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partition coefficient

Vera Kovacevic, André J Simpson, Myrna J Simpson
Organophosphate esters (OPEs) are frequently detected in aquatic environments. Hydrophobic OPEs with high octanol-water partition coefficients (Log KOW ) will likely sorb to dissolved organic matter (DOM) and consequently alter OPE bioavailability and sub-lethal toxicity. ¹H nuclear magnetic resonance (NMR)-based metabolomics was used to evaluate how DOM (5 mg organic carbon/L) alters the metabolic response of Daphnia magna exposed to sub-lethal concentrations of three individual OPEs with varying hydrophobicity...
May 19, 2018: Metabolites
Scott E Belanger, Jane M Rawlings, Ricky Stackhouse
Short to long chain alcohols have a range of ecotoxicity to aquatic life driven by hydrophobic interactions with biological membranes. Carbon chain length and octanol:water partitioning coefficients are surrogates for hydrophobicity and strongly relate to aquatic toxicity. In these investigations, the toxicity of ethanol to 1-n-dodecanol to juvenile fish in standard acute toxicity tests is reviewed. Toxicity tests employing fish embryos (zebrafish Danio rerio and fathead minnow Pimephales promelas) in the Fish Embryo Test (OECD 236) format were conducted from C2 to C10 to compare against standard juvenile fish toxicity...
April 25, 2018: Chemosphere
Lucas P Fonseca, Rafael B Trinca, Maria Isabel Felisberti
Amphiphilic hydrogels are widely reported as systems with great potential for controlled drug release. Nevertheless, the majority of studies make use of functionalization or attachment of drugs to the polymer chains. In this study, we propose a strategy of combining amphiphilic polyurethanes with pH-responsive drugs to develop smart drug carriers. While the amphiphilic character of the polymer imparts an efficient load of hydrophobic and hydrophilic drugs, the drug's characteristics determine the selectivity of the medium delivery...
May 14, 2018: International Journal of Pharmaceutics
L Janoschek, L Grozdev, S Berensmeier
This work focuses on the process development of membrane-assisted solvent extraction of hydrophobic compounds such as monoterpenes. Beginning with the choice of suitable solvents, quantum chemical calculations with the simulation tool COSMO-RS were carried out to predict the partition coefficient (log P ) of (S)-(+)-carvone and terpinen-4-ol in various solvent-water systems and validated afterwards with experimental data. COSMO-RS results show good prediction accuracy for non-polar solvents such as n-hexane, ethyl acetate and n-heptane even in the presence of salts and glycerol in an aqueous medium...
April 2018: Royal Society Open Science
Hui-Suan Ng, Grace Yin Tze Tan, Ka-Heng Lee, Wolfgang Zimmermann, Hip Seng Yim, John Chi-Wei Lan
The α- and γ-mangostins from Garcinia mangostana pericarps (GMP) exhibit antioxidant, anti-bacterial, anti-inflammatory and anti-tumor properties. The extraction yields α- and γ-mangostins are often limited by the presence of the GMP cell walls. Therefore, the extraction and recovery of mangostins from GMP with an Aspergillus niger cellulase-assisted aqueous micellar biphasic system (CA-AMBS) was developed for enhanced yield of mangostins. Effects of the concentration of cellulase, the incubation time and the temperature of the system on the recovery of mangostins were investigated...
May 12, 2018: Journal of Bioscience and Bioengineering
Jianfeng Tang, Xinhu Li, Xinwei Yu, Gang Li, Sardar Khan, Chao Cai
Hexabromocyclododecanes (HBCDs) are a class of widely used brominated flame retardants (BFRs) that exhibit strong hydrophobicity. The ubiquity and persistence of HBCDs in sediment have attracted significant attention because of public health concerns. The environmental fate and ecological risks of HBCDs closely depend on their phase distribution in sediments. However, little information is available regarding the freely dissolved concentrations (C free ) of HBCDs in sediment porewater. In this study, we developed a method to measure C free of HBCDs in sediment porewater using triolein-embedded cellulose acetate membranes (TECAM)...
May 14, 2018: Environmental Science and Pollution Research International
Senpei Yang, Lingyi Li, Tao Chen, Lujia Han, Guoping Lian
PURPOSE: Sebum is an important shunt pathway for transdermal permeation and targeted delivery, but there have been limited studies on its permeation properties. Here we report a measurement and modelling study of solute partition to artificial sebum. METHODS: Equilibrium experiments were carried out for the sebum-water partition coefficients of 23 neutral, cationic and anionic compounds at different pH. RESULTS: Sebum-water partition coefficients not only depend on the hydrophobicity of the chemical but also on pH...
