Nuclear magnetic resonance study of some α-amino acids—II. Rotational isomerism

Pachler, K.G.R.

doi:10.1016/0371-1951(64)80055-2

Cited by 414 publications

(142 citation statements)

References 13 publications

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“…For comparison, the 'random coil' values for valyl residues are also indicated. From the spin-spin coupling constants the rotamer populations for the Val-21 sidechain were calculated with the method of Pachler [10,11], where ' J g = 3.4 Hz and 3Jr = 12.9 Hz, as determined with a series of ferrichrome peptides [12], were used. In the last column of Table 1, the populations of the trans conformation of Val-21 are listed.…”

Section: Resultsmentioning

confidence: 99%

Characterisation of a Local Structure in the Synthetic Parathyroid Hormone Fragment 1-34 by 1H Nuclear-Magnetic-Resonance Techniques

Bundi¹,

Andreatta

Wüthrich³

1978

Eur J Biochem

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Previous studies had shown that the molecular conformation of the synthetic human parathyroid hormone fragment 1 -34 in dilute aqueous solution contained a local non-random structure formed by the four consecutive residues -Val-21 -Gln-22 -Trp-23 -Leu-24 -. This paper gives a detailed description of this local spatial structure obtained from high resolution 'H NMR studies at 360 MHz of several peptide analogs of the partial sequence 20-24. The most important spectral parameters were high-field shifts of the a and y protons of Val-21, the spin-spin coupling constants related to the rotamer populations of the side-chains of Val-21 and Trp-23, and pH titration shifts of the amide proton resonances. It was found that the backbone fragment 20-24 is so arranged that the side-chain of Val-21 is located next to the indole ring plane of Trp-23; evidence is presented that this non-random structure is mainly stabilized by hydrophobic interactions between the side-chains of Val-21 and Trp-23. The thermal population of the observed molecular structure at room temperature was estimated from the nuclear magnetic resonance data to be approximately 20%.In a previous paper it was shown that the synthetic human parathyroid hormone fragment 1 -34 exists in aqueous solution predominantly in a flexible extended form, where, however, a local non-random structure was also clearly manifested in the ' H nuclear magnetic resonance (NMR) parameters [l]. This non-random conformation was then found to involve the amino acid residues -Val-21 -Gln-22-Trp-23 -Leu-24 -, and it was demonstrated that the same structure was preserved in the pentapeptide Arg-Val-Gln-Trp-Leu[l]. Our interest in this structure was further enhanced, since the tetrapeptide sequence 21 -24 in the parathyroid hormone corresponds to the tetrapeptide sequence 23 -26 in glucagon [2,3]. The present paper describes a detailed investigation of the spatial arrangement of the tetrapeptide segment 21 -24 in the parathyroid hormone 1 -34.The strategy used for this study was to compare the spatial structures of different synthetic peptide analogs by high-resolution 'H NMR techniques. On the basis of the requirements of compatibility with all the NMR data and with the criteria of closest interAbhreviations. NMR, nuclear magnetic resonance; parathyroid hormone 1 -34, synthetic N-terminal fragment 1 -34 of the human parathyroid hormone. atomic distances, a molecular model for the tripeptide segment -Val-21 -Gln-22 -Trp-23 -in the parathyroid hormone 1 -34 was constructed. With the use of the atomic coordinates obtained from this model, the thermal population of the local spatial structure was estimated in a quantitative analysis of the NMR data. MATERIALS AND METHODS Peptidr SynthesisThe synthesis of parathyroid hormone 1-34 according to the sequence determined by Brewer et al. [4] and of several partial sequences thereof was described previously [ 5 ] . This concerns in particular the partial sequences Met-1

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Section: Resultsmentioning

confidence: 99%

Characterisation of a Local Structure in the Synthetic Parathyroid Hormone Fragment 1-34 by 1H Nuclear-Magnetic-Resonance Techniques

Bundi¹,

Andreatta

Wüthrich³

1978

Eur J Biochem

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“…Only the side chain of Phe a in 3-~MePro-BK and 7-gMePro-BK has '~J,¢ coupling constants which suggest that one of the gauche rotamers or the trans rotamer is favoured [16,17]. At present the favoured 2', angle cannot be identified because the fl protons have not been stereospecifically assigned.…”

