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Basic Atomic and Nuclear Physics
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Gudrun Alm Carlsson, Michael Ljungberg
The periodic table, first defined by Dmitrij Mendelejev in 1869, describes atomic elements according to their increasing atomic number Z and some of their chemical and physical properties along with their electron configuration in the outer electron shells. The table arranges elements with similar chemical properties in groups (column). The rows (period) define the elements with similar numbers of electrons in the outer shell. Within each period, the metals are in general found on the left side, while the non-metals are found on the right side. In the layout, shown in Figure 2.3, the lower number is the atomic number, and the upper number is the mass number, which is presented as the average mass of the atoms of an element presented as the weighted average of all isotopes of the atomic element.
Chemistry and Isotopes of Iodine
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
Electrons determine the chemical reactivity of an element. Electrons orbit the nucleus in quantum shells, designated by the letters K (innermost shell) and Q (outermost shell). The numbers of electrons that may be held by each shell are K, 2; L, 8; M, 18; N, 32; O, 24; P, 12; and Q, 2. In general, an electron does not occupy an outer quantum shell unless the shells between it and the nucleus are full. The number of electrons present in an atom increases in the periods from left to right. The electron configuration of an atom is determined by the disposition of its electrons in the quantum shells.
Interaction of Drugs of Dependence With Receptors
Published in S.J. Mulé, Henry Brill, Chemical and Biological Aspects of Drug Dependence, 2019
Using physicochemical methods, it has been shown that slight modifications of the psychotomimetic tryptamine derivatives produce ring systems which are similar to LSD, bufotenin, or psilocybin.66–68,93,94 In particular, attempts have been made by Kang and Green68 to relate potency of these drugs to their electronic configuration using molecular orbital calculations. Although it is true that at times such correlations “ are extremely good, this might simply be coincidence. This is inevitable when a series of drugs is examined in animal experiments in which chemical modification can give rise to variable effects on activity, and these effects are modified by such factors as distribution, excretion, metabolism, binding to serum proteins, binding to nonreceptor macromolecules, and ability to penetrate into the CNS. Furthermore, in such complex systems, there is no direct evidence that the drugs are all acting by a common mechanism; this is even true when one is dealing with series of drugs acting on an isolated tissue.95 Such SAR studies carried out in whole animals may have only limited value in defining the configuration of the receptor site which is involved with their effects. A useful test for the ideas which emerged from these various SAR studies would be the antibodies to LSA prepared by Van Vunakis et al.86 Moreover, it was shown that various tryptamine derivatives have graded affinities for this antibody.
Molecular docking study on europium nanoparticles and mussel adhesive protein for effective detection of latent fingerprints
Published in Biomarkers, 2023
T. R. Poorani, C. Ramya, Ramya Manohar
The Europium element whose atomic symbol is Eu and atomic number is 63, is present in Block F, Group 3, Period 6 of the periodic table. Its atomic radius is around 151.964. Each europium shell is filled with the number of electrons of about 2, 8, 18, 25, 8, 2 with an electronic configuration of [Xe]4f76s2. This europium metal belongs to the lanthanide or rare earth series which has an atomic radius of about 180 pm and its Van der Waals radius was about 233 pm. This metal looks like a silvery white and found as a free element in natural environment. Europium nanoparticles (EuNp) also known as nanopowder or nanodots looks like a black spherical particle with higher surface area and are around 10 − 45 nm with the specific surface area (SSA) of about 30 − 50 m2/g. These nanoparticles were also available with the average particle size of 75 − 100 nm. Once these europium nanoparticles were surface functionalised, these can be easily adsorbed onto the surface interface by chemically interacting polymers. The chemical structure of the europium nanoparticles synthesised and its interaction with Mussel adhesive protein amino acid is represented in the Figure 1.
Neuroprotective effects of natural compounds on neurotoxin-induced oxidative stress and cell apoptosis
Published in Nutritional Neuroscience, 2022
Bo Chen, Jingjing Zhao, Rui Zhang, Lingling Zhang, Qian Zhang, Hao Yang, Jing An
Reactive oxygen and nitrogen species are produced by several endogenous and exogenous processes. Free radicals are referred to molecular entities or molecular fragments that contain one or more unpaired electrons and are paramagnetic. Most of the free radicals are short-lived, unstable and highly reactive[11]. ROS represent the most important class of free radicals produced in living systems. ROS are generated during aerobic respiration, cellular metabolism, or in response to pathogens defense. Oxygen molecular (O2) has a unique electronic configuration and is a free radical itself. O2 can easily accept a single electron to form O2•−. O2•− is considered to be the main ROS, which can further interact with other molecules to produce more radical species either directly or through enzyme or metal catalyzed processes[12]. The mitochondrial electron transport chain (ETC, respiratory chain) is one of the primary sources of ATP in mammalian cells. ROS are metabolic byproducts of aerobic respiration occurring in the inner membrane of the mitochondria. During energy transduction, O2 is the final acceptor of electrons and protons, and it is reduced by four electrons to produce two molecules of water (H2O). Some of the redox centers in the ETC may leak electrons to O2, partially reducing this molecule to O2−• and then to H2O2 and HO•[13].
Cell and molecular toxicity of lanthanum nanoparticles: are there possible risks to humans?
Published in Nanotoxicology, 2021
Amir Mohammad Malvandi, Sara Shahba, Abbas Mohammadipour, Seyed Hamidreza Rastegar-Moghaddam, Mahmoud Abudayyak
La NPs are found, naturally or chemically synthesized, in various compositions with other elements, including La(OH)3, LaF3, La2(CO3)3, LaPO4, LaBO3, LaOF, La2Sn2O7, and La2O3 NPs. La2O3 NPs are widespread nanomaterials used in various routes, released into the environment and food chains along which they can transmit and accumulate from lower to higher organisms (Balusamy et al. 2015; Ma et al. 2015). The La2O3 NP contains La and oxygen elements with the electronic configuration, [Xe] 5d1 6s2 and [He] 2s2 2p4, respectively. They are synthesized by calcinating the product resulting from the reaction between La acetate and NaOH at about 600°C. They are irregular sheet structures with spherical morphology and hexagonal crystal structure with less than 100nm size (Sisler et al. 2015,;Salavati-Niasari, Hosseinzadeh, and Davar 2011; Balusamy et al. 2015). Analysis of the chemical composition of La2O3 NP reveals the presence of La and oxygen, allowing the attachment with biomolecules since many biomolecules have a negative surface charge (Balusamy et al. 2012).