Fundamental Concepts and Quantities
Shaheen A. Dewji, Nolan E. Hertel in Advanced Radiation Protection Dosimetry, 2019
The nucleus of an atom is composed of protons and neutrons. Protons are formed by the combination of two up quarks and one down quark, with each up quark having a unit charge of +2/3 and the down quark having a unit charge, yielding a net unit charge for the proton of +1 (1 unit charge = Coulombs). The proton has a rest mass of kg (Baum, Knox, and Miller 2002) or, using the mass-energy relationship , 938.272 where one atomic mass unit (AMU) is taken to be 931.5 . The number of protons in an atom determines its atomic number (Z) and, therefore, the chemical properties of charge-neutral elements.
Finding a Target
Nathan Keighley in Miraculous Medicines and the Chemistry of Drug Design, 2020
Organelles perform different roles in the cell. The mitochondria are responsible for energy generation. Through the process of respiration, they manufacture adenosine triphosphate (ATP); a source of chemical energy. Modification of selected molecules is undertaken at the Golgi apparatus and/or the endoplasmic reticulum. Molecules manufactured by the cell, or assimilated from outside, may need to be changed to make them suitable for a given biochemical process. The Golgi apparatus and endoplasmic reticulum are the organelles with the capacity to perform this role. The nucleus, as previously mentioned, is where DNA is contained and is the control centre for the cell. Having a porous membrane enables passage of selected molecules to facilitate communication between the nucleus and the rest of the cell to ensure that instructions are received for the essential biochemical process of the cell to continue functioning without error.
Mock examination
Damian Tolan, Rachel Hyland, Christopher Taylor, Arnold Cowen in Get Through, 2020
True – the K shell electrons are closer to the nucleus and are subject to a greater attractive force.True – the binding energies of electrons are fixed values.False – the atomic number defines which element an atom is, and corresponds to the number of protons in the nucleus.False – the outer electron shell defines the diameter of an atom. This has a diameter tens of thousands of times the diameter of the nucleus.False – while there are normally more neutrons than protons in heavy nuclei, it is common to find equal numbers, or an excess of protons in light nuclei. For example, hydrogen (1p, On), helium (2p, 2n), carbon-12 (6p, 6n).
Development of computational model for cell dose and DNA damage quantification of multicellular system
Published in International Journal of Radiation Biology, 2019
Ruirui Liu, Tianyu Zhao, Maciej H. Swat, Francisco J. Reynoso, Kathryn A. Higley
In this work, for applying DBSCAN in DNA damage quantification, the homogenous water containment was used to approximate the cell nucleus containing DNA and the complex DNA structure is not considered. Considering that the chromatin formed by DNA in a cell is randomly distributed inside the nucleus, a term named SpointsProb was introduced to quantify the probability of the direct and indirect interactions induced by radiation energy deposition in the nucleus of cell (Francis et al. 2011). The SpointsProb defines the probability that an interaction point is in a sensitive position where it can directly or indirectly reach the DNA. The SpointsProb is determined according to the DNA volume. The diameter of general mammalian cell nucleus is about 10 μm, so the volume of nucleus is as 523.33 3. Roughly, a DNA base pair has a volume about 1 nm3. For mammalian cells, the total number of base pairs is on the order of 3. The fractional DNA volume with respect to the cell nucleus is therefore calculated as fDNA = 1.146%. We can approximately take fDNA as the sensitive fractional volume of cell nucleus to quantify the DNA damage due to radiation interactions within the cell nucleus.
A simple geometric method for 3D morphology reconstruction of a cell based on two orthogonal phase images
Published in Computer Assisted Surgery, 2019
Yawei Wang, Hao Han, Lei Wang, Jingrong Liao, Bing Xie, Ying Ji, Yuanyuan Xu
Binucleate cells are very common in human blood cells, such as binucleate eosinophils and binucleate neutrophils. Figure 1(a) is a diagram of binuclear cell captured by a conventional microscope. We establish its appropriate model, as shown Figure 1(b). It is composed of a cell membrane, cytoplasm, and two nuclei. Among which, the membrane is a sphere with the radius of 8.0 μm, one nucleus is an ellipse and its semiaxis lengths along x, y and z axes are 4.0 μm, 2.7 μm and 2.5 μm, respectively. The other nucleus is a sphere, and its radius is 2.5 μm. The central coordinates of the membrane, ellipsoidal nucleus and spherical nucleus are (0, 0, 0) μm, (−3.0, 0, 0) μm and (4.5, 1.5, 0) μm, respectively. For the quantitative phase distribution, the RI of the cytoplasm, the ellipsoidal nucleus and the spherical nucleus are set to be 1.37, 1.40 and 1.45, respectively. In addition, similar to the real phase imaging, the cell is required to be immersed in the matched environmental medium. Here, the refractive index of the environmental medium is set to be 1.33 in simulation.
DFT based QSAR study on quinolone-triazole derivatives as antibacterial agents
Published in Journal of Receptors and Signal Transduction, 2022
Niloofar Ghasedi, Shahin Ahmadi, Sepideh Ketabi, Ali Almasirad
Considering the structures, it seems that the presence of a phenyl ring with an electron-withdrawing group on the para position is an adequate substitution on triazole's N1, which has resulted in a more negative partial charge on this nitrogen atom. The partial atomic charge (Q) for C7 atom of the quinolone nucleus shows a positive contribution, indicating a more positive charge and low electron density on this atom is favorable. The presence of a substitute with electronegative atoms attached to C7 carbon and electronegative and electron-withdrawing groups such as halogens or nitrogen at the 6 and 8 positions of the quinolone nucleus can help lower the electron density on C7. According to the structures, piperazine or aminopyrrolidine substitutions on C7 have significantly increased the positive partial charge on this atom. Bond length is one of the geometrical descriptors attributed to the 3 D structures of molecules [49].
Related Knowledge Centers
- Cytoplasm
- Eukaryote
- Genome
- Multinucleate
- Nuclear Envelope
- Osteoclast
- Organelle
- Red Blood Cell
- Cell
- Nuclear Matrix