Partition coefficient

Last updated

In the physical sciences, a partition coefficient (P) or distribution coefficient (D) is the ratio of concentrations of a compound in a mixture of two immiscible solvents at equilibrium. This ratio is therefore a comparison of the solubilities of the solute in these two liquids. The partition coefficient generally refers to the concentration ratio of un-ionized species of compound, whereas the distribution coefficient refers to the concentration ratio of all species of the compound (ionized plus un-ionized). [1]

Contents

In the chemical and pharmaceutical sciences, both phases usually are solvents. [2] Most commonly, one of the solvents is water, while the second is hydrophobic, such as 1-octanol. [3] Hence the partition coefficient measures how hydrophilic ("water-loving") or hydrophobic ("water-fearing") a chemical substance is. Partition coefficients are useful in estimating the distribution of drugs within the body. Hydrophobic drugs with high octanol-water partition coefficients are mainly distributed to hydrophobic areas such as lipid bilayers of cells. Conversely, hydrophilic drugs (low octanol/water partition coefficients) are found primarily in aqueous regions such as blood serum. [4]

If one of the solvents is a gas and the other a liquid, a gas/liquid partition coefficient can be determined. For example, the blood/gas partition coefficient of a general anesthetic measures how easily the anesthetic passes from gas to blood. [5] Partition coefficients can also be defined when one of the phases is solid, for instance, when one phase is a molten metal and the second is a solid metal, [6] or when both phases are solids. [7] The partitioning of a substance into a solid results in a solid solution.

Partition coefficients can be measured experimentally in various ways (by shake-flask, HPLC, etc.) or estimated by calculation based on a variety of methods (fragment-based, atom-based, etc.).

If a substance is present as several chemical species in the partition system due to association or dissociation, each species is assigned its own Kow value. A related value, D, does not distinguish between different species, only indicating the concentration ratio of the substance between the two phases.[ citation needed ]

Nomenclature

Despite formal recommendation to the contrary, the term partition coefficient remains the predominantly used term in the scientific literature. [8] [ additional citation(s) needed ]

In contrast, the IUPAC recommends that the title term no longer be used, rather, that it be replaced with more specific terms. [9] For example, partition constant, defined as

where KD is the process equilibrium constant, [A] represents the concentration of solute A being tested, and "org" and "aq" refer to the organic and aqueous phases respectively. The IUPAC further recommends "partition ratio" for cases where transfer activity coefficients can be determined, and "distribution ratio" for the ratio of total analytical concentrations of a solute between phases, regardless of chemical form. [9]

Partition coefficient and log P

An equilibrium of dissolved substance distributed between a hydrophobic phase and a hydrophilic phase is established in special glassware such as this separatory funnel that allows shaking and sampling, from which the log P is determined. Here, the green substance has a greater solubility in the lower layer than in the upper layer. Separatory funnel with oil and colored water.jpg
An equilibrium of dissolved substance distributed between a hydrophobic phase and a hydrophilic phase is established in special glassware such as this separatory funnel that allows shaking and sampling, from which the log P is determined. Here, the green substance has a greater solubility in the lower layer than in the upper layer.

The partition coefficient, abbreviated P, is defined as a particular ratio of the concentrations of a solute between the two solvents (a biphase of liquid phases), specifically for un-ionized solutes, and the logarithm of the ratio is thus log P. [10] : 275ff  When one of the solvents is water and the other is a non-polar solvent, then the log P value is a measure of lipophilicity or hydrophobicity. [10] : 275ff  [11] : 6  The defined precedent is for the lipophilic and hydrophilic phase types to always be in the numerator and denominator respectively; for example, in a biphasic system of n-octanol (hereafter simply "octanol") and water:

To a first approximation, the non-polar phase in such experiments is usually dominated by the un-ionized form of the solute, which is electrically neutral, though this may not be true for the aqueous phase. To measure the partition coefficient of ionizable solutes, the pH of the aqueous phase is adjusted such that the predominant form of the compound in solution is the un-ionized, or its measurement at another pH of interest requires consideration of all species, un-ionized and ionized (see following).

A corresponding partition coefficient for ionizable compounds, abbreviated log PI, is derived for cases where there are dominant ionized forms of the molecule, such that one must consider partition of all forms, ionized and un-ionized, between the two phases (as well as the interaction of the two equilibria, partition and ionization). [11] : 57ff, 69f  [12] M is used to indicate the number of ionized forms; for the I-th form (I = 1, 2, ... , M) the logarithm of the corresponding partition coefficient, , is defined in the same manner as for the un-ionized form. For instance, for an octanol–water partition, it is

To distinguish between this and the standard, un-ionized, partition coefficient, the un-ionized is often assigned the symbol log P0, such that the indexed expression for ionized solutes becomes simply an extension of this, into the range of values I > 0.[ citation needed ]

Distribution coefficient and log D

The distribution coefficient, log D, is the ratio of the sum of the concentrations of all forms of the compound (ionized plus un-ionized) in each of the two phases, one essentially always aqueous; as such, it depends on the pH of the aqueous phase, and log D = log P for non-ionizable compounds at any pH. [13] [14] For measurements of distribution coefficients, the pH of the aqueous phase is buffered to a specific value such that the pH is not significantly perturbed by the introduction of the compound. The value of each log D is then determined as the logarithm of a ratio—of the sum of the experimentally measured concentrations of the solute's various forms in one solvent, to the sum of such concentrations of its forms in the other solvent; it can be expressed as [10] : 275–8 

In the above formula, the superscripts "ionized" each indicate the sum of concentrations of all ionized species in their respective phases. In addition, since log D is pH-dependent, the pH at which the log D was measured must be specified. In areas such as drug discovery—areas involving partition phenomena in biological systems such as the human body—the log D at the physiologic pH = 7.4 is of particular interest.[ citation needed ]

