Higher Kd Values Research Articles

Measuring Light Attenuation in Shallow Coastal Systems

Photosynthetic Active Radiation (PAR) was measured using single planar and two-bulb spherical light sensors. The attenuation coefficient (Kd) was found to vary significantly during the year. The highest Kd values were obtained in the station with higher influence of currents and run-off. Our data suggested a reflection of 50% of light that reaches the bottom, which is associated with a decrease in the Kd value obtained with the spherical sensor of 0.15 m-1. This means that flat sensors may underestimate PAR and that spherical sensor may underestimate Kd. This is a critical issue given that knowledge on light attenuation is essential for modeling approaches and quality assessments.

Effects of the presence of Fe(0) on the sorption of lanthanum and lutetium mixtures in smectites

The sorption of La and Lu mixtures was examined in two bentonites after incubation for three months at 20 and 80°C with Fe(0), as a laboratory approach to evaluate the effects of waste canister corrosion in a deep repository on the performance of clay engineered barriers. The sorption/desorption parameters were determined from batch tests in two ionic media: deionized water and, to consider the additional effect of cement leachates, 0.02molL−1 Ca.Results from XRD analyses showed the formation of crystalline FeO(OH), goethite, in a few samples and the degradation of the bentonites due to Fe(0) oxidation during incubation. Moreover, the EDX spectra showed that the lanthanides were sorbed primarily at smectite sites, although sorption onto goethite was also observed, whereas Fe(0) particles did not contribute to lanthanide sorption. The formation of goethite could explain the high Kd values measured in a few scenarios (e.g., those with single solutions or mixtures with the lowest initial concentration of the competitive lanthanide in which high affinity sites governed sorption), with up to 3-fold increases over the values obtained without Fe incubation. However, at higher lanthanide concentration, Kd values decreased or remained constant compared to the samples without Fe incubation, which could be explained by bentonite degradation. In the Ca medium, as much as 5 times lower Kd values were obtained, because of the competitive effect of the Ca ions, especially for Lu in the MX80 bentonite. This indicated that the small number of high affinity sites had been diminished.The sorption data were satisfactorily fitted to a two-solute Langmuir model. In addition, Kd values correlated well with desorption data, which showed that the larger the decrease in Kd, the larger the increase in sorption reversibility. It is suggested that corrosion products from the metal canister might compromise the long-term radionuclide retention of the clay-engineered barriers.

Radiation impedance of collapsed capacitive micromachined ultrasonic transducers

The radiation impedance of a capacitive micromachined ultrasonic transducer (CMUT) array is a critical parameter to achieve high performance. In this paper, we present a calculation of the radiation impedance of collapsed, clamped, circular CMUTs both analytically and using finite element method (FEM) simulations. First, we model the radiation impedance of a single collapsed CMUT cell analytically by expressing its velocity profile as a linear combination of special functions for which the generated pressures are known. For an array of collapsed CMUT cells, the mutual impedance between the cells is also taken into account. The radiation impedances for arrays of 7, 19, 37, and 61 circular collapsed CMUT cells for different contact radii are calculated both analytically and by FEM simulations. The radiation resistance of an array reaches a plateau and maintains this level for a wide frequency range. The variation of radiation reactance with respect to frequency indicates an inductance-like behavior in the same frequency range. We find that the peak radiation resistance value is reached at higher kd values in the collapsed case as compared with the uncollapsed case, where k is the wavenumber and d is the center-to-center distance between two neighboring CMUT cells.

Impacts of Soil Organic Matter and Temperature on Sorption of Acetazolamide on Four Soils

Batch sorptions of acetazolamide (AZ) were conducted using four soils from China. Sorption of AZ was found to be impacted by OC, clay content, and soil pH, with higher kd values for soils with higher clay content. The kd values of SOM-removed soils are much lower than those of bulk soils. Sorption data were well fitted with a Freundlich model (r2 > 0.99). Chelating with the metal ions on the surfaces of soil particles was probably involved. With pH increase, the electrostatic attraction between anionic AZ and positively charged soil surface may increase. The sorption capacity decreased when the temperature increased from 20 to 40°C, and the calculated thermodynamics parameters of ΔG0, ΔH0, and ΔS0 indicated that the sorption was a non-spontaneous, physisorption, and exothermic process. Sorption coefficients (kd) for the compound in soil were low (ranging from 0.42 to 1.19 L·kg−1) and indicated that low level sorption of AZ with appreciable risk of ground water contamination.

