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This short review highlights the author’s group research on modified vitamin B${}_{12}$ derivatives with a peptide backbone as (1) inhibitors of B${}_{12}$-dependent enzymes and as (2) models of cofactor B${}_{12}$-protein complexes.

The preparation and assessment of carbonic anhydrase and paraoxonase enzyme inhibition properties of 3-(2-(5-amino-4-(4-bromophenyl)-3-methyl-1H-pyrazol-1-yl)ethoxy)phthalonitrile (2) and its nitrogen-containing non-peripheral phthalocyanine derivatives (3 and 4) are reported for the first time. The new phthalonitrile and its phthalocyanine derivatives have been elucidated by FT-IR spectroscopy, ¹H-NMR, ${}^{13}$C-NMR, mass and UV-vis spectroscopy. The results demonstrated that all synthesized compounds moderately inhibited carbonic anhydrase and paraoxonase enzymes. Among the compounds, the most active ones were found to be compound 4 for PON (Ki : 0.14 $\mu$M), compound 3 for hCA I (Ki : 22.52 $\mu$M) and compound 1 for hCA II (Ki : 13.62 $\mu$M).

A competition model between two species with a lethal inhibitor in a chemostat is analyzed. Discrete delays are used to describe the nutrient conversion process. The proved qualitative properties of the solution are positivity, boundedness. By analyzing the local stability of equilibria, it is found that the conditions for stability and instability of the boundary equilibria are similar to those in [9]. In addition, the global asymptotic behavior of the system is discussed and the sufficient conditions for the global stability of the boundary equilibria are obtained. Moreover, by numerical simulation, it is interesting to find that the positive equilibrium may be globally stable.

The effects of grain size reduction on the corrosion inhibition of sodium nitrite were investigated using polarization curves and electrochemical impedance spectroscopy (EIS). Nanocrystalline iron (~ 45 nm) was produced by pulse electrodeposition using citric acid bath. The grain size of a nanocrystalline surface was analyzed by X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM). The most intensive first-order peak (211) of the XRD patterns was taken for detailed analysis using a Gaussian fitting curve. The tests were carried out in 25 mg/lNaCl + 57 mg/lNa₂SO₄ with different concentration of sodium nitrite aqueous solutions.

The results revealed that due to the adsorption process which leads to the formation of a protective layer with a greater charge transfer resistance the inhibition effect and corrosion protection of sodium nitrite inhibitor in near-neutral aqueous solutions increased as the grain size decreased from microcrystalline to nanocrystalline. The standard free energy of adsorption (ΔG_ads) revealed a strong interaction between inhibitor and nanocrystalline surface. This was attributed to the increased number of the active sites caused by nanocrystalline surface.

According to the limited medications for COVID-19, natural products gained increasing attention. Scientific indications revealed the effect of biflavonoids (BFs) against respiratory syndrome viruses. The functional importance of 3-chymotrypsin-like protease (3CLpro) in forming viral RNA raises its potential to be targeted in SARS-CoV2. This study is devoted to the computational analysis of privileged BFs within the SARS-CoV2 3CLpro active site. Docking and molecular dynamics (MD) simulations were collectively used to explore the most probable binding modes and stable ligand–enzyme chemical interactions. Despite the structural resemblance, a wide range of binding affinities was retrieved for BFs ($\mathrm{\Delta }{G}_b-7.11-12.66$kcal/mol). Garciniaflavone C ($\mathrm{\Delta }{G}_b-12.66$kcal/mol), 7,7${}^{\prime \prime }$, 4${}^{\prime \prime \prime }$-tri-O-methylagathisflavone ($\mathrm{\Delta }{G}_b-12.16$kcal/mol) and 8,8${}^{\prime \prime }$-biapigenil ($\mathrm{\Delta }{G}_b-12.08$kcal/mol) were top enzyme binders. The stability of acquired complexes was analyzed through 50-ns all-atom MD simulations. Garciniaflavone C, 7,7${}^{\prime \prime }$, 4${}^{\prime \prime \prime }$-tri-O-methylagathisflavone and 8,8${}^{\prime \prime }$-biapigenil showed 29%, 22% and 23% persevered binding residues, respectively. SARS-CoV2-garciniaflavone C complex was mediated by several nonpolar interactions. MD simulations assigned H-bond interaction between the catalytic dyad residue Cys145 and garciniaflavone C. 7,7${}^{\prime \prime }$, 4${}^{\prime \prime \prime }$-tri-O-methylagathisflavone participated in a $\pi$-cation interaction to His41. Solvent accessible surface area distribution indicated the sufficiency of MD simulation time (50ns) to screen equilibrated complex systems. Although a detailed pharmacological mechanism is to be elucidated, our findings indicated superior binding stability of 7,7${}^{\prime \prime }$, 4${}^{\prime \prime \prime }$-tri-O-methylagathisflavone within SARS-CoV2 active site. While the biological function of the majority of BF derivatives remains to be elucidated, results of the current study revealed key structural features and potentials of privileged BFs for further structure-guided optimization toward potent SARS-CoV2 3CLpro inhibitors.

Angiotension-converting enzyme 2 (ACE2) is the host receptor of the serious-acute respiratory syndrome coronavirus 2 (Sars-CoV-2) spike protein. In this article, the interaction of ACE2 with the receptor binding domains (RBD) of Wuhan-Hu-1 and United Kingdom (UK) and South African (SA) variants is examined in silico. Their Gibbs free energies were computed using a protein binding energies prediction model. The interaction characteristics of RBDs with possible inhibitory compounds as well as a standard drug, Paxlovid, were also investigated, and Gibbs free energies were computed. Molecular modeling, molecular dynamics and molecular docking methods were employed and the results are compared and discussed.

A simple model of phytoplankton-zooplankton interaction with a periodic input nutrient is presented. The model is then used to study a nutrient-plankton interaction with a toxic substance that inhibits the growth rate of phytoplankton. The effects of the toxin upon the existence, magnitude, and stability of the periodic solutions are discussed.

Earlier studies have shown that the two types of sinks- bold and small grains-developing in the same spike or spikelet of wheat (Triticum aestivum L.) had their inherent variable metabolic profiles, which were steered by their endogenous hormones. In the present investigation, it is being demonstrated that a check on electron transport chain during respiration led to the partial truncation of the dry matter of the developing grains. The study indicates that another subtle phenomenon, involving the feed off of the electrons to an alternate oxidase pathway, switches-on in vivo during the mid-ripening stage of the grains and may be detrimental to their growth. It is being advocated that the modulation of this pathway, through the judicious use of its specific inhibitor salicylhydroxamic acid may go a long way in achieving a higher economic yield. The data further imply that it may not be possible to eliminate the disparity between the two types of sinks in their yielding potential, which appears to be their innate character.

The following sections are included:

• Introduction
• Different types of RhoGEF inhibitors
• An example of preclinical application of a RhoGEF inhibitor: Dock5 and osteolytic diseases
• Acknowledgments
• References

The rheological properties and the components analyzing of styrene butadiene styrene (SBS) inhibitor modified asphalt was investigated by dynamic shear rheology (DSR) and four composition analyzer, respectively. Compared with the compositions and fundamental properties of asphalts, the results show that the addition of SBS inhibitor to asphalt results in reducing of the penetration and ductility and enhancement of the softening point. The complex shear modulus reduces slightly while the phase angle increases when the inhibitors are added. Meanwhile, the components of saturates and aromatics change slightly. With the increase of SBS inhibitor, the content of resin decreased and the content of asphaltene increased.