Partition Constants Research Articles

Dengue and Zika virus capsid proteins bind to membranes and self-assemble into liquid droplets with nucleic acids

Dengue virus (DENV) and Zika virus (ZIKV) capsid proteins efficiently recruit and surround the viral RNA at the endoplasmic reticulum (ER) membrane to yield nascent viral particles. However, little is known either about the molecular mechanisms by which multiple copies of capsid proteins assemble into nucleocapsids (NCs) or how the NC is recruited and wrapped by the ER membrane during particle morphogenesis. Here, we measured relevant interactions concerning this viral process using purified DENV and ZIKV capsid proteins, membranes mimicking the ER lipid composition, and nucleic acids in in vitro conditions to understand the biophysical properties of the RNA genome encapsidation process. We found that both ZIKV and DENV capsid proteins bound to liposomes at liquid-disordered phase regions, docked exogenous membranes, and RNA molecules. Liquid–liquid phase separation is prone to occur when positively charged proteins interact with nucleic acids, which is indeed the case for the studied capsids. We characterized these liquid condensates by measuring nucleic acid partition constants and the extent of water dipolar relaxation, observing a cooperative process for the formation of the new phase that involves a distinct water organization. Our data support a new model in which capsid–RNA complexes directly bind the ER membrane, seeding the process of RNA recruitment for viral particle assembly. These results contribute to our understanding of the viral NC formation as a stable liquid–liquid phase transition, which could be relevant for dengue and Zika gemmation, opening new avenues for antiviral intervention.

Critical Membrane Concentration and Mass-Balance Model to Identify Baseline Cytotoxicity of Hydrophobic and Ionizable Organic Chemicals in Mammalian Cell Lines.

All chemicals can interfere with cellular membranes and this leads to baseline toxicity, which is the minimal toxicity any chemical elicits. The critical membrane burden is constant for all chemicals; that is, the dosing concentrations to trigger baseline toxicity decrease with increasing hydrophobicity of the chemicals. Quantitative structure-activity relationships, based on hydrophobicity of chemicals, have been established to predict nominal concentrations causing baseline toxicity in human and mammalian cell lines. However, their applicability is limited to hydrophilic neutral compounds. To develop a prediction model that includes more hydrophobic and charged organic chemicals, a mass balance model was applied for mammalian cells (AREc32, AhR-CALUX, PPARγ-BLA, and SH-SY5Y) considering different bioassay conditions. The critical membrane burden for baseline toxicity was converted into nominal concentration causing 10% cytotoxicity by baseline toxicity (IC10,baseline) using a mass balance model whose main chemical input parameter was the liposome-water partition constants (Klip/w) for neutral chemicals or the speciation-corrected Dlip/w(pH 7.4) for ionizable chemicals plus the bioassay-specific protein, lipid, and water contents of cells and media. In these bioassay-specific models, log(1/IC10,baseline) increased with increasing hydrophobicity, and the relationship started to level off at log Dlip/w around 2. The bioassay-specific models were applied to 392 chemicals covering a broad range of hydrophobicity and speciation. Comparing the predicted IC10,baseline and experimental cytotoxicity IC10, known baseline toxicants and many additional chemicals were identified as baseline toxicants, while the others were classified based on specificity of their modes of action in the four cell lines, confirming excess toxicity of some fungicides, antibiotics, and uncouplers. Given the similarity of the bioassay-specific models, we propose a generalized baseline-model for adherent human cell lines: log[1/IC10,baseline (M)] = 1.23 + 4.97 × (1 - e-0.236logDlip/w). The derived models for baseline toxicity may serve for specificity analysis in reporter gene and neurotoxicity assays as well as for planning the dosing for cell-based assays.

Ionic Liquids [M3+ ][A- ]3 with Three-Valent Cations and Their Possible Use to Easily Separate Rare Earth Metals.

We introduce a simple way to liquify rare earth metals (REM) by incorporating the corresponding cations, in particular Eu3+, La3+, and Y3+, into polyvalent ionic liquids (ILs). In contrast to conventional methods, this is achieved not by transforming them into anionic complexes, but by keeping them as bare cations and combining them with convenient, cheap and commercially available anions (A) in the form [REM3+][A − ]3. To do so, we follow the COncept of Melting Point Lowering due to EThoxylation (COMPLET) with alkyl polyethylene oxide carboxylates as anions. We provide basic properties, such as glass transition temperatures, viscosities, electrical conductivities, as well as water‐octanol partition constants P and show that these ILs have remarkably different properties, despite the similarity of their cations. In addition, we show that the ionic liquids possess interesting luminescent properties as non‐conventional fluorophores.

