GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Natural Sciences  (3)
  • 1
    Online Resource
    Online Resource
    Circular dichroism spectra of short, fixed-nucleus alanine helices
    Proceedings of the National Academy of Sciences ; 2002
    In:  Proceedings of the National Academy of Sciences Vol. 99, No. 24 ( 2002-11-26), p. 15416-15421
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 99, No. 24 ( 2002-11-26), p. 15416-15421
    Abstract: Very short alanine peptide helices can be studied in a fixed-nucleus, helix-forming system [Siedlicka, M., Goch, G., Ejchart, A., Sticht, H. & Bierzynski, A. (1999) Proc. Natl. Acad. Sci. USA 96, 903–908]. In a 12-residue sequence taken from an EF-hand protein, the four C-terminal peptide units become helical when the peptide binds La 3+ , and somewhat longer helices may be made by adding alanine residues at the C terminus. The helices studied here contain 4, 8, or 11 peptide units. Surprisingly, these short fixed-nucleus helices remain almost fully helical from 4 to 65°C, according to circular dichroism results reported here, and in agreement with titration calorimetry results reported recently. These peptides are used here to define the circular dichroism properties of short helices, which are needed for accurate measurement of helix propensities. Two striking properties are: ( i ) the temperature coefficient of mean peptide ellipticity depends strongly on helix length; and ( ii ) the intensity of the signal decreases much less rapidly with helix length, for very short helices, than supposed in the past. The circular dichroism spectra of the short helices are compared with new theoretical calculations, based on the experimentally determined direction of the NV 1 transition moment.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.232591399
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2002
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    A general two-process model describes the hydrogen exchange behavior of RNase A in unfolding conditions.
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 5 ( 1996-03-05), p. 1982-1987
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 5 ( 1996-03-05), p. 1982-1987
    Abstract: When NMR hydrogen exchange was used previously to monitor the kinetics of RNase A unfolding, some peptide NH protons were found to show EX2 exchange (detected by base catalysis) in addition to the expected EX1 exchange, whose rate is limited by the kinetic unfolding process. In earlier work, two groups showed independently that a restricted two-process model successfully fits published hydrogen exchange rates of native RNase A in the range 0-0.7 M guanidinium chloride. We find that this model predicts properties that are very different from the observed properties of the EX2 exchange reactions of RNase A in conditions where guanidine-induced unfolding takes place. The model predicts that EX2 exchange should be too fast to measure by the technique used, whereas it is readily measurable. Possible explanations for the contradiction are considered here, and we show that removing the restriction from the earlier two-process model is sufficient to resolve the contradiction; instead of specifying that exchange caused by global unfolding occurs by the EX2 mechanism, we allow it to occur by the general mechanism, which includes both the EX1 and EX2 cases. It is logical to remove this restriction because global unfolding of RNase A is known to give rise to EX1 exchange in these unfolding conditions. Resolving the contradiction makes it possible to determine whether populated unfolding intermediates contribute to the EX2 exchange, and this question is considered elsewhere. The results and simulations indicate that moderate or high denaturant concentrations readily give rise to EX1 exchange in native proteins. Earlier studies showed that hydrogen exchange in native proteins typically occurs by the EX2 mechanism but that high temperatures or pH values above 7 may give rise to EX1 exchange. High denaturant concentrations should be added to the list of variables likely to cause EX1 exchange.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.5.1982
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    Alanine is helix-stabilizing in both template-nucleated and standard peptide helices
    Proceedings of the National Academy of Sciences ; 1999
    In:  Proceedings of the National Academy of Sciences Vol. 96, No. 7 ( 1999-03-30), p. 3682-3687
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 96, No. 7 ( 1999-03-30), p. 3682-3687
    Abstract: Alanine-based peptides of defined sequence and length show measurable helix contents, allowing them to be used as a model system both for analyzing the mechanism of helix formation and for investigating the contributions of side-chain interactions to protein stability. Extensive characterization of many peptide sequences with varying amino acid contents indicates that the favorable helicity of alanine-based peptides can be attributed to the large helix-stabilizing propensity of alanine. Based on their analysis of alanine-rich sequences N-terminally linked to a synthetic helix-inducing template, Kemp and coworkers [Kemp, D. S., Boyd, J. G. & Muendel, C. C. (1991) Nature (London) 352, 451–454; Kemp, D. S., Oslick, S. L. & Allen, T. J. (1996) J. Am. Chem. Soc. 118, 4249–4255] argue that alanine is helix-indifferent, however, and that the favorable helix contents of alanine-based peptides must have some other explanation. Here, we show that the helix contents of template-nucleated sequences are influenced strongly by properties of the template–helix junction. A model in which the helix propensities of residues at the template–peptide junction are treated separately brings the results from alanine-based peptides and template-nucleated helices into agreement. The resulting model provides a physically plausible resolution of the discrepancies between the two systems and allows the helix contents of both template-nucleated and standard peptide helices to be predicted by using a single set of helix propensities. Helix formation in both standard peptides and template–peptide conjugates can be attributed to the large intrinsic helix-forming tendency of alanine.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.96.7.3682
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1999
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...