It is often convenient to express the log D in terms of PI, defined above (which includes P0 as state I = 0), thus covering both un-ionized and ionized species. [12] For example, in octanol–water:

which sums the individual partition coefficients (not their logarithms), and where indicates the pH-dependent mole fraction of the I-th form (of the solute) in the aqueous phase, and other variables are defined as previously. [12] [ verification needed ]

Example partition coefficient data

The values for the octanol-water system in the following table are from the Dortmund Data Bank. [15] [ better source needed ] They are sorted by the partition coefficient, smallest to largest (acetamide being hydrophilic, and 2,2',4,4',5-pentachlorobiphenyl lipophilic), and are presented with the temperature at which they were measured (which impacts the values).[ citation needed ]

Componentlog POWT (°C)
Acetamide [16] −1.1625
Methanol [17] −0.8119
Formic acid [18] −0.4125
Diethyl ether [17] 0.8320
p-Dichlorobenzene [19] 3.3725
Hexamethylbenzene [19] 4.6125
2,2',4,4',5-Pentachlorobiphenyl [20] 6.41Ambient

Values for other compounds may be found in a variety of available reviews and monographs. [2] : 551ff  [21] [ page needed ] [22] : 1121ff  [23] [ page needed ] [24] Critical discussions of the challenges of measurement of log P and related computation of its estimated values (see below) appear in several reviews. [11] [24]

Applications

Pharmacology

A drug's distribution coefficient strongly affects how easily the drug can reach its intended target in the body, how strong an effect it will have once it reaches its target, and how long it will remain in the body in an active form. [25] Hence, the log P of a molecule is one criterion used in decision-making by medicinal chemists in pre-clinical drug discovery, for example, in the assessment of druglikeness of drug candidates. [26] Likewise, it is used to calculate lipophilic efficiency in evaluating the quality of research compounds, where the efficiency for a compound is defined as its potency, via measured values of pIC50 or pEC50, minus its value of log P. [27]

Drug permeability in brain capillaries (y axis) as a function of partition coefficient (x axis) Log P examples 01.png
Drug permeability in brain capillaries (y axis) as a function of partition coefficient (x axis)

Pharmacokinetics

In the context of pharmacokinetics (how the body absorbs, metabolizes, and excretes a drug), the distribution coefficient has a strong influence on ADME properties of the drug. Hence the hydrophobicity of a compound (as measured by its distribution coefficient) is a major determinant of how drug-like it is. More specifically, for a drug to be orally absorbed, it normally must first pass through lipid bilayers in the intestinal epithelium (a process known as transcellular transport). For efficient transport, the drug must be hydrophobic enough to partition into the lipid bilayer, but not so hydrophobic, that once it is in the bilayer, it will not partition out again. [29] [30] Likewise, hydrophobicity plays a major role in determining where drugs are distributed within the body after absorption and, as a consequence, in how rapidly they are metabolized and excreted.

Pharmacodynamics

In the context of pharmacodynamics (how the drug affects the body), the hydrophobic effect is the major driving force for the binding of drugs to their receptor targets. [31] [32] On the other hand, hydrophobic drugs tend to be more toxic because they, in general, are retained longer, have a wider distribution within the body (e.g., intracellular), are somewhat less selective in their binding to proteins, and finally are often extensively metabolized. In some cases the metabolites may be chemically reactive. Hence it is advisable to make the drug as hydrophilic as possible while it still retains adequate binding affinity to the therapeutic protein target. [33] For cases where a drug reaches its target locations through passive mechanisms (i.e., diffusion through membranes), the ideal distribution coefficient for the drug is typically intermediate in value (neither too lipophilic, nor too hydrophilic); in cases where molecules reach their targets otherwise, no such generalization applies.[ citation needed ]

Environmental science

The hydrophobicity of a compound can give scientists an indication of how easily a compound might be taken up in groundwater to pollute waterways, and its toxicity to animals and aquatic life. [34] Partition coefficient can also be used to predict the mobility of radionuclides in groundwater. [35] In the field of hydrogeology, the octanol–water partition coefficient Kow is used to predict and model the migration of dissolved hydrophobic organic compounds in soil and groundwater.

Agrochemical research

Hydrophobic insecticides and herbicides tend to be more active. Hydrophobic agrochemicals in general have longer half-lives and therefore display increased risk of adverse environmental impact. [36]

Metallurgy

In metallurgy, the partition coefficient is an important factor in determining how different impurities are distributed between molten and solidified metal. It is a critical parameter for purification using zone melting, and determines how effectively an impurity can be removed using directional solidification, described by the Scheil equation. [6]

Consumer product development

Many other industries take into account distribution coefficients, for example in the formulation of make-up, topical ointments, dyes, hair colors and many other consumer products. [37]

Measurement

A number of methods of measuring distribution coefficients have been developed, including the shake-flask, separating funnel method, reverse-phase HPLC, and pH-metric techniques. [10] : 280 

Separating-funnel method

In this method the solid particles present into the two immiscible liquids can be easily separated by suspending those solid particles directly into these immiscible or somewhat miscible liquids.

