| Peptide libraries have been widely used to identify and examine the specificities of immune system, for screening bioactive ligands that bind to DNA and enzymes, and recognized as powerful tools for searching detailed information about protein-protein interactions and so on. Also, it has been widely used by the drug industry to discover biological active compounds. There are some methods for constructing peptide libraries such as: multipin synthesis, tea-bag method, split synthesis and combinatorial library by light directed. Organophosphorus compounds have been used as coupling regents to synthesize bioactive peptides, but rarely reported for construction of peptide libraries. In previous work of Prof. Zhao Yu-Fen, it was discovered that polypeptides were formed by self-assembly of N, O-bis(trimethylsilyl) amino acids with the assistance of O, O-phenylene phosphoryl chloride.In this paper, the reactions of amino acids and phosphorus oxychloride were studied. The homo-peptide libraries, hetro-peptide libraries and the peptide conjugate libraries were constructed by this method. 31P NMR and ESI-MS/MS were used to study the mechanism and products of the reaction and confirm the structures of the peptides. These results were illustrated as following:The reactions of twenty natural amino acid and phosphorus oxychloride were studied. It was found that nonpolar a-amino acids could be assembled into 2-14 homo-peptides by phosphorus oxychloride activation, after quenching with water or various alcohols, the reaction mixtures yielded the corresponding peptides or peptide esters, respectively, which were analyzed by ESI-MS and ESI-MS/MS. As the reaction time was prolonged, the length of peptides increased, but after 96 hours later, the maximum length of the peptides appeared to reach equilibrium. It was found that withthe same reaction time, the lengths of peptides increased as the polarity of the solvent increased and decreased as the polarity of amino acids increased. Some polar amino acids could be assembled into 2-4 short peptides. Multistage electrospray mass spectrometry of homo-peptides and peptide esters were studied, and the results showed that the fragmentation pathway for these protonated homo-peptides yielded mainly "b" type ions, consistent with the conclusion that the products were the oligo-peptides and peptide esters.The reaction mechanisms of peptide formation by phosphorus oxychloride activation were investigated. It was found that with phosphorus oxychloride assistance, trimethylsilyl amino acids could form cyclic or spiro penta-coordinate phosphorus compounds firstly, then assembled into polypeptide. There were three steps involved in the self organization reactions of trimethylsilyl amino acids, namely, the activation of amino acid, the elongation of peptide chain and the termination of the chain reaction. The result of theoretical calculations showed that the reactions of amino acids and phosphorus oxychloride might go through penta-coordinate phosphorus compounds intermediate.The reactions of two non-polar amino acids with phosphorus oxychloride were investigated. It was found that in addition to the homo-peptides, the hetro-peptides were also formed. Several hetro-peptide libraries were synthesized and analyzed by Bio-Tools?software with ESI-MS/MS technique. The products of the libraries were studied and the diversity of the peptide libraries was discussed. It was discovered that the reaction of phosphorus oxychloride with L-Val/L-Leu produced the most abundant hetro-peptide libraries with sixty and eight kinds of peptides sub-libraries based on molecular weight difference.Glycosylation and phosphorylation of peptides drug play an important role in the pharmacokinetic phase. The synthesis of modified glycopeptide and phosphoryl peptide may therefore represent a mean to improve thevabsorption and distribution of bio-available therapeutic peptides. It was proposed that glycopeptide and phosphoryl peptide not only could increase their resistance to enzymatic degradation, but a...
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