Section: Assignment Procedure Chemical Shifts and Coupling Constan Ismentioning

confidence: 98%

β‐Turns induced in bradykinin by (S)‐α‐methylproline

1992

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The ability of (S).g-methylprolin¢ (g-MePro) to stabilis¢ reversequrn conformations in the peptlde hormone brad~/kinin (BK = Argt-Pro:-ProLGly 4-PheS-Ser6-ProLPhe~-Arg ~) has been investigated. Two BK analogues containing ,)-MePro at position 3 or position 7 were synthesised and their conformations in aqueous solution investigated by NMR spectroscopy. Whereas BK is largely disordered on the NMR time scale both analogues showed ROE connectivities in 2D-ROESY spectra indicative of reverse-turn conformations at both Pro2-Phe ~ and Ser~-Arg °. whose formation appears to be cooperative. Some potential applications of ~z-McPro as a reverse-turn mimetic in the construction of synthetic peptide libraries is discussed.

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“…assuming 3Jgauche=2.56 Hz and 3J,,,,,=13.6 Hz for the H-C"CP-H coupling [34] and auche = 0.4 Hz and J,,,,, = 11.9 Hz [25,26] for the 1H-Cilc"-'3C' coupling. Correction for the orientational effect of the substituent electronegativity on the value of the H-CaCP-H coupling [18,35] has no crucial significance for the results obtained.…”

Section: C Signal Assignments and Coupling Constant Measurementsmentioning

confidence: 99%

Refinement of the Solution Conformation of Valinomycin with the Aid of Coupling Constants from the 13C-Nuclear-Magnetic-Resonance Spectra

Bystrov¹,

Gavrilov²,

Иванов³

et al. 1977

Eur J Biochem

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The C′= O and Cα signals in the 13C nuclear magnetic resonance (NMR) spectra of valinomycin have been assigned and the vicinal 1H…13C coupling constants have been determined by double and triple heteronuclear resonance. In conjunction with the vicinal H‐NCα‐H and H‐CαCβ‐H proton‐proton constants, the results led to unequivocal determination of the torsion angles φ and of the population distribution of the Cα‐Cβ rotational states. The Φ torsion angles for the hydroxy acid residues were estimated from the vicinal 1H‐CαC′‐15N constants. The combined data permitted refinement of the conformational states of valinomycin in different solvents. For the KS+ complex of valinomycin the observed couplings are in complete accord with the conformations we had earlier proposed for solutions and that had also been established by X‐ray analysis. In the 13C spectra of the valinomycin‐Tl+ complex 13C…203,205Tl+ spin‐spin couplings were observed for the l and d‐valine carbonyls, unequivocal proof of the donor‐acceptor interaction with the cation. In media of weak polarity (cyclohexane, chloroform) the conformation of the valinomycin molecule is similar to that of the K+ complex. In such a ‘bracelet’ structure formed by six fused β‐turns of type II and II′, the amino acid carbonyls are axial with certain inclination towards the symmetry axis. On formation of a 1:1 complex with a cation the carbonyl orientation changes, now bending towards the center of the molecular cavity. In the ‘propeller’ conformation, predominant in solvents of medium polarity (for instance CCl4/(C2H3)2SO, 3/1) the three β‐turns are of type II. The 1H and 13C chemical shifts are interpreted in terms of conformational changes in the valinomycin molecule, intermolecular and intramolecular hydrogen bonds and interaction with the metal cation.

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Nuclear magnetic resonance study of some α-amino acids—II. Rotational isomerism

Cited by 414 publications

References 13 publications

Characterisation of a Local Structure in the Synthetic Parathyroid Hormone Fragment 1-34 by 1H Nuclear-Magnetic-Resonance Techniques

Characterisation of a Local Structure in the Synthetic Parathyroid Hormone Fragment 1-34 by 1H Nuclear-Magnetic-Resonance Techniques

β‐Turns induced in bradykinin by (S)‐α‐methylproline

Refinement of the Solution Conformation of Valinomycin with the Aid of Coupling Constants from the 13C-Nuclear-Magnetic-Resonance Spectra

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