Dictionary
Mario P. Iturralde in Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Notation of atomic and nuclear composition. The notation used to summarize atomic and nuclear composition is A/Z XN, where X represents the chemical element to which the atomic belongs; A is the mass number of the nucleus, or the total number of protons in the nucleus (this determines also the number of orbital electrons in the electrically neutral atom and therefore the chemical element to which the atom belongs; and Πis the neutron number, or the difference of A — Z. For example, an atom comprised of 6 protons, 8 neutrons (and thus 14 nucleons), and 6 orbital electrons represents the element carbon and is symbolized by 14/6 C-8. Since all carbon atoms have atomic number (Z) 6, either “C†or the “6†is redundant, and the “6†can be omitted. The neutron number (N), 8, can be inferred from the difference 14−6 and also can be omitted. Therefore, a shortened but still complete notation for this atom is 14C. Acceptable alternatives in terms of medical terminology are 14-C, or the complete work, carbon-14. The notations C14, 14C, and C14 are obsolete and therefore not acceptable. Excited states are identified by an asterisk (*) and metastable states by the letter m (AmX or X-Am) such as 99mTc, Tc−99m, or technetium-99m.
Structure of Matter
W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald in Handbook of Radiotherapy Physics, 2021
Unified atomic mass unit: As seen previously, the mass of a given atom is close to the sum of the masses of the nucleons and the electrons. Remember that the mass of an electron is about 1840 times smaller than the mass of a nuclear particle. The actual mass of an atom, expressed in terms of kilograms, the usual international unit of mass, is very small and not of much practical use. Consequently, another approach is often used: defining a special unit of atomic mass (symbol u).* The atomic mass unit was defined to be approximately the mass of a nuclear particle, permitting the atomic mass of an atom to be expressed with numbers close to the mass number. The official definition of the unified atomic mass unit is related to 1/12 of the mass of the carbon atom with six protons and six neutrons, i.e. 1 u ≈ 1.661 × 10−27 kg. Because the mass of a carbon atom is exactly 12 u, expressed with this unit, it is strictly equal to its mass number. However, the mass of an atom of oxygen 16, for example, is 15.9991 u, which is slightly different from its mass number.
Ion Beam Analysis: Analytical Applications
Vlado Valković in Low Energy Particle Accelerator-Based Technologies and Their Applications, 2022
Three isotopes of carbon are present in nature; 12C, 13C and 14C. 12C accounts for ~99.8% of all carbon atoms, 13C accounts for ~1% of carbon atoms while 14C represents only 1 ppb (one part per billion) of natural carbon. Carbon isotope 14C is radioactive and has a half-life of 5730 years. Because this decay is constant it can be used as a “clock” to measure elapsed time assuming the starting amount is known. A unique characteristic of 14C is that it is constantly formed in the upper atmosphere where neutrons from cosmic rays knock a proton from 14N atoms. These newly formed 14C atoms rapidly oxidize to form 14CO2 that is chemically indistinguishable from 12CO2 and 13CO2. Photosynthesis incorporates 14C into plants and therefore animals that eat the plants. 14C enters the dissolved inorganic carbon pool in the oceans, lakes and rivers. From there it is incorporated into shell, corals and other marine organisms. When a plant or animal dies it no longer exchanges CO2 with the atmosphere. This starts the radioactive decay “clock”. 14C decays by emitting an electron, which converts a neutron to a proton, converting it back to its original 14N form.
MSDC-0602K, a metabolic modulator directed at the core pathology of non-alcoholic steatohepatitis
Published in Expert Opinion on Investigational Drugs, 2018
Jerry R. Colca, William G McDonald, Wade J. Adams
Since the carbonyl moiety of MSDC-0602 is a pro-chiral center, reduction of the carbonyl moiety may result in R- or S-alcohols on reduction. Each of these alcohol molecules would exist as diastereomers as the 5-position of the thiazolidinedione ring also has an asymmetric carbon, as is the case for all marketed first-generation TZDs. This asymmetric carbon is indicated by the asterisk in Figure 1. A chiral method for the quantification of all four diastereomers of the alcohol in plasma for human, cynomolgus monkey, and Sprague Dawley rat demonstrated that following single- and repeated-dose administration of micronized MSDC-0602 free acid or the potassium salt of MSDC-0602 (MSDC-0602K), the R-diastereomers were the major alcohols observed in plasma of all three species, with overall mean percentages of R-MSDC-0597 in human, monkey, and rat being estimated at 86.1%, 94.0%, and 66.2%, respectively. This is of interest because there is a very significant stereochemical difference in the abilities of the alcohols to directly activate PPARγ-driven transcription in a transactivation reporter assay using human PPARγ (Figure 2). Consistent with numerous reports in the literature, rosiglitazone is 10 times more potent that pioglitazone in activating PPARγ, whereas MSDC-0602 and the R-alcohol are significantly less potent and efficacious in this assay (Figure 2).
