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Search Results: 1 - 10 of 21447 matches for " log P "
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Studies on Log Po/w of Quinoxaline di-N-Oxides: A Comparison of RP-HPLC Experimental and Predictive Approaches
Elsa Moreno,Elisabetta Gabano,Enrique Torres,James A. Platts,Mauro Ravera,Ignacio Aldana,Antonio Monge,Silvia Pérez-Silanes
Molecules , 2011, DOI: 10.3390/molecules16097893
Abstract: As reported in our previous papers, a series of quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives were synthesized and studied as anti-tuberculosis agents. Here, the capability of the shake-flask method was studied and the retention time (expressed as log K) of 20 compounds were determined by RP-HPLC analysis. We found that the prediction of log P by the RP-HPLC analysis can result in a high accuracy and can replace the shake-flask method avoiding the experimental problems presented by quinoxaline di-N-oxides. The studied compounds were subjected to the ALOGPS module with the aim of comparing experimental log Po/w values and predicted data. Moreover, a preliminary in silico screening of the QSAR relationship was made confirming the influence of reduction peak potential, lipophilicity, H-bond donor capacity and molecular dimension descriptors on anti-tuberculosis activity.
Evaluation of the use of partition coefficients and molecular surface properties as predictors of drug absorption: a provisional biopharmaceutical classification of the list of national essential medi
R Shawahna,NU Rahman
DARU : Journal of Pharmaceutical Sciences , 2011,
Abstract: Background and the purpose of the study: Partition coefficients (log D and log P) and molecular surface area (PSA) are potential predictors of the intestinal permeability of drugs. The aim of this investigation was to evaluate and compare these intestinal permeability indicators. Methods: Aqueous solubility data were obtained from literature or calculated using ACD/Labs and ALOGPS. Permeability data were predicted based on log P, log D at pH 6.0 (log D6.0), and PSA. Results: Metoprolol's log P, log D6.0 and a PSA of <65 correctly predicted 55.9%, 50.8% and 54.2% of permeability classes, respectively. Labetalol's log P, log D6.0, and PSA correctly predicted 54.2%, 64.4% and 61% of permeability classes, respectively. Log D6.0 correlated well (81%) with Caco-2 permeability (Papp). Of the list of national essential medicines, 135 orally administered drugs were classified into biopharmaceutical classification system (BCS). Of these, 57 (42.2%), 28 (20.7%), 44 (32.6%), and 6 (4.4%) were class I, II, III and IV respectively. Conclusion: Log D6.0 showed better prediction capability than log P. Metoprolol as permeability internal standard was more conservative than labetalol.
Asymptotic Inference for the Weak Stationary Double AR(1) Model  [PDF]
Fang Chang, Augustine C. M. Wong, Yanyan Wu
Open Journal of Statistics (OJS) , 2012, DOI: 10.4236/ojs.2012.22016
Abstract: An AR(1) model with ARCH(1) error structure is known as the first-order double autoregressive (DAR(1)) model. In this paper, a conditional likelihood based method is proposed to obtain inference for the two scalar parameters of interest of the DAR(1) model. Theoretically, the proposed method has rate of convergence O(n-3/2). Applying the proposed method to a real-life data set shows that the results obtained by the proposed method can be quite different from the results obtained by the existing methods. Results from Monte Carlo simulation studies illustrate the supreme accuracy of the proposed method even when the sample size is small.
Estudo QSPR sobre os coeficientes de parti??o: descritores mecanico-quanticos e análise multivariada
Borges, Edilson Grünheidt;Takahata, Yuji;
Química Nova , 2002, DOI: 10.1590/S0100-40422002000700003
Abstract: quantum chemistry and multivariate analysis were used to estimate the partition coefficients between n-octanol and water for a serie of 188 compounds, with the values of the q 2 until 0.86 for crossvalidation test. the quantum-mechanical descriptors are obtained with ab initio calculation, using the solvation effects of the polarizable continuum method. two different hartree-fock bases were used, and two different ways for simulating solvent cavity formation. the results for each of the cases were analised, and each methodology proposed is indicated for particular case.
Estudo QSPR sobre os coeficientes de parti o: descritores mecanico-quanticos e análise multivariada
Borges Edilson Grünheidt,Takahata Yuji
Química Nova , 2002,
Abstract: Quantum chemistry and multivariate analysis were used to estimate the partition coefficients between n-octanol and water for a serie of 188 compounds, with the values of the q 2 until 0.86 for crossvalidation test. The quantum-mechanical descriptors are obtained with ab initio calculation, using the solvation effects of the Polarizable Continuum Method. Two different Hartree-Fock bases were used, and two different ways for simulating solvent cavity formation. The results for each of the cases were analised, and each methodology proposed is indicated for particular case.
Reverse Phase Thin Layer Chromatography of Aminoalkanethiosulfuric Acids, Mercaptoalkanamines and Aminoalkyl Disulfides
Maria Das Gra?as Cardoso,David Lee Nelson,Ant?nia Tavares do Amaral,Custódio Donizete Dos Santos,Alcilene De Abreu Pereira,Ana Cláudia Barneche De Oliveira
International Journal of Molecular Sciences , 2002, DOI: 10.3390/i3070755
Abstract: The experimental Rm values for a series of aminoalkanethiosulfuric acids, mercaptoalkanamines and aminoalkyl disulfides were determined by reverse phase thin layer chromatography. The Rm values were determined for various concentrations of methanol: water and the correlation obtained was extrapolated to 100% water. These values permitted the calculation of the log P values for each substance. The log P values obtained by this method were compared with those obtained using the shake-flask method and by theoretical calculations utilizing fragment constants.
