Divsalar A, Saboury A A, Mansoori-Torshizi H, Moosavi-Movahedi A A
Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
J Biomol Struct Dyn. 2007 Oct;25(2):173-82. doi: 10.1080/07391102.2007.10507166.
An new water soluble palladium (II) complex of formula [Pd(bpy)(Oct-Gly)]NO(3), (where bpy is 2,2'-bipyridine and Oct-Gly is octylglycine) have been synthesised. The Pd(II) complex has been characterized by elemental analysis and conductivity measurements as well as spectroscopic methods such as infrared, (1)H NMR, and ultraviolet-visible. The interaction between the new Pd(II)-complex (2,2'-bipyridin octylglycinato Pd(II) nitrate), an anti-tumor component, with beta-lactoglobulin-A and -B (BLG-A and -B) was studied by fluorescence spectroscopy and far and near-UV circular dichroism (CD) spectrophotometric techniques. A strong fluorescence quenching interaction of Pd(II) complex with BLG-A and -B was observed. The quenching constant was determined using the modified Stern-Volmer equation. The calculated binding constants of Pd(II) complex with BLG-A and -B were 0.51 and 0.28 (x 10(6) M(-1)) and the corresponding average number of binding sites were 2.8 and 1.5, respectively. Far-UV CD studies showed that the Pd(II) complex can significantly change the secondary structure of BLG-A and -B via an increase in the content of alpha-helix structure, which stabilizes the secondary structure of the proteins. Near-UV CD data clearly indicate the alteration in the tertiary structure of BLG-A and -B due to the interaction with Pd(II) complex. Pd(II) complex can change and stabilize both the secondary and tertiary structures of BLG-A more than BLG-B. These conformational changes may be considered to be a deleterious effect of the designed ligand on the protein structures. The difference in the interaction properties observed for BLG-A and -B with Pd(II) complex is due to the difference in the amino acid sequences between these two variants.
已合成了一种新的式为[Pd(bpy)(Oct-Gly)]NO₃的水溶性钯（II）配合物（其中bpy为2,2'-联吡啶，Oct-Gly为辛基甘氨酸）。通过元素分析、电导率测量以及红外、¹H NMR和紫外可见等光谱方法对该钯（II）配合物进行了表征。采用荧光光谱法以及远紫外和近紫外圆二色（CD）分光光度技术研究了新型钯（II）配合物（2,2'-联吡啶辛基甘氨酸钯（II）硝酸盐）这种抗肿瘤成分与β-乳球蛋白-A和-B（BLG-A和-B）之间的相互作用。观察到钯（II）配合物与BLG-A和-B之间存在强烈的荧光猝灭相互作用。使用修正的Stern-Volmer方程测定了猝灭常数。计算得到钯（II）配合物与BLG-A和-B的结合常数分别为0.51和0.28（×10⁶ M⁻¹），相应的平均结合位点数分别为2.8和1.5。远紫外CD研究表明，钯（II）配合物可通过增加α-螺旋结构的含量显著改变BLG-A和-B的二级结构，从而稳定蛋白质的二级结构。近紫外CD数据清楚地表明，由于与钯（II）配合物相互作用，BLG-A和-B的三级结构发生了改变。钯（II）配合物对BLG-A二级和三级结构的改变及稳定作用比BLG-B更大。这些构象变化可能被认为是所设计的配体对蛋白质结构的有害影响。观察到的BLG-A和-B与钯（II）配合物相互作用性质的差异是由于这两种变体之间氨基酸序列的不同。
