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Published on: April 22, 2016
Chelation of calcium ions by poly(gamma-glutamic acid) from Bacillus subtilis(chungkookjang)
Takashi Tsujimoto1, Junya Kimura, Yasushi Takeuchi
1Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan.
Abstract:
Many studies have clarified that poly(gamma-glutamic acid) (PGA) increases the solubility of Ca(2+), suggesting that PGA enhances calcium absorption in small intestine. However, there has been no report on the specific interaction between PGA and Ca(2+) in water. We studied the aqueous solution properties of PGA calcium salt (PGA-Ca complex). The chelating ability and binding strength of PGA for Ca(2+) were evaluated. PGA-Ca complex was soluble in water in contrast with the insolubility of poly(acrylic acid) (PAA) calcium salt and the chelating ability of PGA for Ca(2+) was almost the same than that of PAA. The globular conformation of PGA-Ca complex in water was estimated by SEC and viscosity measurements. The chelation of PGA for Ca(2+) was examined by ¹H NMR. The present study showing the characteristics of PGA-Ca complex will provide useful information of the calcium absorption by PGA in vivo.
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