Current Perspectives and Methods for the Characterization of Natural Medicines
Rohit Dutt, Anil K. Sharma, Raj K. Keservani, Vandana Garg in Promising Drug Molecules of Natural Origin, 2020
Mass spectrometry records the spectral data by plotting the mass-to-charge ratio (m/z) against the intensity of ions. The spectrum is generated from the gas phase ions. Mass spectrometer performs three basic fundamental functions like (i) The metabolites are converted into ions by the bombardment by high-energy electrons; (ii) The ions are accelerated and separated by the changes of mass-to-charge ratios in an electric or magnetic field; and (iii) detection of ions. Mass spectrometry is classed into different categories based on its working principle, i.e., (1) Direct infusion mass spectrometer (DIMS) - in DIMS, the sample is directly injected into the spectrometer; and (2) Tandem mass spectrometer (MS/MS) - the mass analyzer is combined with the additional mass analyzer. The ions of the first mass analyzer were ionized further in the second mass analyzer. Car-19 is the most thermostable κ-carrageenase. The κ-carrageenase producing thermophilic bacterial strains were obtained from sediment samples in Indonesia. carrageenase was characterized by electrospray ionization method of mass spectrometry from hot spring bacterium by Li et al. (2019). Car-19 is used for the preparation of carrageenan oligosaccharides with plant protection activity (Li et al., 2018). The mass spectroscopy-based characterized phytoconstituents and marine compounds are listed in Table 2.2.
Field Sensors: Military and Civilian
Brian J. Lukey, James A. Romano, Salem Harry in Chemical Warfare Agents, 2019
GC-MS breaks chemical compounds into small fragments and then matches these fragments to a library of known chemicals. In essence, a compound is identified by the sum of its parts. The technical basis of GC-MS is to fragment chemicals through vaporization based on molecular weight and ionize the fragments to generate a mass spectrum for identification. The collected sample is injected into the gas chromatograph (GC) injection port for vaporization and then enters a capillary column, where the sample is focused and separated using flows and temperatures. The separated sample passes through the MS interface into the ion source box. The sample is now ionized and then focused by a lens stack into a quadrupole electron mass filter equipped with pre-rods. The ions are separated by mass and detected by an electron multiplier. The ionization, separation, and detection are performed under a high vacuum. The instrument is operated with specialized software or on-unit controls. This data provides peak retention times as well as mass spectrum information such as mass and relative abundance of the ionized fragments. Finally, the spectrum information at specific retention times (peaks) can be compared with a library to identify the collected sample (Brian A. Moore, personal communication, January 23, 2018).
Spectroscopic Techniques
Ravindra Kumar Pandey, Shiv Shankar Shukla, Amber Vyas, Vishal Jain, Parag Jain, Shailendra Saraf in Fingerprinting Analysis and Quality Control Methods of Herbal Medicines, 2018
Mass Spectrometry is a powerful technique for identifying unknowns, studying molecular structure, and probing the fundamental principles of chemistry. It can provide us with useful structural information for drug discovery and has been recognized as a sensitive, rapid, and high-throughput technology for advancing drug discovery from herbal medicine in the post-genomic era. It is essential to develop an efficient, high-quality, high-throughput screening method integrated with mass spectroscopy (Zhang et al., 2016). Mass spectroscopy is one of the primary spectroscopic methods for molecular analysis available to an organic chemist. It is a microanalytical technique requiring only a few nanomoles of the sample to obtain characteristic information pertaining to the structure and molecular weight of an analyte. It involves the production and separation of ionized molecules and their ionic decomposition products and finally the measurement of the relative abundance of the different ions produced (Yerlekar and Kshirsagar, 2014). It is, thus, a destructive technique in that the sample is consumed during analysis. In most cases, the nascent molecular ion of the analyte produces fragment ions by cleavage of the bond and the resulting fragmentation pattern constitutes the mass spectrum. Thus, the mass spectrum of each compound is unique and can be used as a “chemical fingerprint” to characterize the sample.
