排序方式: 共有18条查询结果,搜索用时 62 毫秒
1.
Trina M. Arola William H. Ojala Nell Herrera Barjeta Balidemaj Charles R. Ojala 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(4):o207-o211
Two isomeric pairs of Schiff bases, N,N′‐bis(2‐methoxybenzylidene)‐p‐phenylenediamine, C22H20N2O2, (I), and 2,2′‐dimethoxy‐N,N‐(p‐phenylenedimethylene)dianiline, C22H20N2O2, (II), and (E,E)‐1,4‐bis(3‐iodophenyl)‐2,3‐diazabuta‐1,3‐diene (alternative name: 3‐iodobenzaldehyde azine), C14H10I2N2, (III), and N,N′‐bis(3‐iodophenyl)ethylenediimine, C14H10I2N2 [JAYFEV; Cho, Moore & Wilson (2005). Acta Cryst. E 61 , o3773–o3774], differ pairwise only in the orientation of their imino linkages and in all four individual cases occupy inversion centers in the crystal, yet all four compounds are found to assume unique packing arrangements. Compounds (I) and (II) differ substantially in molecular conformation, possessing angles between their ring planes of 12.10 (15) and 46.29 (9)°, respectively. Compound (III) and JAYFEV are similar to each other in conformation, with angles between their imino linkages and benzene rings of 11.57 (15) and 7.4 (3)°, respectively. The crystal structures are distinguished from each other by different packing motifs involving the functional groups. Intermolecular contacts between methoxy groups define an R22(6) motif in (I) but a C(3) motif in (II). Intermolecular contacts are of the I⋯I type in (III), but they are of the N⋯I type in JAYFEV. 相似文献
2.
Using classical Monte Carlo trajectory methods, we have fitted a new kind of empirical potential energy hypersurface to combined experimental observations on the tritium-methane hot atom reactions. All channels (including Walden inversion) are now present and the degree of uniqueness is apparently high. We present our predicted cross sections as a function of tritium energy for the abstraction, inverting substituting, and total substitution reactions. 相似文献
3.
Mst. Sharmin Sultana Shimu Shafi Mahmud Trina Ekwati Tallei Saad Ahmed Sami Ahmad Akroman Adam Uzzal Kumar Acharjee Gobindo Kumar Paul Talha Bin Emran Shahriar Zaman Md. Salah Uddin Md. Abu Saleh Sultan Alshehri Mohammed M Ghoneim Maha Alruwali Ahmad J. Obaidullah Nabilah Rahman Jui Junghwan Kim Bonglee Kim 《Molecules (Basel, Switzerland)》2022,27(3)
4.
Trina Valencich 《Chemical physics letters》1983,97(6):557-561
Product yields and collision density are calculated for nuclear-recoil tritium ions generated in situ with 4 Mkcal/mole of translational energy in gaseous methane or methane mixed with argon. The distribution of collision experienced in the reactive region and the yield of stable products are independent of the starting energy when it is large. 相似文献
5.
Pramanik A Thompson B Hayes T Tucker K Powell DR Bonnesen PV Ellis ED Lee KS Yu H Hossain MA 《Organic & biomolecular chemistry》2011,9(12):4444-4447
Structural characterization of a hydrogen sulfate complex with a tren-based urea suggests that the anion is coordinated with six NH···O bonds (d(N···O) = 2.857 (3) to 3.092 (3) ?) and one OH···O bond (d(O···O) = 2.57 (2) ?) from three receptors; however, in solution the anion is bound within the pseudo-cavity of one receptor. 相似文献
6.
Trina Dutta Shakri Banerjee Dhananjay Soren Sagar Lahiri Shinjinee Sengupta Juhi Augusta Rasquinha Anil K. Ghosh 《Applied biochemistry and biotechnology》2012,168(8):2358-2375
The present study explored both spontaneous and stress-induced deamidation in acid trehalase and endo-xylanase. An alteration in optimum pH by 1.5 units and optimum temperature by 20 °C accelerated the process of deamidation with a rise in isoaspartate formation and ammonia loss. Spontaneous deamidation during an enzyme-substrate reaction at physiological conditions resulted in accretion of isoaspartyl residues within the enzymes which gradually impaired their catalytic efficacy. Deamidation appeared to be more pronounced in endo-xylanase owing to its secondary structure conformation and high asparagine content. The active sites, Ala 549 in acid trehalase and His184 and Trp188 in endo-xylanase contributed to the loss of enzyme activity as they were flanking the deamidation-susceptible Asn residues. Protein l-isoaspartyl methyl transferase seemed to have a repairing capability, which enabled the heat-damaged enzymes to regain their partial activity as evident from there rise in K cat/K m. Endo-xylanase could regain 38.1 % of its biological activity while a lesser 17.5 % reactivation was obtained in acid trehalase. A unique protein l-isoaspartyl methyl transferase recognition site, Asn 151 was also identified in acid trehalase. A mass increment of the tryptic peptides of repaired enzyme due to methylation catalyzed by protein l-isoaspartyl methyl transferase substantiated the repair hypothesis. 相似文献
7.
