Yb(Ⅲ)、Gd(Ⅲ)与EHPG配合物的光谱研究

Spectral Studies on the Complexes of Yb(Ⅲ) and Gd(Ⅲ)to EHPG

在0.01mol·LN-2-羟乙基哌嗪-N'-2-乙磺酸(Hepes),pH7.4和室温条件下,应用荧光光谱和紫外差光谱研究了Yb?,Gd?与N-N'-乙烯-二犤2-(2-羟基苯基)甘氨酸犦(EHPG)的配合反应。结果表明,随着稀土离子Yb?或Gd?的不断滴加,EHPG在310nm处的最大荧光峰强度逐渐降低,而其紫外差光谱在238和292nm处的吸收峰逐渐增强,当稀土离子Yb?或Gd?达到一定量时,310nm处的荧光强度、238和292nm处的吸收峰强度不再发生变化,实验证明Yb?或Gd?与EHPG结合形成1∶1的配合物;在238nm处配合物Yb-EHPG和Gd-EHPG的摩尔吸光系数分别为:ΔεYb=(22.35±0.13)×103cm-1·mol-1·L,ΔεGd=(21.64±0.28)×103cm-1·mol-1·L;条件稳定常数分别是:lgKYb-EHPG=15.67±0.13,lgKGd-EHPG=13.21±0.23,符合线性自由能关系。Yb?或Gd?与脱铁伴清蛋白(apoOTf)的结合导致蛋白质荧光有18%的猝灭。

Under the conditions of ￡°￡(r)01mol·L -1 N￡-￡¨￡2￡-hydroxyethyl￡(c)￡-piperazine￡-N'￡-￡2￡-ethanesulfonic acid￡¨Hepes￡(c)and room temperature and pH ￡*￡(r)4,the reac tion process of ethylene-N,N'-bis(o￡-hydroxyphenylglycine￡(c)￡¨EHPG￡(c)with Yb ?or Gd?was monitored by fluorescence spectra and UV difference spectrophotome try￡(r)The molar absorptivities for Yb-EHPG and Gd￡-EHPG complexes we re￡¨￡2￡2￡(r)￡3￡μ?à￡°￡(r)￡±￡3￡(c)×103cm-1·mol￡-￡±?¤L and￡¨￡2￡±￡(r)￡?￡′?à￡°￡(r)￡2￡?￡(c)×103cm-1·mol-1 ?¤L respectively￡(r)When EDTA was added,the UV difference peak at 238nm of Yb￡-EHPG or Gd￡-EHPG decreased￡(r)Using EDTA as com peting agent conditional equilibrium constants of the complexes were lg K Yb-EHPG ￡?￡±￡μ￡(r)￡?￡*?à￡°￡(r)13and lg K Gd-EHPG ￡?￡±￡3￡(r)￡2￡±?à￡°￡(r)￡2￡3￡(r)A linear free energy re lationship for the complexes of Yb ￡#and Gd ￡#was established by using equilibriu m data of ￡±￡?complexes￡(r)The EHPG bindi ng constants to Yb?and Gd ?were in accordance with the linear fr ee energy relationship￡(r)Under the sa me conditions,apoovotransferrin(apoOTf ￡(c)was titrated with Yb ￡#and Gd￡#￡?respectively￡(r)Their fluorescent i ntensities at ￡3￡3￡?nm was quenched￡±￡?￡$￡(r)It means that tyrosine residues in apoovotransferrin coordinate to Yb ￡#or Gd ￡#directly￡(r)