Chen C H, Berns D S
Biophys Chem. 1978 Jul;8(3):203-13. doi: 10.1016/0301-4622(78)87002-1.
Protein unfolding of eight different phycocyanins was investigated utilizing circular dichroism and visible spectra. The phycocyanin samples were extracted from algae that are normally found in vastly different environments, and are classified as mesophilic, thermophilic, halophilic and psychrophilic. The ability of these proteins to resist the denaturant urea is in the order of thermophile greater than mesophile, halophile greater than psychrophile. Based on a two-state approximation the apparent free energies of protein unfolding at zero urea denaturant concentration, deltaGH2Oapp, were found to range from 2.4 to 8.8 kcal/mole for the eight phycocyanins at pH 6 and 25 degrees C. The proteins from the thermophile are generally more stable than those from the mesophile. An extra stability of the halophile is believed due to the specific interaction of the proteins and the ions in solution. A correction for deltaGH2Oapp due to minor amino acid differences reveals that the stability and the structural properties of these proteins are primarily affected by this minor difference in amino acid compositions.
利用圆二色光谱和可见光谱研究了八种不同藻蓝蛋白的蛋白质解折叠情况。藻蓝蛋白样品取自通常生长在截然不同环境中的藻类，这些藻类被归类为嗜温、嗜热、嗜盐和嗜冷藻类。这些蛋白质抵抗变性剂尿素的能力顺序为：嗜热藻大于嗜温藻，嗜盐藻大于嗜冷藻。基于二态近似，发现在pH 6和25℃条件下，八种藻蓝蛋白在零尿素变性剂浓度下蛋白质解折叠的表观自由能ΔG H2O app在2.4至8.8千卡/摩尔之间。嗜热藻类的蛋白质通常比嗜温藻类的蛋白质更稳定。嗜盐藻类的额外稳定性被认为是由于蛋白质与溶液中离子的特异性相互作用。由于氨基酸的微小差异对ΔG H2O app进行校正后发现，这些蛋白质的稳定性和结构性质主要受氨基酸组成的这种微小差异影响。
