Department of Applied Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden.
Biomacromolecules. 2010 Dec 13;11(12):3359-66. doi: 10.1021/bm1008487. Epub 2010 Nov 5.
The time-dependent diffusion and mechanical properties of gelatin in solution, in the gel state, and during the sol/gel transition were determined using fluorescence recovery after photobleaching (FRAP) and rheology. The parameters in the experimental design were 2% w/w and 5% w/w gelatin concentration; 15, 20, and 25 °C end quench temperatures; and Na(2)-fluorescein, 10 kDa FITC-dextran, and 500 kDa FITC-dextran as diffusion probes. The samples were monitored in solution at 60 °C, during quenching, for 75 min at end quench temperatures and after 1, 7, and 14 days of storage at the end quench temperature. The effect of temperature on the probe diffusion was normalized by determining the free diffusion of the probes in pure water for the different temperatures. The results gained by comparing FRAP and rheology showed that FRAP is able to capture structural changes in the gelatin before gelation occurs, which was interpreted as a formation of transient networks. This was clearly seen for 2% w/w gelatin and 20 and 25 °C end quench temperatures. The structural changes during sol/gel transition are detected only by the larger probes, giving information about the typical length scales in the gelatin structure. The normalized diffusion rate increased after 7 and 14 days of storage. This increase was most pronounced for fluorescein but was also seen for the larger probes.
使用荧光恢复后光漂白（FRAP）和流变学技术，测定了明胶在溶液、凝胶状态和溶胶-凝胶转变过程中随时间的扩散和力学性能。实验设计中的参数为 2%w/w 和 5%w/w 的明胶浓度；15、20 和 25°C 的终淬温度；以及 Na(2)-荧光素、10 kDa FITC-葡聚糖和 500 kDa FITC-葡聚糖作为扩散探针。在 60°C 下监测溶液中的样品，在终淬温度下淬灭 75 分钟，并在终淬温度下储存 1、7 和 14 天后进行监测。通过确定不同温度下探针在纯水中的自由扩散，对温度对探针扩散的影响进行归一化。通过比较 FRAP 和流变学获得的结果表明，FRAP 能够在凝胶化发生之前捕捉明胶的结构变化，这被解释为瞬态网络的形成。在 2%w/w 明胶和 20 和 25°C 终淬温度下，这一点表现得尤为明显。溶胶-凝胶转变过程中的结构变化只能通过较大的探针检测到，提供了关于明胶结构中典型长度尺度的信息。储存 7 和 14 天后，归一化扩散率增加。这种增加在荧光素中最为明显，但在较大的探针中也可以看到。
