Abstract: This invention generally relates to stabilized non-blood-based samples in which microbial biomolecules in non-blood-based samples are stable at high temperatures. The stabilized non-blood-based samples include effective amounts of stabilization components to stabilize the microbial biomolecules in the samples. Stabilization components are typically effective at low levels in these stabilized non-blood-based samples. This provides the advantage of minimizing reagent expenses related to the stabilized non-blood-based samples of the invention. The invention also provides methods of stabilizing microbial biomolecules in non-blood-based samples and related kits.

Abstract: Muteins of enzyme acceptor polypeptide fragments of .beta.-galactosidase are provided which exhibit substantially increased kinetic complementation activity with no significant loss in stability. A preferred enzyme acceptor fragment has an amino acid other than cysteine located at position 500 of the natural sequence. An especially preferred substitution is serine or valine. Other preferred muteins have an amino acid other than methionine located at position 443, with leucine being especially preferred, or an amino acid other than cysteine at position 76, with leucine being an especially preferred substitution. Also provided are methods for producing the novel muteins, reagent compositions comprising the novel muteins, and immunoassay methods for determining an analyte in which the novel mutein recombines with an enzyme donor polypeptide fragment to form enzymatically active .beta.-galactosidase.

Abstract: A mutein of an enzyme acceptor polypeptide fragment of .beta.-galactosidase which is resistant to oxidation is provided. The enzyme acceptor fragment has an amino acid other than cysteine located at position 602 of the natural sequence. An especially preferred substitution is serine. Also provided are a method for producing the novel mutein, a reagent composition comprising the novel mutein, and an immunoassay method for determining an analyte in which the novel mutein recombines with an enzyme donor polypeptide fragment to form enzymatically active .beta.-galactosidase.

Abstract: The use of omega-acceptor and omega-donor polypeptides (comprising about two-thirds and one-third of the .beta.-galactosidase molecule amino and carboxyl termini, respectively), prepared by recombinant DNA techniques, DNA synthesis, or chemical polypeptide synthesis techniques, which are capable of interacting to form an active enzyme complex having catalytic activity characteristic of .beta.-galactosidase, is described along with improved methods and novel compositions for enzyme complementation assays for qualitative and quantitative determination of a suspected analyte in a sample.