A major research plan entitled “Integrated research on the ecohydrological process of the Heihe River Basin” was launched by the National Natural Science Foundation of China in 2010. One of the key aims of this research plan is to establish a research platform that integrates observation, data management, and model simulation to foster twenty-first-century watershed science in China. Based on the diverse needs of interdisciplinary studies within this research plan, a program called the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) was implemented. The overall objective of HiWATER is to improve the observability of hydrological and ecological processes, to build a world-class watershed observing system, and to enhance the applicability of remote sensing in integrated ecohydrological studies and water resource management at the basin scale. This paper introduces the background, scientific objectives, and experimental design of HiWATER. The instrumental setting and airborne mission plans are also outlined. The highlights are the use of a flux observing matrix and an eco-hydrological wireless sensor network to capture multiscale heterogeneities and to address complex problems, such as heterogeneity, scaling, uncertainty, and closing water cycle at the watershed scale. HiWATER was formally initialized in May 2012 and will last four years until 2015. Data will be made available to the scientific community via the Environmental and Ecological Science Data Center for West China. International scientists are welcome to participate in the field campaign and use the data in their analyses.

We have reported a set of electrokinetically pumped sheath flow nanoelectrospray interfaces to couple capillary zone electrophoresis with mass spectrometry. A separation capillary is threaded through a cross into a glass emitter. A side arm provides fluidic contact with a sheath buffer reservoir that is connected to a power-supply. The potential applied to the sheath buffer drives electro-osmosis in the emitter to pump the sheath fluid at nanoliter/minute rates. Our first generation interface placed a flat-tipped capillary in the emitter. Sensitivity was inversely related to orifice size and to the distance from the capillary tip to the emitter orifice. A second generation interface used a capillary with an etched tip that allowed the capillary exit to approach within a few hundred micrometers of the emitter orifice, resulting in a significant increase in sensitivity. In both the first and second-generation interfaces, the emitter diameter was typically 8-μm; these narrow orifices were susceptible to plugging and tended to have limited lifetime. We now report a third-generation interface that employs a larger diameter emitter orifice with very short distance between the capillary tip and the emitter orifice. This modified interface is much more robust and produces much longer lifetime than our earlier designs with no loss in sensitivity. We evaluated the third-generation interface for a 5,000-min (127 runs, 3.5 days) repetitive analysis of bovine serum albumin digest using an uncoated capillary. We observed a 10% relative standard deviation in peak area, an average of 160,000 theoretical plates, and very low carry-over (much less than 1%). We employed a linear-polyacrylamide (LPA) coated capillary for single-shot, bottom-up proteomic analysis of 300 ng of Xenopus laevis fertilized egg proteome digest, and identified 1,249 protein groups and 4,038 peptides in a 110 min separation using an LTQ-Orbitrap Velos mass spectrometer; peak capacity was ~330. The proteome dataset using this third generation interface based CZE-MS/MS is similar in size to that generated using a commercial ultra-performance liquid chromatographic analysis of the same sample with the same mass spectrometer and similar analysis time.

Femtogram proteomics: We report an ultrasensitive capillary zone electrophoresis-mass spectrometry system based on an improved nanospray interface. This system is used for analysis of picogram to femtogram amounts of E. coli digests. Over 100 proteins were identified based on tandem mass spectra from 16 pg digests; over 60 proteins were identified from 400 fg digests based on accurate mass and time tags in 10 min.

No abstract

Capillary zone electrophoresis (CZE)-electrospray ionization-tandem mass spectrometry (ESI-MS/MS) was optimized and applied for analysis of 1–100 ng E. coli protein digests in a single run (single-shot analysis). The system employed an electrokinetically-pumped nanospray interface, a coated capillary, and stacking conditions for sample injection. More than 1,250 peptides were identified by optimized single-shot CZE-ESI-MS/MS with 100 ng digest loaded and 50 min analysis time. When 10 ng and 1 ng digests were loaded, about 1,000 and 600 peptides were identified in a single-shot analysis, respectively. Compared with single-shot ultra-performance liquid chromatography (UPLC)-ESI-MS/MS, CZE-ESI-MS/MS produced fewer peptide IDs (1,377 ± 128 vs. 1,875 ± 32) for large sample loading amounts (100 ng) with the same mass spectrometer time (50 min). However, when the loaded digest was mass limited (1 ng), CZE-ESI-MS/MS generated many more peptide identifications than UPLC-ESI-MS/MS (627 ± 38 vs. 342 ± 113). In addition, CZE-ESI-MS/MS and UPLC-ESI -MS/MS provided complementary peptide level identifications. These results suggest that CZE-ESI-MS/MS may be useful for large-scale, comprehensive, and confident proteomics analysis.