Determination of Easy Axis in a Chemical Ferromagnet, 4-(p-Chlorobenzylideneamino)–TEMPO (TEMPO=2,2,6,6-Tetramethylpiperidin-1-Oxyl)

The trapping sites for muon and muonium in ferromagnetic p-Cl–Ph–CH=N–TEMPO [(4-(p-chlorobenzylideneamino)–TEMPO (TEMPO = 2,6,6-tetramethyl-piperidin-1-yloxyl)] and the hyperfine interaction tensors for these sites are obtained using first-principles Unrestricted Hartree–Fock theory. The calculated hyperfine interactions are used to compare the calculated zero field muon spin rotation (μSR) frequencies for different choices for the easy axis and the observed frequency. It has been concluded that the two trapping centers that can best explain the observed μSR frequency are a trapped singlet muonium near the radical oxygen and a trapped muon site near the chlorine. The direction of the easy axis also is determined to be the b-axis of the monoclinic lattice. This direction for the easy axis is confirmed by determining the direction of the distributed magnetization in the molecular solid which leads to a minimum dipole–dipole interaction energy. The consequences of this agreement for the easy axis direction by two independent procedures are discussed. This revised version was published online in September 2006 with corrections to the Cover Date.     

Gödel Kink Spacetime

A 2+1 version of a rotating perfect fluid spacetime of Gödel type is examined to see whether it has a Finkelstein-Misner kink. It is shown, by three different methods, that the kink number is one.     

The Extracts of Polygonum cuspidatum Root and Rhizome Block the Entry of SARS-CoV-2 Wild-Type and Omicron Pseudotyped Viruses via Inhibition of the S-Protein and 3CL Protease

COVID-19, resulting from infection by the SARS-CoV-2 virus, caused a contagious pandemic. Even with the current vaccines, there is still an urgent need to develop effective pharmacological treatments against this deadly disease. Here, we show that the water and ethanol extracts of the root and rhizome of Polygonum cuspidatum (Polygoni Cuspidati Rhizoma et Radix), a common Chinese herbal medicine, blocked the entry of wild-type and the omicron variant of the SARS-CoV-2 pseudotyped virus into fibroblasts or zebrafish larvae, with IC₅₀ values ranging from 0.015 to 0.04 mg/mL. The extracts were shown to inhibit various aspects of the pseudovirus entry, including the interaction between the spike protein (S-protein) and the angiotensin-converting enzyme II (ACE2) receptor, and the 3CL protease activity. Out of the chemical compounds tested in this report, gallic acid, a phytochemical in P. cuspidatum, was shown to have a significant anti-viral effect. Therefore, this might be responsible, at least in part, for the anti-viral efficacy of the herbal extract. Together, our data suggest that the extracts of P. cuspidatum inhibit the entry of wild-type and the omicron variant of SARS-CoV-2, and so they could be considered as potent treatments against COVID-19.     

Structure revision of ent-kaurane diterpenoids,isoserrins A,B, and D,enabled by DU8+ computation of their NMR spectral data

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Identification and quantification of anticarcinogens in garlic extract and licorice root extract powder

Nine organosulfur compounds present in an aged garlic extract and two isoflavonoids and one triterpenoid present in a licorice root extract powder have been identified and quantified. Quantification involved solvent extraction and gas chromatographic – mass spectrometric analysis (garlic extract) or hydrolysis, solvent extraction, and liquid chromatographic analysis (licorice root extract powder). Although the garlic extract proved to be unstable and the concentration of the organosulfur compounds varied with time, one analysis of the extract gave the following results: methyl disulfide (0.607 μg/g), methyl trisulfide (0.181 μg/g), allyl sulfide (2.02 μg/g), allyl disulfide (0.784 μg/g), allyl trisulfide (0.795 μg/g), allyl methyl sulfide (1.64 μg/g), allyl methyl disulfide (0.411 μg/g), allyl methyl trisulfide (0.695 μg/g), and ethyl 2-propenesulfinate (11.4 μg/g). The analysis of the licorice root extract powder gave the following results: formononetin (1.92 mg/g), isoliquiritigenin (9.61 mg/g), and 18β-glycyrrhetinic acid (43.9 mg/g). Methods were successfully developed to quantify the same compounds in the serum of test animals which had consumed feed spiked with garlic extract or licorice root extract powder. Only the 18β-glycyrrhetinic acid could be detected in the sera of such animals, however. An effort was also made to determine serum levels of prostaglandin E2 to correlate its inhibition with levels of the dietary components, but the prostaglandin E2 levels were too low to measure.     

