The invention generally relates to compositions for maximizing capture of affinity-labeled molecules on solid supports. The disclosed methods and compositions were developed to maximize depletion of ribosomal RNA from total RNA samples, which is useful to improve the quality of RNA preparations used for applications such as massively parallel sequencing. The RNA depletion method is based on using long affinity-labeled RNA molecules that are complementary to all or part of the target ribosomal RNAs, as subtractive hybridization probes.