Investigation Of Bio-inspired Signal Transduction System Based On Aminoacyl-lipid On Artificial Membrane

An artificial signal transduction system with intercellular communication activities was constructed,inspired by G-Protein mediated cell signal transduction.A cationic peptide lipid named N,N-dihexadecyl-N^α-[6-(trimethylammonio)hexanoyl]-alaninamide bromide(N⁺C₅Ala2C₁₆),which used to build bi-layer vesicle,was synthesized with 1-hexadecylamine and 1-bromo- hexadecane through five steps,including substitution and condensation reactions.Three aminoacyl-lipid,named N,N-dihexadecyl-glyninamide (Gly2C₁₆),N,N-dihexadecyl-alaninamide(Ala2C₁₆) and N,N-dihexadecyl-tryptophanamide (Trp2C₁₆),were synthesized with dihexadecylamine and corresponding Boc-amino acids through two steps reactions,respectively.Using pyridoxal 5'-phosphate as artificial signal,synthesized aminoacyl-lipid(Gly2C₁₆, Ala2C₁₆ or Trp2C₁₆) as artificial receptor,Cu²⁺ ions as the second messenger,LDH enzyme as effector enzyme and the bi-layer vesicle(liposome) as cell membrane,in condition of pH 7.00 and 40℃,three artificial signal transduction systems were individually constructed.In these systems,whether aminoacyl-lipid could interact with artificial signal? Whether aminoacyl-lipid could act as artificial receptor? Whether signal-receptor complex could capture Cu²⁺ ions and recover the LDH activity,which was inhibited by Cu²⁺ ions,to reduce sodium pyruvate to sodium lactate with NADH? These matters were investigated one by one.Our results showed that the aminoacyl-lipid could be used as artificial receptor in artificial signal transduction system;the reaction between aminoacyl-lipid and pyridoxal 5'-phosphate was affected by the side-chain group of the amino acids in aminoacyl-lipid. Three kinds of aminoacyl-lipid all could recognize and bind signal molecule(PLP) to form Schiff-base and the Schiff-base complex exhibited extremely high binding affinity towards Cu²⁺ ions,thus recovered the catalytic activity of LDH which was inhibited by Cu²⁺ ions, effectively,then the sodium pyruvate was reduced to sodium lactate when NADH was added.