Abstract: The present disclosure describes compositions of matter comprising a ribonucleoprotein complex comprising a nucleic acid-guided nuclease and a guide RNA, and further comprising a blocking nucleic acid molecule represented by Formula IV, wherein Formula IV in the 5?-to-3? direction comprises: T-D-M-A-Lp-C; wherein T is 17-31 nucleotides in length; D is 0-15 nucleotides in length; M is 1-25 nucleotides in length; A is 0-15 nucleotides in length and comprises a sequence complementary to D; and L is 3-25 nucleotides in length; p is 0 or 1; C is 4-15 nucleotides in length and comprises a sequence complementary to T; and wherein the blocking nucleic acid molecule comprises a sequence complementary to a gRNA.

Abstract: Compositions, methods and kits are disclosed for high-sensitivity single molecule digital counting by the stochastic labeling of a collection of identical molecules by attachment of a diverse set of labels. Each copy of a molecule randomly chooses from a non-depleting reservoir of diverse labels. Detection may be by a variety of methods including hybridization based or sequencing. Molecules that would otherwise be identical in information content can be labeled to create a separately detectable product that is unique or approximately unique in a collection. This stochastic transformation relaxes the problem of counting molecules from one of locating and identifying identical molecules to a series of binary digital questions detecting whether preprogrammed labels are present. The methods may be used, for example, to estimate the number of separate molecules of a given type or types within a sample.