Shake flask-type

The classical and most reliable method of log P determination is the shake-flask method, which consists of dissolving some of the solute in question in a volume of octanol and water, then measuring the concentration of the solute in each solvent. [38] [39] The most common method of measuring the distribution of the solute is by UV/VIS spectroscopy. [38]

HPLC-based

A faster method of log P determination makes use of high-performance liquid chromatography. The log P of a solute can be determined by correlating its retention time with similar compounds with known log P values. [40]

An advantage of this method is that it is fast (5–20 minutes per sample). However, since the value of log P is determined by linear regression, several compounds with similar structures must have known log P values, and extrapolation from one chemical class to another—applying a regression equation derived from one chemical class to a second one—may not be reliable, since each chemical classes will have its characteristic regression parameters.[ citation needed ]

pH-metric

The pH-metric set of techniques determine lipophilicity pH profiles directly from a single acid-base titration in a two-phase water–organic-solvent system. [10] : 280–4  Hence, a single experiment can be used to measure the logarithms of the partition coefficient (log P) giving the distribution of molecules that are primarily neutral in charge, as well as the distribution coefficient (log D) of all forms of the molecule over a pH range, e.g., between 2 and 12. The method does, however, require the separate determination of the pKa value(s) of the substance.

Electrochemical

Polarized liquid interfaces have been used to examine the thermodynamics and kinetics of the transfer of charged species from one phase to another. Two main methods exist. The first is ITIES, "interfaces between two immiscible electrolyte solutions". [41] The second is droplet experiments. [42] Here a reaction at a triple interface between a conductive solid, droplets of a redox active liquid phase and an electrolyte solution have been used to determine the energy required to transfer a charged species across the interface. [43]

Single-cell approach

There are attempts to provide partition coefficients for drugs at a single-cell level. [44] [45] This strategy requires methods for the determination of concentrations in individual cells, i.e., with Fluorescence correlation spectroscopy or quantitative Image analysis. Partition coefficient at a single-cell level provides information on cellular uptake mechanism. [45]

Prediction

There are many situations where prediction of partition coefficients prior to experimental measurement is useful. For example, tens of thousands of industrially manufactured chemicals are in common use, but only a small fraction have undergone rigorous toxicological evaluation. Hence there is a need to prioritize the remainder for testing. QSAR equations, which in turn are based on calculated partition coefficients, can be used to provide toxicity estimates. [46] [47] Calculated partition coefficients are also widely used in drug discovery to optimize screening libraries [48] [49] and to predict druglikeness of designed drug candidates before they are synthesized. [50] As discussed in more detail below, estimates of partition coefficients can be made using a variety of methods, including fragment-based, atom-based, and knowledge-based that rely solely on knowledge of the structure of the chemical. Other prediction methods rely on other experimental measurements such as solubility. The methods also differ in accuracy and whether they can be applied to all molecules, or only ones similar to molecules already studied.

Atom-based

Standard approaches of this type, using atomic contributions, have been named by those formulating them with a prefix letter: AlogP, [51] XlogP, [52] MlogP, [53] etc. A conventional method for predicting log P through this type of method is to parameterize the distribution coefficient contributions of various atoms to the overall molecular partition coefficient, which produces a parametric model. This parametric model can be estimated using constrained least-squares estimation, using a training set of compounds with experimentally measured partition coefficients. [51] [53] [54] In order to get reasonable correlations, the most common elements contained in drugs (hydrogen, carbon, oxygen, sulfur, nitrogen, and halogens) are divided into several different atom types depending on the environment of the atom within the molecule. While this method is generally the least accurate, the advantage is that it is the most general, being able to provide at least a rough estimate for a wide variety of molecules. [53]

Fragment-based

The most common of these uses a group contribution method and is termed cLogP. It has been shown that the log P of a compound can be determined by the sum of its non-overlapping molecular fragments (defined as one or more atoms covalently bound to each other within the molecule). Fragmentary log P values have been determined in a statistical method analogous to the atomic methods (least-squares fitting to a training set). In addition, Hammett-type corrections are included to account of electronic and steric effects. This method in general gives better results than atomic-based methods, but cannot be used to predict partition coefficients for molecules containing unusual functional groups for which the method has not yet been parameterized (most likely because of the lack of experimental data for molecules containing such functional groups). [21] : 125ff  [23] : 1–193 

Knowledge-based

A typical data-mining-based prediction uses support-vector machines, [55] decision trees, or neural networks. [56] This method is usually very successful for calculating log P values when used with compounds that have similar chemical structures and known log P values. Molecule mining approaches apply a similarity-matrix-based prediction or an automatic fragmentation scheme into molecular substructures. Furthermore, there exist also approaches using maximum common subgraph searches or molecule kernels.

Log D from log P and pKa

For cases where the molecule is un-ionized: [13] [14]

For other cases, estimation of log D at a given pH, from log P and the known mole fraction of the un-ionized form, , in the case where partition of ionized forms into non-polar phase can be neglected, can be formulated as [13] [14]

The following approximate expressions are valid only for monoprotic acids and bases: [13] [14]

Further approximations for when the compound is largely ionized: [13] [14]

For prediction of pKa, which in turn can be used to estimate log D, Hammett type equations have frequently been applied. [57] [58]

Log P from log S

If the solubility, S, of an organic compound is known or predicted in both water and 1-octanol, then log P can be estimated as [46] [59]

There are a variety of approaches to predict solubilities, and so log S. [60] [61]

Octanol-water partition coefficient

The partition coefficient between n-Octanol and water is known as the n-octanol-water partition coefficient, or Kow. [62] It is also frequently referred to by the symbol P, especially in the English literature. It is also known as n-octanol-water partition ratio. [63] [64] [65]

Kow, being a type of partition coefficient, serves as a measure of the relationship between lipophilicity (fat solubility) and hydrophilicity (water solubility) of a substance. The value is greater than one if a substance is more soluble in fat-like solvents such as n-octanol, and less than one if it is more soluble in water.[ citation needed ]

Example values

Values for log Kow typically range between -3 (very hydrophilic) and +10 (extremely lipophilic/hydrophobic). [66]

The values listed here [67] are sorted by the partition coefficient. Acetamide is hydrophilic, and 2,2′,4,4′,5-Pentachlorobiphenyl is lipophilic.

