Open AccessTHE USE OF N -METHYLNICOTINAMINDE CHLORIDE AS A CONFORMATIONAL PROBE FOR CHICKEN EGG-WHITE LYSOZYME
Author(s) -
David A. Deranleau,
Ralph A. Bradshaw,
R. Schwyzer
Publication year - 1969
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.63.3.885
Subject(s) - lysozyme , egg white , white (mutation) , chloride , chemistry , egg albumen , biology , biochemistry , food science , organic chemistry , gene
Chicken egg-white lysozyme forms a yellow complex withN -methylnicotinamide chloride. Titration studies utilizing the appearance of the yellow color as a measure of complex formation indicate that the weak complex (association constantk = 3.2 liter mole-1 ) involves a single class of binding sites on the lysozyme molecule. By analogy with similar titration studies on model compounds containing the indole moiety, the site forN -methylnicotinamide binding is probably the indole ring of a single, solvent-available tryptophan residue. The yellow color itself apparently arises from a charge transfer transition, with the indole ring system serving as the donor andN -methylnicotinamide as the acceptor. Complete resolution of the charge transfer spectrum of the lysozyme-N -methylnicotinamide complex was not achieved due to the very high absorbance of the protein near the short-wavelength absorption edge of the band. However, it is possible to consider the spectrum as the sum of two Gaussian bands whose positions and relative intensities agree remarkably well with the positions and relative intensities obtained by Gaussian fitting of the charge transfer spectra of several model complexes between substituted indoles andN -methylnicotinamide. The geometry for such complex formation requires that the ring faces of both donor and acceptor be more or less completely available for complexation. The possible use ofN -methylnicotinamide as a molecular probe for tryptophan residues having at least one indole ring face freely available to the solvent is discussed.