posted on 2018-10-29, 00:00authored byShi-Shu Yang, Yu-Jie Chang, Hao Zhang, Xizhong Yu, Wenbin Shang, Gui-Quan Chen, David Da Yong Chen, Zhi-Yuan Gu
Capturing phosphopeptides
from complicated biological samples is
essential for the discovery of new post-translational modification
sites and disease diagnostics. Although several two-dimensional (2-D)
materials have been used for phosphopeptides capturing, metal–organic
framework (MOF) nanosheets have not been reported. The Ti-based MOF
nanosheets have well-defined 2-D morphology, high density of active
sites, large surface area, and an ultrathin structure. Phosphopeptides
can be efficiently extracted and superior detection limits of 0.1
fmol μL–1 can be achieved even for an extremely
low molar ratio of phosphoprotein/nonphosphoprotein (1:10000) mixtures.
The selectivity over nonphosphopeptides can be enhanced further by
pretreatment with a 10 mM salt solution (β-glycerophosphate
disodium, NaCl, or KCl). The performance of 2-D Ti-based MOF nanosheets
is much better than Zr-based MOF (Zr-BTB) nanosheets or any other
Ti-based 3-D MOF counterpart, such as MIL-125 and NH2-MIL-125.
The nanosheets were used for in situ isotope labeling for abnormally
regulated phosphopeptides analysis from serum samples of type 2 diabetes
patients. The relative quantitative results showed that three of the
phosphorylated fibrinogen peptides A (FPA, DpSGEGDFLAEGGGV, DpSGEGDFLAEGGGVR,
and ADpSGEGDFLAEGGGVR) were down-regulated, while the other isoform
(ADpSGEGDFLAEGGGV) was up-regulated in the serum samples of type 2
diabetes patients compared with those of healthy volunteers. Finally,
proteomics analysis showed selective enrichment of phosphopeptides
with 2-D Ti-based MOF nanosheets from real samples, including tryptic
digests of mouse brain neocortex lysate, mouse spinal cord lysate,
and mouse testis lysate, followed by LC-MS/MS analysis. Total numbers
of 2601, 3208, and 2866 phosphopeptides were successfully identified
from the three samples, respectively. The 2-D Ti-based MOF nanosheets
significantly improved sample preparation for mass spectrometric analysis
in phosphopeptides and phosphoproteomics research.