Substancelog KOWTReference
Acetamide −1.15525 °C
Methanol −0.82419 °C
Formic acid −0.41325 °C
Diethyl ether 0.83320 °C
p-Dichlorobenzene 3.37025 °C
Hexamethylbenzene 4.61025 °C
2,2′,4,4′,5-Pentachlorobiphenyl 6.410Ambient

See also

Related Research Articles

<span class="mw-page-title-main">Solvation</span> Association of molecules of a solvent with molecules or ions of a solute

Solvation describes the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the solute, including solubility, reactivity, and color, as well as influencing the properties of the solvent such as its viscosity and density. If the attractive forces between the solvent and solute particles are greater than the attractive forces holding the solute particles together, the solvent particles pull the solute particles apart and surround them. The surrounded solute particles then move away from the solid solute and out into the solution. Ions are surrounded by a concentric shell of solvent. Solvation is the process of reorganizing solvent and solute molecules into solvation complexes and involves bond formation, hydrogen bonding, and van der Waals forces. Solvation of a solute by water is called hydration.

In chemistry, an acid dissociation constant is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction

<span class="mw-page-title-main">Solubility</span> Capacity of a substance to dissolve in a homogeneous way

In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.

Solubility equilibrium is a type of dynamic equilibrium that exists when a chemical compound in the solid state is in chemical equilibrium with a solution of that compound. The solid may dissolve unchanged, with dissociation, or with chemical reaction with another constituent of the solution, such as acid or alkali. Each solubility equilibrium is characterized by a temperature-dependent solubility product which functions like an equilibrium constant. Solubility equilibria are important in pharmaceutical, environmental and many other scenarios.

<span class="mw-page-title-main">Lipinski's rule of five</span> Rule of thumb to predict if a chemical compound is likely to be an orally active drug

Lipinski's rule of five, also known as Pfizer's rule of five or simply the rule of five (RO5), is a rule of thumb to evaluate druglikeness or determine if a chemical compound with a certain pharmacological or biological activity has chemical properties and physical properties that would likely make it an orally active drug in humans. The rule was formulated by Christopher A. Lipinski in 1997, based on the observation that most orally administered drugs are relatively small and moderately lipophilic molecules.

<span class="mw-page-title-main">Ion chromatography</span> Separates ions and polar molecules

Ion chromatography is a form of chromatography that separates ions and ionizable polar molecules based on their affinity to the ion exchanger. It works on almost any kind of charged molecule—including small inorganic anions, large proteins, small nucleotides, and amino acids. However, ion chromatography must be done in conditions that are one pH unit away from the isoelectric point of a protein.

In physical organic chemistry, a free-energy relationship or Gibbs energy relation relates the logarithm of a reaction rate constant or equilibrium constant for one series of chemical reactions with the logarithm of the rate or equilibrium constant for a related series of reactions. Free energy relationships establish the extent at which bond formation and breakage happen in the transition state of a reaction, and in combination with kinetic isotope experiments a reaction mechanism can be determined. Free energy relationships are often used to calculate equilibrium constants since they are experimentally difficult to determine.

<span class="mw-page-title-main">Liquid–liquid extraction</span> Method to separate compounds or metal complexes

Liquid–liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds or metal complexes, based on their relative solubilities in two different immiscible liquids, usually water (polar) and an organic solvent (non-polar). There is a net transfer of one or more species from one liquid into another liquid phase, generally from aqueous to organic. The transfer is driven by chemical potential, i.e. once the transfer is complete, the overall system of chemical components that make up the solutes and the solvents are in a more stable configuration. The solvent that is enriched in solute(s) is called extract. The feed solution that is depleted in solute(s) is called the raffinate. Liquid–liquid extraction is a basic technique in chemical laboratories, where it is performed using a variety of apparatus, from separatory funnels to countercurrent distribution equipment called as mixer settlers. This type of process is commonly performed after a chemical reaction as part of the work-up, often including an acidic work-up.

Reversed-phase liquid chromatography (RP-LC) is a mode of liquid chromatography in which non-polar stationary phase and polar mobile phases are used for the separation of organic compounds. The vast majority of separations and analyses using high-performance liquid chromatography (HPLC) in recent years are done using the reversed phase mode. In the reversed phase mode, the sample components are retained in the system the more hydrophobic they are.

Implicit solvation is a method to represent solvent as a continuous medium instead of individual “explicit” solvent molecules, most often used in molecular dynamics simulations and in other applications of molecular mechanics. The method is often applied to estimate free energy of solute-solvent interactions in structural and chemical processes, such as folding or conformational transitions of proteins, DNA, RNA, and polysaccharides, association of biological macromolecules with ligands, or transport of drugs across biological membranes.

A hydrotrope is a compound that solubilizes hydrophobic compounds in aqueous solutions by means other than micellar solubilization. Typically, hydrotropes consist of a hydrophilic part and a hydrophobic part, but the hydrophobic part is generally too small to cause spontaneous self-aggregation. Hydrotropes do not have a critical concentration above which self-aggregation spontaneously starts to occur. Instead, some hydrotropes aggregate in a step-wise self-aggregation process, gradually increasing aggregation size. However, many hydrotropes do not seem to self-aggregate at all, unless a solubilizate has been added. Examples of hydrotropes include urea, tosylate, cumenesulfonate and xylenesulfonate.

Micellar liquid chromatography (MLC) is a form of reversed phase liquid chromatography that uses an aqueous micellar solutions as the mobile phase.

