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  • 1
    ISSN: 1573-5001
    Keywords: Acyclovir analogs ; Thymidine kinase ; Transferred NOE ; Relaxation matrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A purine derivative with an acyclic sugar analog, 3,9-dihydro-3-[(2-hydroxyethoxy)methyl]-6-ethyl-9-oxo-5H-imidazo[1,2-a]purine, was studied in the free state and in complex with herpes simplex virus thymidine kinase (HSV1 TK). Transferred NOE experiments, combined with a full relaxation matrix analysis of the substrate's spin system, resulted in a set of distance constraints for all proton pairs. These constraints were used in structure determination procedures based on simulated annealing and molecular dynamics simulations to obtain a family of structures compatible with the experimental NMR data. The results indicate that, although in both states the chains have the syn orientation with respect to the aromatic rings, in the free state the substrate's acyclic moiety is relatively disordered, while in the bound state only one specific conformation is preferred. Fluctuations can only be seen in the case of the terminal hydroxyl group, for which no NOE was recorded and hence no constraints were available.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5001
    Keywords: Transferred NOE ; Distance geometry ; Tachykinin ; Active conformation ; NK3 receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Senktide is a highly specific and potent analog of neurokinin B, the natural ligand of the tachykinin receptor NK-3. The membrane-bound conformation of senktide, interacting with negatively charged membrane vesicles composed of perdeuterated phosphatidylcholine and phosphatidylglycerol (70:30), has been investigated using two-dimensional transferred nuclear Overhauser effect spectroscopy (TRNOESY). The occurrence of an N-methylated phenylalanine in the peptide's sequence induces a cis-trans-isomerisation of the corresponding peptide bond which is slow on the chemical-shift scale. NMR data indicate a much stronger membrane affinity of the trans isomer, allowing the determination of a highly resolved membrane-bound conformation using distance geometry and energy minimization. The membrane-bound backbone conformation of several residues is found to be close to a left-handed helix, certainly due to the presence of nonnatural residues (succinylated N-terminal, N-methyl-phenylalanine) as well as a glycine. The results are discussed in the context of a possible biological relevance of the membrane-bound conformation, in terms of the affinity and specificity of this neuropeptide.
    Type of Medium: Electronic Resource
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