title: Comparison of the solution conformations of a human immunodeficiency virus peptidomimetic and its retro-inverso isomer using 1H NMR spectroscopy.
abstract: The solution conformations of the all L-alpha-peptide 1 and the corresponding retro-all D-alpha-peptide 2, two 20-metric peptides which generate antibodies that cross-react with the gp 120 envelop protein of human immunodeficiency virus-1 (HIV-1), have been investigated by high-field 1H NMR spectroscopy. Complete sequential and inter-residue interaction assignments were made from the 2D NMR spectra acquired at 500 MHz and 600 MHz in 40% deuterotrifluoroethanol (d3-TFE)/H2O at pH 2.3, and in 300 mM sodium dodecyl sulphate (SDS) in 100% D2O or 90% H2O/10% D2O at pH 2.6. Based on analysis of the nuclear Overhauser effect (NOE) and amide exchange data, peptide 1 and its retro-inverso isomer 2 in the polar solvent environment of 40% d3-TFE/H2O at pH 2.3 show very similar topological features. However, in the relatively non-polar 300 mM SDS micellar environment, peptides 1 and 2 exhibit differences in their solution structures in terms of the amide backbone and side-chain orientations. In particular, under the SDS micellar condition, peptide 1 maintains much of the secondary structure observed for this 20-mer peptide in 40% d3-TFE/H2O, pH 2.3, whereas peptide 2 adopts a more extended structure. These NMR results provide the first confirmation that the secondary structure of the all L-a-peptide 1 is maintained in both polar and non-polar environments, whereas the secondary structure and topology of the notionally equivalent retro-inverso isomer depends more on the solvent conditions. These results with the all L-a-peptide 1 and its retro-inverso isomer 2 provide important insight into the conformational influences of the C- and N-end group with L-alpha- and retro-D-alpha-isomer pairs in non-polar environments, and thus have general relevance to the design of bioactive retro-inverso peptidomimetic analogues related to immunogenic or hormonal peptides.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
authors.forename: K A
authors.initials: KA
authors.lastname: Higgins
authors.forename: W
authors.initials: W
authors.lastname: Bicknell
authors.forename: H H
authors.initials: HH
authors.lastname: Keah
authors.forename: M T
authors.initials: MT
authors.lastname: Hearn
mesh_terms: D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002851:Chromatography, High Pressure Liquid; D015699:HIV Envelope Protein gp120 / Q000737:chemistry*; D015497:HIV-1 / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008823:Micelles; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012996:Solutions
chemical_list: D015699:HIV Envelope Protein gp120; D008823:Micelles; D010455:Peptides; D012996:Solutions