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Molecular configuration of gelatin

1955; Wiley; Volume: 16; Issue: 82 Linguagem: Inglês

10.1002/pol.1955.120168226

1542-6238

E. V. Gouinlock, Paul J. Flory, Harold A. Scheraga,

Gold and Silver Nanoparticles Synthesis and Applications

Abstract Intrinsic viscosities, light scattering turbidities and dissymmetries, and sedimentation constants have been determined for each of two high molecular weight gelatin fractions in 1 M KCNS, pH 6.5, at 30°. Their weight‐average molecular weights and z ‐average radii of gyration were 6.0 × 10 5 and 280 A., and 3.8 × 10 5 and 240 A., respectively. The ratio [η] M /( r 2 ) 3/2 , after allowance for the influence of molecular weight heterogeneity, approximates the accepted value of the viscosity parameter Φ. The values of \documentclass{article}\pagestyle{empty}\begin{document}$ {{M(1 - \bar \upsilon \rho )} \mathord{\left/ {\vphantom {{M(1 - \bar \upsilon \rho )} {NS_{0\eta 0} }}} \right. \kern-\nulldelimiterspace} {NS_{0\eta 0} }}(\overline {r^2 } )^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} very nearly agree with the normal value of the parameter P for the frictional coefficient when the experimental errors, molecular weight heterogeneity, and a possible small amount of selective binding of KCNS are taken into account. Similarly, the ratio \documentclass{article}\pagestyle{empty}\begin{document}$ {{NS_0 [\eta ]^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} \eta _0 } \mathord{\left/ {\vphantom {{NS_0 [\eta ]^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} \eta _0 } {M^{{\raise0.7ex\hbox{$2$} \!\mathord{\left/ {\vphantom {2 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} }}} \right. \kern-\nulldelimiterspace} {M^{{\raise0.7ex\hbox{$2$} \!\mathord{\left/ {\vphantom {2 3}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$3$}}} }}(1 - \bar \upsilon \rho ) $\end{document} is almost equal to, though somewhat lower than, the normal value of Φ 1/3 P −1 if the same factors are taken into account. The molecular dimension ratio \documentclass{article}\pagestyle{empty}\begin{document}$ ({{\overline {r_0^2 } } \mathord{\left/ {\vphantom {{\overline {r_0^2 } } M}} \right. \kern-\nulldelimiterspace} M})^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}} $\end{document} computed for the unperturbed gelatin molecule is indistinguisahble from that for various synthetic polymers. The ratio of \documentclass{article}\pagestyle{empty}\begin{document}$ (\overline {r_0^2 } )^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}} $\end{document} to the value calculated assuming free rotation is 1.8 to 1.9, which indicates a degree of chain flexibility similar to that occuring in synthetic polymers. We conclude that the configurational character of the gelatin chain in aqueous media is not much affected by its polar linkages or by intramolecular hydrogen bonding.