Structure of Alamethicin in solution. One- and two-dimensional 1H nuclear magnetic resonance studies at 500 MHz

Utpal Banerjee, Fai Po Tsui, T. N. Balasubramanian, G. R. Marshall, Sunney I. Chan

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


We report here the 500 MHz 1H nuclear magnetic resonance spectra of Alamethicin, an icosapeptide antibiotic isolated from Trichoderma viride, in methanol, water and methanol/water mixtures. At this frequency, resonances from all the protons are well-resolved in methanol and may be assigned unambiguously. Spectral assignments were made using two-dimensional spin-echo correlated spectroscopy and by spin-decoupling experiments. The amide coupling constants (JNH-αCH) facilitated conformational predictions, which were confirmed in part by two-dimensional nuclear Overhauser experiments. On the basis of these data, we propose a secondary structure for Alamethicin that is α-helical toward the N terminus and extended β-sheet at the C-terminal end. This structure is consistent with earlier circular dichroism measurements (McMullen et al., 1971), infrared attenuated total reflection spectroscopy studies (Frigeli & Fringeli, 1979) and proton exchange data (Davis & Gisin, 1981). The proposed structure is a tightly bound dimer, wherein the β-sheet is stabilized by intermolecular hydrogen-bonds between opposing molecules. An interesting feature of this structure is that it exhibits both a hydrophobic and a hydrophilic surface. This highly amphiphilic nature of the dimer structure may account for the extensive further aggregation of Alamethicin in water. The 1H n.m.r. spectrum of Alamethicin in water is broad, suggesting extensive association. However, spectral assignments and amide coupling constant measurements in water, which were accomplished by titration of methanolic solution of Alamethicin by water, revealed no gross changes in the basic secondary structure of the molecule.

Original languageEnglish
Pages (from-to)757-775
Number of pages19
JournalJournal of Molecular Biology
Issue number4
StatePublished - Apr 25 1983


Dive into the research topics of 'Structure of Alamethicin in solution. One- and two-dimensional 1H nuclear magnetic resonance studies at 500 MHz'. Together they form a unique fingerprint.

Cite this