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  • Calbindin D9k  (1)
  • Chemistry  (1)
  • Keywords:β-Elicitin  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Reductive methylation andpKa determination of the lysine side chains in calbindin D9k (1994)
    Springer
    The protein journal 13 (1994), S. 527-535 
    Details
    ISSN: 1573-4943
    Keywords: Calbindin D9k ; lysine ; reductive methylation ; pKa ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Lys residues in the 75-residue Ca2+-binding protein calbindin D9k were reductively methylated with13C-enriched formaldehyde. The possible structural effects resulting from the chemical modification were critically investigated by comparing two-dimensional NMR spectra and the exchange rates of some of the amide protons of the native and the modified protein. Our results show that the protein retains its structure even though 10 Lys out of a total of 75 amino acid residues were modified. In the Ca2+- and apo-forms of the protein, the13C-methylated Lys residues can be detected with high sensitivity and resolution using two-dimensional (1H,13C)-heteronuclear multiple quantum coherence (HMQC) NMR spectroscopy. ThepKa values of the individual Lys residues in Ca2+-calbindin D9k and apo-calbindin D9k were obtained by combiningpH titration experiments and (1H,13C)-HMQC NMR spectroscopy. Each Lys residue in the Ca2+- and apo-forms of calbindin D9k has a uniquepKa value. The LyspKa values in the calcium protein range from 9.3 to 10.9, while those in the apo-protein vary between 9.7 and 10.7. Although apo-calbindin D9k has a very similar structure compared to Ca2+-calbindin D9k, the removal of two Ca2+ ions from the protein leads to an increase of thepKa values of the Lys residues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01901534
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical pKa calculations of proteins; the tyrosine and lysine residues of b-elicitin (1999)
    Springer
    Theoretical chemistry accounts 101 (1999), S. 159-162 
    Details
    ISSN: 1432-2234
    Keywords: Keywords:β-Elicitin ; pKa Calculations ; Continuum electrostatics ; boundary element method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. Elicitins are small proteins that are secreted by plant pathogenic fungi. In this work we have used a computer program that utilizes the boundary element method for heterogeneous dielectrics with ionic strength to calculate the pK a of all titrating groups in the 98-residue protein β-cryptogein. Our results are in reasonable agreement with the experimentally determined pK a values for the Tyr residues in the protein. We find that the functionally important Lys13 residue has a normal pK a of 10.3. Our work also shows that there is no direct correlation between the exposure of an amino acid sidechain and its pK a.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002140050423
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  • 3
    Electronic Resource
    Electronic Resource
    14N and 15N NMR spectroscopic characterization and analysis of cyclic sulfur imides (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 177-182 
    Details
    ISSN: 0749-1581
    Keywords: 14N and 15N NMR ; Cyclic sulfur imides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 14N and 15N NMR spectra of natural abuadance and 15N-enriched samples of S7NH and S4(NH)4 were obtained by direct detection and by a variety of polarization transfer techniques. Sensitivity enhancements of ca 10 (compared with direct detection) for the INEPT pulse sequence and ca 100 for the HMQC (heteronuclear multiple quantum coherence) + BIRD (bilinear rotation decoupling) sequence were observed for the imides. 15N spin-lattice relaxation constants (T1) of 10.2 ± 0.1 and 12.6 ± 0.1 s were determined for S7NH and S4(NH)4, respectively. The HMQC procedure was used to obtain the 15N and 1H NMR chemical shifts and 11J(15N, 1H) values for 1,3-,1,4- and 1,5-S6(NH)2, 1,3,5- and 1,3,6-S5(NH)3. The trends in NMR chemical shifts and coupling constants are discussed in the context of the known molecular structurts of cyclic sulfur imides. The use of NMR techniques for the analysis of mixtures of cyclic sulfur imides is compared with the well established methods of infrared spectroscopy and thin-layer chromatography.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300216
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