Markowski V, Posner T B, Loftus P, Roberts J D
Proc Natl Acad Sci U S A. 1977 Apr;74(4):1308-9. doi: 10.1073/pnas.74.4.1308.
The 15N chemical shifts of eight aliphatic tripeptides have been measured at the natural-abundance level. For a given tripeptide, the resonances of the COOH-terminal and NH2-terminal amino acids can be identified by measurements at low or high pH. The shifts of the NH2-terminal amino acid nitrogens are essentially independent of the amino acids in the rest of the peptide. The shifts of the other nitrogens are characteristic of the amino acids themselves and of the immediately preceding amino acid toward the NH2 terminus. Non-terminal amide nitrogens have shifts of about 6 ppm upfield of COOH-terminal amide nitrogens at the isoelectric point of measurement. 15N chemical shifts appear to have considerable potential value for peptide sequencing.
已在天然丰度水平下测量了八种脂肪族三肽的15N化学位移。对于给定的三肽，通过在低pH或高pH下进行测量，可以识别出COOH末端和NH2末端氨基酸的共振峰。NH2末端氨基酸氮的化学位移基本上与肽其余部分的氨基酸无关。其他氮的化学位移是氨基酸本身以及靠近NH2末端的紧邻前一个氨基酸的特征。在测量的等电点，非末端酰胺氮的化学位移比COOH末端酰胺氮的化学位移高约6 ppm。15N化学位移对于肽测序似乎具有相当大的潜在价值。