Analysis of high-affinity assembly for AMPA receptor amino-terminal domains.

Analytical ultracentrifugation (AUC) and steady-state fluorescence anisotropy were used to measure the equilibrium dissociation constant (Kd) for formation of dimers by the amino-terminal domains (ATDs) of the GluA2 and GluA3 subtypes of AMPA receptor. Previous reports on GluA2 dimerization differed in their estimate of the monomer–dimer Kd by a 2,400-fold range, with no consensus on whether the ATD forms tetramers in solution. We find by sedimentation velocity (SV) analysis performed using absorbance detection a narrow range of monomer–dimer Kd values for GluA2, from 5 to 11 nM for six independent experiments, with no detectable formation of tetramers and no effect of glycosylation or the polypeptide linker connecting the ATD and ligand-binding domains; for GluA3, the monomer–dimer Kd was 5.6 µM, again with no detectable tetramer formation. For sedimentation equilibrium (SE) experiments, a wide range of Kd values was obtained for GluA2, from 13 to 284 nM, whereas for GluA3, the Kd of 3.1 µM was less than twofold different from the SV value. Analysis of cell contents after the ∼1-week centrifuge run by silver-stained gels revealed low molecular weight GluA2 breakdown products. Simulated data for SE runs demonstrate that the apparent Kd for GluA2 varies with the extent of proteolysis, leading to artificially high Kd values. SV experiments with fluorescence detection for GluA2 labeled with 5,6-carboxyfluorescein, and fluorescence anisotropy measurements for GluA2 labeled with DyLight405, yielded Kd values of 5 and 11 nM, consistent with those from SV with absorbance detection. However, the sedimentation coefficients measured by AUC using absorbance and fluorescence systems were strikingly different, and for the latter are not consistent with hydrodynamic protein models. Thus, for unknown reasons, the concentration dependence of sedimentation coefficients obtained with fluorescence detection SV may be unreliable, limiting the usefulness of this technique for quantitative analysis.

Ni(II) sorption on natural chlorite

Sorption of Ni(II) onto chlorite surfaces was studied as a function of pH (5–10), ionic strength (0.01–0.5 M) and Ni concentration (10−8–10−6 M) in an Ar atmosphere using batch sorption with radioactive 63Ni as tracer. Such studies are important since Ni(II) is one of the major activation products in spent nuclear fuel and sorption data on minerals such as chlorite are lacking. The sorption of Ni(II) onto chlorite was dependent on pH but not ionic strength, which indicates that the process primarily comprises sorption by surface complexation. The maximum sorption was at pH ∼ 8 (Kd = ∼10−3 cm3/g). Desorption studies over a period of 1–2 weeks involving replacement of the aqueous solution indicated a low degree of desorption. The acid–base properties of the chlorite mineral were determined by titration and described using a non-electrostatic surface complexation model in FITEQL. A 2-pK NEM model and three surface complexes, Chl_OHNi2+, Chl_OHNi(OH)+ and Chl_OHNi(OH)2, gave the best fit to the sorption results using FITEQL. The high Kd values and low degree of desorption observed indicate that under expected groundwater conditions, a large fraction of Ni(II) that is potentially leachable from spent nuclear fuel may be prevented from migrating by sorption onto chlorite surfaces.

SST diurnal variability in the North Sea and the Baltic Sea

Five years of sea surface temperature (SST) retrievals from a geostationary platform are utilised to identify and characterise diurnal warming in the North and Baltic Seas. Observations from the Spinning Enhanced Visible Infrared Imager (SEVIRI) on board the Meteosat Second Generation satellite are proven valuable for quantifying the daily SST cycle in shallow and coastal waters at latitudes 48–60N. Satellite minus in situ observations from moored buoys show biases ranging from −0.3K to 0.1K. A thorough analysis is carried out to obtain the optimal reference field used for calculating the daytime temperature anomalies. The best night-time reference field candidate is demonstrated to be an average of 3days of satellite observations from local midnight to 0300. When compared against night-time in situ measurements from various locations, mean biases are found in the order of ±0.1K and standard deviation (σ) between 0.4K and 0.9K. The 5year record with daytime temperature anomalies is used to derive robust statistical description of duration, spatial extent, proximity to coast and water depth of the diurnal warming events. Seasonal and inter-annual variations in the diurnal warming are also quantified. Daytime anomalies exceeding 2K are identified during the spring and summer months of every year, peaking at 1500 LT. Events with daily anomalies exceeding 5K are observed. Areas where diurnal variability is often observed coincide with areas of frequently observed low winds and turbid waters (high Kd(490) values).