Effect of nonionic surfactant on micellization thermodynamics and spectroscopic profile of dye-surfactant aggregation

Interactional study of triphenylmethane-based cationic dye i.e., basic violet-4 dye (BV) in the mixed-micellar system of two anionic surfactants viz. sodium dodecyl sulfate (NaDS) and sodium stearate (NaS) is encompassed in this manuscript. The composite micelles of nonionic surfactant triton X-100 (TX) served as better colloidal carriers to facilitate aggregation, deep penetration, and stability of dye molecules than single surfactants. The thermodynamics of the micellization was assessed conductometrically, whereas the extent of dye-surfactant interaction was quantified spectroscopically. The nonionic/anionic mixture favored micellization and lowered critical micellar concentration (CMC). Furthermore, it is observed that dye partitioning, binding, and micellization were spontaneous processes. The thermodynamic parameters including entropy, enthalpy, and Gibb’s free energy of micellization along with the determination of the CMC, degree of ionization are also explained. The parameters in terms of partition constant, partition coefficient, binding constant, Gibb’s free energy of partition, and binding were calculated from differential absorption spectroscopy. The comparative study revealed that NaDS/TX showed superior performance in dye penetration as compared to NaS/TX system.

Comparative solubilization of reactive dyes in single and mixed surfactants

Physicochemical attributes and solubilization of reactive dyes in single and mixed micellar media are elaborated in this study. The enhanced entrapment of reactive dyes was observed in the mixed-micellar media of cationic surfactant, cetyltrimethylammonium bromide (CTAB) and nonionic surfactant, (Triton X-100) as compared to single-micellar media of CTAB. Two reactive dyes viz. Reactive Black 5 (RB) and Reactive Yellow 145 (RY) were used for this interactional study. The solubilization in terms of partition constant (Kc ), partition coefficient (Kx ), binding constant (Kb ), Gibbs free energies (ΔGp and ΔGb ) and the approximate location of dye molecules in the micelles, was assessed by UV–Vis spectroscopy. From the experimental findings, it was concluded that the mixing of CTAB with a nonionic surfactant is recommended to achieve a superior degree of entrapment of dye molecules as compared to the single surfactant. The RB, the magnitude of Kx was 520 × 105 in CTAB media, whereas this value lowered to 195 × 105 in the mixed-micellar system (MMS). A similar trend was observed in RY and the single and MMSs showed respective Kx values of 207 × 105 and 19.7 × 105. The higher negative magnitudes in the case of single surfactant indicated greater partitioning of dyes while the mixed system caused deep penetration of dyes. The lower values of Gibb’s free energies of partition and binding were indicative of greater penetration of dyes within the micelles.

Fluoroquinolone-Transition Metal Complexes: A Strategy to Overcome Bacterial Resistance.

Fluoroquinolones (FQs) are antibiotics widely used in the clinical practice due to their large spectrum of action against Gram-negative and some Gram-positive bacteria. Nevertheless, the misuse and overuse of these antibiotics has triggered the development of bacterial resistance mechanisms. One of the strategies to circumvent this problem is the complexation of FQs with transition metal ions, known as metalloantibiotics, which can promote different activity and enhanced pharmacological behaviour. Here, we discuss the stability of FQ metalloantibiotics and their possible translocation pathways. The main goal of the present review is to frame the present knowledge on the conjunction of biophysical and biological tools that can help to unravel the antibacterial action of FQ metalloantibiotics. An additional goal is to shed light on the studies that must be accomplished to ensure stability and viability of such metalloantibiotics. Potentiometric, spectroscopic, microscopic, microbiological, and computational techniques are surveyed. Stability and partition constants, interaction with membrane porins and elucidation of their role in the influx, determination of the antimicrobial activity against multidrug-resistant (MDR) clinical isolates, elucidation of the mechanism of action, and toxicity assays are described for FQ metalloantibiotics.

