Ultrasonic absorption measurements in dilute aqueous poly(a,L-glutamic acid)(PGA) have been carried out over the frequency range 40 kHz-35 MHz by the resonance, statistical reverberation, and pulse techniques. Data at the two PGA concentrations 2.7 X 10-3 and 1.1 X 10-3 (mol residue)/!, in 0.03 MNaCl at 37°exhibited relaxational absorption over the pH range 4.8-S.6. Both the relaxational amplitude (A) and relaxation time (t) passed through maximum values at pH 5.21, the midpoint of the helix-coil transition. The maximum values of A and r were found to be 100 X 10-17 sec2 cm-1 and 1.0 gsec, respectively. The value of the rate constant for helical growth in the Schwarz theory was estimated to be (8 ± 5) X 107 sec-1.

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