Correlation between retention constants obtained in reversed-phase liquid chromatography and partition coefficients of some benzimidazole derivatives
A?anski Marijana M.,?akovi?-Sekuli? Tatjana Lj.
Acta Periodica Technologica , 2004, DOI: 10.2298/apt0435165a
Abstract: Several calculation procedures for log P values based on the fragmental and atomic contributions are compared with experimental reversed-phase liquid chromatography (RPLC) retention constants of benzimidazole derivatives. The RPLC experiments were performed on HPLC comerrcially available LiChrosorb RP(-18 column with binary solvent mixtures of methanol-phosphate buffer (pH 7) as mobile phase. Retention constant log k0 was determined by the extrapolation method. Good correlaton was found between the retention constants log k0 and log P, as well as m and log P of the compounds investigated.
Avalia o das estruturas de concordancia e discordancia nos estudos de confiabilidade
Silva Eduardo Freitas da,Pereira Maurício Gomes
Revista de Saúde Pública , 1998,
Abstract: OBJETIVO: Complementar dados de investiga o anterior sobre o risco de indu o de cancer devido à ingest o de 226Ra, 228Ra e 222Rn em fontes de águas minerais de uma regi o de altos níveis de radioatividade natural, do Brasil. Desta forma, foi realizada a estimativa de indu o de cancer devido à ingest o de 238U e 234U nessas mesmas águas. MéTODO: O coeficiente de risco para os isótopos naturais de uranio foi considerado como sendo o mesmo daquele utilizado para a indu o de sarcoma ósseo pelo 226Ra e que a quantidade depositada no osso corresponde a 25 vezes a ingest o diária de 226Ra e a 11 vezes a ingest o diária dos isótopos de uranio de meia-vida longa. Amostras de água das fontes ultilizadas pela popula o de água da Prata, Estado de S o Paulo, foram coletadas, num período de um ano, de forma a abranger todas as esta es. RESULTADOS: Foram encontradas concentra es variando de 2,0 a 28,4 mBq/L e de 4,7 a 143m Bq/L para 238U e 234U, respectivamente. Baseando-se nessas concentra es foi estimado o risco devido à ingest o dos isótopos de uranio: um total de 0,3 casos de cancer por 10(6) indivíduos expostos. Este dado indica que a ingest o cr nica de uranio nas concentra es observadas nas fontes analisadas resultará em um acréscimo no número de casos de cancer fatais de 0,1 %. CONCLUS ES: Se as incertezas na estimativa dos efeitos carcinogênicos forem levadas em considera o, pode-se concluir que praticamente nenhum caso de cancer ocorrerá devido à ingest o de uranio presente nas águas minerais analisadas.
INSILICO DRUG ACTIVITY OF N-OXIDES
VALLI G,LALITHISWARI T,JOTHIMALAR S,JOTHIMALAR S
International Journal of Bioinformatics Research , 2011,
Abstract: N-Oxides were found to have antimicrobial activity. In continuation of our work on synthesis, characterizationand biological activities (in vitro method) of N-Oxides and knowing their biological activities against micro organisms, wehave correlated the biological activity of these N-Oxides against the micro organisms like Staphylococcus aureus,Salmonella typhi “H”, Escherichia Coli, Pseudomonas aeruginosa, Klebsiella aerogenes, Enterobacteraerogenes,Citrobacter, Staphylococcus epidermidis, and Aeromonas hydrophila by Insilico method. The target molecules(microorganism) were taken from Protein data bank. Various soft wares were used to find out the drug likeness propertiesof these N-Oxides. Online software “Molinspiration” was used to calculate log P (ie) Hydrophobicity of a drug. ACD/Chemsketch was used to draw the structures of N-Oxides. Hex 4.2, docking software was used to predict the drugactivities of these N-Oxides. The drug activities were measured in terms of drug likeness property by recording the ETotalvalue and compared with the marketed standard drugs for the above micro organism infections. Standard drugswere taken from drug bank. As per the standard norms, it was observed that the compounds that have negative E-Totalvalues could be used as a drug. We have selected Ceftazidime ,Cefepime and Ceftizoxime as standard drugs among theavailable drugs for these microorganism for correlating the drug activities of these N-Oxides. We observed that some ofour N-Oxides were found to have higher drug activities compared to standard drugs.
On powers of -hyponormal and log-hyponormal operators
Furuta Takayuki,Yanagida Masahiro
Journal of Inequalities and Applications , 2000,
Abstract: A bounded linear operator on a Hilbert space is said to be -hyponormal for if , and is said to be log-hyponormal if is invertible and . Firstly, we shall show the following extension of our previous result: If is -hyponormal for , then and hold for all positive integer . Secondly, we shall discuss the best possibilities of the following parallel result for log-hypponormal operators by Yamazaki: If is log-hyponormal, then and hold for all positive integer .
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