Sonic Degradation of High Polymers in Solution

Abstract

SONIC DEGRADATION OF HIGH POLYMERS IN SOLUTION1725 about the pro-hypro peptide linkage sets the hydrogen-bonded configuration which the remainder of the chain may assume. The so-called "collagen fold" is thus directly related t o the trans pro-hypro form.The data presented here cannot answer another important question-whether the proline and hydroxyproline are concentrated in only one of the three collagen peptide chains, as has been suggested in connection with X-ray diffraction data.I6 (16) P. M. Cowan. 5. h9cGarin and A. C. J. North, Nature, 116, 1062 (1955).However, this seems to be unlikely in view of the viscosity data in the 40-100% FA range. On the basis of our data it does appear that there is a decided possibility that long segments of each of the polypeptide chains are essentially free of proline and hydroxyproline. Grassman has found large peptide fragments in gelatin that do not have a full complement of hydroxyproline. This means that other parts of the chain must have more than their average share.17 (17) W. Grassman, K. Hannig, H. Endres and A. Riedel, 2. physiol. Chem., 806, 123 (1956).The rates of sonic degradation of polymethyl methacrylate, polyisobutene polylauryl methacrylate and polystyrene are determined by use of 2,2-diphenyl-l-picryl hydrazyl to measure free radicai fragments. Using fractionated samples it is found (1) that the rate of degradation per polymer backbone bond, under constant conditions of cavitation, is directly proportional to the degree of polymerization; ( 2 ) that large side chains accelerate the rate of degradation; and (3) that a 10-2070 change in the carbon-carbon bond dissociation energy of the polymer chain has little effect upon the rate. A simple model is roposed whereby the rupturing stress arises from the radial velocity gradient surrounding a collapsing cavity. The modef yields a kinetic expression in agreement with the experimental results.

Ultrasonic compatibilization of polyelectrolyte complex based on polysaccharides for biomedical applications

“…Ultrasound also induces structural and chemical changes in the polymer systems as a result of cavitational process [11]. In particular, a remarkable effect of ultrasound on polymers degradation reactions was observed in solution and melt conditions [12][13][14][15]. The breakage of molecular chains under ultrasound occurs near the center of the chain and results in formation of macroradicals, as previously demonstrated by Tabata et al [16].…”

Ultrasonication: An Efficient Agitation for Accelerating the Supersaturation-Limited Amyloid Fibrillation of Proteins

“…56) However, because 2-m is intact even after extensive ultrasonication, 35,38) sonochemical reactions do not seem to be the main mechanisms responsible for the breakdown and formation of the fibrils. On the other hand, the repeated growth and collapse of cavitation bubbles and concomitant large shearing forces [62][63][64] seem to be directly linked to triggering of the amyloid nucleation in supersaturated monomeric solutions. One possible mechanism of ultrasonication-dependent nucleation is the formation of glassy (i.e., amorphous) aggregates at the hydrophobic liquid-gas interface of cavitation bubbles.…”

High-throughput Analysis of Ultrasonication-forced Amyloid Fibrillation Reveals the Mechanism Underlying the Large Fluctuation in the Lag Time

“…Ultrasonication was originally used in studies examining amyloid fibrils to fragment preformed long fibrils into shorter fibrils (8,19,22,23) by taking advantage of the strong shearing forces produced by the repeated growth and collapse of cavitation bubbles (24,25). The ends of fibrils act as the templates of subsequent growth; therefore, ultrasonic treatments effectively maximize the seeding potential of preformed fibrils.…”