SDS and MES showed very low absorbance both in the UV and visible range and thus did not affect phage stability upon UV irradiation (Figure , Supporting Information) It should be noted that we did not find any obvious relationship between extinction coefficient and magnitude of protection, as long as the absorption is non-zero (also in the case of food dyes). Only a slight change in the structure, i.e., replacing the -CH3 group (TSA) with the -OH group (HBSA), resulted in completely different results. We assumed that the possibility of hydrogen bond formation was also a crucial requirement for the compound to protect phages. This was confirmed as not only HBSA but also NSA and ISA were active in our experiment, maintaining virion stability upon UV exposure. Additionally, when chaotropic SDS (0.1%) was added to BB (at EC50), the number of UV surviving phages dropped by around 1-log compared to only BB. This again proved the importance of hydrogen bonds for such systems.