Interactional study of a polymeric organotin complex in micellar media

In this manuscript, a study on interactions of a polymeric derivative of Tributyltin(IV) with [(2-Methylpropanoyl)amino]propanoic acid (TMP) in micellar media is presented. The study was conducted using two surfactants viz. Sodium 2-ethylhexylsulphate (SES) and Cetyltrimethylammonium bromide (CTAB). The solubilization parameters in terms of partition constant (K c ), partition coefficient (K x ), binding constant (K b ), Gibb’s free energy of partition (ΔG p ), and binding (ΔG b ) were investigated by UV–Visible spectrophotometer. The estimation of micellization thermodynamics including entropy (ΔS m ), enthalpy (ΔH m ), and Gibb’s free energy (ΔG m ) were determined conductometrically. The compound showed more interaction with the cationic surfactant as compared to anionic participating surfactant due to comparative electrostatic interactions. The partition coefficient (K x ) in the micellar media of CTAB was significantly higher (4.22 × 107) than SES media (1.33 × 105). The Gibb’s free energies of partition. Binding and micellization were higher in CTAB as compared to SES.

Kinetics of Equilibrium Passive Sampling of Organic Chemicals with Polymers in Diverse Mammalian Tissues.

Equilibrium passive sampling employing polydimethylsiloxane (PDMS) as a sampling phase can be used for the extraction of complex mixtures of organic chemicals from lipid-rich biota. We extended the method to lean tissues and more hydrophilic chemicals by implementing a mass-balance model for partitioning between lipids, proteins, and water in tissues and by accelerating uptake kinetics with a custom-built stirrer that effectively decreased time to equilibrium to less than 8 days even for a homogenized liver tissue with an only 4% lipid content. The partition constants log Klipid/PDMS between tissues and PDMS were derived from measured concentration in PDMS and the mass-balance model and were very similar for 40 neutral chemicals with octanol-water partition constants 1.4 < log Kow < 8.7, that is, log Klipid/PDMS of 1.26 (95% CI, 1.13-1.39) for the adipose tissue, 1.16 (1.00-1.33) for the liver, and 0.58 (0.42-0.73) for the brain. This conversion factor can be applied to interpret chemical analysis and in vitro bioassays after additionally accounting for a small fraction of coextracted lipids of <0.7% of the PDMS weight. PDMS is more widely applicable for passive sampling of mammalian tissues than previously thought, both, in terms of diversity of chemicals and the range of lipid contents of tissues and, therefore, an ideal method for human biomonitoring to be combined with in vitro bioassays.

Mixed-micellar approach for enhanced dye entrapment: A spectroscopic study

The interactional study of two anionic dyes viz. Reactive Blue-250 and Reactive Red-198 in the presence of single cationic surfactant and mixed-surfactant media is reported in this manuscript. To unveil the dye-surfactant interactions, a cationic surfactant Cetyltrimethylammonium bromide (CTAB) and its mixture with a nonionic surfactant Triton X-100 (TX), were used. The interactions were investigated using UV–Visible spectroscopy in sub-micellar, micellar, and post-micellar concentrations. The extent of solubilization in terms of partition constant (Kc), partition coefficient (Kx), binding constant (Kb), Gibbs free energies (ΔGp and ΔGb), and the approximate location of dye molecules in the micelles was assessed from spectroscopic measurements. The mixing of nonionic/cationic surfactants in appropriate amounts enhanced the solubilization of both reactive dyes. The experimental results revealed the spontaneous nature of solubilization and the dye-surfactant aggregates in single and mixed-surfactant media were stable. The synergism of cationic surfactant with nonionic counterpart is favorable to attain deep entrapment in the micelles than the single cationic surfactant. This method may provide inexpensive, highly efficient, and time-saving procedures in the removal of dyes from water resources.

Evaluating the fate of hexabromocyclododecanes in the coastal environment: Fugacity analysis using field data

Abundant use of plastic materials has increased the amount of microplastics (MPs) and related hazardous chemicals in the marine environment. Hexabromocyclododecanes (HBCDs), brominated flame retardants added to expanded polystyrene (EPS), have been detected in biotic and abiotic samples. In this study, the partition constants of HBCDs between plastics and seawater (KPsw) were determined. Fugacities of HBCDs in EPS, seawater, sediment, and mussels were obtained to determine the directions of the diffusive flux. The fugacities in EPS (fEPS) were greater than those in seawater (fsw), sediment (fsed), and mussels (fswmussel-EPS and fmussel-rock) by three orders of magnitude, indicating that EPS plastics are a significant source of HBCDs. The fmussel-rock of α-HBCD in rock mussels was greater than fsw by factors of 1.7, whereas the fmussel-rock of γ-HBCD was smaller than fsw by factors of 16, indicating the bioisomerization from γ-to α-HBCD. The relatively constant concentration ratio of β-HBCD to the total HBCDs indicated that β-HBCD is a sufficient tracer for determining the diffusive flux. The fsed values of HBCDs were greater than fsw by factors of 17–28, implying a probable advective vertical flow of HBCDs from the EPS plastics, which requires further investigation.

