1. For the purpose of studying alteration of muscle proteins, especially of actomyosin which is notable for its streaming birefringence, a simple apparatus for detecting streaming birefringence has been constructed (fig. 1). If a solution gives intense streaming birefringence (S. B. ), the liquid lights up brilliantly under the polaroids on flowing with a slow rotary motion (e. g. 100-200 r. p. m.) and a dark cross of isocline on the bright field can readily be observed. 2. Extracts with KCl (pH 8.1) of muscles of most aquatic animals tested showed S. B. This had a relation with the fact that actomyosin is extractable with salt solution. In spite of insolubility of actomyosin in water, pronounced S. B. was observed in extracts of mollusk muscles with water (table 1). In this connection, it may be pointed out that H2O extracts of mollusk muscles were found to contain a large amount of muscle protein belonging to myosin fraction4). S. B. was also detected in aquatic suspension of water-extracted-residue of fish or shrimp muscle. In KCl extracts of some bivalve muscles, S. B. could not be detected. When H2O extract of fan shell was diluted with H2O or KCl stepwisely, S. B. could be still detected as far as eightfold-dilution with H2O but dilution only up to fourfold with KCl gave S. B. 3. It is well known that actomyosin begins to coagulate rapidly near 38-40°C. When commi-nutated muscle was heated in water above 40°C. for 5 minutes, KCl extract of heated muscle of fish or shrimp did not give S. B., but extract of mollusk muscle heated at 60°C. with KCl or water remained to show intense S. B. (table 2). It was interesting to see that in extract of squid moat heated at 40°C. for 5 minutes, S. B. could not be detected. While on prolonged heating at this temperature, or heating at 45°C. for 5 minutes, the extracts did not lose their S. B. S. B. of KCl extracts of muscles was destroyed on heating above 42°C., except that of squid meat which did not lose its S. B. at 50°C. (table 2). It was surprising to find that H2O extract of mollusk meat retained the S. B. even when heated at 70-80°C. for 5 minutes. If KCl was added to H2O extract, S. B. was destroyed on heating at the same temperature as that of KCl extract (table 3). It seems that KCl might cause dissociation of particles contained in the H2O extract into ones which were perhaps as smaller as those contained in KCl extract. 4. When meat was kept at -15°C. for 1-2 weeks, S. B. did not appear in extracts of frozen meats of most animals experimented, but it did in extract of squid meat kept frozen even for one month (table 4). Stability of squid meat against freezing was also observed in case of freezing KCl extract ; namely, when KCl extract of muscle was frozen, fish lost its S. B. after 1-2 days in contrast with squid giving S. B. as long as 5 days (table 5). If, H2O extract of squid meat was frozen even for one day, a bulk of precipitate formed and S. B. was not observed. In this connection, Snow8) found that freezing caused extensive denaturation of actomyosin when the protein was in the form of suspended gels, but not when it was dispersed in salt solution. 5. It could be suggested that water extract of mollusk muscle might contain actomyosin as suspended particles composed of many molecules.
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Feb 21, 2015
J.-L Si + 3
Open Access