Removal of endocrine disrupting chemicals in a large scale membrane bioreactor plant combined with anaerobic-anoxic-oxic process for municipal wastewater reclamation

The removal of eight typical endocrine disrupting compounds (EDCs) in a full scale membrane bioreactor combined with anaerobic-anoxic-oxic process (A(2)/O-MBR) for municipal wastewater reclamation located in Beijing was investigated. These EDCs, including 4-octylphenol (4-OP), 4-n-nonylphenol (4-n-NP), bisphenol A (BPA), estrone (E1), 17α-estradiol (17α-E2), 17β-estradiol (17β-E2), estriol (E3) and 17α-ethinylestradiol (EE2), were simultaneously analyzed by gas chromatography/mass spectrometry after derivatization. The concentrations of eight EDCs were also measured in sludge of anaerobic, anoxic, oxic and membrane tanks to measure sludge-water distribution coefficients (K(d) values) as the indicator of adsorption propensity of target compound to sludge. The removal efficiencies of EDCs reached above 97%, except for 4-n-NP removal efficiency of 72%, 4-OP removal efficiency of 75% and EE2 removal efficiency of 87% in the A(2)/O-MBR process. The high K(d) values indicated that the sludge had a large adsorption capacity for these EDCs, and significantly contributed to removal of EDCs. Yeast estrogen screen assay was performed on samples to assess the total estrogenic activity by measuring the 17β-E2 equivalent quantity (EEQ), expressed in ng-EEQ/L. The measured EEQ value was markedly reduced from 72.1 ng-EEQ/L in the influent to 4.9 ng-EEQ/L in the effluent. Anoxic tank and anaerobic tank contributed to 80% and 37% in total EEQ removal, respectively.

Kinetics of plutonium and americium sorption to natural clay

Kinetics of Pu(IV) and Am(III) sorption from natural groundwater to three types of clays were studied at trace concentrations of the elements. Higher Kd values were determined for sorption of Pu than of Am, and no clear dependence of the Kd values and the kinetic coefficients on the composition of the clays can be deduced. Kinetic data evaluated by models for six different control processes indicated a sorption mechanism controlled by Pu or Am diffusion in the inert layer on the surface of the clays. Apart from the kinetics of the elements sorption, time-dependent changes in their bonding nature were also studied using a sequential extraction. It was found that Pu(IV) was predominantly associated with amorphous and crystalline Fe oxides as well as natural organic matter sites on the clays, whereas in the case of Am(III) the exchangeable and carbonate sites played the principal role.

Thiol-disulfide Redox Dependence of Heme Binding and Heme Ligand Switching in Nuclear Hormone Receptor Rev-erbβ

Rev-erbβ is a heme-binding nuclear hormone receptor that represses a broad spectrum of target genes involved in regulating metabolism, the circadian cycle, and proinflammatory responses. Here, we demonstrate that a thiol-disulfide redox switch controls the interaction between heme and the ligand-binding domain of Rev-erbβ. The reduced dithiol state of Rev-erbβ binds heme 5-fold more tightly than the oxidized disulfide state. By means of site-directed mutagenesis and by UV-visible and EPR spectroscopy, we also show that the ferric heme of reduced (dithiol) Rev-erbβ can undergo a redox-triggered switch from imidazole/thiol ligation (via His-568 and Cys-384, based on a prior crystal structure) to His/neutral residue ligation upon oxidation to the disulfide form. On the other hand, we find that change in the redox state of iron has no effect on heme binding to the ligand-binding domain of the protein. The low dissociation constant for the complex between Fe(3+)- or Fe(2+)-heme and the reduced dithiol state of the protein (K(d) = ∼ 20 nM) is in the range of the intracellular free heme concentration. We also determined that the Fe(2+)-heme bound to the ligand-binding domain of Rev-erbβ has high affinity for CO (K(d) = 60 nM), which replaces one of the internal ligands when bound. We suggest that this thiol-disulfide redox switch is one mechanism by which oxidative stress is linked to circadian and/or metabolic imbalance. Heme dissociation from Rev-erbβ has been shown to derepress the expression of target genes in response to changes in intracellular redox conditions. We propose that oxidative stress leads to oxidation of cysteine(s), thus releasing heme from Rev-erbβ and altering its transcriptional activity.

