Yaser NejatyJahromy

Background: Nitric oxide synthase (NOS) catalyzes the formation of nitric oxide (NO) and citrulline from L-arginine, dioxygen (O2), and nicotinamide adenine dinucleotide phosphate (NADPH) in a two-step reaction, with the enzyme-bound intermediate Nω-hydroxy-L-arginine (NHA). Previous electron paramagnetic resonance (EPR) studies of NOS reaction have shown that (6R, 1'R, 2'S)-6-(l',2'-dihydroxypropyl)-5,6,7,8-tetrahydropterin (H4B) acts as a single electron donor in both steps of the reaction, resulting in the transient generation of a tetrahydropterin cation radical (H₄B^•+). Results: H₄B^•+can also be chemically generated in strongly acidic solutions. EPR studies of chemically generated H₄B^•+and similar pterin radicals date back to the 1960s. However, the reported paramagnetic parameters of H₄B^•+in NOS do not seem to match the corresponding reported parameters for either H₄B^•+or other pterin centered radicals chemically generated in solution. In particular, the rather isotropic hyperfine coupling of ca. 45 MHz for 1H6 of H₄B^•+in NOS is at least 15 MHz larger than that of H₄B^•+ or any other previously studies pterin solution radical. In the work reported here, a combination of 9.5 - 9.8 GHz contentious wave (cw-) EPR, 34GHz 1H electron nuclear double resonance (ENDOR), spectral simulation and Density Functional Theory (DFT) calculations were used to investigate this seeming discrepancy. Conclusion: We demonstrated that the differences in the paramagnetic parameters of the chemically generated H₄B radicals in solutions and those of the H₄B radicals in NOS are consistent with the presence of two different conformers of the same cation radical in the two media.

Since the COVID-19 outbreak was acknowledged by the WHO on 30 January 2020, much research has been conducted to unveil various features of the responsible SARS-CoV-2 virus. Different rates of contagion in adults, children, and pregnant women may guide us to understand the underlying infection conditions of COVID-19. In this study, we first provide a review of recent reports of COVID-19 clinical outcomes in children and pregnant women. We then suggest a mechanism that explains the curious case of COVID-19 in children/pregnant women. The unique stem cell molecular signature, as well as the very low expression of angiotensin-converting enzyme 2 and the lower ACE/ACE2 ratio in stem cells of children/pregnant women compared to adults might be the cause of milder symptoms of COVID-19 in them. This study provides the main molecular keys on how stem cells can function properly and exert their immunomodulatory and regenerative effects in COVID-19-infected children/pregnant women, while failing to replicate their role in adults. This can lay the groundwork for both predicting the pattern of spread and severity of the symptoms in a population and designing novel stem cell-based treatment and prevention strategies for COVID-19.

Different structure types of vanadyl(V) orthophosphate [i.e. (V^V ≡O)³⁺ orthophosphate] have been subjects of research due to their catalytic activity in the oxidation of n-butane to maleic anhydride. Electron paramagnetic resonance (EPR) spectroscopy can be exploited to elucidate the electronic structure of such compounds. When tuning the oxidation state of vanadium in (V_1-xW_x)OPO₄, X-band EPR spectra have confirmed the presence of paramagnetic V⁴⁺ ions. However, some of the features in these spectra could not be explained. Here, powder samples of β-(V^IV_0.01V^V_.98W^VI_.01)OPO₄ are investigated at S-, X- and Q- band, along with X-band EPR measurements on single crystals. Thereby, the discrepancies between the spectra and their simulations could be resolved. In particular, it could be shown that the g and A tensors are not coaxial. The resulting consistent EPR picture and the refined paramagnetic parameters are reported. The work underlines the indispensability of a multi-frequency approach in EPR for unequivocal conclusions.

The effect of the implementation of student response systems (SRSs) in teaching on the critical thinking (CT) of young students was investigated. The study benefited from a quasi‐experimental design and a pretest/posttest set‐up. Subjects consisted of 156 K‐8 students in Tehran during 2016–2017, selected through a multistage cluster sampling, and randomly assigned to either the experimental group (EG) or the control group (CG). The regular curriculum of the students contained a weekly session of a course titled “Thinking and Lifestyle.” Ten sessions of the course were conducted using SRS (aka clickers) for EG, whereas CG kept receiving the same content in the conventional form. The teaching period was followed by the posttest. ANCOVA showed that, in contrast with CG, EG scored significantly higher on CT test after the intervention. The effect was shown to be only significant for the students at the lower side of the performance spectrum. Thus, in this inaugural study of clickers in schools in Iran, it was empirically demonstrated that clickers, as a relatively new piece of technology, can be successfully utilized during early adolescence in the pedagogical strategies in general and for the improvement of CT of students in particular.

Cooperative teaching is the result of efforts made by two educators for teaching a heterogeneous group of students, especially one including those with specific needs, due to reading disorders for instance. The present study serves as an experimental investigation focusing on the effect of cooperative teaching on the development of reading skills among students with a reading disorder. To achieve this, three female students were selected from a regular primary school in the 2nd education district of Tabriz, Iran. The research design was a multiple baseline single subject design with different children, in which we used the reading and dyslexia test (RDT) and the revised Wechsler Intelligence Scale to diagnose reading disorders, and a researcher‐made hundred‐word test to measure the development of reading skills. The children received five cooperative teaching sessions during only the (experimental) intervention, i.e. in the baseline and the follow‐up stages, they were not exposed to any cooperative teaching. The comparisons of the students’ performance in experimental phases showed that cooperative teaching is an effective technique for developing reading skills and that the effectiveness of this technique was also maintained over time. This work is the first empirical demonstration of the effectiveness of co‐teaching in dealing with dyslexic reading disabilities. It additionally serves as the first instance of applying co‐teaching to any form of reading disability in Iran.

Novel types of spin‐labeled N,N′‐dicyclohexylcarbodiimides (DCC) are reported that bear a 2,2,6,6‐tetramethylpiperidinyloxyl (TEMPO) residue on one side and different aromatic and aliphatic cyclohexyl analogues on the other side of the diimide core. These readily available novel reagents add efficiently to aliphatic and aromatic carboxylic acids, forming two possible spin‐labeled amide derivatives with different radical distances of the resulting amide. The addition of aromatic DCC analogues proceeds with excellent selectivity, giving amides where the carboxylic acid is exclusively connected to the aromatic residue, while little or no selectivity was observed for the aliphatic congeners. The usefulness of these adducts in structural studies was demonstrated by EPR (electron paramagnetic resonance) measurements of biradical adducts of biphenyl‐4,4′‐dicarboxylic acids. These analyses also reveal high degrees of conformational bias for aromatic DCC derivatives, which further underlines the powerfulness of these novel reagents. This observation was further corroborated by quantum chemical calculations, giving a detailed understanding of the structural dynamics, while detailed information on the solid state structure of all novel reagents was obtained by X‐ray structure analyses.