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111.
Xiufang Xu Yumei Xing Xia Yang Guichang Wang Zunsheng Cai Zhenfeng Shang Yinming Pan Xuezhuang Zhao 《International journal of quantum chemistry》2005,101(2):160-168
A total of eight possible isomers of C50O, an oxide of fullerene C50 (D5h), have been investigated by B3LYP/3‐21G calculations. The isomer, which has an annulene‐like structure with oxygen bridging across a [5,6] type C? C bond at the site between the pole and the equatorial belt, is found being the ground state of C50O. Four isomers are relatively more stable and the energy differences between them are not large. This result indicates that more than one C50O isomer will coexist once C50O is synthesized. The relative stabilities of the C50O isomers may be determined mainly by the strain release and by the formation of the cyclic phenylene substructure at the equatorial belt of the cage. The calculated nucleus independent chemical shifts (NICS) of the C50O isomers will be useful because from them one can expect outstanding NMR properties that can lead to their identification and characterization. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
112.
Nevin Çelebi Osamu Shirakura Yoshiharu Machida Tsuneji Nagai 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(4):407-413
Inclusion complex formation of piromidic acid (PA) with dimethyl--cyclodextrin (DM--CD) in aqueous solution and in the solid state was confirmed by the solubility method, differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The apparent stability constant,K
c
, of the complex was estimated to be 244 M–1. The stoichiometry of the complex was given as the ratio 1:2 of PA to DM--CD. The dissolution rate of the PA/DM--CD complex was much greater than that of intact PA.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986. 相似文献
113.
Determining PPARγ-ligand binding affinity using fluorescent assay with cis-parinaric acid as a probe
Gao Zhenting Luo Haibin Chen Lili Shen Jianhua CHEN Kaixian JIANG Hualiang SHEN Xu 《中国科学B辑(英文版)》2005,48(2)
Upon the study of small-molecules binding to proteins, the traditional methods for calculating dissociation constants (Kd and Ki) have shortcomings in dealing with the single binding site models. In this paper, two equations have been derived to solve this problem. These two equations are independent of the total concentration or initial degree of saturation of receptor and the activity of the competitive molecule. Through nonlinear fitting against these two equations, Kd value of a probe can be obtained by binding assay, and Ki value of a ligand can be obtained by competitive assay. Moreover, only the total concentrations of receptor([R]t), ligand([L]t) and probe([P]t) are required for the data fitting. In this work, Ki values of some typical ligands of PPARγ were successfully determined by use of our equations, among which the Ki value of PPARγ-LY171883 was reported for the first time. 相似文献
114.
A family of of open subsets of the real line is called an ω-cover of a set X iff every finite subset of X is contained in an element of . A set of reals X is a γ-set iff for every ω-cover of X there exists such that In this paper we show that assuming Martin's axiom there is a γ-set X of cardinality the continuum. 相似文献
115.
Let f C[a, b]. LetP be a subset ofC[a, b], L b – a be a given real number. We say thatp P is a best approximation tof fromP, with arc length constraintL, ifA[p]
b
a
[1 + (p(x))
2]dx L andp – f q – f for allq P withA[q] L. represents an arbitrary norm onC[a, b]. The constraintA[p] L might be interpreted physically as a materials constraint.In this paper we consider the questions of existence, uniqueness and characterization of constrained best approximations. In addition a bound, independent of degree, is found for the arc length of a best unconstrained Chebyshev polynomial approximation.The work of L. L. Keener is supported by the National Research Council of Canada Grant A8755. 相似文献
116.
M. Marzo G.J. Lavado F. Como A.P. Toropova A.A. Toropov D. Baderna 《SAR and QSAR in environmental research》2020,31(3):227-243
ABSTRACTBiocides are multi-component products used to control undesired and harmful organisms able to affect human or animal health or to damage natural and manufactured products. Because of their widespread use, aquatic and terrestrial ecosystems could be contaminated by biocides. The environmental impact of biocides is evaluated through eco-toxicological studies with model organisms of terrestrial and aquatic ecosystems. We focused on the development of in silico models for the evaluation of the acute toxicity (EC50) of a set of biocides collected from different sources on the freshwater crustacean Daphnia magna, one of the most widely used model organisms in aquatic toxicology. Toxicological data specific for biocides are limited, so we developed three models for daphnid toxicity using different strategies (linear regression, random forest, Monte Carlo (CORAL)) to overcome this limitation. All models gave satisfactory results in our datasets: the random forest model showed the best results with a determination coefficient r2 = 0.97 and 0.89, respectively, for the training (TS) and the validation sets (VS) while linear regression model and the CORAL model had similar but lower performance (r2 = 0.83 and 0.75, respectively, for TS and VS in the linear regression model and r2 = 0.74 and 0.75 for the CORAL model). 相似文献
117.
