ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A technique for the measurement of the dynamic Young's modulus E and logarithmic decrement v 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) × 103 kg/cm2, v = 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 v 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 v. The final values of E = (40-60) × 103 kg/cm2 and v ≃ 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.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1981.360200304
