Dataset Information

Top-down study of ?2-microglobulin deamidation.

ABSTRACT: Although differentiation of the isomeric Asn deamidation products (Asp and isoAsp) at the peptide level by electron capture dissociation (ECD) has been well-established, isoAsp identification at the intact protein level remains a challenging task. Here, a comprehensive top-down deamidation study is presented using the protein beta2-microglobulin (?(2)M) as the model system. Of the three deamidation sites identified in the aged ?(2)M, isoAsp formation was detected at only one site by the top-down ECD analysis. The absence of diagnostic ions likely resulted from an increased number of competing fragmentation channels and a decreased likelihood of product ion separation in ECD of proteins. To overcome this difficulty, an MS(3) approach was applied where a protein ion was first fragmented by collisionally activated dissociation (CAD) and the resulting product ion was isolated and further analyzed by ECD. IsoAsp formation at all three deamidation sites was successfully identified by this CAD-ECD approach. Furthermore, the abundance of the isoAsp diagnostic ion was found to increase linearly with the extent of deamidation. These results demonstrated the potential of ECD in the detection and quantitative analysis of isoAsp formation using the top-down approach.

SUBMITTER: Li X

PROVIDER: S-EPMC4170183 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature

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Top-down study of β2-microglobulin deamidation.

Li Xiaojuan X Yu Xiang X Costello Catherine E CE Lin Cheng C O'Connor Peter B PB

Analytical chemistry 20120629 14

Although differentiation of the isomeric Asn deamidation products (Asp and isoAsp) at the peptide level by electron capture dissociation (ECD) has been well-established, isoAsp identification at the intact protein level remains a challenging task. Here, a comprehensive top-down deamidation study is presented using the protein beta2-microglobulin (β(2)M) as the model system. Of the three deamidation sites identified in the aged β(2)M, isoAsp formation was detected at only one site by the top-down ...[more]

PMID: 22746280

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Project description:Backgroundβ-Trace protein (BTP) and β2-microglobulin (B2M) are novel glomerular filtration markers that have stronger associations with adverse outcomes than creatinine. Comparisons of BTP and B2M to creatinine and cystatin C are limited by the absence of rigorously developed glomerular filtration rate (GFR) estimating equations for the novel markers.Study designStudy of diagnostic test accuracy.Setting & participantsPooled database of 3 populations with chronic kidney disease (CKD) with mean measured GFR of 48 mL/min/1.73 m2 (N=3,551; MDRD [Modification of Diet in Renal Disease] Study, AASK [African American Study of Kidney Disease and Hypertension], and CRIC [Chronic Renal Insufficiency Cohort] Study).Index testsGFR estimated using creatinine, cystatin C, BTP, or B2M level.Reference testGFR measured as the urinary clearance of iothalamate.ResultsFor BTP and B2M, coefficients for age, sex, and race were smaller than for creatinine and were similar or smaller than for cystatin C. For B2M, coefficients for sex, age, and race were smaller than for creatinine and were similar (age and race) or smaller (sex) than for cystatin C. The final equations with BTP (BTP, age, and sex) or B2M (B2M alone) were less accurate than either the CKD-EPI (CKD Epidemiology Collaboration) creatinine or cystatin C equations. The combined BTP-B2M equation (BTP and B2M alone) had similar accuracy to the CKD-EPI creatinine or cystatin C equation. The average of the BTP-B2M equation and the CKD-EPI creatinine-cystatin C equation was not more accurate than the CKD-EPI creatinine-cystatin C equation.LimitationsNo external validation population, study population was restricted to CKD, few participants older than 65 years, or nonblack nonwhite race.ConclusionsBTP and B2M are less influenced by age, sex, and race than creatinine and less influenced by race than cystatin C, but provide less accurate GFR estimates than the CKD-EPI creatinine and cystatin C equations. The CKD-EPI BTP and B2M equation provides a methodological advance for their study as filtration markers and in their associations with risk and adverse outcomes, but further study is required before clinical use.

Dataset Information

Top-down study of ?2-microglobulin deamidation.

Publications

Top-down study of β2-microglobulin deamidation.

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