DL-Homoproline tetrahydrate

Bhattacharjee, S. K.; Chacko, K. K.

doi:10.1107/s0567740879003617

Cited by 22 publications

(8 citation statements)

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“…The main difficulty arising in the case of XRD analysis of polyhydrates is the common statistic disorder of hydrogen atoms in solvate water molecules. We have thus chosen the previously studied9 ordered tetrahydrate of piperidine‐2‐carboxylic acid ( 1 ) racemate crystals for performing high‐resolution XRD investigations10 (see Experimental Section). In the crystal, the molecules of amino acid 1 are zwitterionic and assembled into infinite chains by intermolecular NH⋅⋅⋅O H‐bonds [N(1)⋅⋅⋅O(1) 2.793(1) Å, NHO 163.82(2)°].…”

Section: The Overall Energy Of H‐bonds (Eh) and Stabilization Energy mentioning

confidence: 99%

Water Clusters in Crystal: Beyond the “Hydrogen‐Bonding Graphs”

2006

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Section: The Overall Energy Of H‐bonds (Eh) and Stabilization Energy mentioning

confidence: 99%

Water Clusters in Crystal: Beyond the “Hydrogen‐Bonding Graphs”

2006

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“…At this stage, it was interesting to test the conformational characteristics of the Pip/AzPip couple, the six‐membered heterocycle of which contains one more methylene group. The pipecolic residue (Pip) (22) is not one of the 20 natural amino acids but is often encountered in the plant kingdom (white clover, green beans) and in some antibiotics [efrapeptins, elvapeptins, rapamycin, ascomycin (23, 24)]. It is also one of the few ring homologues of the conformationally restricted proline residue, which has been incorporated into analogues of bioactive peptides, whereas recently the synthesis, molecular structure and conformation of two particular AzPip derivatives, namely ones containing a new conformationally restricted analogue of Phe, AzTic[3,4‐dihydro‐2(1H)‐phtalazine‐carboxylic acid], have been reported to be topographically constrained aromatic α‐aza‐amino acids (25).…”

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confidence: 99%

Structural features of thePip/AzPip couple in the crystalline state: influence of the relative AzPip location in an azadipeptide sequence upon the induced chirality and conformational characteristics

Didierjean

Aubry

Wyckaert

et al. 2000

The Journal of Peptide Research

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Azapipecolic (AzPip) is a pipecolic (Pip) residue analogue containing a nitrogen atom in place of the C(alpha)H group. AzPip was introduced into two reverse dipeptide sequences, Piv-AzPip-L-Ala-NHiPr I and Boc-L-Ala-AzPip-NHiPr II in order to evaluate, in the crystalline state, the influence of the L-Ala-induced chirality upon the prochiral AzPip residue, and therefore the resulting conformational characteristics, according to the relative position of the AzPip residue. Piv-DL-Pip-NHMe III served as a control derivative for comparison between the properties of the two different heterocycles of Pip and AzPip residues. Piperidine and hexahydropyridazine rings have a few characteristics in common: chair conformation, axial disposition of the C-terminal backbone substituent and the cisoid form of the N-terminal tertiary amide function. An almost pure sp3 hybridization state is observed for the substituted nitrogen atom N(alpha), so that L-Ala induces an AzPip (R) or (S) chirality when it follows or precedes, respectively, the azaresidue in such a pseudodipeptide sequence. If both I and II compounds present a short NH...N contact between the sp2 tertiary amide nitrogen atom and the NH of the next secondary amide function, whatever the chiral nature of the sequence, the heterochiral azadipeptide I adopts a rather totally extended conformation while the homochiral azadipeptide II is folded by a beta-VI turn-like structure stabilized by a classical 4-->1 intramolecular hydrogen bond.

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“…The criteria used was th a t the crystal structure should contain carbon, nitrogen, oxygen and hydrogen atoms, but no ions such as chlorine or bromine should be present to complicate the number of different interactions. The homoproline structure (Bhattacharjee & Chacko 1979) was chosen because it has four water molecules per asymmetric unit and four asymmetric units per unit cell and these solvent molecules show a variety of types of coordination. L-Arginine (Lehmann et al 1973) has only eight waters per unit cell but also has the advantage th a t the hydrogen t---------------------------V (------------------------ c o c o c o c o c o c o c o c o c o c o c o c positions have been determined from neutron diffraction.…”

Section: (Iv) Test Structuresmentioning

confidence: 99%

Monte Carlo computer simulation of water–amino acid interactions

Goodfellow

Finney

Barnes

1982

Proc. R. Soc. Lond. B.

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The sensitivity of computer simulated solvent structures to changes in both non-bonded (Lennard-Jones) coefficients and partial atomic charges has been investigated with use of amino acid hydrate crystals in which the water structure is well defined experimentally. The polarizable electropole (p.e.) model of water has been extended to describe water-protein interactions; thus, the cooperative nature of the hydrogen bond (i.e. non-pair additive effects) is allowed for through a polarizable dipole. By means of Monte Carlo calculations, the predicted water positions were found to be very sensitive to the input parameters used to define both the non-bonded and electrostatic interactions. Root mean square deviations between simulated and X-ray structures were not always adequate to describe these differences and so more detailed comparisons were made. Non-pair additive effects were shown to lead to large changes in water dipoles, the values of which depended specifically on the system under consideration.

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DL-Homoproline tetrahydrate

Cited by 22 publications

References 1 publication

Water Clusters in Crystal: Beyond the “Hydrogen‐Bonding Graphs”

Water Clusters in Crystal: Beyond the “Hydrogen‐Bonding Graphs”

Structural features of thePip/AzPip couple in the crystalline state: influence of the relative AzPip location in an azadipeptide sequence upon the induced chirality and conformational characteristics

Monte Carlo computer simulation of water–amino acid interactions

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