Polypeptides, synthetic, solid-state

Gougeon, R.D., Soulard, M., Reinholdt, M., Miehe-Brendle, J., Chezeau, J.M., Le Dred, R., Marchal, R., Jeandet, P. (2003). Polypeptide adsorption onto a synthetic montmoiillonite A combined solid-state NMR, X-ray diffraction, thermal analysis and N2 adsorption study, Eur. J. Inorg. Chem., 7, 1366-1372... 

Gougeon, R.D., Reinholdt, M., Delmotte, L., Miehe-Brendle, J., Chezeau, J.M., Le Dred, R., Mar-chal, R., Jeandet, P. (2002). Direct observation of polylysine side-chain interaction with smectites interlayer surfaces through H- A1 heteronuclear correlation NMR spectroscopy. Langmuir, the American Chemical Society Journal of Surfaces and Colloids, 18, 3396-3398 Gougeon, R.D., Soulard, M., Reinholdt, M., Miehe-Brendle, J., Chezeau, J.M., Le Dred, R., Mar-chal, R., Jeandet, P. (2003). Polypeptide adsorption onto a synthetic montmoriUonite A combined solid-state NMR, X-ray diffraction, thermal analysis and N2 adsorption study. Eur. J. Inorg. Chem., 2003, 1366-1372... 

The synthetic polypeptide most completely studied in the solid state by optical rotation is poly-n-alanine, which Elliott et al. (1957b, 1958) treat as though it were an L-polypeptide with opposite helical sense in order to make straightforward comparison of the results with other studies. The 6o for the pure L-polymer is —475, and for two helical DL-copolymers, —500 and —505 extrapolated values for the meso-polypeptide lead to a fio of — 560. These compare favorably with Pasman s result of about —425 in 30% dichloroacetic acid in chloroform, a solvent in which the conformation is helical (I asman, 1961a). The [m ] values were found to be less than those obtained for solution, a result probably attributable to environmental changes, yet of meso-poly-DL-alanine is -f 70° at 578 m/u, which is... 

Can H cramps NMR become an effective means for conformational analysis of polypeptides and proteins in the solid state In order to answer this question, in this section, we focus on and discuss a study on correlation between the H chemical shifts and the main-chain conformation (secondary structure) of synthetic polypeptides.Homopolypeptides and copolypeptides are useful as models for structural analysis of natural proteins. Homopolypeptide is the simplest and the most basic model polypeptide for NMR studies of proteins. 

A well-defined monodisperse penta(L-alanine)- -butylamide H-[Ala]5-NHBu was synthesized by an activated ester method " and other natural abundant polypeptides, [Ala]n-5, [Leu]n-1 and [Leu]n-2, were synthesized by the N-carboxy a-amino-acid anhydride (NCA) method.Fully N-labelled homopolypeptides, [Ala ]n (99 at.% of N purity MASSTRACE, Inc.) and [Leu ]n (99 at.% of N purity MASSTRACE, Inc.), which show characteristic differences in conformation such as the a-helix and /3-sheet forms, were prepared by the heterogeneous polymerization of the corresponding NCAs in acetonitrile with -butylamine as an initiator. Conformational characterization of these samples was made on the basis of the conformation-dependent C and chemical shifts determined from the CP-MAS NMR method and from the characteristic bands in the IR and far-IR spectra. Figs. 38 and 39 show the 75.5 MHz C and 30.4 MHz N CP-MAS NMR spectra respectively of these fully N-labelled (99 at.% purity of N) homopolypeptides adopting the a-helical and /3-sheet forms (A) [Ala ]n-2 (a-helix), (B) [Ala ]n-1 (/3-sheet), (C) [Leu ]n-2 (a-helix), (D) [Leu ]n-1 (/3-sheet) in the solid state. Synthetic conditions and conformational characteristics of these samples are summarized... 

The relation between the isotropic I5N chemical shift and the structural parameters of various kinds of synthetic copolypeptides in the solid state have been studied.58,59,61,67 For this, a series of 15N-labelled polypeptides were prepared, [Ala, X] , [Gly, X] and [Leu, X] , consisting of 15N-labelled amino acids (Ala L-alanine, Gly glycine, Leu L-leucine) and other normal amino acids (X natural abundance of 15N), where the following amino acids were selected for the X residue (1) L-alanine, D-alanine and L-leucine, which contain... 

Fig. 1. Left Birefringent fluid liquid crystalline solution of poly-y-benzyl-L-glutamate in /n-cresol. Right Birefringent solid film of poly-y-benzyl-L-glutamate plasticized by 3,3 -dimethyl bisphenyl. Retardation lines characteristic of a helicoidal supramolecular structure are observed in the photomicrographs of both the liquid and solid states of this synthetic polypeptide.

Susi et al. (1967) have observed spectra of poly-L-lysine, poly-L-glutamic acid, )S-lactoglobulin, myoglobin, and a -casein in the region of absorption of the amide I band in HjO and DjO solutions, and in the solid state. Their results indicated that characteristic frequencies exhibited by specific conformations of the synthetic polypeptides studied are not transferable to corresponding conformations of globular proteins. 

Studies on synthetic oligomers performed by Aisenbrey et al. provided information on the interaction of N-labelled amphiphilic helices with oriented lipid membranes and revealed the antimicrobial nature of these oligomers. Solid-state NMR helped to characterize the structure, dynamics and membrane topology of antimicrobial polypeptides such as alamethicin or p-hairpin antimicrobials,a novel dendrimeric peptide with antimicrobial potency against Gram-negative bacteria and tachyplesin-1, a disulfide stabilized p-hairpin antimicrobial peptide. 

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