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Medium Design for Cell Culture Processing
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Five transition metals—iron, copper, manganese, zinc, and cobalt—play key roles in the biological functions of all mammalian cells (for review, see reference 5). They are naturally present in serum, but must be included in serum-free media (Table 7.5). Additionally, some other heavy metal ions, including molybdenum (Mo), vanadium (V), strontium (Sr), and selenium (Se), also appear to participate in biological reactions. Among these metals, iron and zinc are present in cells and human bodies at much higher levels than other trace elements (Panel 7.18).
Chemicals from Olefin Hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
By way of clarification, the IUPAC definition defines a transition metal as (quote) an element whose atom has a partially filled d subshell, or which can give rise to cations with an incomplete d subshell (end quote). Most scientists describe a transition metal as any element in the d-block of the periodic table, which includes groups 3–12 on the periodic table. In actual practice, the f-block lanthanide and actinide series are also considered transition metals and are called inner transition metals. The word transition was first used to describe the elements now known as the d-block by the English chemist Charles Bury in 1921, who referred to a transition series of elements during the change of an inner layer of electrons from a stable group of 8 to1 of 18, or from 18 to 32.
Rubber—CNT Nanocomposites
Published in Mahmood Aliofkhazraei, Advances in Nanostructured Composites, 2019
M. Balasubramanian, P. Jawahar
It is widely used to produce CNT on a larger scale. The materials required are carbon containing gaseous materials, and catalyst or catalyst coated substrate. Methane, acetylene and carbon monoxide are widely used as gaseous source materials. Transition metals like iron, cobalt, nickel and vanadium are used as catalyst. The parameters such as the type of catalyst, gas flow rate and temperature control the quality and quantity of CNTs formed (Mukhopadhyay et al. 1999, Li et al. 2002). The type of catalyst influences the formation of either SWCNT or MWCNT (Cassell et al. 1999, Satishkumar et al. 1998). The CNT growth is also influenced by the particle size of the catalyst. The carbon vapor is formed by the dissociation of carbonaceous gases at high temperature. This carbon is then deposited on the catalyst coated substrate in a controlled manner, leading to the growth of CNT.
Computational mechanistic insights into hafnium catalyzed CO2 activation and reduction
Published in Molecular Physics, 2022
Jenbrie M. Kessete, Taye B. Demissie, Ahmed M. Mohammed
There are considerable efforts undergoing which use catalysts made of transition metals. Among the transition metal complexes, palladium complexes showed an increased rate of CO2 reduction to CO at low over-potential [14]. In such a case, phosphine ligands have the potential to control the electronic structure of the central metal of the complex because of the phosphine π-accepting and σ-donating capabilities [15,16]. Pincers [16] and phosphine [17] ligands combined with iron, [18] nickel, [19] and cobalt [20] have also shown turnover number (TON, the maximum number of CO2 conversions per second that a single catalytic site will execute) of more than 106 [16]. Nitrogen and sulphur ligands were also used in transition metal complexes for CO2 reduction [7,8,21,22]. For example, replacing two nitrogen atoms in cyclam with two sulphur atoms (dithiacyclam) considerably enables the electrochemical reduction of CO2 to CO [23]. In this aspect, Hafnium, which is one of the early transition metals, complexes have been used to activate small molecules such as CO, N2 and CO2 [1,3,13]. One of the oxygen atoms of CO2 coordinates to Hf and forms a strong Hf–O bond (with dissociation enthalpy of 191 ± 3 kcal/mol) [24]. This strong Hf–O bond assists the O=CO bond breaking process [12]. The presence of phosphine and amine groups can further enhance extra CO2 insertion to the Hf complexes [25]. For instance, Hf-phosphinoamide cation complexes have been observed to activate two CO2 molecules [13].
Molecular geometry, vibrational, NBO, HOMO–LUMO, first order hyper polarizability and electrostatic potential studies on anilinium hydrogen oxalate hemihydrate – an organic crystalline salt
Published in Inorganic and Nano-Metal Chemistry, 2022
N. Kanagathara, R. Usha, V. Natarajan, M.K. Marchewka
Frontier molecular orbital theory can be used to predict the strength and stability of the transition metal complexes as well as the colors produce in solution. Frontier molecular orbitals are the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) that take part in chemical stability and lower reactivity in chemical reactions.[20,21] The HOMO represents the stability to donate an electron whereas LUMO as an electron acceptor that represents the ability to obtain an electron.[22] This electron transition absorption corresponds to the transition from the ground state to the first excited state is mainly described by an electron excitation from the HOMO to the LUMO. The frontier orbital gap assists to distinguish the kinetic stability and chemical reactivity of the molecular system.[23] The values of HOMO, LUMO, and frontier orbital gap energies are computed as −9.523, −5.468, and 4.055 eV, respectively as shown in Figure 4. Moreover, the calculated ionization potential, electron affinity, global softness, global hardness, chemical potential, and global electrophilicity of ANIOXA are +9.523 eV, +5.468 eV, 0.246 eV, 2.027 eV, 7.495 eV, and 13.856 eV, respectively and are listed in Table 3.
Bio-medical potential of chalcone derivatives and their metal complexes as antidiabetic agents: a review
Published in Journal of Coordination Chemistry, 2021
The incorporation of iron, copper, manganese, magnesium, zinc, cobalt and nickel in biological systems play a pivotal role in many biological processes like electron transfer, catalysis, and activation of enzymes, metabolism, and respiration [74]. Similarly, coordination of metal ions can enhance the mechanistic impact in biological products by stabilizing them [75]. Transition metals are essential cellular components with redox activity, variable coordination modes, and reactivity towards organic substrates, selected by nature to function in indispensable biochemical processes for living organisms [76]. So, transition metal complexes can be utilized as drugs to restore and heal human diseases like infection control, carcinomas, lymphomas, anti-inflammatory, diabetes, neurological disorders and the list is endless [77]. Moreover, complexation of metal ions with chalcones has substantial therapeutic potential which has been shown in the study of Habib [78]. Seema I. Habib has studied the complexation of 2′-hydroxy chalcones with Fe(II) and Zn(II) metal ions as shown in Figure 4(a). The complexes have enhanced activity against four bacterial strains viz. E. coli, Salmonella typhi, S. aureus and Bacillus subtilis, over ligands [78].