Druglikeness is a qualitative concept used in drug design for how "druglike" a substance is with respect to factors like bioavailability. It is estimated from the molecular structure before the substance is even synthesized and tested. A druglike molecule has properties such as:

Hydrophobicity scales are values that define the relative hydrophobicity or hydrophilicity of amino acid residues. The more positive the value, the more hydrophobic are the amino acids located in that region of the protein. These scales are commonly used to predict the transmembrane alpha-helices of membrane proteins. When consecutively measuring amino acids of a protein, changes in value indicate attraction of specific protein regions towards the hydrophobic region inside lipid bilayer.

In aquatic toxicology, bioconcentration is the accumulation of a water-borne chemical substance in an organism exposed to the water.

This page provides supplementary data and solvent coefficients for linear free-energy relationships.

<span class="mw-page-title-main">1-Octanol</span> Chemical compound

1-Octanol, also known as octan-1-ol, is the organic compound with the molecular formula CH3(CH2)7OH. It is a fatty alcohol. Many other isomers are also known generically as octanols. 1-Octanol is manufactured for the synthesis of esters for use in perfumes and flavorings. It has a pungent odor. Esters of octanol, such as octyl acetate, occur as components of essential oils. It is used to evaluate the lipophilicity of pharmaceutical products.

<span class="mw-page-title-main">Cosolvent</span>

In chemistry, cosolvents are substances added to a primary solvent in small amounts to increase the solubility of a poorly-soluble compound. Their use is most prevalent in chemical and biological research relating to pharmaceuticals and food science, where alcohols are frequently used as cosolvents in water to dissolve hydrophobic molecules during extraction, screening, and formulation. Cosolvents find applications also in environmental chemistry and are known as effective countermeasures against pollutant non-aqueous phase liquids, as well as in the production of functional energy materials and synthesis of biodiesel.

The n-octanol-water partition coefficient,Kow is a partition coefficient for the two-phase system consisting of n-octanol and water. Kow is also frequently referred to by the symbol P, especially in the English literature. It is also called n-octanol-water partition ratio.

Klara Valko is a scientist, consultant, academic and author. She is the director of Bio-Mimetic Chromatography as well as an honorary professor at University College London School of Pharmacy.

