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Arsenals of Pharmacotherapeutically Active Proteins and Peptides: Old Wine in a New Bottle
Published in Debarshi Kar Mahapatra, Swati Gokul Talele, Tatiana G. Volova, A. K. Haghi, Biologically Active Natural Products, 2020
Hemoglobin is a heme protein involved in the transport of oxygen. It comprises of iron ion, porphyrin ring (heme complex), and globin (protein). The hemoglobin molecule is tetramer of two α and two β subunits. The α-subunit is 141 amino acids in length while the β subunit is 146 amino acids in length. The α-subunit has Val-Leu sequence at N-terminal and β subunit has Val-His-Leu sequence at N-terminal [69]. The α-subunit possesses seven α-helices (designated as A-G) and the β subunit comprises eight α-helices (designated as A-H). The subunits are compacted to form a globe-shaped structure with space within each subunit for the heme complex. The heme complex (iron-protoporphyrin IX) consists of porphyrin ring and iron ion, Fe2+ as shown in Figure 2.28.
Recent Advances in Artificial Cells With Emphasis on Biotechnological and Medical Approaches Based on Microencapsulation
Published in Max Donbrow, Microcapsules and Nanoparticles in Medicine and Pharmacy, 2020
The presence of blood group antigens in red cell membrane, requires transfusion of compatible red blood cells. Hemoglobin, the protein contained in red blood cells, is responsible for oxygen uptake from the lungs and its release to the tissues. It cannot be used as a blood substitute for the following reason. The hemoglobin molecule consists of 4 units as a tetramer. When free in plasma, it breaks down into two smaller dimeric units. These dimers are rapidly excreted by the kidneys. Furthermore, outside the red blood cells the important cofactor, 2,3-diphosphoglycerate, is no longer available to facilitate the release of oxygen by hemoglobin.
Toxic and Asphyxiating Hazards in Confined Spaces
Published in Neil McManus, Safety and Health in Confined Spaces, 2018
Hemoglobin is a tetramer composed of four molecular units. Each of the four subunits can bind an oxygen molecule. The binding site is the iron-containing heme group. The heme group lies in a depression on the surface of the hemoglobin molecule. During the binding process, the oxygen atom fits into the depression, yet does not increase the volume of the molecule (Fenn 1971). Binding causes a slight change in the radius of the iron atom. This change, in turn, causes slight movement of the peptide chains of the hemoglobin subunit near the heme group. Associated with this movement is weakened attraction between the subunits (Perutz 1970).
Effect of end group of amorphous perfluoro-polymer electrets on electron trapping
Published in Science and Technology of Advanced Materials, 2018
Seonwoo Kim, Kuniko Suzuki, Ai Sugie, Hiroyuki Yoshida, Masafumi Yoshida, Yuji Suzuki
Isomer analysis is firstly performed in order to find representative structure. We prepared possible monomer and dimer structures of targets: PE, ETFE, PTFE, CTL-S, CTL-A, and CTL-M. Preliminary geometries are prepared in molecular dynamic simulation with universal force field parameters [36], finding the most stable structure at 0 K condition. Quantum mechanical (QM) geometry optimization is followed with NWChem [37] with 6-31+g* basis set to discover an initial ground-state structure. After that, we changed dihedral angles of interest from 0° to 360° by every 45°. QM geometry optimization is followed to changed structures, and the energy of ground-state molecular system after optimization is compared. The structure having the most stable energy among them is used for further study. With the representative structures in hand, we build chain structures made from 8 carbons for PE, ETFE, and PTFE. Monomer and tetramer structures are prepared for CTL-S, CTL-A and CTL-M. Then, an extra electron is added to the systems and geometry optimization is performed once again to find stable ground-state structure of negatively-charged state (−1).
Studies on the mesophase formation mechanism of polybenzoxazines: polymerisation induction
Published in Liquid Crystals, 2020
Ying Liu, Xiaoshan Zhen, Sheng Gao, Qingbin Xue, Zaijun Lu
Interestingly, when the polymerisation carries on for 50 min, many bright LC spots appear. At this moment, 62% PC-AC oligomers are formed based on GPC calculation (see Figure 5A(e)), leading to the formation of an LC phase. In other words, the LC phase can be formed only when oligomer content exceeds a critical value of 62%. With increasing polymerisation time, the amount of bright LC spots gradually increases due to the increment of oligomer content. After 52 min, a bright LC region fills the entire viewing window. Even after 2 h of polymerisation at 223°C, the bright LC region still exists. As shown in Figure 5A(g), one can easily see that poly(PC-AC) synthesised by curing PC-AC at 223°C for 120 min is an LC oligomer [28,29] composed of tetramer and dimer.
DFT study of stability and electronic properties of cyclic tetramer involving dinucleobase monomers, comprising acetylene central block substituted at both edges with guanine and cytosine nucleobases
Published in Molecular Physics, 2022
Hamid Reza Masoodi, Sotoodeh Bagheri, Alireza Gholipour, Masoud Rohani Moghadam, Alireza Bazmandegan-Shamili
Table 1 presents the formation energy of the tetrameric arrangement in gas phase and in the solvents. The formation energy has been calculated using equation where Etetramer and Emon are optimised energies of cyclic tetramer and each individual monomer, respectively. As evident from Table 1, the negative values of ΔE show an upward trend as can be seen for cyclic tetramer in gas phase and in the solvents. The relation between ΔE and ε can be expressed as