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Slow aggregation of lysozyme in alkaline pH monitored in real time employing the fluorescence anisotropy of covalently labelled dansyl probe
Author(s) -
Homchaudhuri Lopamudra,
Kumar Satish,
Swaminathan Rajaram
Publication year - 2006
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2006.03.012
Subject(s) - lysozyme , chemistry , fluorescence anisotropy , guanidine , covalent bond , fluorescence , chromatography , biophysics , denaturation (fissile materials) , analytical chemistry (journal) , nuclear chemistry , biochemistry , organic chemistry , physics , quantum mechanics , membrane , biology
The onset of hen egg white lysozyme aggregation on exposure to alkaline pH of 12.2 and subsequent slow growth of soluble lysozyme aggregates (at 298 K) was directly monitored by steady‐state and time‐resolved fluorescence anisotropy of covalently attached dansyl probe over a period of 24 h. The rotational correlation time accounting for tumbling of lysozyme in solution (40 μM) increased from ∼3.6 ns (in pH 7) to ∼40 ns on exposure to pH 12.2 over a period of 6 h and remained stable thereafter. The growth of aggregates was strongly concentration dependent, irreversible after 60 min and inhibited by the presence of 0.9 M l ‐arginine in the medium. The day old aggregates were resistant to denaturation by 6 M guanidine · HCl. Our results reveal slow segmental motion of the dansyl probe in day old aggregates in the absence of l ‐arginine (0.9 M), but a much faster motion in its presence, when growth of aggregates is halted.