Abstract: This invention provides a method for preserving cells which comprises the steps of (a) suspending cells in a physiologically-acceptable, isotonic medium; and (b) fixing the cells so suspended at a temperature of less than about 10.degree. C. under sufficiently hypertonic conditions so as to disperse the cells in a single, unagglutinated state, thereby preserving cells. This invention also provides a method for detecting cells separated from a sample which have been preserved according to the aforementioned method. This invention also provides a method for visualizing cells. Also provided is a method for detecting a metabolic process in cells present in a sample. This invention also provides a method for detecting the presence of rare cells in a sample which specifically possess on their surfaces a moiety recognized by a known ligand comprising preserving cells separated from the sample according to the aforementioned method for preserving cells.

Abstract: The invention relates to bis-protein-DNA conjugates. A protein having a specific ligand binding activity is covalently linked to each end of a derivatized DNA molecule. These bis-protein-DNA conjugates can be used for immunoassays, PCR assays and measuring distances between proteins at up to 3.4 A resolution. The invention also relates to methods of synthesizing these bis-protein-DNA conjugates. Synthesis of the conjugates entails derivatizing the 5' or 3' end of a DNA oligonucleotide and covalently linking that DNA to a protein. The DNA can be conjugated to the proteins, including antibodies or Fab' fragments, using disulfide bond linkage.

Abstract: This invention provides a method for preserving cells which comprises the steps of (a) suspending cells in a physiologically-acceptable, isotonic medium; and (b) fixing the cells so suspended at a temperature of less than about 10.degree. C. under sufficiently hypertonic conditions so as to disperse the cells in a single, unagglutinated state, thereby preserving cells. This invention also provides a method for detecting cells separated from a sample which have been preserved according to the aforementioned method. This invention also provides a method for visualizing cells. Also provided is a method for detecting a metabolic process in cells present in a sample. This invention also provides a method for detecting the presence of rare cells in a sample which specifically possess on their surfaces a moiety recognized by a known ligand comprising preserving cells separated from the sample according to the aforementioned method for preserving cells.

Abstract: The invention relates to bis-protein-DNA conjugates. A protein having an antigen specific binding activity is covalently linked to each end of a derivatized DNA molecule. The bis-protein-DNA conjugates can be used for immunoassays and measuring distances between proteins at up to 3.4 .ANG. resolution. The invention also relates to methods of synthesizing these bis-protein-DNA conjugates. Synthesis of the conjugates entails derivatizing the 5' or 3' end of a DNA oligonucleotide and covalently linking that DNA to a protein. The DNA can be indirectly conjugated to an antibody or Fab' fragment, using a avidin/streptavidin-biotin linkage. The conjugates of the invention can be used in immunoassays and PCR assays.