References

  1. ↑ Kwon Y (2001). "4.2.4: Partition and Distribution Coefficients". Handbook of Essential Pharmacokinetics, Pharmacodynamics and Drug Metabolism for Industrial Scientists. New York: Kluwer Academic/Plenum Publishers. p. 44. ISBN   978-1-4757-8693-4.
  2. 1 2 Leo A, Hansch C, Elkins D (1971). "Partition coefficients and their uses". Chem. Rev. 71 (6): 525–616. doi:10.1021/cr60274a001.
  3. ↑ Sangster J (1997). Octanol–Water Partition Coefficients: Fundamentals and Physical Chemistry. Wiley Series in Solution Chemistry. Vol. 2. Chichester: John Wiley & Sons Ltd. p. 178. ISBN   978-0-471-97397-3.
  4. ↑ Shargel L, Susanna WP, Yu AB (2012). "Chapter 10: Physiological Drug Distribution and Protein Binding". Applied Biopharmaceutics & Pharmacokinetics (6th ed.). New York: McGraw-Hill Medical. p. 211. ISBN   978-0-07-160393-5.
  5. ↑ Golan DE, Tashjian AH, Armstrong EJ, Armstrong AP (2008). "Chapter 15: General Anesthetic Pharmacology". Principles of Pharmacology: The Pathophysiologic Basis of Drug Therapy (2nd ed.). Philadelphia, Pa.: Lippincott Williams & Wilkins. p. 243. ISBN   978-0-7817-8355-2.
  6. 1 2 Stallman RE, Ngan AH (2014). "Chapter 3: Solidification". Modern Physical Metallurgy (8th ed.). Amsterdam: Elsevier/Butterworth-Heinemann. pp. 93–120, esp. 106ff. ISBN   978-0-08-098204-5.
  7. ↑ Machlin ES (2007). "Chapter 3: Free Energy and Phase Diagrams". An Introduction to Aspects of Thermodynamics and Kinetics Relevant to Materials Science (3rd ed.). Amsterdam: Elsevier. p. 98. ISBN   978-0-08-054968-2. Solid–solid equilibria equivalent to the solid–liquid case
  8. ↑ McAuley W (2013). "Hydrophobicity and Partitioning". In Denton P, Rostron C (eds.). Pharmaceutics: The Science of Medicine Design. OUP Oxford. p. 129. ISBN   978-0-19-965531-1.
  9. 1 2 Wilkinson AM, McNaught AD (1997). "Partition Coefficient". In Miloslav N, Jirát J, Košata B, Jenkins A, McNaught A (eds.). Compendium of Chemical Terminology: IUPAC Recommendations. Oxford: Blackwell Science. doi:10.1351/goldbook. ISBN   978-0-86542-684-9.
  10. 1 2 3 4 5 Comer J, Tam K (2001). "Lipophilicity Profiles: Theory and Measurement". In Testa B, van de Waterbed H, Folkers G, Guy R, Comer J, Tam K (eds.). Pharmacokinetic Optimization in Drug Research: Biological, Physicochemical, and Computational Strategies. Weinheim: Wiley-VCH. pp. 275–304. doi:10.1002/9783906390437.ch17. ISBN   978-3-906390-22-2.
  11. 1 2 3 Martin YC (2010). "Chapter 4: The Hydrophobic Properties of Molecules". Quantitative Drug Design: A critical introduction (2nd ed.). Boca Raton: CRC Press/Taylor & Francis. pp.  66–73. ISBN   978-1-4200-7099-6.
  12. 1 2 3 Pagliara A, Carrupt PA, Caron G, Gaillard P, Testa B (1997). "Lipophilicity Profiles of Ampholytes". Chemical Reviews. 97 (8): 3385–3400. doi:10.1021/cr9601019. PMID   11851494.
  13. 1 2 3 4 5 Scherrer RA, Howard SM (January 1977). "Use of distribution coefficients in quantitative structure-activity relationships". Journal of Medicinal Chemistry. 20 (1): 53–8. doi:10.1021/jm00211a010. PMID   13215.
  14. 1 2 3 4 5 Manners CN, Payling DW, Smith DA (March 1988). "Distribution coefficient, a convenient term for the relation of predictable physico-chemical properties to metabolic processes". Xenobiotica; the Fate of Foreign Compounds in Biological Systems. 18 (3): 331–50. doi:10.3109/00498258809041669. PMID   3289270.
  15. ↑ "Octanol–Water Partition Coefficients". ddbst.com. Retrieved 19 March 2016.
  16. ↑ Wolfenden R (January 1978). "Interaction of the peptide bond with solvent water: a vapor phase analysis". (primary). Biochemistry. 17 (1): 201–4. doi:10.1021/bi00594a030. PMID   618544.
  17. 1 2 Collander R, Lindholm M, Haug CM, Stene J, Sörensen NA (1951). "The partition of organic compounds. between higher alcohols and water" (PDF). Acta Chem. Scand. 5: 774–780. doi: 10.3891/acta.chem.scand.05-0774 .
  18. ↑ Whitehead KE, Geankoplis CJ (1955). "Separation of Formic and Sulfuric Acids by Extraction". Ind. Eng. Chem. 47 (10): 2114–2122. doi:10.1021/ie50550a029.
  19. 1 2 Wasik SP, Tewari YB, Miller MM, Martire DE (1981). "Octanol–Water Partition Coefficients and Aqueous Solubilities of Organic Compounds". NBS Techn. Rep. 81 (2406): S1–56.
  20. ↑ Brodsky J, Ballschmiter K (1988). "Reversed phase liquid chromatography of PCBs as a basis for calculation of water solubility and Kow for polychlorobiphenyls". Fresenius' Z. Anal. Chem. 331 (3–4): 295–301. doi:10.1007/BF00481899. S2CID   91775126.
  21. 1 2 Hansch C, Leo A (1979). "Chapter 5: Calculation of Octanol-Water Partition Coefficients from Fragments, etc.". Substituent Constants for Correlation Analysis in Chemistry and Biology. New York: John Wiley & Sons Ltd. ISBN   978-0-471-05062-9.
  22. ↑ Sangster J (1989). "Octanol–Water Partition Coefficients of Simple Organic Compounds" (PDF). Journal of Physical and Chemical Reference Data. 18 (3): 1111–1227. Bibcode:1989JPCRD..18.1111S. doi:10.1063/1.555833.
  23. 1 2 Leo A, Hoekman DH, Hansch C (1995). "Octanol log P". Exploring QSAR, Hydrophobic, Electronic, and Steric Constants . Washington, DC: American Chemical Society. ISBN   978-0-8412-3060-6.
  24. 1 2 Mannhold R, Poda GI, Ostermann C, Tetko IV (March 2009). "Calculation of molecular lipophilicity: State-of-the-art and comparison of log P methods on more than 96,000 compounds". Journal of Pharmaceutical Sciences. 98 (3): 861–93. doi:10.1002/jps.21494. PMID   18683876. S2CID   9595034.