Thermodynamic and solubilization properties of a polynuclear copper complex in ionic surfactants media

The solubilization behavior of hexanuclear copper complex, [Cu6(η1 :μ2 -C4H10NO)4(η1 :η1 :μ2 -C5H9O2)4(η1 :μ1 -C5H9O2)2(μ 3-OH)2] (1) (where, C4H10NO = N,N-dimethylethanolamine and C5H9O2 = pivalic acid) ionic micellar media has been explored in this study. The interaction of copper cluster under investigation (1) was experimented with an anionic surfactant (sodium lauryl sulfate; SLS) and a cationic surfactant (cetyltrimethyl ammonium bromide; CTAB). Solubilization was observed in aqueous solutions of ionic surfactants at their pre-micellar, micellar and post-micellar concentrations ranges using UV–Visible spectroscopy and electrical conductivity. The thermodynamic attributes of micellization including standard entropy (ΔSmic ), enthalpy (ΔHmic ) and free energy (ΔGmic ) were estimated from electrical conductivity measurements. The negative values of ΔGmic and ΔHmic indicated the stability of micellization, in addition to the enthalpy and entropy-driven nature of the process. Thermodynamic studies demonstrate increases in the CMC of both surfactants due to incorporation of the copper complex in the micelles. Partitioning and binding parameters were revealed by UV–Vis spectroscopy to quantitatively measure the interaction of the copper cluster with the surfactant in terms of partition constant (Kc ), partition coefficient (Kx ), binding coefficient (Kbind ), and free energies of free energy of partition (ΔGpart ) and binding (ΔGbind ). The presence of cationic CTAB led to greater red-shift in UV–Vis study of 1 as compared to SLS due to stronger ionic interactions. The strong interaction and high solubility have been seen in 1 with CTAB as compared to SLS.

Optimisation of stormwater purification in progressive freeze concentration: Stirring speed and initial concentration

A method has been earnestly studied which is progressive freeze concentration (PFC). In this study, zinc chloride dissolved in distilled water has been used to signify stormwater as its amount is the highest and high toxicity in actual stormwater. Response surface methodology (RSM) was employed to determine the optimum condition of the process. The experiment was run by using the data generated from STATISTICA software with constant coolant temperature and rotation time which is at −8 °C and 15 minutes. The interaction between the process conditions gave significant effects to the effective partition constant (K) and solute recovery (Y). The predicted optimum condition for the system within the experimental ranges would be a stirring speed of 245 rpm and initial concentration of 6.846 mg/L with the best value for K and Y are predicted at 0.3357 and 0.5856, respectively. Shortage of clean water supply, flooding and excessive stormwater runoff became a concern towards the human being as these problems cannot be simply solved by building a specific pipeline system. Thus, an excellent approach and process needed to manage and purify the stormwater as well as transform it as one of the clean water resources.

Comparing the interaction of the antibiotic levofloxacin with zwitterionic and anionic membranes: Calorimetry, fluorescence, and spin label studies

The present work compares the interaction of the antibiotic levofloxacin (LVX) with zwitterionic and anionic liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DPPG), respectively. By using differential scanning calorimetry (DSC), and with spin labels incorporated into liposomes at two different depths of the bilayers, we investigated the changes induced on the membrane by increasing concentrations of LVX. Further information was obtained using intrinsic LVX fluorescence. Under the conditions used here, all techniques evinced that LVX has little affinity for DPPC zwitterionic membrane. Opposite to that, LVX exhibits a considerable affinity for anionic bilayers, with membrane partition constants Kp = (3.3 ± 0.5) × 102 and (4.5 ± 0.3) × 102, for gel and fluid DPPG membranes, respectively. On binding to DPPG, LVX seems to give rise to the coexistence of LVX -rich and -poor domains on DPPG membranes, as detected by DSC. At the highest LVX concentration used (20 mol%), DSC trace shows an increase in the cooperativity of DPPG gel-fluid transition, also detected by spin labels as an increase in the bilayer packing. Moreover, LVX does not induce pore formation in either DPPG or POPG vesicles. Considering the possible relevance of LVX-membrane interaction for the biological and toxicological action of the antibiotic, the findings discussed here certainly contribute to a better understanding of its action, and the planning of new drugs.

