electrophoresis or MS. This method is particularly suited to measure pharmacokinetic parameters of a recombinant protein of interest, such as a biopharmaceutical, in a mammal in clinical or pre-clinical studies. It allows for the use of a small sample volume and the possibility to operate with high throughput, such as in a 96-well plate sample preparation. It also provides high sensitivity and allows analysis of protein variants individually.

Deamidation is usually viewed as a post-translational modification that sets an expiration date on proteins. Among apoptosis regulators of the Bcl-2 family, Bcl-xL shows a unique eligibility to be either singly or doubly deamidated. The inventors therefore analysed Bcl-xL deamidation state in platelets from mice models where platelets lifespan was manipulated. In parallel, the inventors compared human platelets obtained at steady state from healthy controls, to platelets newly synthesized after recovery from acute thrombocytopenia: they found that while expression levels of Asn52 monodeamidated Bcl-xL remains unchanged, Asn52Asn66 doubly-deamidated Bcl-xL is virtually absent in young platelets and accumulates in old platelets. Therefor the Asn52Asn66 doubly-deamidated Bcl-xL could be used as a reliable biomarker for determining the age of platelets.