Determination of the relaxation time of the helix–coil transition of poly(γ‐benzyl‐<scp>L</scp>‐glutamate) by the nmr technique

Nagayama, Kuniaki; Wada, Akira

doi:10.1002/bip.1975.360141206

Cited by 20 publications

(7 citation statements)

References 22 publications

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“…Furthermore, it appears incompatible with the experimental observations that sizeable amounts of a-helical structure are admixed in the dynamic ensemble constituting the solution conformation. From a population of a-helical structures of the order of 10% one would expect chemical shifts of the a-proton resonances of the order of 0.1 ppm [23,24], while the shifts observed for the residues 22 and 23 in the peptides of Table 1 coincide to within 0.01 ppm with the corresponding random coil values. Since over the entire temperature range studied the methyl groups of Val-21 give rise to single sharp doublet resonances of intensity three protons, the 'H NMR spectra (Fig.…”

Section: Resultsmentioning

confidence: 99%

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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%

“…This concerns in particular the partial 24, which were all used for the NMR studies described here and in the preliminary communication [l].…”

Section: Peptidr Synthesismentioning

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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“…Many theoretical interpretations have been given to these observations in efforts to resolve this problem. [16][17][18][19][20][21][22][23][24][25][26] Polypeptides with ionizable side chains have appeared to be either a special case or an anomaly with respect to the above considerations. Heretofore, when the helix-coil transition was induced by changes in pH, no doubling of the resonances was observed with either lH or l3C nmr.27- 30 However, experiments such as polarimetric temperature jump,2 ultrasonic a b s o r p t i~n ,~-~~~J~J~ polarimetric electric field jump,14 and electric field pulse methodI5 with poly(L-glutamic) acid yield relaxation times of the order of sec.…”

Section: Introductionmentioning

confidence: 99%

A nuclear magnetic resonance study of the helix–coil transition of poly(L‐glutamic acid)

1977

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SynopsisThere have been many reports that the nuclear magnetic resonance (nrnr) spectra of a large number of polypeptides exhibit peak doubling of the a-carbon and the a-carbon proton in the helix-coil transition region. One apparent exception to this generalization has been polypeptides with ionizable side chains, where the helix-coil transition is induced by changes in pH in aqueous solution. Because it is important to establish the proper theoretical reason for the peak doubling and its relation to the rate of conformational change of amino acid residues, we have reexamined the proton and carbon-13 nrnr spectra, a t high field, for two polydisperse samples of poly(L-glutamic acid). Doubling of the a-carbon proton resonance as well as those of the a-and &carbon, and backbone carbonyl are observed for a low-molecular-weight sample (DP = 54), while a higher molecular weight sample (DP = 309), exhibits only single resonances. Thus, polydispersity by itself is not sufficient to observe peak doubling; low-molecular weight is also required.

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“…Thus the angle ¢ between the two rods is ( 9) as shown in Figure 3. Now, it is convenient to introduce another angle 0 0=A01 +B62 A+B=l (10) (11) with two constants A and B to be determined later.…”

Section: Mobilitymentioning

confidence: 99%

“…Ferretti, et al, 8 • 9 have indicated this to be the time for the formation of a first helix unit from an allcoil chain. However, Nagayama and Wada, 10 and Ullman 11 are of the opinion that the polydispersity of samples is the prime cause for the double peak and the analysis of the linewidth gives the time as being from 10-3 -10-4 sec.…”

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confidence: 99%

Dynamics of the Helix—Coil Transition in Isotope Exchange of Polypeptide

Fujiwara

Saitô

1977

Polym J

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Isotope exchange experiments in the study of the helical conformation of a polypeptide suggest that the rate constant of the helix-coil change of a unit depends on its location and that it is very low in the central portion of the chain. In this paper, a model is presented to explain the low rate constant and its site dependence. When an inner residue in the helix state unwinds to the coil state, the entire helix should move in viscous medium. The mobility of unwinding in the complete helical polypeptide is calculated by the method of Kirkwood. As a result of this frictional effect, the transition rate constants obtained are in reasonable agreement with experimental results.

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Determination of the relaxation time of the helix–coil transition of poly(γ‐benzyl‐L‐glutamate) by the nmr technique

Cited by 20 publications

References 22 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

A nuclear magnetic resonance study of the helix–coil transition of poly(L‐glutamic acid)

Dynamics of the Helix—Coil Transition in Isotope Exchange of Polypeptide

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