This phenomenon, which is probably amplified by the approximation introduced in the calculation of the MT bead form factors, shows that for small 𝑞 values the atomic details are not critical in the determination of the intensity. Considering B1, which is the worst-case scenario we observed, the SAXS intensity computed with 1B only differs by less than 0.5% from that calculated at atomistic resolution in the range 0-0.3 Å -1 . Regarding the SANS intensity calculation with 1B mapping, the results obtained for GSN (Figure ) and GFP (Figure , right panel) were comparable to those of SAXS, whereas for B1 the accuracy decreased, with a maximum difference between 1B and AA scattering profiles of about 1.5% (Figure , right panel). As for the proteins, the calculation of the SAXS intensity on RNA with 3B mapping also proves to be accurate, with better agreement to AA resolution than with MT (Figure ). Finally, the difference between the RNA SANS intensity computed with 3B and AA shows a level of accuracy close to that observed for SAXS (Figure ). These results were obtained without considering the solvation layer contribution. To assess the transferability and validate the 1B parameters obtained from GSN, we generated additional independent sets of parameters from B1 and GFP. Using the 1B parameters obtained from B1, we calculated the SAXS intensities on the B1 trajectory frames and compared them with the corresponding AA intensities. The same B1 frames were employed to calculate the 1B intensity using the parameters obtained from GSN, and these intensities were also compared with the AA profiles. The two obtained residuals are nearly superimposable (Figure ), differing from each other by less than 0.1% at most. We followed the same procedure with GFP, and similarly, the residuals calculated with the 1B parameters from GFP are in strong agreement with the residuals calculated with the 1B parameters from GSN (Figure ). To validate the 3B parameters, the nucleic acid repositories previously described in the methods section were divided into two subsets. We selected 120 DNA and 43 RNA PDB files as the training set to compute the 3B form factor parameters, since all the heavy atoms are solved in these structures. We calculated the SAXS intensity of each structure belonging to this set with 3B mapping and at AA resolution, and we evaluated the respective residuals. We performed the same analysis using the 3B parameters obtained from the training set on the remaining 47 DNA and 32 RNA structures, which we considered as the validation subset. The average of the residuals from the training set and the average of the residuals from the validation set differ by a maximum of 0.12%. Furthermore, although the residuals from the validation set are more dispersed, the average is closer to the reference than the average of the residuals from the training set (Figure ). The 1B and 3B form factors can be modified to include the solvation layer contribution (SLC) in the SAS intensity calculation. Whether for a single PDB file or an MD trajectory, this process requires the calculation of SASA to assess which beads are exposed to the solvent. This procedure is performed by the LCPO 54 algorithm implemented in PLUMED. The reliability of the method was verified by comparing the results obtained with LCPO with the results obtained for the same frames with the sasa module 75 integrated in GROMACS (Figure ). To evaluate the SLC, we used as a reference the intensities calculated by WAXSiS (Wide Angle X-ray Scattering in Solvent), a web server hosted at Saarland University, which allows the calculation of SAXS/WAXS profiles based on short MD simulations in explicit solvent . We extracted 10 equidistant frames from each of the previously described trajectories of GSN, B1, GFP and 12-mer RNA. For all these frames we calculated the SAXS intensity using 1B/3B mapping with the SLC parameter set to 0.04, 0.06, 0.07, 0.08, 0.09, 0.095, 0.10, 0.11, 0.12 and with the SASA cut-off (SC) of 0.4 nm 2 , 0.6 nm 2 , 0.7 nm 2 , 0.8 nm 2 , 1.0 nm 2 , 1.2 nm 2 , in all the possible combinations. The same frames were used as input to calculate the SAXS profiles with WAXSiS. We specified in the web server options an explicit solvent envelope of 7 Å from the surface of the biomolecule and we selected the maximum available simulation length (2⋅10 6 /N - 0.77 frames, where N is the approximate number of atoms in the hydration layer). As in the previous analyses, we calculated the residuals between the intensity computed with 1B/3B and the intensity computed with WAXSiS, that we consider as the reference. Although some combinations of SLC and SC gave surprising results, leading to SAXS profiles practically identical to those calculated by WAXSiS (Figure , Figure ), we found that using any of the indicated values of SLC and SC gave a better agreement with WAXSiS intensity than using 1B/3B without SLC. For a clearer overview, we computed the root mean square error (RMSE) between the logarithm (base 10) of the SAXS intensity calculated with AA, MT, 1B/3B (with all the SLC/SC combinations) and the logarithm of the SAXS intensity calculated with WAXSiS.