Analytical Sciences

Polydispersity as a Parameter for Indicating the Thermal Stability of Proteins by Dynamic Light Scattering

Kohei SHIBA,*1,*2 Takuro NIIDOME,*1,*3,*4 Etsuko KATOH,*5 Hongyu XIANG,*5 Lu HAN,*5 Takeshi MORI,*1,*3 and Yoshiki KATAYAMA*1,*3

*1 Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
*2 Sysmex Corporation, 4-4-4 Takatsuka-dai, Nishi, Kobe, Hyogo 651-2271, Japan
*3 Center for Future Chemistry, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
*4 PRESTO, Japan Science and Technology Corporation, Kawaguchi 332-0012, Japan
*5 Division of Plant Research, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan

A physical parameter for predicting the thermal stability of proteins was provided by a new approach using dynamic light scattering (DLS). The relationship between the melting point measured by differential scanning calorimetry (DSC) and the polydispersity of the hydrodynamic diameter determined by DLS analysis was examined. Calmodulin (CaM) and concanavalin A (ConA) were used as model proteins. The melting point measured by DSC, an indicator for thermal stability, increased and the polydispersity decreased on binding of the proteins to specific ligands, suggesting that the polydispersity could be used an indicator to predict thermal stability. In addition, the increase of thermal stability that resulted from forming a complex could be quantified by polydispersity analysis even when the melting point changed only slightly.

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