| Summary: | 碩士 === 國立臺灣科技大學 === 高分子系 === 97 === In this work, we are interested in the aggregation phenomenon of supersaturated lysozyme solution near the metastable liquid-liquid （L-L） coexistence curve. Solution properties are fixed by addition of salt and buffer, and its pH value is adjusted to 4.5. We probe the aggregation of lysozyme solution at different temperatures by measurements of cloud point, polarized optical microscopy （POM）, scanning electron microscopy （SEM）, falling-sphere method, and small angle light scattering （SALS）. From our composition-temperature phase diagram, the aggregation of lysozyme solution can be divided into four regions. In addition, these results of cloud-point measurement show interesting two-step decay in transmit light intensity within a small temperature range. This evidence suggests the aggregation of supersaturated lysozyme solution is different from the crystallization/gelation in common polymer systems. Moreover, when the temperature of lysozyme solution （ ） is slightly higher than the L-L coexistence curve, pictures of POM show the time evolution of crystallization in solution. This special structure formation is so called dense-drop to crystal transition. Nucleation process is two-step mechanism due to critical fluctuation. As the solution temperature decrease below the L-L coexistence curve （ ）, by contrast, the structure of lysozyme solution seems like as a transient gel or jamming solid. Through the analysis of SALS data, we find that the structural evolution of lysozyme solution near its L-L coexistent cure are partially in agreement with model predictions of diffusion limited cluster aggregation （DLCA）. This implies the final structure of lysozyme in solution is the outcome of hierarchical aggregation.
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