Interestingly and also unexpectedly, we can observe an obvious difference on the position of the peak in MALDI-MS corresponding to BSA-AuNCs mixed with three matrices (CHCA, SA, DHB, which means different gold number can be obtained with different matrices for the same sample. This is better highlighted in Fig. and Fig. for BSA-protected gold nanoclusters in both negative and positive modes. As usually addressed for BSA-protected gold nanoclusters, a broad mass distribution is observed corresponding to a distribution of the number of gold atoms in the protein template. While the width of the mass distribution is not too much affected by the nature of matrix, the average number of gold atoms (centre of the mass distribution) strongly depends on matrix. For instance, using CHCA the mass distribution is centred around m/z 68958, corresponding to an average of 12 Au atoms. In contrast, with DHB, the average mass is at m/z 70216, consistent with an average of 18 gold atoms attached to the protein. An intermediate result is obtained with SA.