PMC:6194691 / 48602-49788 JSONTXT

{"project":"MyTest","denotations":[{"id":"30340614-10696512-30706075","span":{"begin":1108,"end":1111},"obj":"10696512"},{"id":"30340614-25675910-30706076","span":{"begin":1113,"end":1116},"obj":"25675910"}],"namespaces":[{"prefix":"_base","uri":"https://www.uniprot.org/uniprot/testbase"},{"prefix":"UniProtKB","uri":"https://www.uniprot.org/uniprot/"},{"prefix":"uniprot","uri":"https://www.uniprot.org/uniprotkb/"}],"text":"In the simplest view the rate limiting steps in the transcellular, passive, unmediated transfer of substances can be thought of as occurring by dissolution in a liquid hydrophobic core of the membranes and diffusion through it. For molecules not much larger than those of the solvent the diffusion constant for the various compounds is taken to be inversely proportional to the square root of their molecular weights [155–157]. The exact relationship assumed is not critical because the dominant factor determining the relative permeabilities is the free energy cost of the transfer from water into the core of the membrane, ΔGmembrane/water. This cost determines the relative concentrations in the membrane and the aqueous phase,5 cmembranecwater=Kmembrane/water=e-ΔGmembrane/water/RTwhere Kmembrane/water is the partition coefficient, R the universal gas constant, and T the absolute temperature. The free energy cost and the partition coefficient are usually estimated by assuming that the membrane core can be described as being like a layer of n-octanol (see [158, 159] and for more recent discussions [160, 161]), and thus6 cmembranecwater∝Kn-octanol/water=e-ΔGn-octanol/water/RT."}

{"project":"2_test","denotations":[{"id":"30340614-10696512-30706075","span":{"begin":1108,"end":1111},"obj":"10696512"},{"id":"30340614-25675910-30706076","span":{"begin":1113,"end":1116},"obj":"25675910"}],"text":"In the simplest view the rate limiting steps in the transcellular, passive, unmediated transfer of substances can be thought of as occurring by dissolution in a liquid hydrophobic core of the membranes and diffusion through it. For molecules not much larger than those of the solvent the diffusion constant for the various compounds is taken to be inversely proportional to the square root of their molecular weights [155–157]. The exact relationship assumed is not critical because the dominant factor determining the relative permeabilities is the free energy cost of the transfer from water into the core of the membrane, ΔGmembrane/water. This cost determines the relative concentrations in the membrane and the aqueous phase,5 cmembranecwater=Kmembrane/water=e-ΔGmembrane/water/RTwhere Kmembrane/water is the partition coefficient, R the universal gas constant, and T the absolute temperature. The free energy cost and the partition coefficient are usually estimated by assuming that the membrane core can be described as being like a layer of n-octanol (see [158, 159] and for more recent discussions [160, 161]), and thus6 cmembranecwater∝Kn-octanol/water=e-ΔGn-octanol/water/RT."}