Effect of Diluent on the Extraction of Oxoethanoic (Glyoxylic) Acid by N,N-Dioctyloctan-1-amine (TOA)

The extractability of aqueous solutions of oxoethanoic acid by N,N-dioctyloctan-1-amine (TOA) in various diluents, including isoamyl alcohol, octan-1-ol, nonan-1-ol, decan-1-ol, methyl ethyl ketone, diisobuthyl ketone, hexan-2-one, toluene, kerosene, and n-hexane has been investigated. Batch extraction results at 25 °C have been calculated and reported as distribution coefficients (KD), loading factors (Z), and extraction efficiencies (E). With these solvents, using TOA has been found to be very effective (KD ≫ 1). Decan-1-ol was found to be the most effective diluent with the highest value of KD (13.43) at 1.37 mol·kg−1 concentration of TOA. The results of the liquid−liquid equilibrium measurements were correlated with a linear solvation energy relationship (LSER) model that takes into account physical interactions as well as with modified Freundlich and Langmuir equations. The experimental results for the oxoethanoic acid extraction are compared to the model results.

Research Article: Quantitative Sequence–Kinetics Relationship in Antigen–Antiboby Interaction Kinetics Based on a Set of Descriptors

The interaction between recombinant Fab57P and the coat protein of tobacco mosaic virus was studied using quantitative structure–activity relationship (QSAR) method. The development of quantitative multivariate model has shown to be a promising approach for unraveling protein–protein interactions by designed mutations in peptide sequence. This approach makes it possible to stereo‐chemically determine which residue properties contribute most to the interaction. A set of side‐chain descriptors was proposed and applied in structural characterization of three positions (positions 142, 145 and 146) in the peptide antigen. Quantitative sequence–kinetics relationship (QSKR) models describing the dissociation rates (log kd) were developed successfully using orthogonal signal correction–partial least squares method. The results showed that peptides will have high log kd values when the amino acids in position 142 and 145 have high net charge index, and when residue 145 has high hydrophobicity and residue 146 has low hydrophobicity.

Extractive Separation of Glutaric Acid by Aliquat 336 in Different Solvents

The reactive extraction equilibria for aqueous solutions of glutaric acid, with trioctylmethyl ammonium chloride (Aliquat 336) in various diluents, including 3-methyl-butan-1-ol, octan-1-ol, nonan-1-ol, decan-1-ol, methyl ethyl ketone, 2,6-dimethyl-4-heptanone, hexan-2-one, toluene, kerosene, and hexane, were determined at various Aliquat 336 (A336) concentrations. Experimental results of batch extraction experiments are calculated and reported as distribution coefficients (KD), loading factors (Z), and extraction efficiency (E). All measurements were carried out at 25 °C. 2,6-Dimethyl-4-heptanone was found to be the most effective diluent with the highest value of KD (8.51) for the glutaric acid + Aliquat 336 extraction system. The effect of pH has been investigated for octan-1-ol + A336 on glutaric acid extraction in the range of pH 2 to 8. The linear solvation energy relationship (LSER) model has been used to fit the experimental data.

Reengineering natural design by rational design and in vivo library selection: the HLH subdomain in bHLHZ proteins is a unique requirement for DNA-binding function

To explore the role of the HLH subdomain in bHLHZ proteins, we designed sets of minimalist proteins based on bHLHZ protein Max, bHLH/PAS protein Arnt and bZIP protein C/EBP. In the first, the Max bHLH and C/EBP leucine zipper were fused such that the leucine heptad repeats were not in register; therefore, the protein dimerization interface was disrupted. Max1bHLH-C/EBP showed little ability to activate transcription from the E-box (5'-CACGTG) in the yeast one-hybrid assay, and no E-box binding by quantitative fluorescence anisotropy. Max1bHLH-C/EBP's activity was significantly improved after library selection (three amino acids randomized between HLH and leucine zipper), despite the Max bHLH and C/EBP zipper still being out of register: a representative mutant gave a high nanomolar K(d) value for E-box binding. Thus, selection proved to be a powerful tool for salvaging the flawed Max1bHLH-C/EBP, although the out-of-register mutants still did not achieve the strong DNA-binding affinities displayed by their in-register counterparts. ArntbHLH-C/EBP hybrids further demonstrated the importance of maintaining register, as out-of-register mutants showed no E-box-responsive activity, whereas the in-register hybrid showed moderate activity. In another design, we eliminated the HLH altogether and fused the Max basic region to the C/EBP zipper to generate bZIP-like hybrids. Despite numerous designs and selections, these hybrids possessed no E-box-responsive activity. Finally, we tested the importance of the loop sequence in MaxbHLHZ by fluorescence and circular dichroism. In one mutant, the loop was shortened by two residues; in the other, the Lys57:DNA-backbone interaction was abolished by mutation to Gly57. Both showed markedly decreased E-box-binding relative to MaxbHLHZ. Our results suggest that, in contrast to the more rigid bZIP, the HLH is capable of significant conformational adaptation to enable gene-regulatory function and is required for protein dimerization and positioning the basic region for DNA recognition.