  25. ↑ Bodor N, Buchwald P (2012). "Chapter 2.2: Pharmacokinetic Phase: ADME". Retrometabolic Drug Design and Targeting. (secondary). John Wiley & Sons, Inc. ISBN   978-1-118-40776-9.
  26. ↑ Leeson PD, Springthorpe B (November 2007). "The influence of drug-like concepts on decision-making in medicinal chemistry". Nature Reviews. Drug Discovery. 6 (11): 881–90. doi:10.1038/nrd2445. PMID   17971784. S2CID   205476574.
  27. ↑ Edwards MP, Price DA (2010). Role of Physicochemical Properties and Ligand Lipophilicity Efficiency in Addressing Drug Safety Risks. Annual Reports in Medicinal Chemistry. Vol. 45. pp. 381–391. doi:10.1016/S0065-7743(10)45023-X. ISBN   978-0-12-380902-5.
  28. ↑ Bodor N, Buchwald P (April 1999). "Recent advances in the brain targeting of neuropharmaceuticals by chemical delivery systems". Advanced Drug Delivery Reviews. 36 (2–3): 229–254. doi:10.1016/S0169-409X(98)00090-8. PMID   10837718.
  29. ↑ Kubinyi H (March 1979). "Nonlinear dependence of biological activity on hydrophobic character: the bilinear model". Il Farmaco; Edizione Scientifica. 34 (3): 248–76. PMID   43264.
  30. ↑ Kubinyi H (1979). "Lipophilicity and biological activity. Drug transport and drug distribution in model systems and in biological systems". Arzneimittel-Forschung. 29 (8): 1067–80. PMID   40579.
  31. ↑ Eisenberg D, McLachlan AD (1986). "Solvation energy in protein folding and binding". Nature. 319 (6050): 199–203. Bibcode:1986Natur.319..199E. doi:10.1038/319199a0. PMID   3945310. S2CID   21867582.
  32. ↑ Miyamoto S, Kollman PA (September 1993). "What determines the strength of noncovalent association of ligands to proteins in aqueous solution?". Proceedings of the National Academy of Sciences of the United States of America. 90 (18): 8402–6. Bibcode:1993PNAS...90.8402M. doi: 10.1073/pnas.90.18.8402 . PMC   47364 . PMID   8378312.
  33. ↑ Pliska V, Testa B, Van De Waterbed H (1996). Lipophilicity in Drug Action and Toxicology. New York: John Wiley & Sons Ltd. pp. 439 pages. ISBN   978-3-527-29383-4.
  34. ↑ Cronin D, Mark T (2006). "The Role of Hydrophobicity in Toxicity Prediction". Current Computer-Aided Drug Design. 2 (4): 405–413. doi:10.2174/157340906778992346.
  35. ↑ Heuel-Fabianek B (2006). "Partition Coefficients (Kd) for the Modelling of Transport Processes of Radionuclides in Groundwater" (PDF). Current Computer-Aided Drug Design. 2 (4): 405–413. doi:10.2174/157340906778992346.
  36. ↑ Noble A (July 1993). "Partition coefficients (n-octanol—water) for pesticides". Journal of Chromatography A. 642 (1–2): 3–14. doi:10.1016/0021-9673(93)80072-G.
  37. ↑ van Leeuwin CJ, Hermens JL, eds. (2012). "Transport, Accumulation and Transformation Processes (Ch. 3), Properties of Chemicals and Estimation Methodologies (Ch. 7), and Procedures of Hazard and Risk Assessment (Ch. 8)". Risk Assessment of Chemicals: An Introduction. Dordrecht: Kluwer Acad. Publ. pp. 37–102, and 239–338, esp. 39ff, 240ff, 306, and passim. ISBN   978-0-7923-3740-9.
  38. 1 2 Dearden JC, Bresnan GM (1988). "The Measurement of Partition Coefficients". Quantitative Structure-Activity Relationships. 7 (3): 133–144. doi:10.1002/qsar.19880070304.
  39. ↑ Andrés A, Rosés M, Ràfols C, Bosch E, Espinosa S, Segarra V, Huerta JM (August 2015). "Setup and validation of shake-flask procedures for the determination of partition coefficients (log D) from low drug amounts". European Journal of Pharmaceutical Sciences. 76: 181–91. doi:10.1016/j.ejps.2015.05.008. hdl: 2445/143737 . PMID   25968358.
  40. ↑ Valkó K (May 2004). "Application of high-performance liquid chromatography based measurements of lipophilicity to model biological distribution". Journal of Chromatography A. 1037 (1–2): 299–310. doi:10.1016/j.chroma.2003.10.084. PMID   15214672.
  41. ↑ Ulmeanu SM, Jensen H, Bouchard G, Carrupt PA, Girault HH (August 2003). "Water-oil partition profiling of ionized drug molecules using cyclic voltammetry and a 96-well microfilter plate system" (PDF). Pharmaceutical Research. 20 (8): 1317–22. doi:10.1023/A:1025025804196. PMID   12948031. S2CID   9917932.
  42. ↑ Scholz F, Komorsky-Lovrić Š, Lovrić M (February 2000). "A new access to Gibbs energies of transfer of ions across liquid|liquid interfaces and a new method to study electrochemical processes at well-defined three-phase junctions". Electrochemistry Communications. 2 (2): 112–118. doi:10.1016/S1388-2481(99)00156-3.
  43. ↑ Bond AM, Marken F (1994). "Mechanistic aspects of the electron and ion transport processes across the electrode". Journal of Electroanalytical Chemistry . 372 (1–2): 125–135. doi:10.1016/0022-0728(93)03257-P.
  44. ↑ Karpińska, Aneta; Pilz, Marta; Buczkowska, Joanna; Żuk, Paweł J.; Kucharska, Karolina; Magiera, Gaweł; Kwapiszewska, Karina; Hołyst, Robert (2021). "Quantitative analysis of biochemical processes in living cells at a single-molecule level: a case of olaparib–PARP1 (DNA repair protein) interactions" (PDF). Analyst. 146 (23): 7131–7143. doi:10.1039/D1AN01769A. PMID   34726203. S2CID   240110114.
  45. 1 2 Karpinska, Aneta; Magiera, Gaweł; Kwapiszewska, Karina; Hołyst, Robert (2023). "Cellular Uptake of Bevacizumab in Cervical and Breast Cancer Cells Revealed by Single-Molecule Spectroscopy". J. Phys. Chem. Lett. 14 (5): 1272–1278. doi:10.1021/acs.jpclett.2c03590. PMC   9923738 . PMID   36719904. S2CID   256415374.
  46. 1 2 Nieto-Draghi C, Fayet G, Creton B, Rozanska X, Rotureau P, de Hemptinne JC, Ungerer P, Rousseau B, Adamo C (December 2015). "A General Guidebook for the Theoretical Prediction of Physicochemical Properties of Chemicals for Regulatory Purposes". Chemical Reviews. 115 (24): 13093–164. doi:10.1021/acs.chemrev.5b00215. PMID   26624238.
