In the next step, we investigated whether the recently reported variable-time RIDME experiment (vtRIDME) would enable a further sensitivity increase particularly valuable at these low concentrations. To ensure reproducibility and minimise errors from sample positioning and experiment optimisation, four experiments were recorded on the samples of the dilution series. A ctRIDME similar to the measurement described above, a vtRIDME with otherwise identical parameters, and corresponding reference traces for both, the ctRIDME and the vtRIDME to enable deconvolution of the data (division by the reference trace). Non-deconvoluted vtRIDME data are shown in Figure , for a complete set of the ct/vtRIDME data see Figure . For convenience, the four different experiments have been combined into a single pulse programme. For samples with a protein concentration below 100 nM, recording the reference traces became unfeasible due to extended averaging times required and was therefore only done for concentrations of 100 nM or higher. As observed previously, modulation depths were slightly higher for the vtRIDME than for the ctRIDME. Deconvolution reduced the observed modulation depths for both, ct-and vtRIDME measurements as expected. vtRIDME data were processed in the same way as described for the ctRIDME. Notably, here the additional processing with the ConsensusDeerAnalyzer2.0 only failed for the lowest concentration (10 nM GB1) (Table ) and a high-confidence distance distribution was obtained at 50 nM in 8 h. Sensitivity analysis revealed an approximately 2.5-fold increase in sensitivity for vtRIDME compared to ctRIDME (Table ), which is in excellent agreement with recently published data. While for the 50 nM vtRIDME a modulation-to-noise ratio > 20 was achieved with 8 h averaging time, the 25 nM and 10 nM samples yielded ratios < 10 with 8 h and 18 h averaging time, respectively; data of this quality should not be used to interpret distance distributions. Thus, together with the change from CuNTA-nitroxide to CuNTA-SLIM labelling, an overall increase in sensitivity of almost an order of magnitude (approximately 8-fold) compared to the previous study 6 has been achieved.