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Viscoelastic properties of protein crystals: Triclinic crystals of hen egg white lysozyme in different conditions
Author(s) -
Morozov V. N.,
Morozova T. Ya.
Publication year - 1981
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1981.360200304
Subject(s) - lysozyme , triclinic crystal system , chemistry , crystallography , amorphous solid , protein crystallization , globular protein , myoglobin , analytical chemistry (journal) , crystallization , crystal structure , chromatography , organic chemistry , biochemistry
A technique for the measurement of the dynamic Young's modulus E and logarithmic decrement of protein crystals and other microscopic samples by the resonance method modified to a microscale is described. Monoclinic crystals of horse hemoglobin and sperm whale myoglobin; triclinic hen egg white lysozyme crystals, crosslinked by glutaraldehyde; and native and crosslinked needlelike lysozyme crystals were studied, as were amorphous protein films. The E of wet protein crystals is shown to be in the range (3–15) × 10 3 kg/cm 2 , = 0.3–0.7. The crosslinking does not significantly affect the values. General elastic properties were analyzed for triclinic lysozyme crystals. No frequency dependence of E and was found over the frequency range of 2.5–65 kHz. The temperature dependence was found to be characteristic for glassy polymers; the decrement of Young's modulus was −2.4 ± 0.1%/°C. The guanidine HCl denaturation caused a 1000‐fold decrease of E , its temperature dependence becoming similar to that of rubberlike materials. Studies of pH and salt effects showed E to be influenced by ionization of the acidic groups at pH 3–4.5. A humidity decrease from 100 to 30% caused a three‐ to fourfold increase of E and a decrease of . The final values of E = (40–60) × 10 3 kg/cm 2 and ≃ 0.1 were the same for dry crystals and amorphous films, whether crosslinked or not. These values may be attributed to the protein globular material.