S. S. Sane 《Aequationes Mathematicae》1981,23(1):223-232
A generalization and an improvement of the results of Drake and Lenz on the constructions of projective Hjelmslev planes are obtained. Using this, some new series of invariant pairs including 4 new pairs (t, 2),t 1000, for projective Hjelmslev planes are obtained. 相似文献
118.
We synthesized Leu‐Arg‐Pro‐Val‐Ala‐Ala‐Glu, the peptide contained in lactoferrin (Lf), to identify the angiotensin converting enzyme (ACE) inhibition. In an attempt to know the structure‐activity relationship of this peptide, we replaced Pro (the third amino acid residues from N‐terminal) or Val (the fourth amino acid residues from N‐terminal) with Ala (neutral amino acid), Glu (acidic amino acid) or Lys (basic amino acid) to produce six peptides. From the in vitro ACE inhibition (IC50) of these synthesized peptides, the original peptide (Leu‐Arg‐Pro‐Val‐Ala‐Ala‐Glu) showed higher ACE inhibition than the replaced six peptides. Thus, replacement of Pro at the third amino acid residues or Val at the fourth position with Ala, Glu or Lys revealed the ACE inhibition to be lower than the original form of Leu‐Arg‐Pro‐Val‐Ala‐Ala‐Glu. Otherwise, we added one peptide at the C‐terminal of Leu‐Arg‐Pro‐Val‐Ala‐Ala‐Glu and found both products with an addition of Val (Leu‐Arg‐Pro‐Val‐Ala‐Ala‐Glu‐Val) or Ile (Leu‐Arg‐Pro‐Val‐Ala‐Ala‐Glu‐Ile) showing a lower ACE inhibition than the original one. The ACE inhibitions produced by both replaced peptides were without significance. Also, deletion of the last peptide at the C‐terminal (Leu‐Arg‐Pro‐Val‐Ala‐Ala) failed to produce a marked change of ACE inhibition as compared to the original one. These results suggest that Pro and Val are essential in the peptide for inhibition of ACE activity. 相似文献
119.
《Arabian Journal of Chemistry》2022,15(4):103712
Although recent decades have witnessed the synthesis of 1,3,4-thiadiazoles via phosphorus POCl3-promoted cyclization reaction, simultaneous access to 2-amino-1,3,4-thiadiazole and 2-amino-1,3,4-oxadiazole analogs remains unexpected and elusive. Herein, a detailed regiocontrolled synthesis of 2-amino-1,3,4-thiadiazoles in good to high yields with good regioselectivities from readily available thiosemicarbazides using POCl3 was disclosed. Meantime, to establish a comprehensive structure–activity relationship, 2-amino-1,3,4-oxadiazole derivatives as single regioisomers were prepared via EDCI·HCl-triggered cyclization of the thiosemicarbazide intermediates. The in vitro anti-influenza assays proved that the selected compounds with the pyrazine/pyridine ring exhibited certain inhibitory activities against influenza A virus strains A/HK/68 (H3N2) and A/PR/8/34 (H1N1) in MDCK cells. Among them, N-(adamantan-1-yl)-5-(5-(azepan-1-yl)pyrazin-2-yl)-1,3,4-thiadiazol-2-amine (4j) was the most active compound, and exhibited favorable activity with EC50 values of 3.5 μM and 7.5 μM, respectively. In addition, the molecular docking results explained the reason why compound 4j had dual inhibitory activity and revealed the reasonable binding mode of this compound with the M2-S31N and M2-WT ion channels. This compound had the potential to be further developed as an anti-influenza drug. 相似文献
120.
Summary In this paper we consider the alternative Cauchy functional equationg(xy) g(x)g(y) impliesf(xy) = f(x)f(y) wheref, g are functions from a topological group (X, ·) into a group (S,·). First we prove that, ifS is a Hausdorff topological group andX satisfies some weak additional hypotheses, then (f, g) is a continuous solution if and only if eitherf org is a homomorphism. Then we describe a more general class of solutions forX =R
n
.Partially supported by M.U.R.S.T. Research funds (40%)Dedicated to the memory of Alexander M. Ostrowski on the occasion of the 100th anniversary of his birth. 相似文献