Purification of Anthocyanin Extract from Roselle by Progressive Freezing: Effect of coolant temperature and stirring rate

This study presents the process of progressive freezing as a potentially new and alternative approach for the purification of anthocyanin extract to replace the conventional methods of the aqueous two-phase system (ATPS) and adsorption. Specifically, anthocyanins extract was obtained from the roselle plant or also known as red hibiscus. It is essential to purify the anthocyanins extract before it can be used in various applications to remove the by-products of the extract i.e. free sugar, sugar alcohol, organic acids, amino acids, and proteins. Before the purification step, the anthocyanin was first extracted from the roselle flower through a maceration process. The total amount of anthocyanins in the extract was measured by a UV-VIS spectrophotometer. The extract was then concentrated via the progressive freezing process and the influence of cooling temperature and rate of stirring were analysed vis a vis the process performance, which was represented by the effective partition constant (K) and concentration efficiency. The highest concentration efficiency of 55% and the smallest K value of 0.3 were found at the coolant temperature of -14 °C and 250 rpm rate of stirring. It was also found that lower coolant temperature and higher stirring rate produced a K value that was smaller and superior efficiency.

Bioaccumulation of Heavy Metals in Perennial Wetland Vegetation Components from a Sector of the Arges River

The potential bioaccumulation of hazardous transitional heavy metals in components of the aquatic environment (such as water column, sedimentary matter, plants) constitutes one of the concerns in environmental protection engineering. This experimental investigative study used systematic measurements of the presence of selected heavy metals (cadmium, chromium, copper, lead, nickel and zinc) in components of the aquatic environment to give an indication of their availability and their potential bioaccumulation in the perennial wetland plants. Through environmental quality data processing, this study allowed both the assessment of interphase partitioning constants of these metals throughout the analyzed aquatic environment and the estimation of their cumulative toxicity coëfficiënt. The data analysis highlighted the different potential degrees of dangers caused by metals as pollutants and the synergistic way in which they act on the aquatic environment.

The Interaction of Glymes with Surfactant Micelles

AbstractThe critical micelle concentrations (CMC) values and counterion dissociation (α values) have been determined for a number of mixed micellar systems consisting of two typical ionic surfactants and glycol ethers (glymes) as cosurfactants, namely diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Conductance experiments were used to determine the CMC and α values of the mixed micelles as a function of glyme concentration in the aqueous mixed solvent. Favorable interactions between sodium dodecyl sulfate micelles and glyme cosurfactants were deduced from the decreases in the CMC values and the large increase in the α values of these systems as a function of increasing glyme concentration in the mixed solvents. In contrast to the anionic surfactant/glyme systems, in general, there appeared to be little favorable interactions between the surfactant and glymes when micelles of the cationic surfactant dodecyltrimethylammonium bromide were formed in water/glyme solvent systems containing an increasing amount of the glymes. The interaction of glymes with the surfactant micelles was examined closely via 13C nuclear magnetic resonance (NMR) chemical shifts for both surfactant and glyme carbons; these chemical shifts changes were interpreted in terms of the distribution and the localization of the glymes in the aggregates. Finally, partition constants, determined from two‐dimensional diffusion‐oriented spectroscopy (2D‐DOSY) experiments, were used to calculate thermodynamic quantities of transfer of the glymes between the bulk phase and the self‐assembled aggregates. All these results are interpreted in terms of the key contributions that both the glyme ethoxylated groups and alkyl endgroups make to the hydrophobic interactions.

Determination of physicochemical properties of small molecules by reversed-phase liquid chromatography.

