Objective To understand the toxicity and application prospect of polypeptide formed by the same amino acids. Methods This study focused on the solid-phase polypeptide synthesis of Asp and Lys polypeptide, and analyzed their toxicity by the method of tail vein injection to observe the lethal effect on mice. Results When the concentration of the nine kinds of single-strand asp-peptides were 0.15, 0.1, 0.09, 0.03, 0.0065, 0.03, 0.034, 0.035and 0.04 mol/L, respectively, the death rate of the BALB/c mouse was LD50. When the concentration of the nine kinds of single-strand lys-peptides were 0.28, 0.1, 0.047, 0.0225, 0.0028, 0.00166, 0.0015, 0.0011and 0.00075 mol/L, respectively, the death rate of the BALB/c mouse was LD50. When the concentration of the ten kinds of double-strand asp-lys-peptides were 0.5, 0.05, 0.017, 0.014, 0.009, 0.006, 0.004, 0.004, 0.004 and 0.004 mol /L, respectively, the death rate of the BALB/c mouse was LD50. Conclusion The toxicity of single-strand peptides was greater than that of double-strands. With the number of amino acids increasing, the toxicity of the single- strand asp-polypeptide, from dipeptide to hexapeptide, was increased, while Asp-heptapeptide to Asp-decapeptide was decreased. In the case of Lys-polypeptide, the toxicity of the single-strands was increased when the number of amino acid was increased. For the double-stranded Asp-Lys- polypeptide, by increasing the number of amino acid, the toxicity of the dipeptide to hexapeptide was increased, while heptapeptide to decapeptide had no change.
