1. Sulfonation of arginine residues as side reaction in Fmoc-peptide synthesis
A G Beck-Sickinger, G Schnorrenberg, J Metzger, G Jung Int J Pept Protein Res. 1991 Jul;38(1):25-31. doi: 10.1111/j.1399-3011.1991.tb01405.x.
Several arginine-rich peptides containing the C-terminus of neuropeptide Y (NPY) were prepared by solid phase peptide synthesis using Fmoc chemistry and cleaved from the resin with trifluoroacetic acid (TFA). The products were characterized by fast atom bombardment-MS, LC-thermospray-MS, ion spray-MS/MS, and Edman degradation. The side products could be identified as peptides with sulfonated arginine residues resulting from an unexpected cleavage of Mtr or Pmc protecting groups. The degree of sulfonation depended on the choice and composition of the cleavage solution. Several scavenger mixtures were used and a mixture of thioanisole/thiocresol was found to be the most efficient for suppressing sulfonation. Furthermore treatment with the enzyme arylsulfate-sulfohydrolase desulfonated the peptides yielding the correct sequence.
2. Interfacial reactions of ozone with surfactant protein B in a model lung surfactant system
Hugh I Kim, et al. J Am Chem Soc. 2010 Feb 24;132(7):2254-63. doi: 10.1021/ja908477w.
Oxidative stresses from irritants such as hydrogen peroxide and ozone (O(3)) can cause dysfunction of the pulmonary surfactant (PS) layer in the human lung, resulting in chronic diseases of the respiratory tract. For identification of structural changes of pulmonary surfactant protein B (SP-B) due to the heterogeneous reaction with O(3), field-induced droplet ionization (FIDI) mass spectrometry has been utilized. FIDI is a soft ionization method in which ions are extracted from the surface of microliter-volume droplets. We report structurally specific oxidative changes of SP-B(1-25) (a shortened version of human SP-B) at the air-liquid interface. We also present studies of the interfacial oxidation of SP-B(1-25) in a nonionizable 1-palmitoyl-2-oleoyl-sn-glycerol (POG) surfactant layer as a model PS system, where competitive oxidation of the two components is observed. Our results indicate that the heterogeneous reaction of SP-B(1-25) at the interface is quite different from that in the solution phase. In comparison with the nearly complete homogeneous oxidation of SP-B(1-25), only a subset of the amino acids known to react with ozone are oxidized by direct ozonolysis in the hydrophobic interfacial environment, both with and without the lipid surfactant layer. Combining these experimental observations with the results of molecular dynamics simulations provides an improved understanding of the interfacial structure and chemistry of a model lung surfactant system subjected to oxidative stress.
3. Efficient Fmoc/solid-phase synthesis of Abu(P)-containing peptides using Fmoc-Abu(PO3Me2)-OH
J W Perich Int J Pept Protein Res. 1994 Sep;44(3):288-94. doi: 10.1111/j.1399-3011.1994.tb00172.x.
The synthesis of the two 4-phosphono-2-aminobutanoyl-containing peptides, Leu-Arg-Arg-Val-Abu(P)-Leu-Gly-OH.CF3CO2H and Ile-Val-Pro-Asn-Abu(P)-Val-Glu-Glu-OH.CF3CO2H was accomplished by the use of Fmoc-Abu(PO3Me2)-OH in Fmoc/solid-phase peptide synthesis. The protected phosphoamino acid, Fmoc-Abu(PO3Me2)-OH, was prepared from Boc-Asp-OtBu in seven steps, the formation of the C-P linkage being effected by the treatment of Boc-Asa-OtBu with dimethyl trimethylsilyl phosphite. Peptide synthesis was performed using Wang Resin as the polymer support with both peptides assembled by the use of PyBOP for the coupling of Fmoc amino acids and 20% piperidine for cleavage of the Fmoc group from the Fmoc-peptide after each coupling cycle. Cleavage of the peptide from the resin and peptide deprotection was accomplished by the treatment of the peptide-resin with 5% thioanisole/TFA followed by cleavage of the methyl phosphonate group by 1 M bromotrimethylsilane/1 M thioanisole in TFA.
