Physics for medical imaging
Ken Holmes, Marcus Elkington, Phil Harris in 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.
Nutrition for health and sports performance
Nick Draper, Helen Marshall in Exercise Physiology, 2014
An ionic bond is formed between two atoms when one of the atoms donates an electron to another, thus completing the outer shell of electrons for each and creating a stable chemical product. An example of this can be found in Figure 2.3 where chlorine (Cl) accepts one electron from sodium (Na). By doing this Cl becomes a negatively charged chloride ion (Cl−) as it has more electrons than protons and Na becomes a positively charged sodium ion (Na+) because it has one electron fewer. Atoms that lose electrons and become positively charged are called cations (to remember this think of the t as + and positive) and those that accept electrons and become negatively charged ions are called anions (think of the n as n egative). The resultant compound for this example is sodium chloride (NaCl) or table salt. It is this compound in our sweat that gives sweat a salty taste.
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
A molecule or ATOM that is electrically charged, having either gained or lost electrons. A CATION has a positive charge, an ANION has a negative charge. In solution many substances break down into their component parts: common salt—sodium chloride (NaCl)—for example breaks down in water into positively charged sodium ions (Na+) and negatively charged chloride ions (Cl ). The relative balance of positively and negatively charged ions on either side of a neuronal MEMBRANE determines the RESTING POTENTIAL of a NEURON. The movement of ions across the membrane is critical for ACTION POTENTIAL generation. Movement of ions across a membrane can be a RECEPTOR-mediated process, occurring via the receptor-regulated ION CHANNEL system, or a process mediated by specialized transport mechanisms such as the SODIUM-POTASSIUM PUMP and the CALCIUM PUMP.
Anion inhibition studies of the α-carbonic anhydrases from Neisseria gonorrhoeae
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Alessio Nocentini, Chad S. Hewitt, Margaret D. Mastrolorenzo, Daniel P. Flaherty, Claudiu T. Supuran
NgCA, a high activity α-CA present in the genome of the bacterial pathogen N. gonorrhoeae was investigated for its inhibition with a series of inorganic and organic anions. Perchlorate and hexafluorophosphate, did not inhibit NgCA significantly, whereas the halides, azide, bicarbonate, carbonate, stannate, perosmate, diphosphate, divanadate, perruthenate, and trifluoromethanesulfonate showed inhibition constants in the range of 1.3–9.6 mM. Anions/small molecules such as cyanate, thiocyanate, nitrite, nitrate, bisulphite, sulphate, hydrogensulfide, phenylboronic acid, phenylarsonic acid, selenate, tellurate, tetraborate, perrhenate, peroxydisulfate, selenocyanate, iminodisulfonate, and fluorosulfonate showed KIs in the range of 0.15–1.0 mM. The most effective inhibitors detected in this study were sulfamide, sulfamate, trithiocarbonate and N,N-diethyldithiocarbamate, which had KIs in the range of 5.1–88 µM. These last compounds incorporating the CS2- zinc-binding group may be used as leads for developing even more effective NgCA inhibitors, as this enzyme was recently validated as an antibacterial drug target for obtaining novel antigonococcal agents.
Design and optimization of cranberry extract loaded bile salt augmented liposomes for targeting of MCP-1/STAT3/VEGF signaling pathway in DMN-intoxicated liver in rats
Published in Drug Delivery, 2022
Sara M. Soliman, Shaimaa Mosallam, Mohamed A. Mamdouh, Mohammed Abdalla Hussein, Shady M. Abd El-Halim
As demonstrated in (Table 3), the fabricated CBE loaded BSALs exhibited negative ZP values that ranged from −6.93 ± 0.67 to −32.43 ± 0.91 mV. The negative charge is probably imparted by the phospholipid (Subongkot et al., 2014) and the anionic nature of SGC (Mosallam et al., 2021b). ANOVA analysis revealed that all three independent variables (X1, X2, and X3) had a significant influence on ZP, (p < .0001 for X1 and X2 and P = 0.0028 for X3). Regarding phospholipid type (X1), BSALs prepared using Epikuron 100 manifested higher ZP values than those prepared using Epikuron 200. This might be explained by the larger VS obtained by Epikuron 200, which resulted in a reduction of the surface area carrying charge (El Kayal et al., 2020).
Vanillin enones as selective inhibitors of the cancer associated carbonic anhydrase isoforms IX and XII. The out of the active site pocket for the design of selective inhibitors?
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Leonardo E. Riafrecha, Macarena S. Le Pors, Martín J. Lavecchia, Silvia Bua, Claudiu T. Supuran, Pedro A. Colinas
MD simulations were performed on poses resulting from molecular docking for CA I and CAII. The system, CAs, and ligands have a positive net charge, so chloride anions were added as counterions with the Leap module to achieve electroneutrality. The neutralised ligand/CA complexes were immersed in a box of TIP3P waters which extended up to 15 Å from the solute. CAs were described using the Amber14SB force field36. The ligand was described using the Generalised Amber Force Field37 with charges derived from RESP, which were calculated with the Antechamber module. Leap and Antechamber are included in the package AmberTools 20.038. Zn2+ cation, neighbouring residues and a water molecule were modelled with MCPB.py39, also included in AmberTools 20.0.
Related Knowledge Centers
- Atom
- Ionization
- Molecule
- Oxygen
- Solvation
- Salt
- Dissociation
- Dianion
- Zwitterion
- Adenosine Triphosphate