Introduction to advanced separation
Zhen
Liu
a,
Wenwan
Zhong
b and
Takuya
Kubo
c
aState Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China. E-mail: zhenliu@nju.edu.cn
bDepartment of Chemistry, University of California – Riverside, Riverside, California 92521, USA. E-mail: wenwan.zhong@ucr.edu
cGraduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan. E-mail: kubo.takuya.6c@kyoto-u.ac.jp
Abstract
Separation is an essential aspect in analytical chemistry or chemical measurement science. With the capability to separate components within a sample into individual bands or zones distributed spatially or/and temporally, separation makes the analysis or measurement more accurate through separating different components into individual fractions and reducing or even eliminating the interference from sample matrix species. Such a power also makes separation an important tool to purify components of interest from mixtures or natural products for further investigations. Meanwhile, separation can make a subsequent analytical method more sensitive through enriching or concentrating the components of interest in the samples to be tested. Modern separation science and techniques have been well established and are quite mature, making them widely employed in routine scientific research and practices. However, due to the increasing complexity and challenge of analytical tasks that we are facing, advanced separation science and techniques are still in high demand. This inspired us to organize this themed collection to reflect some trends and features of this practically useful, technically diverse and forever progressive area.
This themed collection is composed of 5 review papers and 8 research papers, with contributions from three major countries: China (10 papers), Japan (2 papers) and the USA (1 paper). The topics of this themed collection can be loosely categorized into advanced materials for separation, advanced methods and prospective applications. It also highlights many recent advances in both materials science and hyphenated methods for advanced separation. The advanced materials discussed in this collection include molecularly imprinted polymers (MIPs), metal organic frameworks (MOFs), porous organic frameworks (POFs), nanoparticles and nanowires. The advanced methods cover hyphenated methods, particularly liquid chromatography (LC)-tandem mass spectrometry (MS/MS), nanoparticle-assisted ultrafiltration, cationic surfactant-assisted sample preparation, magnetic solid-phase extraction, and so on. The prospective applications range from chiral separation, affinity isolation, selective enrichment, selective labeling, sample preparation, proteomics analysis and multi-omics analysis. In fact, the sample scope and the analyte range that the methods and materials aimed to separate largely reflect the wide applicable breadth of the separation techniques discussed in this issue, ranging from herbicide residue, peptides, proteins, metabolites, enantiomers, single-stranded DNA (ssDNA), messenger RNA, extracellular vesicles, epigenetically modified histones and mass-limited samples. Particularly, these also reflect the increasing challenges of the analytical tasks faced in biological/biomedical research nowadays, such as -omics and epigenetic analysis.
Two interesting works in this collection highlight well the recent advances in separation science. In a research paper, the team led by Dr Yoshinobu Baba at Nagoya University in Japan reported a ZnO/SiO2 core/shell nanowires-based microfluidic device for capturing CpG rich ssDNAs (DOI: 10.1039/D0AY02138E). DNA methylation at CpG sites has been considered to be a promising diagnostic marker for the early detection of cancer. CpG-rich ssDNAs can be a binding material of interest, especially for aptamers to be further extended as capture probes for the recognition of DNA methylation on CpG sites. The authors modified the surface of ZnO nanowires through atomic layer deposition (ALD) and fabricated ZnO/SiO2 (core/shell) nanowires. The ZnO/SiO2 nanowires were embedded in a microchip device that was integrated with a syringe pump system. The microfluidic device was applied for capturing CpG-rich ssDNAs. A high capture efficiency of ssDNAs (86.7%) was achieved, showing great potential to be further extended for the analysis of CpG sites in cancer-related genes. In another research paper, the team of Professor Yukui Zhang at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, reported a promising proteomics approach for the quantitative analysis of epigenetic histone modifications in MCF-7 cells under estradiol stimulation (DOI: 10.1039/D0AY02146F). Estrogen exposure has already been documented to be associated with tumorigenesis and breast cancer progression. A stable isotope labeling of amino acid (SILAC) based quantitative proteomics approach was developed and used for the analysis of histone post-translational modifications (PTMs) and protein differential expressions in MCF-7 cells under estrogen exposure. In total, 49 histone variants were unambiguously identified and 42 of them were quantified, in which two differentially expressed proteins were found to be associated with breast cancers. Via the quantitative analysis of 470 histone peptides with a combination of different PTM types, which include methylation (mono-, di- and tri-), acetylation and phosphorylation, 150 of them were found to be differentially expressed. Interestingly, the histone variants H10 and H2AV were found to have an effect on the adjustment of the nucleosome or chromatin structure and the activation of target genes. In addition, after estrogen receptor (ER) activation by estrogen, the recruitment of the histone acetyltransferase KAT7 was found to likely affect the acetylation at the N terminal of H4 (K5, K8 and K12) and results in cross-talk between different acetylation sites. Furthermore, the different expression of histone deacetylase HDAC2 and its nucleo-cytoplasmic transportation process were found be important in the regulation of histone acetylation in MCF-7 cells under estrogen exposure. This work demonstrated well the power of LC-MS/MS-based quantitative proteomics in revealing the physiological roles of epigenetic histone modifications.
Although there are many other interesting topics that are worthy of inclusion, they have to be omitted due to space restrictions. As the guest editors of this themed collection, we would like to thank all of the authors for their high-quality contributions. Also, we would like to thank the editorial staff from the journal Analytical Methods for their assistance and support throughout the creation process. We expect that researchers in analytical chemistry and related areas will enjoy reading these papers and get inspiration from their innovative ideas or solutions to their own tasks.
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