DERMORPHIN CAS 77614-16-5

The endothelial cell membrane of the blood-brain barrier is based on a lipid bilayer, through which lipophilic substances can easily pass. The transmembrane transport of dermorphin depends on the following characteristics:

Enhanced lipophilicity of D-Ala: The methyl side chain of D-Ala increases the overall hydrophobicity of the peptide chain, resulting in a distribution coefficient (logP) of 1.2, significantly higher than linear opioid peptides (such as enkephalin, logP ≈ -0.5).
Dynamic conformational adjustment: In the membrane environment, the rotation of the benzene ring of Phe ³ increases the hydrophobic surface area by 20%, promoting membrane insertion; At the same time, the hydroxyl group of Ser ⁷ forms hydrogen bonds with the head group of membrane phospholipids, reducing the penetration energy barrier.

The process of entering the brain involves multiple carrier systems:

Transferrin receptor (TfR) mediated endocytosis: Dermopin can enter endothelial cells through TfR mediated endocytosis by binding to transferrin (Tf) or Tf antibodies to form complexes. After endocytic body acidification, Deromorphin is released into the cytoplasm and then enters the brain parenchyma through efflux transporters (such as MRP1) on the basal membrane.
Low density lipoprotein receptor associated protein (LRP) mediated transport: LRP can recognize the C-terminal sequence of dermorphin and promote its transmembrane transport through receptor-mediated endocytosis.

In experimental studies, the blood-brain barrier can be temporarily opened through physical methods to enhance the delivery efficiency of dermorphin

Ultrasound mediated: Low frequency ultrasound (0.1-1 MHz) combined with microbubbles generates mechanical force, temporarily opening the tight junctions of endothelial cells and allowing dermorphin to enter brain tissue through intercellular spaces.
Hyperosmotic solution induction: High osmotic solutions such as mannitol contract endothelial cells, open tight junctions, and increase blood-brain barrier permeability.

The binding of dermorphin to the μ receptor follows a "conformational selection induced fit" mechanism:

Pre organized conformation: Dermorphin exists in an active conformation with N-terminal β - rotation and C-terminal random curling in solution;
Receptor screening: The receptor conformational pocket only accommodates specific conformations and excludes other low-energy states;
Induced binding: After binding, the side chain of Ser ⁷ rotates 120 ° and forms a new hydrogen bond with the receptor Glu ③¹⁰, stabilizing the complex. This process results in a binding rate constant (k ₁) of 1.2 × 10 ⁸ M ⁻¹ s ⁻¹, much higher than morphine (3.5 × 10 ⁶ M ⁻¹ s ⁻¹).

The resistance of dermorphin to peptidases originates from:

Stereoscopic shielding of D-Ala: The methyl group of D-Ala obstructs the approach of trypsin (cleavage of Lys/Arg-C end) and chymotrypsin (cleavage of aromatic residues - C end);
Compact structure: The β - angle makes the peptide chain spherical, reducing the contact area with the active center of the peptidase;
Charge distribution: Negative charges are concentrated at the N-terminus, repelling negatively charged peptidase surfaces. Experiments have shown that the half-life of dermorphin in serum is 10 times that of natural opioid peptides.

The physical and chemical properties of dermorphin make its efficiency in penetrating the blood-brain barrier significantly higher than other opioid peptides:

Lipolysis enhancement: The introduction of D-Ala increased logP from -0.5 to 1.2 in enkephalin;
Moderate molecular weight: The molecular weight is 802.87 Da, which is lower than the interception threshold of the blood-brain barrier for small molecule drugs (about 1000 Da);
Receptor mediated transport: Efficient transmembrane transport is achieved through carrier systems such as TfR and LRP.