May 14, 2018: Pharmaceutical Research
Mohammed A Khairy, Rainer Lohmann
There is scant information on the presence of the polybrominated diphenyl ethers (PBDEs) and other alternative flame-retardants (NFRs) in Africa. Hence, to investigate their levels, sources, and human exposure scenarios, elevated fine dust (EFD) samples from apartments (n = 12), working places (n = 9) and cars (n = 12), floor dust (FD) samples (n = 5) and outdoor dust samples (n = 21) were collected from Alexandria, Egypt, during 2014. Gaseous concentrations were estimated using low density polyethylene sheets (n = 33 and 21 for indoor and outdoor sites, respectively)...
August 15, 2018: Science of the Total Environment
Lutz Ahrens, Atlasi Daneshvar, Anna E Lau, Jenny Kreuger
Three passive sampler types including Chemcatcher® C18 , polar organic chemical integrative sampler-hydrophilic-lipophilic balance (POCIS-HLB) and silicone rubber (SR) based on polydimethylsiloxane (PDMS) were evaluated for 124 legacy and current used pesticides at two sampling locations in southern Sweden over a period of 6 weeks and compared to time-proportional composite active sampling. In addition, an in situ calibration was performed resulting in median in situ sampling rates (RS , L day-1 ) of 0...
May 11, 2018: Science of the Total Environment
Jay P Kitt, David A Bryce, Shelley D Minteer, Joel M Harris
The phospholipid-water partition coefficient is a commonly measured parameter that correlates with drug efficacy, small-molecule toxicity, and accumulation of molecules in biological systems in the environment. Despite the utility of this parameter, methods for measuring phospholipid-water partition coefficients are limited. This is due to the difficulty of making quantitative measurements in vesicle membranes or supported phospholipid bilayers, both of which are small-volume phases that challenge the sensitivity of many analytical techniques...
May 14, 2018: Analytical Chemistry
A Lara, M Riquelme, E Vöhringer-Martinez
Partition coefficients serve in various areas as pharmacology and environmental sciences to predict the hydrophobicity of different substances. Recently, they have also been used to address the accuracy of force fields for various organic compounds and specifically the methylated DNA bases. In this study, atomic charges were derived by different partitioning methods (Hirshfeld and Minimal Basis Iterative Stockholder) directly from the electron density obtained by electronic structure calculations in a vacuum, with an implicit solvation model or with explicit solvation taking the dynamics of the solute and the solvent into account...
May 11, 2018: Journal of Computational Chemistry
Bleddyn Jones, John W Hopewell
OBJECTIVE: To provide simpler models for adjusting total dose to compensate for significant variations in CNS radio-surgical treatment times, which vary and will influence treatment bio-effectiveness. At present, no allowance is made for time variations. A framework of simpler equations would allow radio-surgical outcomes to be analysed with respect to treatment time, and a system for dose adjustments between radio-isotope and linac-based techniques with different treatment durations...
May 10, 2018: British Journal of Radiology
Rebecca D Usery, Thais A Enoki, Sanjula P Wickramasinghe, V P Nguyen, David G Ackerman, Denise V Greathouse, Roger E Koeppe, Francisco N Barrera, Gerald W Feigenson
A number of highly curved membranes in vivo, such as epithelial cell microvilli, have the relatively high sphingolipid content associated with "raft-like" composition. Given the much lower bending energy measured for bilayers with "nonraft" low sphingomyelin and low cholesterol content, observing high curvature for presumably more rigid compositions seems counterintuitive. To understand this behavior, we measured membrane rigidity by fluctuation analysis of giant unilamellar vesicles. We found that including a transmembrane helical GWALP peptide increases the membrane bending modulus of the liquid-disordered (Ld) phase...
May 8, 2018: Biophysical Journal
Rakesh Shiradkar, Soumya Ghose, Ivan Jambor, Pekka Taimen, Otto Ettala, Andrei S Purysko, Anant Madabhushi
BACKGROUND: Radiomics or computer-extracted texture features derived from MRI have been shown to help quantitatively characterize prostate cancer (PCa). Radiomics have not been explored depth in the context of predicting biochemical recurrence (BCR) of PCa. PURPOSE: To identify a set of radiomic features derived from pretreatment biparametric MRI (bpMRI) that may be predictive of PCa BCR. STUDY TYPE: Retrospective. SUBJECTS: In all, 120 PCa patients from two institutions, I1 and I2 , partitioned into training set D1 (N = 70) from I1 and independent validation set D2 (N = 50) from I2 ...