Novel amides of mycophenolic acid and some heterocyclic derivatives as immunosuppressive agents
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Juliusz Maksymilian Walczak, Dorota Iwaszkiewicz-Grześ, Michalina Ziomkowska, Magdalena Śliwka-Kaszyńska, Mateusz Daśko, Piotr Trzonkowski, Grzegorz Cholewiński
MPA as a fully substituted aromatic compound possesses no protons in the aromatic region. This fact simplifies amides’ 1H NMR spectrum analyses since newly incorporated moieties contribute aromatic and amide protons solely. All spectra are determined by the deshielded amide proton and phenolic one as well as recently introduced aromatic species. Remaining signals represent MPA structure and are sometimes shifted due to magnetic environment modifications. Some lapping may occur as implemented amines bear functional groups or spacers appearing in the same 1H NMR regions as MPA structural units. 13C NMR spectra are also characterised by MPA core and added value in the shape of newly introduced carbon atoms. Some dissimilarities in the nucleus characteristics may occur (especially in the case of amide group carbon) as well as for amine-based units. The latter one is represented by deshielded C(2) heteroaromatic carbon and C(3a)/C(7a) positions. Remaining loci differ with heteroatom electronegativity and substituent character, sometimes precluding precise carbon atoms assignment. Some 1H and 13C NMR spectra show long and short distance spin decoupling brought by fluorine atoms, namely in A11 and A14 cases. More detailed information about the character of heteroaromatic interactions within 13C NMR spectroscopy may be found in the literature38,39.
Mouse pulmonary dose- and time course-responses induced by exposure to nitrogen-doped multi-walled carbon nanotubes
Published in Inhalation Toxicology, 2020
Dale W. Porter, Marlene Orandle, Peng Zheng, Nianqiang Wu, Raymond F. Hamilton, Andrij Holian, Bean T. Chen, Michael Andrew, Michael G. Wolfarth, Lori Battelli, Shuji Tsuruoka, Mauricio Terrones, Vince Castranova
Figures 1 and 2 show the TEM and HRTEM images obtained from MWCNT and NDMWCNT, respectively. The multilayer structure of the MWCNT was observed in both samples with an average layer distance of 0.36 nm. Nitrogen doping did not change the crystal structure or the layer distance. Figures 3 and 4 show the XPS spectra obtained from MWCNT and NDMWCNT, respectively. The survey scan in Figure 3 reveals that carbon was the major element contained in the MWCNT; and oxygen was barely seen in the survey scan due to its trace content. The detailed scan of C 1 score-level has confirmed that C existed mainly in the form of a graphite-like ring structure, evidenced by a single peak at 284.6 eV. The tiny tail at the higher binding energy side of this scan shows there was a trace level of carbon in the form of C–O. This was consistent with the O 1 s peak at 532.5 eV. In addition, no nitrogen (N 1 s) was observed in the MWCNT sample. The NDMWCNT sample showed similar XPS spectra as the MWCNT sample except two N 1 s peaks were present in the detailed N1s scan (Figure 4). The N 1 s peak at 400.3 eV can be ascribed to the O–C–N or the –C–NH2 bond; and the N 1 s peak at 405.0 eV might be due to the oxidation of nitrogen.
Related Knowledge Centers
- Atom
- Helium
- Organic Compound
- Oxygen
- Polymer
- Radionuclide
- Carbon-13
- Half-Life
- Hydrogen
- Carbon-Based Life