The physicochemical properties of small molecules that can be determined by retention measurements in reversed-phase liquid chromatography include solvent-based properties inferred from equilibrium processes occurring predominantly in the mobile phase and sorption properties for materials which can be used as stationary phases inferred from solute-stationary phase interactions. In addition, physicochemical properties can be estimated from correlation models based on surrogate chromatographic systems with a similar capability for intermolecular interactions to the chemical or biological system. Examples of properties determined by direct methods include molecular descriptors (solvation parameter model), acid dissociation constants, formation constants, and surface properties of solids determined by inverse liquid chromatography. Examples of properties estimated by indirect methods include hydrophobicity, lipophilicity, n-octanol-water partition constant, soil-water sorption constant, non-specific toxicity to fish and microorganisms, and permeation coefficients for the blood-brain and skin-water barriers. Since all approaches depend on an accurate measurement of chromatographic retention parameters typical operational and mechanistic problems are discussed from the perspective of data quality. Fundamentally the accuracy of direct methods is limited by stationary phase heterogeneity and indirect methods by the limited number of suitable surrogate chromatographic models.

Synthesis, In Vitro Antioxidant Properties and Distribution of a New Cyanothiophene-Based Phenolic Compound in Olive Oil-In-Water Emulsions.

We synthesized and determined the antioxidant activity and distribution of a new cyanothiophene-based compound, N-(3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophen-2-yl)-3,5-dihydroxybenzamide (SIM-53B), in intact stripped olive oil-in-water emulsion. The in vitro antioxidant properties of SIM-53B were evaluated and compared to those for Trolox and resveratrol. Addition of an emulsifier (Tween 20) creates a narrow region, the aqueous–oil interface, and the distribution of SIM-53B can be described by two partition constants: PWI (between aqueous/interfacial regions) and POI (between oil/interfacial regions). The effects of emulsifier concentration expressed in terms of the volume fraction, ΦI, and O/W ratio were also evaluated on its distribution. SIM-53B is predominantly distributed (>90%) in the interfacial region of 1:9 (O/W) olive oil-in-water emulsions at the lowest emulsifier volume fraction (ΦI = 0.005) and only a small fraction is located in the aqueous (<5%) and the oil (<5%) regions. Besides, the concentration of SIM-53B in the interfacial region of the emulsions is ~170–190-fold higher than the stoichiometric concentration, emphasizing the compartmentalization effects. Results suggest that the emulsifier volume fraction is a key parameter that may modulate significantly its concentration in the interface. Our study suggests that cyanothiophene-based compounds may be interesting additives for potential lipid protection in biomembranes or other lipid-based systems.

Reverse micelle chromatography for evaluation of partition of organic solutes to micellar pseudophases

The evaluation of solute partition from an organic solvent to a reverse micelle (RM) is critical for designing effective reaction systems and for synthesizing functional materials using the nano water-phase in the RM. Although spectroscopic methods have been extensively employed for determining the partition constants of solutes in the RM systems, their applications are limited to the case, in which the background absorption is low and the spectroscopic features of the solute are effectively varied by its partitioning to RMs. This paper proposes a novel chromatographic method to overcome this limitation of conventional methods. In the present system, a size-exclusion chromatographic column is used with RM solutions as mobile phases. The RM is excluded from the stationary phase and, therefore, is eluted first. A solute is eluted with the retention volume determined by its affinities to the stationary phase and the RM. The elution volumes of a solute measured by varying the concentrations of RM in the mobile phase allow us to determine its partition constant to the RM. The partition of phenols in hexadecyltrimethylammonium chloride and bromide RMs in chloroform is successfully evaluated without interferences from the UV-absorption of the media. The larger partition constant is confirmed for a smaller water/surfactant molar ratio (w) and for chloride than bromide as the RM counterion. This suggests that the nature of water is more strongly influenced by confinement in the RM cores for smaller w and the chloride counterion because water molecules are strongly imbibed by the interface.

Multiscale Modeling of Human Skin Oil-Induced Indoor Air Chemistry: Combining Kinetic Models and Molecular Dynamics.

We performed classical molecular dynamics simulations to quantify and understand the nonreactive, dermal uptake of volatile organic compounds formed during the ozonolysis of human skin oils. Our results include surface accommodation coefficients, partitioning constants, bulk diffusivities, and desorption lifetimes. These parameters were used to improve and to constrain the kinetic multilayer model of the surface and bulk chemistry of skin (KM-SUB-Skin). By comparing common outputs (bulk accommodation coefficients), we cross-validate the two approaches and, thus, increase the level of trust in their predictions relevant to indoor air chemistry.