Phosphopeptide enrichment with high selectivity and detection sensitivity is essential for phosphoproteomic studies and remains a long-standing challenge. In this study, new immobilized metal affinity chromatography nanocomposite adsorbents with a phosphonate-functionalized ionic liquid (PFIL) as a surface modifier are successfully prepared via a reaction sequence of amination, quaternization, phosphonate hydrolyzation, and metal immobilization. Taking advantages of integrated features of a flexible and strong tripodal phosphonate chelator, a hydrophilic ionic liquid linker, a large surface area, and the size-exclusion effect, the resulting nanocomposite G@mSiO 2 -PFIL-Ti 4+ exhibits excellent detection sensitivity to enrich phosphorylated peptides from a tryptic β-casein digest (0.15 fmol), and superior enrichment selectivity to capture phosphorylated peptides from a digest mixture of β-casein and bovine serum albumin (a molar ratio of 1:10,000). Strong immobilization of tripodal chelation to metal ions endows the nanocomposite adsorbent with high tolerance to experimental conditions, and thus excellent reusability of the adsorbent has been achieved without remarkable loss of enrichment efficiency for 10 cycles. Due to the excellent size-exclusion effect, high enrichment specificity of G@mSiO 2 -PFIL-Ti 4+ to phosphopeptides has been observed and 23 endogenous phosphopeptides have been captured from human saliva. In addition, 924 phosphopeptides (enrichment specificity, 56.1%) have been identified from the tryptic digest of mouse brain lysate. Particularly, six of 975 phosphorylation sites were Alzheimer's disease-related hyperphosphorylation sites within tau protein. These results demonstrate that G@mSiO 2 -PFIL-Ti 4+ nanocomposite affinity materials show great application potential for a proteomic study of complicated biological samples.
This paper investigated the factors driving the changes in industrial wastewater emission intensity (IWEI) across provinces in China. To do this, we proposed a Super-efficiency Slacks-based Measure-Global Malmquist Index (SSBM-GMI) to decompose the change in IWEI into the effects from efficiency change (ECE), technological change (TCE), capital–wastewater substitution (KWE) and labor–wastewater substitution (LWE). The method was applied to conduct an empirical study using Chinese provincial data from 2003–2015. The main findings include the following: firstly, TCE was the dominant driving force behind the reduction in IWEI with an average annual contribution of −6.4% at the national level, followed by KWE (−5.3%), LWE (−1.8%) and ECE (1.2%). Secondly, significant differences exist in the driving factors behind the reduction in IWEI across regions. The reduction in IWEIs in the Northeast area and the Great Northwest area was mainly driven by productivity growth, while the reduction in IWEIs in the other areas was mainly driven by factor substitution. Thirdly, the shortage of KWE and LWE has impeded IWEI reduction in the Great Northwest area, the Middle Reaches of the Yellow River, the Northeast area and the North area. Finally, some particular policy implications were also recommended for reducing industrial wastewater emission in China.
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