SOLUTION CONFORMATION OF MODEL PEPTIDES WITH THE USE OF PARTICLE-BEAMLC FT-IR SPECTROMETRY AND ELECTROSPRAY MASS-SPECTROMETRY/

Solution conformations of the peptides angiotensin I (Ang I) and POMC- X (an octapeptide fragment of proopiomelanocortin) were investigated w ith the use of particle beam liquid chromatography/Fourier transform i nfrared (LC/FT-IR) spectrometry. Gradient elution high-performance liq uid chromatography (HPLC) with mobile phases that contain acetonitrile , 2-propanol, 0.1% heptafluorobutyric acid (HFBA) and 0.1% trifluoroac etic acid (TFA) were used. The conformations of both peptides were stu died in 0.9% sodium chloride injection USP, 5% dextrose in water injec tion USP and sterile water for Injection USP. Additional conformationa l studies over a pH range of 2-10, to a temperature of 75 degrees C an d after a storage time of 24 h were investigated. The studies indicate d that the two peptides do not behave similarly under identical condit ions. It was observed that both Ang I and POMC-X had slightly differen t conformations in the various parenteral solutions. It was also shown that the conformation of Ang I changed with both pH and temperature w hile POMC-X was conformationally stable to both temperature and pH. Th e identity of the peptides and the conformationally sensitive charge-s tate intensities of the peptides were investigated with electrospray i onization mass spectrometry (ESI/MS). The combination of infrared and mass spectrometric data allowed a thorough estimation of solution effe cts on the conformations of the model peptides. (C) 1998 Elsevier Scie nce B.V. All rights reserved.