  47. ↑ Judson R, Richard A, Dix DJ, Houck K, Martin M, Kavlock R, Dellarco V, Henry T, Holderman T, Sayre P, Tan S, Carpenter T, Smith E (May 2009). "The toxicity data landscape for environmental chemicals". Environmental Health Perspectives. 117 (5): 685–95. doi:10.1289/ehp.0800168. PMC   2685828 . PMID   19479008.
  48. ↑ Matter H, Baringhaus KH, Naumann T, Klabunde T, Pirard B (September 2001). "Computational approaches towards the rational design of drug-like compound libraries". Combinatorial Chemistry & High Throughput Screening. 4 (6): 453–75. doi:10.2174/1386207013330896. PMID   11562252.
  49. ↑ Schuffenhauer A, Ruedisser S, Marzinzik AL, Jahnke W, Blommers M, Selzer P, Jacoby E (2005). "Library design for fragment based screening". Current Topics in Medicinal Chemistry. 5 (8): 751–62. doi:10.2174/1568026054637700. PMID   16101415.
  50. ↑ Rutkowska E, Pajak K, Jóźwiak K (2013). "Lipophilicity--methods of determination and its role in medicinal chemistry" (PDF). Acta Poloniae Pharmaceutica. 70 (1): 3–18. PMID   23610954.
  51. 1 2 Ghose AK, Crippen GM (1986). "Atomic Physicochemical Parameters for Three-Dimensional Structure-Directed Quantitative Structure–Activity Relationships I. Partition Coefficients as a Measure of Hydrophobicity" (PDF). Journal of Computational Chemistry. 7 (4): 565–577. doi:10.1002/jcc.540070419. hdl: 2027.42/38274 . S2CID   4272062.
  52. ↑ Cheng T, Zhao Y, Li X, Lin F, Xu Y, Zhang X, Li Y, Wang R, Lai L (2007). "Computation of octanol-water partition coefficients by guiding an additive model with knowledge". Journal of Chemical Information and Modeling. 47 (6): 2140–8. doi:10.1021/ci700257y. PMID   17985865.
  53. 1 2 3 Moriguchi I, Hirono S, Liu Q, Nakagome I, Matsushita Y (1992). "Simple method of calculating octanol/water partition coefficient". Chem. Pharm. Bull. 40 (1): 127–130. doi: 10.1248/cpb.40.127 .
  54. ↑ Ghose AK, Viswanadhan VN, Wendoloski JJ (1998). "Prediction of Hydrophobic (Lipophilic) Properties of Small Organic Molecules Using Fragmental Methods: An Analysis of AlogP and ClogP Methods". Journal of Physical Chemistry A. 102 (21): 3762–3772. Bibcode:1998JPCA..102.3762G. doi:10.1021/jp980230o.
  55. ↑ Liao Q, Yao J, Yuan S (August 2006). "SVM approach for predicting LogP". Molecular Diversity. 10 (3): 301–9. doi:10.1007/s11030-006-9036-2. PMID   17031534. S2CID   1196330.
  56. ↑ Molnár L, Keseru GM, Papp A, Gulyás Z, Darvas F (February 2004). "A neural network based prediction of octanol-water partition coefficients using atomic5 fragmental descriptors". Bioorganic & Medicinal Chemistry Letters. 14 (4): 851–3. doi:10.1016/j.bmcl.2003.12.024. PMID   15012980.
  57. ↑ Perrin DD, Dempsey B, Serjeant EP (1981). "Chapter 3: Methods of pKa Prediction". pKa Prediction for Organic Acids and Bases. London: Chapman & Hall. pp. 21–26. doi:10.1007/978-94-009-5883-8. ISBN   978-0-412-22190-3.
  58. ↑ Fraczkiewicz R (2013). "In Silico Prediction of Ionization". In Reedijk J (ed.). Reference Module in Chemistry, Molecular Sciences and Chemical Engineering. Reference Module in Chemistry, Molecular Sciences and Chemical Engineering [Online]. Vol. 5. Amsterdam, the Netherlands: Elsevier. doi:10.1016/B978-0-12-409547-2.02610-X. ISBN   9780124095472.
  59. ↑ Pinsuwan S, Li A, Yalkowsky SH (May 1995). "Correlation of Octanol/Water Solubility Ratios and Partition Coefficients". Journal of Chemical & Engineering Data. 40 (3): 623–626. doi:10.1021/je00019a019.
  60. ↑ Wang J, Hou T (June 2011). "Recent advances on aqueous solubility prediction". Combinatorial Chemistry & High Throughput Screening. 14 (5): 328–38. doi:10.2174/138620711795508331. PMID   21470182.
  61. ↑ Skyner RE, McDonagh JL, Groom CR, van Mourik T, Mitchell JB (March 2015). "A review of methods for the calculation of solution free energies and the modelling of systems in solution" (PDF). Physical Chemistry Chemical Physics. 17 (9): 6174–91. Bibcode:2015PCCP...17.6174S. doi: 10.1039/c5cp00288e . PMID   25660403.
  62. ↑ Sangster J (1997). Octanol-water partition coefficients : fundamentals and physical chemistry. Chichester: Wiley. ISBN   0-471-97397-1. OCLC   36430034.
  63. ↑ Mackay, D; Parnis, J. Mark (2021). Multimedia Environmental Models: The Fugacity Approach (Third ed.). Boca Raton, FL: CRC Press. ISBN   978-1-000-09499-2. OCLC   1182869019.
  64. ↑ Hodges G, Eadsforth C, Bossuyt B, Bouvy A, Enrici MH, Geurts M, et al. (2019). "A comparison of log Kow (n-octanol–water partition coefficient) values for non-ionic, anionic, cationic and amphoteric surfactants determined using predictions and experimental methods". Environmental Sciences Europe. 31 (1). doi: 10.1186/s12302-018-0176-7 .
  65. ↑ Hendriks AJ, van der Linde A, Cornelissen G, Sijm DT (July 2001). "The power of size. 1. Rate constants and equilibrium ratios for accumulation of organic substances related to octanol-water partition ratio and species weight". Environmental Toxicology and Chemistry. 20 (7): 1399–420. doi:10.1002/etc.5620200703. PMID   11434281. S2CID   25971836.
  66. ↑ Cumming H, Rücker C (September 2017). "Octanol-Water Partition Coefficient Measurement by a Simple 1H NMR Method". ACS Omega. 2 (9): 6244–6249. doi:10.1021/acsomega.7b01102. PMC   6644330 . PMID   31457869.
  67. ↑ "Dortmund Data Bank (DDB)". Dortmund Data Bank Software & Separation Technology (DDBST) GmbH. Retrieved 2020-05-20.

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.