Matrix Assisted Laser Desorption/Ionization-Time-of-Flight mass spectrometry (MALDI-TOF-MS) is the mostwidely used MS technique for glycan analysis. However, the poor point-to-point and sample-to-sample reproducibility becomes alimit in glycan biomarker research. A prespotted MALDI plate which overcomes the large crystal formation of 2,5-dihydroxybenzoicacid (DHB) has been developed and applied for glycan analysis. A homogeneous matrix coated surface without a crystal structurewas formed on a hydrophilic/ hydrophobic patterned surface using a piezoelectric device. The reproducible MALDI-TOF-MSdata have been presented using MALDI imaging of beer glycan as well as serum glycan eluted from 10% and 20% ACN elutionfractions. The glycan profile from the serum glycan by MALDI-TOF-MS with a DHB prespotted plate was highly conserved for10 different spectra and the coefficient of variations of significant ion peaks of MALDI data varies from 3.59 to 19.95.
The effects of column length and particle size on the efficiency of separation and characterization of phospholipids(PLs) are investigated using nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS-MS). Since PLs are associated with cell proliferation, apoptosis, and signal transduction, it is of increasing interests in lipidomics toestablish reliable analytical methods for the qualitative and quantitative profiling of PLs related to biomarker development inadult diseases. Due to the complexity of PLs, the preliminary separation of PLs is necessary prior to MS analysis. In this study,length of capillary column and the particle size of reversed phase (C18) packing materials are varied to find a reliable conditionfor the high speed and high resolution separation using 8 PL standard mixtures. From experiments, it was found that a capillarycolumn of nLC-ESI-MS-MS analysis for PL mixtures can be minimized to a 5 cm long pulled tip column packed with 3 μm C18particles without losing resolution.
Defective synthesis of the steroid hormones by the adrenal cortex has profound effects on human development andhomeostasis. Due to the time-consuming chromatography procedure combined with mass spectrometry, the matrix-assisted laserdesorption ionization method coupled to the linear ion-trap tandem mass spectrometry (MALDI-LTQ-MS/MS) was developedfor quantitative analysis of 10 adrenal steroids in human serum. Although MALDI-MS can be introduced for its applicability asa high-throughput screening method, it has a limitation on reproducibility within and between samples, which renders poorreproducibility for quantification. For quantitative MALDI-MS/MS analysis, the stable-isotope labeled internal standards wereused and the conditions of crystallization were tested. The precision and accuracy were 3.1~35.5% and 83.8~138.5%, respectively,when a mixture of 10 mg/mL α-cyano-4-hydroxycinnamic acid in 0.2% TFA of 70% acetonitrile was used as the MALDImatrix. The limit of quantification ranged from 5 to 340 ng/mL, and the linearity as a correlation coefficient was higher than0.988 for all analytes in the calibration range. Clinical applications include quantitative analyses of patients with congenital adrenalhyperplasia. The devised MALDI-MS/MS technique could be successfully applied to diagnosis of clinical samples.
In the collisionally-activated dissociation of the proton-bound cluster ions of DNA base guanine (G) and cytosine(C), G••H+••C, the abundance of [CH+] ions was found to be higher than that of [GH+] despite the fact that G has a higher protonaffinity than C. This unexpected observation seems to demonstrate another example that the simple kinetic method scheme doesnot work. We suggest that a kinetic factor or detailed dynamics governing the proton transfer and dissociation should be carefullyconsidered in the applications of the kinetic method to the proton affinity measurements.