Effect of pH and ionic strength modifications on thermal denaturation of the 11S globulin of sunflower (Helianthus annuus).
Effect of pH and ionic strength modifications on thermal denaturation of the 11S globulin of sunflower (Helianthus annuus).
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pH 值和离子强度变化对向日葵 (Helianthus annuus) 11S 球蛋白热变性的影响。
DOI：
10.1021/jf0494175
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发表时间：
2004
影响因子：
6.1
通讯作者：
M. Añón
中科院分区：
文献类型：
--
作者：
M. I. Molina;S. Petruccelli;M. Añón
向日葵黄素是向日葵的主要贮藏蛋白，水溶性低，加热时不会形成凝胶;这种行为与其他11 S球蛋白不同，限制了其食品应用。为了理解这种特殊的行为，在pH值和离子强度的修改引起的向日葵花色素的缔合-解离状态的变化进行了分析。研究了这些不同介质条件对其热稳定性和聚集体形成趋势的影响。向日葵花素在不同pH值和离子强度下的行为与其他11 S球蛋白相似，除了它在pH 11下保持三聚体形式。向日葵黄素的热稳定性高于其他11 S球蛋白，但低于燕麦11 S球蛋白。碱性pH值使其变性温度和变性过程的协同性降低10 ℃，但不影响变性活化能。随着pH值的增加，热稳定性的降低也表现为通过SH/SS交换反应形成聚集体的趋势。当在碱性pH下进行热处理时，所有向日葵黄素亚基形成聚集体，其特征在于β-多肽的比例高于α-多肽，这表明聚集伴随着解离。在80 ℃下处理足以诱导聚集但不产生变性，并且在这些条件下，处理后六聚体形式保留。
Helianthinin, the main storage protein of sunflowers, has low water solubility and does not form a gel when heated; this behavior is different from other 11S globulins and limits its food applications. To understand this particular behavior, changes on helianthinin association-dissociation state induced by modifications in pH and ionic strength were analyzed. The influence of these different medium conditions on its thermal stability and tendency to form aggregates was also studied. Helianthinin behavior at different pH values and ionic strengths is similar to other 11S globulins except that it remains in a trimeric form at pH 11. Helianthinin thermal stability is higher than other 11S globulins but is lower than oat 11S globulin. Alkaline pH produces a 10 degrees C decrease of its denaturation temperature and also of the cooperativity of denaturation process, but it does not affect the denaturation activation energy. The decrease in thermal stability with the pH increase is also manifested by its tendency to form aggregates by SH/SS interchange reactions. When thermal treatments at alkaline pH are performed, all helianthinin subunits form aggregates, characterized by a higher proportion of beta-polypeptides than alpha-polypeptides, which is an indication that aggregation is accompanied by dissociation. Treatments at 80 degrees C are sufficient to induce aggregation but not to produce denaturation, and in these conditions hexameric forms remain after the treatment.