藍藻蛋白(cyanophycin)是一種非核糖體合成的胺基酸聚合物，可以在大部分的藍綠藻菌(cyanobacteria)及少部分異營細菌(heterotrophic bacteria)中發現。由於天然的藍藻蛋白之結構缺少了離胺酸(lysine)，經基因重組後結構則以天門冬胺酸(aspartic acid)為主鏈，精氨酸(arginine)及離胺酸(lysine)為側鏈組成，而離氨酸上之一級胺則使其較容易進行化學修飾。
因此本研究嘗試以非水溶性藍藻蛋白(water-insoluble cyanophycin, inCGP)，與不同醣類、不同碳數醛類進行接枝改質，期望改變非水溶性藍藻蛋白分子內電荷吸引力與氫鍵數量，希望改質後的產物可有效提升其應用性。改質後的產物，經溶解度測試，觀察改質後的產物對不同溫度及酸鹼值之應答。物性測定包括紫外/可見光分光光譜儀(UV Vis spectroscopy)、傅立葉轉換紅外線光譜儀(fourier transform infrared spectroscopy , FT -IR)、粒徑分析儀(dynamic light scattering, DLS)、穿透式電子顯微鏡(transmission electron microscopy , TEM)。
改質後的非水溶性藍藻蛋白，其相轉變行受到許多因素影響，如濃度、酸鹼值、分子量等。尤其是酸鹼值對相轉變之溫度的影響，當酸鹼值降低，由於分子間的氫建強烈相互作用，最高臨界溶解溫度(upper critical solution temperature, UCST)皆有顯著的提升，實現本實驗的主要研究目標。

Cyanophycin is a non-ribosomal polypeptide that can be found in most
cyanobacteria and some heterotrophic bacteria. The structure of natural
cyanophycin lacks lysine, and after the genetic recombination, it contains
aspartic acid as the main chain, and arginine and lysine as the side chain. The
primary amine on lysine makes it easy for chemical modification.
This study tried to graft water-insoluble cyanophycin with different
oligosaccharides and aldehydes in order to change the attraction of hydrogen
bonding. It is expected that such modification can effectively improve its
applications. The study carried out the solubility test of the modified product,
and tried to measure the responses of the conjugates at different pH values.
The measurements of physical properties included UV/Vis spectrometry,
Fourier transform infrared spectrometry, particle size analysis, and
transmission electron microscopy.
Phase transition of the water-insoluble cyanophycin after modification
is affected by many factors, such as concentrations, pH values and molecular
weights, especially the effect of pH values. When the pH value decreased,
the highest critical solution temperature got a rise due to the increased
interactions of the inter-molecular hydrogen bonding.

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