Within the general framework of our past and current studies dealing with the investigation of the photophysical properties and the biological behavior of the family of tetrazolato and tetrazole Re(I) complexes, we have endeavored to investigate their potential in the luminescent staining of proteins purified by acrylamide gel electrophoresis. With the aim to provide the first examples of luminescent Re(I) complexes to be exploited for this specific purpose, we have designed and prepared four new Re(I)-based species with the general formula fac-[Re(CO)₃(N^N)(Tph)]^2−/0, where Tph is the 5-(phenyl)tetrazolato anion and N^N is in turn represented by bathophenanthroline disulfonate (BPS), bathocuproine disulfonate (BCS) or by the SO₃⁻ free bathocuproine (BC). In this latter case, the neutral complex fac-[Re(CO)₃(BC)(Tph)] served as a model species for the characterization of the former disulfonate complexes. Its cationic analogue fac-[Re(CO)₃(BC)(Tph-Me)]⁺ was also prepared by a straightforward methylation reaction. All complexes displayed bright phosphorescence in organic media and, relative to their water solubility, the dianionic species fac-[Re(CO)₃(BPS)(Tph)]²⁻ and fac-[Re(CO)₃(BCS)(Tph)]²⁻ were also highly emissive in aqueous solution. The sulfonate groups played a key role in promoting and significantly enhancing the luminescent staining performances of both the Re(I) complexes fac-[Re(CO)₃(BPS)(Tph)]²⁻ and fac-[Re(CO)₃(BCS)(Tph)]²⁻ for proteins. Highlighting a response superior to that of Coomassie Blue and comparable to the one obtained by the well-known silver staining method, these dianionic Re(I)-complexes could efficiently detect up to 50 ng of pure Bovine Serum Albumin (BSA), as well as all proteins found in a Standard Protein Marker mix and from a total protein extract. A lower but still good response for luminescent protein staining was surprisingly obtained by employing the –SO₃⁻ free neutral and cationic complexes fac-[Re(CO)₃(BC)(Tph)] and fac-[Re(CO)₃(BC)(Tph-Me)]⁺, respectively. These preliminary results open up new possibilities for the further widening of the use of Re(I)-based complexes as luminescent protein staining agents.

中文翻译：

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Re（i）tetrazolato复合物对发光蛋白的染色†

在我们过去和现在的研究的总体框架内，研究四唑酸和四唑Re（I）配合物家族的光物理性质和生物学行为，我们致力于研究它们在通过蛋白质纯化的蛋白质的荧光染色中的潜力。丙烯酰胺凝胶电泳。为了提供用于该特定目的的发光Re（I）配合物的第一个实例，我们设计并制备了四种新的基于Re（I）的通式为fac- [Re（CO）₃（ N ^ N）（Tph）] ^{2- / 0}，其中Tph是5-（苯基）四唑酸酯阴离子，N ^ N又由红菲绕啉二磺酸（表示BPS），浴铜灵磺酸盐（BCS）或者由SO ₃ ^-免费浴铜灵（BC）。在后一种情况下，中性复合物fac- [Re（CO）₃（BC）（Tph）]用作表征前二磺酸盐复合物的模型物种。还通过直接的甲基化反应制备了其阳离子类似物fac- [Re（CO）₃（BC）（Tph-Me）] ⁺。所有配合物在有机介质中均显示出明亮的磷光，相对于其水溶性，双阴离子物种fac- [Re（CO）₃（BPS）（Tph）] ^2-和fac- [Re（CO）₃（BCS（Tph）] ^2-）在水溶液中的发射率也很高。磺酸盐基团在促进和显着增强Re（I）配合物fac- [Re（CO）₃（BPS）（Tph）] ^2-和fac- [Re（CO）₃的发光染色性能中起关键作用（BCS）（Tph）] ^2-用于蛋白质。这些双阴离子Re（I复合物可以有效检测高达50 ng的纯牛血清白蛋白（BSA），以及在标准蛋白质标记混合物中和总蛋白质提取物中发现的所有蛋白质。为发光蛋白染色较低的，但仍然良好的反应令人惊讶地通过采用-SO得到₃ ^-自由中性和阳离子络合物FAC - [的Re（CO）₃（BC）（TPH）]和FAC - [的Re（CO）₃（ BC）（Tph-Me）] ⁺。这些初步结果为进一步扩大基于Re（I）的复合物作为发光蛋白染色剂的使用开辟了新的可能性。