基质辅助激光解吸电离-飞行时间质谱法测定α/β-二羰基类化合物与标准瓜氨酸化肽段之间的衍生化反应活性OA北大核心CSTPCDMEDLINE

Protein citrullination is an irreversible post-translational modification process regula-ted by peptidylarginine deiminases(PADs)in the presence of Ca2+.This process is closely related to the occurrence and development of autoimmune diseases,cancers,neurological disorders,cardiovascular and cerebrovascular diseases,and other major diseases.The analysis of protein citrullination by biomass spectrometry confronts great challenges owing to its low abundance,lack of affinity tags,small mass-to-charge ratio change,and susceptibility to iso-topic and deamidation interferences.The methods commonly used to study the protein citrulli-nation mainly involve the chemical derivatization of the urea group of the guanine side chain of the peptide to increase the mass-to-charge ratio difference of the citrullinated peptide.Affinity-enriched labels are then introduced to effectively improve the sensitivity and accuracy of protein citrullination by mass spectrometry.2,3-Butanedione or phenylglyoxal compounds are often used as derivatization reagents to increase the mass-to-charge ratio difference of the citrullinated peptide,and the resulting derivatives have been observed to contain α-dicarbonyl structures.To date,however,no relevant studies on the reactivity of dicarbonyl compounds with citrullinated peptides have been reported.In this study,we determined whether six α-dicarbonyl and twoβ-dicarbonyl compounds undergo derivatization reactions with standard citrullinated peptides using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry(MALDI-TOF MS).Among the α-dicarbonyl compounds,2,3-butanedione and glyoxal reacted efficiently with several standard citrullinated peptides,but yielded a series of by-products.Phenylglyoxal,methylglyoxal,1,2-cyclohexanedione,and 1,10-phenanthroline-5,6-dione also derivated effi-ciently with standard citrullinated peptides,generating a single derivative.Thus,a new derivat-ization method that could yield a single derivative was identified.Among the β-dicarbonyl com-pounds,1,3-cyclohexanedione and 2,4-pentanedione successfully reacted with the standard cit-rullinated peptides,and generated a single derivative.However,their reaction efficiency was very low,indicating that the β-dicarbonyl compounds are unsuitable for the chemical derivatiza-tion of citrullinated peptides.The above results indicate that the α-dicarbonyl structure is neces-sary for realizing the efficient and specific chemical derivatization of citrullinated peptides.Mo-reover,the side chains of the α-dicarbonyl structure determine the structure of the derivatives,derivatization efficiency,and generation(or otherwise)of by-products.Therefore,the specific enrichment and precise identification of citrullinated peptides can be achieved by synthesizingα-dicarbonyl structured compounds containing affinity tags.The proposed method enables the identification of citrullinated proteins and their modified sites by MS,thereby providing a better understanding of the distribution of citrullinated proteins in different tissues.The findings will be beneficial for studies on the mechanism of action of citrullinated proteins in a variety of diseases.