Here, x i and xi denote the original and predicted coordinates, respectively. The pairwise representations q 0 ij and q L ij correspond to the initial and final states, while U and W are trainable projection matrices. In the masked atom prediction task, the model needs to identify randomly masked atomic types within OOMs. This process helps the model learn both local atomic environments and global molecular interactions. Through these pretraining tasks, Uni-Mol serves as the 3D pretraining backbone of O 2 -GEN, effectively encoding key structural information for downstream tasks such as molecular generation and property screening.