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Structure of Matter
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
If a given atom absorbs external energy at a level equal to or higher than an electron binding energy, an electron becomes free, because its link with the atom has been broken. As a result, the electrical equilibrium in the atom is no longer maintained, and the atom becomes a positive ion. For a given electron to be removed from the atom, the energy transfer must be higher than the binding energy of this electron. The excess of energy is, in principle, shared between the ionised atom and the electron as kinetic energy. Since particle momentum is conserved, most of the kinetic energy is given to the electron because of the very large difference in masses.
Physics for medical imaging
Published in Ken Holmes, Marcus Elkington, Phil Harris, Clark's Essential Physics in Imaging for Radiographers, 2021
In any given atom it is common for there to be the same number of electrons, collectively, within the electron shells as there are protons in the nucleus. This is known as an electrically balanced atom. But what happens if the nucleus and the electron shells become imbalanced electrically?If an atom gains an electron (which is a relatively common occurrence for some atoms), it is referred to as a negatively charged atom, also known as a negative ion or an anion (because it is attracted to a positive electrode or anode).If an atom loses an electron (again, relatively common) it leaves a positively charged atom, known as a positive ion or a cation (pronounced cat-ion), because it is attracted to a cathode.
Mass Spectrometric Analysis
Published in Adorjan Aszalos, Modern Analysis of Antibiotics, 2020
A total of 5 tetraene and 10 heptaene antibiotics with amino sugar and carboxylate groups were examined by FAB [194]. These zwitterionic compounds have not been amenable to other mass spectral techniques without exhaustive reduction or derivatization. In most cases, the positive ion spectra provided (M + H)+ ions and the negative ion spectra showed (M − H)− ions. In addition, aglycone ions with varying degrees of dehydration were observed in both positive and negative ion spectra. Several interesting conclusions were drawn from this study. The data obtained from amphotericin A and nystatin suggest they are identical. The molecular weights of hamycin A and aureofungin A and B were shown to be 16 u less than previously determined, suggesting one less hydroxyl group. Three components of the investigational drug AME were shown to be methyl esters of amphotericin B and analogs containing dimethylated and tetramethylated sugars.
Comparative HPLC-MS/MS-based pharmacokinetic studies of multiple diterpenoid alkaloids following the administration of Zhenwu Tang and Radix Aconiti Lateralis Praeparata extracts to rats
Published in Xenobiotica, 2021
Yanhao Liu, Hua Sun, Chao Li, Zhicheng Pu, Zijing Wu, Maodi Xu, Xianghong Li, Yuanxiang Zhang, Hongjin Li, Jian Dong, Runlei Bi, Haitang Xie, Dahu Liang
To identify optimal MS conditions, six analytes, and appropriate internal standard (IS) compounds were prepared at defined concentrations that were injected into the mass spectrometer using electrospray ionisation (ESI) and MRM scanning mode. Peak ion intensity values in negative and positive ion modes were compared and were found to be more stable in positive ion mode. Optimised MS parameters used for this study are compiled in Table 1. Initially, two eluents (Methanol/water and acetonitrile/water) were evaluated as a mobile phase. The acetonitrile/water mobile phase system was found to yield higher S/N ratios and better separation. After testing different buffers and acid–base solutions in combination with this mobile phase system, higher responses, and better peak shape were observed, followed by adding the ammonium acetate and formic acid to the mobile phase. Column temperature, eluent flow rate, and volume of injection were optimised.
In vitro and in vivo evaluation of a sustained-release once-a-day formulation of the novel antihypertensive drug MT-1207
Published in Pharmaceutical Development and Technology, 2021
Napoleon-Nikolaos Vrettos, Peng Wang, Yan Zhou, Clive J. Roberts, Jinyi Xu, Hong Yao, Zheying Zhu
MT-1207 in plasma samples was determined by a validated UPLC-MS/MS method using verapamil hydrochloride as an internal standard. Each time 10 μL of plasma sample were pipetted in 1.5 ml Eppendorf® tube. 200 μL of verapamil hydrochloride 2 ng/mL in acetonitrile were added and vortex was carried out for 5 min. Centrifugation was then carried out at 15000 rpm for 5 min and 100 µL of supernatant were collected for UPLC-MS/MS analysis. The ion source was an electrospray ionisation source (ESI). A positive ion scanning method was used for detection. The solvent gas (nitrogen) flow rate was 1000 L/h, the temperature of the solvent gas was 500 °C, and the capillary voltage was 3.0 kV. The scanning method was Multiple Response Monitoring (MRM). The cone voltage was set at 40 V, while the collision energy was 20 eV. For quantitative analysis, the ion pairs used had m/z 393.26 → 274.04 (MT-1207) and m/z 455.25 → 156.06 (internal standard). The samples were applied to an ACQUITY Ultra Performance Liquid Chromatography system with Xevo TQ-XS Triple Quadrupole Mass Spectrometer with operating software MassLynx V4.2 (Waters Technology Limited Company). The column used was an ACQUITY UPLC BEH C18 liquid chromatography column (2.1 × 50 mm, 1.7 μm). The mobile phase consisted of 0.1% formic acid in water (mobile phase A) and acetonitrile (mobile phase B). Verapamil hydrochloride was used as the internal standard for determination. The gradient elution was: 0–1.2 min: 20–45% B, 1.2–1.5 min: 45–95% B, 1.5–1.8 min: 95% B, 1.8–2.5 min: 95–20% B. The flow rate was set at 0.5 ml/min. The column temperature was set at 45 °C.
The biotransformation of Bupleuri Radix by human gut microbiota
Published in Xenobiotica, 2020
Cui Tang, Qiachi Fu, Xia Chen, Yang Hu, Helen Renaud, Chong Ma, Tai Rao, Yao Chen, Zhirong Tan, Curtis D. Klaassen, Shuyun Shi, Ying Guo
To propose the potential metabolism of SAPs of BRE incubated with human fecal microbiota, seven main active SAPs (Figure 1) were investigated. More specifically, seven SAPs were individually incubated with HFS anaerobically for 0 − 48 h in vitro, and metabolites were detected by HPLC-DAD-QTOF-MS. Data indicate that incubation with HFS results in a time-dependent decrease of the 7 prototype compounds, which are undetectable after 48 h. A total of 19 dehydrated and deglycosylated metabolites of SAPs were characterized, 10 of these metabolites have not been described previously. Metabolites were identified according to their retention time (tR), extracted ion chromatograms (EICs) and characteristic fragment ions (Table 1). EICs of SAPs as well as their metabolites after incubation with HFS for different times are shown in Figure 2. The metabolic time courses are exhibited in Figure 3. The proposed metabolic pathways of SAPs are shown in Figure 4. Both of the prototype compounds and their metabolites showed good responses in the positive ion mode. Mass spectral information of the prototype compounds and their metabolites are listed in Table 1.