Molten Globule of Human -Lactalbumin: Hydration, Density, and Compressibility of the Interior

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• 作者：Dmitri P. Kharakoz and Valentina E. Bychkova
• 刊名：Biochemistry
• 出版年：1997
• 出版时间：February 18, 1997
• 年：1997
• 卷：36
• 期：7
• 页码：1882 - 1890
• 全文大小：175K
• 年卷期：v.36,no.7(February 18, 1997)
• ISSN：1520-4995

文摘

Specific partial volume, partial compressibility, and soundabsorption changes induced by thenative-to-molten globule state (acid) transition of the humanes/gifchars/alpha.gif" BORDER=0>-lactalbumin were measured by means ofdensitometric and ultrasonic techniques and interpreted in terms of theprotein molecule phase transitionand interphase water transfer. The molten globule is a highlyhydrated state containing about 270 watermolecules inside. Intrinsic mass density of the hydrated (swollen)interior of the protein molecule is 5%smaller and the intrinsic compressibility coefficient 2 times higherthan those in the native molecule.The obtained intrinsic compressibility falls into the range ofvalues characteristic of highly associatedliquids. Water inside the molten globule interior occupies lessvolume and is less compressible than insolvent phase. The acoustic relaxation was found to increaseindicating an appearance of pressure-dependentprocesses. The commonly used approach to the calculation of thevolume fluctuations of protein molecules,based on the well-known relation between the volume fluctuations andcompressibility, is of limitedapplicability to the highly hydrated molten globule state because alarge, if not predominant, part of thefluctuations may be determined by the process of water exchange betweenthe molten globule and bulksolvent.