GTP和GDP是广泛存在于细胞中的重要核苷酸分子，细胞内GTP:GDP比值是细胞代谢和信号转导状态的重要指标，但目前尚未有能够实时检测活细胞内的GTP:GDP比值的方法。应用基因编码的荧光探针技术，我们筛选出了首个能特异性检测GTP:GDP比值的荧光探针。该探针由两部分组成：能够与GTP和GDP结合并产生不同构象变化的蛋白，以及对蛋白构象变化敏感的荧光蛋白cpYFP。前期体外实验结果表明，该探针可以对GTP:GDP比值产生荧光信号响应。我们在293T细胞中表达了该探针蛋白，用糖酵解抑制剂处理细胞后，观察到了细胞内GTP:GDP比值的显著下降，我们将继续在其它肿瘤细胞以及神经细胞中检测该探针对GTP:GDP比值的响应，并进一步应用到果蝇的脑中，开发可检测生物体内GTP:GDP比值的新方法。

GTP and GDP are important nucleotides that are ubiquitous in cells, the intracellular GTP:GDP ratio is an important indicator of cellular metabolism and signal transduction state. However, currently there are no methods available for the real-time detection of GTP:GDP ratio in live cells. Applying the genetically encoded fluorescent sensor techniques, we picked out the first fluorescent sensor for the specific detection of GTP:GDP ratio. The sensor comprises of two modules: a protein which is able to bind both GTP and GDP, triggering divergent conformational changes, and cpYFP, a fluorescent protein that is sensitive to protein conformational changes. The results of previous in vitro experiments indicated that the sensor could respond to the GTP:GDP ratio. we expressed our sensor in 293T cells. After treatment with inhibitors of glycolysis, we observed a dramatic decrease in the intracellular GTP:GDP ratio. We will continue to examine the probe's response to the GTP:GDP ratio in other tumor cells and nerve cells, also further applied to the brains of fruit flies to develop a new method to detect GTP:GDP ratio in vivo.