The material development containing trytophan residues for the visual recognition of the interaction with drugs by its coloration

本文报道了L-色氨酸（Trp）在三氟乙酸（TFA）作用下，在不同pH下的显色现象。例如，从黄色到红色。为了阐明显色机理，对显色化合物进行了分级分离和研究。结果发现，色氨酸形成的黄色化合物组成的三环结构，并在颜色的变化与pH值的变化是由于氮原子的吲哚环的解离。色氨酸残基经三氟乙酸（TFA）处理后形成三环结构，并在中性pH范围内发生正解离，颜色由黄色（pH 8.0以上）变为红色（pH 7.0以下）。用维斯和荧光光谱法研究了TFA处理的GAT（GAT-T）与阴离子分子的相互作用。GAT-T中的色氨酸残基除了与疏水作用外，还与大体积阴离子药物如戊巴比妥（Wf）、氯贝酸（Cf）、保泰松（Pb）等发生静电相互作用，导致颜色由红色变为黄色。考察了GAT-T微球对阴离子药物的释放行为。GAT-T分子筛中阴离子药物的结合量和保留时间均比未处理的GAT分子筛有上级的提高，且GAT-T与阴离子药物的相互作用强度为Cf > Pb > Wf。这源于所用阴离子药物的酸性。

We have reported that the coloration phenomenon of L-tryptophan(Trp) treated with trifluoroacetic acid (TFA) was observed with varying pH, i. e., from yellow to red. In order to elucidate the coloration mechanism, the colored compounds were fractionated and investigated. It was found that Trp forms the yellow compound consisting of a tricyclic structure, and that the change in color with the variation of pH is due to the dissociation of the nitrogen atom in the indole ring. The Trp residues within copoly (L-glutamic acid-co-Trp) (GAT) was also found to form the same tricyclic structure by the treatment with TFA and to show the reversible color change from yellow (above pH 8.0) to red (below pH 7.0) through the positive-dissociation at the neutral pH region. The interaction between TFA-treatment GAT (GAT-T) and anionic molecules was investigated by VIS and fluorescence spectrophotometry. The Trp residues within GAT-T were found to electrostatically interact with bulky anionic drugs such as watrfarin (Wf), clofibric acid (Cf) and phenylbutazone (Pb) besides the hydrophobic interaction, resulting in the color change from red to yellow. Release behavior of the anionic drugs from GAT-T microspheres (Ms) was also investigated. The amount and the retention time of the bound anionic drugs in the GAT-T Ms were found to be superior to those for untreatment GAT Ms. Moreover, GAT-T interacts strongly with the anionic drugs in the order of Cf > Pb > Wf. This originates in the acidity of the anionic drugs used.