<scp>L</scp>-Alanyl-<scp>L</scp>-threonine

Netland, Kjetil Andreas; Andresen, Kim; Görbitz, Carl Henrik; Dalhus, Bjørn

doi:10.1107/s1600536804010578

Cited by 4 publications

(3 citation statements)

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“…The influence of multipolar population parameters transfer on the improvement of the principal refinement parameters was investigated on the compounds l-alanyl-l-threonine (Netland et al, 2004), l-seryl-l-phenylalanine (Helle et al, 2004), l-threonyl-l-alanine (Gö rbitz, 2005), l-seryl-l-valine (Moen et al, 2004) and triglycine (Pichon-Pesme & . A pseudo-peptide of significantly larger molecular weight (1158 g mol À1 ), pseudophomin A (Quail et al, 2002) with primary structure hydroxydecanoyl-l-Leu-d-Glu-d-allo-Thr-d-Ile-d-Leu-d-Ser-l-Leu-d-Ser-l-Ile monohydrate was also tested.…”

Section: Refinement Of Peptides With and Without Library Transfermentioning

confidence: 99%

On the application of an experimental multipolar pseudo-atom library for accurate refinement of small-molecule and protein crystal structures

et al. 2007

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With an increasing number of biomacromolecular crystal structures being measured to ultra-high resolution, it has become possible to extend to large systems experimental charge-density methods that are usually applied to small molecules. A library has been built of average multipole populations describing the electron density of chemical groups in all 20 amino acids found in proteins. The library uses the Hansen & Coppens multipolar pseudo-atom model to derive molecular electron density and electrostatic potential distributions. The library values are obtained from several small peptide or amino acid crystal structures refined against ultra-high-resolution X-ray diffraction data. The library transfer is applied automatically in the MoPro software suite to peptide and protein structures measured at atomic resolution. The transferred multipolar parameters are kept fixed while the positional and thermal parameters are refined. This enables a proper deconvolution of thermal motion and valence-electron-density redistributions, even when the diffraction data do not extend to subatomic resolution. The use of the experimental library multipolar atom model (ELMAM) also has a major impact on crystallographic structure modelling in the case of small-molecule crystals at atomic resolution. Compared to a spherical-atom model, the library transfer results in a more accurate crystal structure, notably in terms of thermal displacement parameters and bond distances involving H atoms. Upon transfer, crystallographic statistics of fit are improved, particularly free R factors, and residual electron-density maps are cleaner.

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Section: Refinement Of Peptides With and Without Library Transfermentioning

confidence: 99%

On the application of an experimental multipolar pseudo-atom library for accurate refinement of small-molecule and protein crystal structures

et al. 2007

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“…1a. 8 It was the unprecedented observation of an intramolecular hydrogen bond that made us realize that a C-terminal serine or threonine residue may behave like a hydrophobic residue as there is no absolute need to find an intermolecular acceptor for the alcoholic H atom. We thus decided to investigate more compounds in this subfamily of dipeptides in order to find recurring examples of intramolecular hydrogen bonds, and possibly new types of crystal packing patterns.…”

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Microporous organic crystals: an unusual case for l-leucyl–l-serine

et al. 2005

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“…There are no regular peptides among only 31 P4 2 entries in the Cambridge Structural Database (CSD; Version 5.26 of November 2004; Allen, 2002), but related structures in I4 with Z = 8, a $16.0 Å and c $5.2 Å were observed for l-alanyl-lalanine (Fletterick et al, 1971) and l-2-aminobutyryl-lalanine (Gö rbitz, 2002). The retroanalogue of TA, l-alanyl-lthreonine (AT) (Netland et al, 2004), has a completely different crystal packing pattern, in space group P2 1 2 1 2 1 , but nevertheless incorporates the same N-HÁ Á ÁO hydrogen bonds, except that the amide H atom is accepted by the threonine side-chain -OH in AT, but by the carbonyl group of the peptide bond in TA ( Fig. 2 and Table 2).…”

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confidence: 99%