Molecular tissue profiling by MALDI imaging: recent progress and applications in cancer research
Published in Critical Reviews in Clinical Laboratory Sciences, 2021
Pey Yee Lee, Yeelon Yeoh, Nursyazwani Omar, Yuh-Fen Pung, Lay Cheng Lim, Teck Yew Low
MALDI imaging was initially introduced by Caprioli et al. [17] in the late 1990s. MALDI-MS was used for direct imaging of insulin and hormone peptides from rat tissue sections and provided detailed spatial localization of biomolecules that could be displayed as ion images. Since then, MALDI imaging techniques have been adopted in many studies to characterize molecular spatial distribution. It is a versatile analytical tool, applicable not only to protein and peptide analysis, but also to diverse classes of biomolecules including glycans, lipids, drugs, and metabolites [18]. The general workflow for MALDI imaging consists of several steps: (i) tissue sectioning and mounting onto a conductive glass slide, (ii) tissue coating with a homogenous layer of matrix, (iii) irradiation with a laser beam at a predefined number of shots across selected coordinates for data acquisition, (iv) analyte identification and data analysis, and (v) quantification. The mass spectrum comprised of a plot of ion intensity against m/z, is generated for each coordinate that corresponds to molecular content. The acquired dataset can be presented as an image map for each molecular ion across the tissue in a pseudo-color heat map indicating spatial intensity distribution [19]. After data acquisition, the same tissue section can be re-used for histological staining and co-registered with the MALDI imaging data to map the molecular ion to the tissue area [20] (Figure 2). We will discuss the key considerations for each of these steps below.
Applications of MALDI-TOF mass spectrometry in clinical proteomics
Published in Expert Review of Proteomics, 2018
Viviana Greco, Cristian Piras, Luisa Pieroni, Maurizio Ronci, Lorenza Putignani, Paola Roncada, Andrea Urbani
Detection of the ion m/z and generation of a mass spectrum. Ions detection is the last but not the less important step in a MS analysis. Concisely, the detection system is a Secondary Electron Multiplier, generally designed as micro channel plates, which amplifies the impact of ions by producing secondary electrons that are converted into an electric signal. The detector provides the output voltage that is then guided to an analogical to digital converter and delivered to a PC for the analysis. The m/z ratios are calculated by measuring the time it takes for the ions to travel in the flight tube from the source to the detector. The registered ions are generally singly charged [M + H]+; the MS sample profiles are represented by a mass spectrum with peaks characterized by m/z value on the horizontal axis and the relative abundance of that ion on the vertical axis.
Ameliorative effects of hexane extract of Garcinia kola seeds Heckel (Clusiaceae) in cisplatin-induced hepatorenal toxicity in mice
Published in Drug and Chemical Toxicology, 2022
Adeniyi Folayan, Emmanuel Akani, Olayinka A. Adebayo, Olubukola O. Akanni, Solomon E. Owumi, Abiola S. Tijani, Oluwatosin A. Adaramoye
The Agilent technologies 7890 GC system model instrument was used for the analysis. The model of the detector was Agilent technologies 5975 MSD (Mass Spectrometer Detector). The mobile phase was the carrier gas (Helium, 99.99% purity), while the stationary phase was the column. The model of the column was HP5 MS with length 30 m and internal diameter 0.320 mm, while the thickness was 0.25 µm. The oven temperature program was the initial temperature of 80 °C to hold for 1 minute. It increases by 10° C per minute to the final temperature of 240° C to stay for 6 minutes. The injection volume was 1 µL, and the heater or detector temperature was 250°C. The sample (HEGK) was put in a vial, which was later placed in an auto-injector sample compartment. The automatic injector injects the sample into the liner. The mobile phase pushes the sample from the liner into the column, where separation takes place into different components at different retention times. The MS then interpret the spectrum MZ (mass to charge ratio) with molar mass and structures.
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