Because of the large distance of molecules from carbon atoms located at the square groove bottom, substrate-molecules interactions vanish significantly, and thus potassium stearate molecules cannot penetrate completely into the square groove.
Around 98% of small drugs and nearly 100% of large drugs molecules cannot penetrate the brain in sufficient therapeutic amount [ 91].
This production occurs in situ, is independent of all systemic cytokine production because the molecules cannot penetrate the haematomeningeal barrier and therefore comes from the macrophage cells within the meninges itself [ 13, 14].
And since they are big molecules, antibodies cannot penetrate cell membranes to enter cells.
Many water-soluble molecules that cannot penetrate the lipid bilayer are too large to fit through open channels.
In the same way, DNA molecules over 300 bp cannot penetrate efficiently through the nuclear envelope, which constitutes an obvious obstacle for foreign DNA uptake, either from natural origin or from human-developed technologies, such as cell transfection.
An important feature of the highly ordered regions is that the cellulose chains are packed so tightly that even small molecules such as water cannot penetrate these highly organized structural entities [ 14].
The stratum corneum (SC), specifically, is a keratinized layer of skin through which molecules heavier than 500 Da cannot penetrate.
The major anions inside the cell are chlorine ions (Cl−) and negatively charged protein molecules, the latter of which cannot penetrate the membrane.
However, unlike small-molecule compounds such as 2,3-BDZs, RNA aptamers cannot penetrate the blood brain barrier, and are thus required to be delivered to CNS using other means, such as intrathecal injection.
