Abstract: Methods, kits and compositions for separation, identification, and isolation of short nucleic acids (i.e., less than 100 nucleotides) of different length are provided. The invention further provides methods for preparation of small RNA libraries.

Abstract: The present invention generally relates to a new approach for the therapy of allergic responses, based on targeted elimination of cells expressing the Fc?RI receptor by a chimeric cytotoxin Fc2?-3-PE40. A sequence encoding amino acids 301-437 of the Fc region of the mouse IgE molecule was genetically fused to PE40?—a truncated form of PE lacking the cell binding domain. The chimeric protein, produced in E. coli, specifically and efficiently kills mouse mast cell lines expressing the Fc?RI receptor, as well as primary mast cells derived from bone marrow. The present invention provides a chimeric protein for targeted elimination of Fc?RI expressing cells especially useful for the therapy of allergic responses. The said chimeric protein is comprised of a cell targeting moiety for Fc?RI expressing cells and a cell killing moiety. The preferred killing moiety is the bacterial toxin Pseudomonas exotoxin (PE). This Pseudomonas exotoxin is a product of Pseudomonas aeruginosa.