Qualitative and Quantitative Analytical Techniques of Nucleic Acid Modification Based on Mass Spectrometry for Biomarker Discovery.

Nucleic acid modifications play important roles in biological activities and disease occurrences, and have been considered as cancer biomarkers. Due to the relatively low amount of nucleic acid modifications in biological samples, it is necessary to develop sensitive and reliable qualitative and quantitative methods to reveal the content of any modifications. In this review, the key processes affecting the qualitative and quantitative analyses are discussed, such as sample digestion, nucleoside extraction, chemical labeling, chromatographic separation, mass spectrometry detection, and data processing. The improvement of the detection sensitivity and specificity of analytical methods based on mass spectrometry makes it possible to study low-abundance modifications and their biological functions. Some typical nucleic acid modifications and their potential as biomarkers are displayed, and efforts to improve diagnostic accuracy are discussed. Future perspectives are raised for this research field.

In-source fragmentation of nucleosides in electrospray ionization towards more sensitive and accurate nucleoside analysis.

Nucleosides have been found to suffer in-source fragmentation (ISF) in electrospray ionization mass spectrometry, which leads to reduced sensitivity and ambiguous identification. In this work, a combination of theoretical calculations and nuclear magnetic resonance analysis revealed the key role of protonation at N3 near the glycosidic bond during ISF. Therefore, an ultrasensitive liquid chromatography-tandem mass spectrometry system for 5-formylcytosine detection was developed with 300 fold signal enhancement. Also, we established a MS1-only platform for nucleoside profiling and successfully identified sixteen nucleosides in the total RNA of MCF-7 cells. Taking ISF into account, we can realize analysis with higher sensitivity and less ambiguity, not only for nucleosides, but for other molecules with similar protonation and fragmentation behaviors.

Ultrasensitive HPLC-MS Quantification of S-(2-Succino) Cysteine Based on Ethanol/Acetyl Chloride Derivatization in Fumarate Accumulation Cells.

Succination is a nonenzymatic and irreversible post-translational modification (PTM) with important biological significance, yielding S-(2-succino) cysteine (2SC) residue. This PTM is low in abundance and often requires a large amount of protein samples for 2SC quantification. In this work, an efficient quantification method based on ethanol/acetyl chloride chemical derivatization was developed. The three carboxyl groups of 2SC were all esterified to increase hydrophobicity, greatly improving its ionization efficiency. The sensitivity was increased by 112 times; the limit of detection was reduced to 0.885 fmol, and the protein usage was reduced by at least 10 times. The established method was used to detect the overall concentration of 2SC in fumarate accumulation cells quantitatively.

[Adsorption of Pb2+ and Cd2+ from Aqueous Solution Using Vermicompost Derived from Cow Manure and Its Biochar].

Using vermicompost (CV) as raw material, its biochar (CVC350) was prepared at 350℃ and then their physio-biochemical properties were characterized. Furthermore, adsorption studies were performed in a batch system for removing Pb2+ and Cd2+ ions from solution. The characterization results revealed much higher surface area, smaller pore size, greater aromaticity and nonpolarity of CVC350 as compared to CV. Batch adsorption experiments revealed that both the adsorption of Pb2+ and Cd2+ onto CV or CVC350 fitted Langmuir isotherm model very well, and the maximum adsorption capacity of Pb2+ was in the order of CVC350>CV, but no difference was observed for the adsorption capacity of Cd2+ between CV and CVC350. The desorption studies showed that both CV and CVC350 had much higher adsorption rate for Pb2+ than that for Cd2+, and the Cd2+ adsorbed could be more easily desorbed from CV and CVC350 compared with that for the Pb2+ adsorbed. Both the dynamic adsorption process of Pb2+ onto CV and CVC350 was a rapid process, however, the adsorption process of Cd2+ onto CV and CVC350 could be separated into the first rapid step and the second slower step. The adsorption capacity of Pb2+ or Cd2+ onto CV and CVC350 was only affected by the much lower initial pH of the solution, besides, the adsorption capacity of Cd2+ onto CV and CVC350 was relatively more influenced by the initial pH compared with that of Pb2+. Moreover, FTIR analysis showed that the adsorption of Pb2+ and Cd2+on CV depended on the active sites such as aliphatic alcohol, aliphatic acid,carbonates as well as phosphate while that on CVC350 mainly relied on aromatic alcohol, aromatic acid and carbonates.