Non-uniform exponential tension splines

We describe explicitly each stage of a numerically stable algorithm for calculating with exponential tension B-splines with non-uniform choice of tension parameters. These splines are piecewisely in the kernel of D ²(D ²–p ²), where D stands for ordinary derivative, defined on arbitrary meshes, with a different choice of the tension parameter p on each interval. The algorithm provides values of the associated B-splines and their generalized and ordinary derivatives by performing positive linear combinations of positive quantities, described as lower-order exponential tension splines. We show that nothing else but the knot insertion algorithm and good approximation of a few elementary functions is needed to achieve machine accuracy. The underlying theory is that of splines based on Chebyshev canonical systems which are not smooth enough to be ECC-systems. First, by de Boor algorithm we construct exponential tension spline of class C ¹, and then we use quasi-Oslo type algorithms to evaluate classical non-uniform C ² tension exponential splines.      

Substituent effects on carbocation stability: the pK(R) for p-quinone methide

A value of k(H) = 1.5 x 10(-)(3) M(-)(1) s(-)(1) has been determined for the generation of simple p-quinone methide by the acid-catalyzed cleavage of 4-hydroxybenzyl alcohol in water at 25 degrees C and I = 1.0 (NaClO(4)). This was combined with k(s) = 5.8 x 10(6) s(-)(1) for the reverse addition of solvent water to the 4-hydroxybenzyl carbocation [J. Am. Chem. Soc. 2002, 124, 6349-6356] to give pK(R) = -9.6 as the Lewis acidity constant of O-protonated p-quinone methide. Values of pK(R) = 2.3 for the Lewis acidity constant of neutral p-quinone methide and pK(add) = -7.6 for the overall addition of solvent water to p-quinone methide to form 4-hydroxybenzyl alcohol are also reported. The thermodynamic driving force for transfer of the elements of water from formaldehyde hydrate to p-quinone methide to form formaldehyde and p-(hydroxymethyl)phenol (4-hydroxybenzyl alcohol) is determined as 6 kcal/mol. This relatively small driving force represents the balance between the much stronger chemical bonds to oxygen at the reactant formaldehyde hydrate than at the product p-(hydroxymethyl)phenol and the large stabilization of product arising from the aromatization that accompanies solvent addition to p-quinone methide. The Marcus intrinsic barrier for nucleophilic addition of solvent water to the "extended" carbonyl group at p-quinone methide is estimated to be 4.5 kcal/mol larger than that for the addition of water to the simple carbonyl group of formaldehyde. O-Alkylation of p-quinone methide to give the 4-methoxybenzyl carbocation and of formaldehyde to give a simple oxocarbenium ion results in very little change in the relative Marcus intrinsic barriers for the addition of solvent water to these electrophiles.     

Scrambling of oxygen-18 during the "borderline" solvolysis of 1-(3-nitrophenyl)ethyl tosylate

[reaction: see text] There is substantial isomerization (kiso=0.32 x 10(-3) s(-1)) of 3-NO2C6H4(13)CH(Me)OS(18O)2Tos during solvolysis (ksolv=1.04 x 10(-3) s(-1)) in 50/50 trifluoroethanol/water, even though the estimated lifetime of the putative 1-(3-nitrophenyl)ethyl carbocation intermediate of solvolysis (ca. 10(-13) s(-1)) is too short to allow rearrangement that exchanges the positions of 16O and 18O at the sulfonate leaving group. This suggests that isomerization proceeds by a mechanism that avoids formation of the carbocation-anion pair intermediate.     

Activation of orotidine 5'-monophosphate decarboxylase by phosphite dianion: the whole substrate is the sum of two parts

We report that the binding of phosphite dianion to orotidine 5'-monophosphate decarboxylase (OMPDC) results in an 80 000-fold increase in kcat/Km for decarboxylation of the truncated substrate, 1-(beta-d-erythrofuranosyl)orotic acid (EO), which lacks a 5'-phosphodianion moiety. The intrinsic binding energy (IBE) of phosphite dianion in the transition state is 7.8 kcal/mol, which represents a very large fraction of the 11.8 kcal/mol IBE of the phosphodianion group of the natural substrate orotidine 5'-monophosphate (OMP). The data give kcat = 160 +/- 70 s-1 for turnover of EO in the active site of OMPDC containing phosphite dianion, which is significantly larger than kcat = 15 s-1 for turnover of OMP. Despite the weaker binding of the individual EO and HPO32- "parts" (KmKd = 0.014 M2) than of OMP (Km = 1.6 x 10-6 M), once bound, OMPDC provides a slightly greater stabilization of the transition state for reaction of the parts than of the whole substrate. Thus, the covalent connection between the reacting portion of the substrate and the nonreacting phosphodianion group is not necessary for efficient catalysis. This implies that a major role of the phosphodianion group of OMP is to provide binding interactions that are used to drive an enzyme conformational change, resulting in formation of an active site environment optimized for transition state stabilization.