Recognition by the Thyroid Hormone Receptor of Canonical DNA Response Elements

To shed more light on the molecular requirements for recognition of thyroid response elements (TREs) by thyroid receptors (TRs), we compared the specific aspects of DNA TRE recognition by different TR constructs. Using fluorescence anisotropy, we performed a detailed and hierarchical study of TR-TRE binding. This was done by comparing the binding affinities of three different TR constructs for four different TRE DNA elements, including palindromic sequences and direct repeats (F2, PAL, DR-1, and DR-4) as well as their interactions with nonspecific DNA sequences. The effect of MgCl(2) on suppressing of nonselective DNA binding to TR was also investigated. Furthermore, we determined the dissociation constants of the hTRbeta DBD (DNA binding domain) and hTRbeta DBD-LBD (DNA binding and ligand binding domains) for specific TREs. We found that a minimum DNA recognition peptide derived from DBD (H1TR) is sufficient for recognition and interaction with TREs, whereas scrambled DNA sequences were unrecognized. Additionally, we determined that the TR DBD binds to F2, PAL, and DR-4 with high affinity and similar K(d) values. The TR DBD-LBD recognizes all the tested TREs but binds preferentially to F2, with even higher affinity. Finally, our results demonstrate the important role played by LBDs in modulating TR-DNA binding.

Behaviour of Nanomaterials in the Environment: A Study of Interaction between Humic Acids and Fullerene C60

Interaction between buckminsterfullerene and humic substances of different origin was investigated using fluorescence spectrometry as function of concentration of humic substances, pH and ionic strength. Binding constants of humic substances and buckminsterfullerene were calculated. It can be suggested that the complexation was driven by hydrophobic interaction depending on properties of the interacting compounds. Hydrophobic interaction model was indicated by linear Stern–Volmer plot, and high Kd values characterized interaction between buckminsterfullerene and humic acids. The results of this study support the development of understanding of fate of nanomaterials in environment as well as development of analytical techniques for nanomaterials in water and wastewater treatment approaches.

Experimental and Modeling Studies on the Extraction of Glutaric Acid by Trioctylamine

The reactive extraction equilibria for aqueous solutions of glutaric acid, with trioctylamine (TOA) in various diluents, including isoamyl alcohol, octan-1-ol, nonan-1-ol, decan-1-ol, methyl ethyl ketone (MEK), diisobutyl ketone (DIBK), hexan-2-one, toluene, kerosene, and n-hexane, were determined at various TOA concentrations. Experimental results of batch extraction experiments are calculated and reported as distribution coefficients (KD), loading factors (Z), and extraction efficiency (E). All measurements were carried out at 25 °C. Kerosene was found to be the most effective diluent with the highest value of KD (7.88). The complexation constants K11 and K21 were calculated for each diluent. The results of the liquid−liquid equilibrium measurements were correlated by a linear solvation energy relationship (LSER) model which takes into account physical interactions and modified Freundlich and Langmuir equations. Experimental results of the glutaric acid extraction are compared to model results.

