This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Peptoids are amino acid analogs whose basic unit consists of N-substituted glycine derivatives. As opposed to the usual case, where the side chain is bound to the alpha-carbon, in a peptoid the side chain or functional group is bonded to the alpha-nitrogen. Relative to polypeptides, polypeptoids have their side chains shifted by one position along the backbone. Peptoids were designed as a new series of potentially bioactive compounds due to the variety of possible functional groups and the potential in drug delivery following from their expected metabolic stability. The structure of peptoids is of particular interest and has been studied extensively with NMR. For larger peptoid molecules spin-labeling techniques and large distance measurements by pulsed ESR can be routinely used in structural work. With Kirshenbaum we conducted a collaborative study on several spin-labeled peptoids. The distances were measured by DQC, which has proven to be a powerful tool for distances in the range of 11 to 70 ?. We examined several peptoids with their side chains substituted by nitroxides. In particular, we determined the following distances for the respective peptoid mutants of AF71 labeled at the C-terminus and progressively at C1-C5 residues: AF71-C1 (12.5 ?, fwhm 4 ?), AF71-C2 (15.0 ?), AF71-C3 (15.0 ?, fwhm 4.0A), AF71-C4 (16.0?), and AF71-C5 (18.0?). Also AF69-D6, a peptoid of more flexible structure caused by a different side-chain, was studied. Evidence for peptoid flexibility was supported by DQC yielding an average distance of 18? with fwhm of 9.5 ?.
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