May 7, 2018: Journal of Magnetic Resonance Imaging: JMRI
Du Yung Kim, Jung-Hwan Kwon
Because the freely dissolved fraction of highly hydrophobic organic chemicals is bioavailable, knowing the partition coefficient between dissolved organic carbon and water (KDOCw ) is crucial to estimate the freely dissolved fraction from the total concentration. A kinetic method was developed to obtain KDOCw that required a shorter experimental time than equilibrium methods. The equilibrium partition coefficients of four polychlorinated biphenyls (PCBs) (2,4,4'-trichlorobiphenyl (PCB 28), 2,2',3,5'-tetrachlorobiphenyl (PCB 44), 2,2',4,5,5'-pentachlorobiphenyl (PCB 101), and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153)) between dissolved organic carbon and seawater (KDOCsw ) were determined using seawater samples from the Korean coast...
May 4, 2018: Environmental Pollution
Soohyung Park, Wonpil Im
We have devised a practical simulation protocol for quantitative characterization of cholesterol (Chol) partitioning between bilayers with different lipid types. The simulation model contains two patches of laterally contacting lipid bilayers, where the host lipids of each bilayer are allowed to self-adjust their packing. For two combinations of bilayers with different lipid types, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), the simulation model has been verified by self-adjusted lipid packing in each bilayer, convergence of Chol partitioning between different Chol initial distributions, and relative diffusion coefficients consistent to those from experiments...
May 7, 2018: Journal of Chemical Theory and Computation
Muhammad Zia Ullah Khan, Petre Makreski, Ghulam Murtaza
The aim of present explorative study was to prepare and optimize finasteride loaded topical gel formulations by using three factor [propylene glycol (PG), Tween® 80, and sodium lauryl sulphate (SLS)], five level central composite design. Optimized finasteride topical gel formulation (F4), containing PG, Tween® 80, and SLS in a concentration of 0.8 mg, 0.4 mg and 0.2 mg, respectively, showed 6-fold higher values of cumulative drug release, flux, partition coefficient, input rate, lag time, and diffusion coefficient, when compared to control formulation without permeation enhancer...
May 2, 2018: Current Drug Delivery
Patrick H Donohue, Eddy Hill, Gary R Huss
Pallasite meteorites, which consist primarily of olivine and metal, may be remnants of disrupted core-mantle boundaries of differentiated asteroids or planetesimals. The early thermal histories of pallasites are potentially recorded by minor- and trace-element zonation in olivine. However, constraining this history requires knowledge of element behavior under the conditions of pallasite formation, which is lacking for many of the main elements of interest (e.g., Co, Cr, Mn). In this study, we experimentally determined metal/olivine partition coefficients for Fe, Ni, Co, Cr, and Mn in a pallasite analogue at subsolidus temperatures...
February 1, 2018: Geochimica et Cosmochimica Acta
Yu Ting, Chi Chen, Boon-Lek Ch'ng, Ying-Lin Wang, Hsing-Cheng Hsi
Sulfur-impregnated activated carbon (SAC) has been reported with a high affinity to Hg, but little research has done on understanding its potential as active cap for inhibition of Hg release from contaminated sediments. In this study, high-quality coconut-shell activated carbon (AC) and its derived SAC were examined and shown to have great affinity to both aqueous Hg2+ and methylmercury (MeHg). SAC had greater partitioning coefficients for Hg2+ (KD  = 9.42 × 104 ) and MeHg (KD  = 7.661 × 105 ) as compared to those for AC (KD  = 3...
April 30, 2018: Journal of Hazardous Materials
Chantel I Nicolas, Kamel Mansouri, Katherine A Phillips, Christopher M Grulke, Ann M Richard, Antony J Williams, James Rabinowitz, Kristin K Isaacs, Alice Yau, John F Wambaugh
The structures and physicochemical properties of chemicals are important for determining their potential toxicological effects, toxicokinetics, and route(s) of exposure. These data are needed to prioritize the risk for thousands of environmental chemicals, but experimental values are often lacking. In an attempt to efficiently fill data gaps in physicochemical property information, we generated new data for 200 structurally diverse compounds, which were rigorously selected from the USEPA ToxCast chemical library, and whose structures are available within the Distributed Structure-Searchable Toxicity Database (DSSTox)...
May 2, 2018: Science of the Total Environment
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