Isotopically Exchangeable Concentrations of Elements Having Multiple Oxidation States: The Case of Fe(II)/Fe(III) Isotope Self-Exchange in Coastal Lowland Acid Sulfate Soils

Isotope exchange techniques have been used to probe isotopically exchangeable concentrations of Fe (E value) that are in dynamic equilibrium between the aqueous- and solid-phase of coastal lowland acid sulfate soils. Isotope self-exchange between Fe(II) and Fe(III) was rapid and complete in <1 min (p < 0.05) indicating that this reaction was initially occurring solely in the aqueous-phase and the surface of the soil solid-phase. It is further demonstrated that accurate and valid measurements of isotopically exchangeable concentrations of Fe do not require corrections for Fe speciation. This also holds for any element existing in two or more oxidation states which are completely isotopically self-exchangeable in soils. As isotope self-exchange between Fe(II) and Fe(III) is rapid, the distribution coefficient (Kd) and E value determined via this methodology are, therefore, truly representative of Fe regardless of the relative importance of Fe(II) or Fe(III) to the isotopically exchangeable pool of Fe. In the 21 soil samples examined, isotopically exchangeable concentrations of Fe varied from 90 mg/kg to values as high as 3610 mg/kg in acidic, saturated samples collected below the groundwater table from the transition soil horizon. The combination of low Evalues and extremely high Kd values in the upper oxidized layers of these soils indicate that these soil horizons are a relatively insignificant source of transportable (labile) Fe. As such, given our knowledge on the general rates of microbial Fe(III) reduction in, and the hydraulic properties of, the coastal lowland acid sulfate soils of this region, only those soils adjacent to agricultural drains are likely to contribute to the load of Fe entering surrounding aquatic systems.

Abstract: P1228 THE SIGNIFICANCE OF THE METABOLIC SYNDROME IN THE DEVELOPMENT OF CHRONIC RENAL DISEASE (CKD) IN NONDIABETIC OBESE SUBJECTS

Sorption of Ni(II) onto chlorite surfaces was studied as a function of pH (5–10), ionic strength (0.01–0.5 M) and Ni concentration (10−8–10−6 M) in an Ar atmosphere using batch sorption with radioactive 63Ni as tracer. Such studies are important since Ni(II) is one of the major activation products in spent nuclear fuel and sorption data on minerals such as chlorite are lacking. The sorption of Ni(II) onto chlorite was dependent on pH but not ionic strength, which indicates that the process primarily comprises sorption by surface complexation. The maximum sorption was at pH ∼ 8 (Kd = ∼10−3 cm3/g). Desorption studies over a period of 1–2 weeks involving replacement of the aqueous solution indicated a low degree of desorption. The acid–base properties of the chlorite mineral were determined by titration and described using a non-electrostatic surface complexation model in FITEQL. A 2-pK NEM model and three surface complexes, Chl_OHNi2+, Chl_OHNi(OH)+ and Chl_OHNi(OH)2, gave the best fit to the sorption results using FITEQL. The high Kd values and low degree of desorption observed indicate that under expected groundwater conditions, a large fraction of Ni(II) that is potentially leachable from spent nuclear fuel may be prevented from migrating by sorption onto chlorite surfaces.

The use of fluorescent dyes as tracers in highly saline groundwater

Summary The capability of five fluorescent dyes to serve as conservative tracers in highly saline groundwater was evaluated by a series of batch experiments on pure minerals and natural sediments. Dye sorption was tested in four different salinities (from fresh rainwater to Dead Sea water) on five pure minerals and four natural sediments taken from boreholes drilled along the Dead Sea shore. It was found that the dyes Sulfo-Rhodamine B and Eosin are strongly adsorbed on pure minerals and sediments and therefore cannot be used as conservative tracers in saline groundwater. Uranine and Pyranine sorption is increased at higher salinities, therefore they can be used as tracers in moderately saline groundwater only. Na Naphthionate was found to be the best tracer for fresh and saline water, with minimal sorption in all cases. Sorption of the dyes on four natural sediments was measured and values were found to be in accord with those of previous sorption on pure minerals. Sorption on natural sediments was also estimated based on the mineral composition of the sediment and the known sorption on the pure minerals. The estimated sorption values were usually 25% lower than those of the sorption directly measured. Nevertheless, sorption on pure minerals can be used as a first approximation for sorption on natural sediments. The impact of sediment to solution ratio was tested for Uranine as a model dye. The distribution coefficient (Kd) of Uranine in highly saline Dead Sea water was found to be dependent on the sediment to solution ratio (mass/volume), where low ratios resulted in higher values of Kd. Also, higher Kd values were calculated for fine grain size due to higher sorption capacity on larger surface areas. The difference in Kd, however, is not directly related to the specific surface size of the grains and should be examined separately.