A method for observing near-surface fluctuations in pH caused by a water–air flux of carbon dioxide under conditions of ambient
atmospheric carbon dioxide levels is developed and tested. Peaks in fluorescence intensity measured as a function of pH and
turbulence are shown to be consistent with predictions from a chemical kinetics model of CO2 exchange. The square root of the frequency of the pH fluctuations scale linearly with independently measured bulk air–water
gas transfer velocities in agreement with surface divergence models for air–water gas transfer. These data indicate that the
method proposed here is tracking changes in near-surface CO2 concentrations. This laser-induced fluorescence method can be used to study the air–water exchange of CO2 in wind-wave tunnels without the need for elevated CO2 concentrations in the gas phase. 相似文献
8.
Abdul Hawil Abas Siti Marfuah Rinaldi Idroes Diah Kusumawaty Fatimawali Moon Nyeo Park Abolghasem Siyadatpanah Fahad A. Alhumaydhi Shafi Mahmud Trina Ekawati Tallei Talha Bin Emran Bonglee Kim 《Molecules (Basel, Switzerland)》2022,27(7)
The coronavirus disease 2019 (COVID-19) pandemic is still ongoing, with no signs of abatement in sight. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the causative agent of this pandemic and has claimed over 5 million lives, is still mutating, resulting in numerous variants. One of the newest variants is Omicron, which shows an increase in its transmissibility, but also reportedly reduces hospitalization rates and shows milder symptoms, such as in those who have been vaccinated. As a result, many believe that Omicron provides a natural vaccination, which is the first step toward ending the COVID-19 pandemic. Based on published research and scientific evidence, we review and discuss how the end of this pandemic is predicted to occur as a result of Omicron variants being surpassed in the community. In light of the findings of our research, we believe that it is most likely true that the Omicron variant is a natural way of vaccinating the masses and slowing the spread of this deadly pandemic. While the mutation that causes the Omicron variant is encouraging, subsequent mutations do not guarantee that the disease it causes will be less severe. As the virus continues to evolve, humans must constantly adapt by increasing their immunity through vaccination. 相似文献
9.
The reaction of [Fe22+(H2Hbamb)2(N-MeIm)2], [1], a binuclear, non-heme iron complex, with 2-methyl-1-phenylprop-2-yl hydroperoxide (MPPH) shows that [1] induces heterolytic cleavage of the peroxy O-O bond. Catalytic atom transfer reactions (1:MPPH:PhSMe 1:596:6011) resulted in the highly efficient (99 +/- 1%), catalytic oxidation of phenyl methyl sulfide to phenyl methyl sulfoxide/sulfone (T.N. = 500/11 respectively) and cyclohexane to cyclohexanol/cyclohexanone (T.N. = 230/5 respectively) showing the highly efficient, catalytic capacity of [1] to carry out oxygen insertion chemistry. 相似文献
10.
Liudis L. Pino Trina H. García Livan Delgado-Roche Idania Rodeiro Ivonne Hernández Wagner Vilegas 《Natural product research》2020,34(10):1481-1485
AbstractMedium and high polarity extracts from Maytenus species are known to contain polyphenolic compounds such as proanthocyanidins. The high polarity and structural complexity of these compounds make very difficult their isolation even by modern chromatographic techniques. Maytenus cajalbanica (Borhidi & O. Muñiz) Borhidi & O. Muñiz is endemic from Cuba. So far, there are reports neither of phytochemical work nor of biological evaluation of extracts from this subspecies. The goal of this work is to determine the polyphenolic profile and the antioxidant capacity of the ethanolic extract from the barks of Maytenus cajalbanica. FIA/ESI/IT/MSn analysis allowed the identification of 5 flavan-3-ol monomers, 33 proanthocyanidins, 2 free flavonoids and their respective glycosides as major compounds of the ethanolic extract, which showed a strong radical scavenging capacity and a significant ferric reduction power. FIA/ESI/IT/MSn technique led the rapid, effective and sensitive determination of the polyphenolic profile of Maytenus cajalbanica without previous separation. 相似文献