A sample of material to be tested for the presence of biologically active agents, such as bacteria, is introduced into a sealable container partially filled with a culture medium comprising a .sup.13 C-labeled fermentable substrate, the remainder of the container being filled with a culture gas, the container and its contents are subjected to conditions conducive to biological activity for a predetermined period sufficient for fermentation of the medium to produce carbon dioxide after which the ratio of .sup.13 CO.sub.2 to .sup.12 CO.sub.2 in the culture gas in the container is determined and compared to the initial ratio of .sup.13 CO.sub.2 to .sup.12 CO.sub.2 in the culture gas in order to detect any differences indicating the presence of biologically active agents in the sample.
A nutrient medium comprising amino acids and other substrates used by mammalian or insect cells in protein synthesis that are either double-labeled with .sup.2 H and .sup.13 C or triple-labeled with .sup.2 H, .sup.13 C and .sup.15 N is disclosed. The invention is also directed to a method for producing the nutrient medium.
There is disclosed a method for detecting microorganisms comprising the steps of: providing a plurality of cultures by culturing said microorganisms on a plurality of different media; making measurements of the cultures; collating the measurements of the cultures; and correlating the collated measurements with the presence of the microorganisms.
An apparatus and method for the detection of the growth of microorganisms through infrared analysis of a sample of the gas produced by growth of the microorganism is descirbed. In the method, a sample of the headspace gas in a vial containing a growth medium which has been inoculated with a sample suspected of containing a microorganism is removed and transferred to a sample cell where infrared analysis is used to determine the presence of carbon dioxide, if any, produced by the growth of the microorganism.
A new class of chemical reagents called release tags which comprise signal, release and reactivity groups is disclosed and a release tag involving a pentafluorobenzoyl signal group, a methionylamide release group, and an active ester reactivity group is used to analyze the hormone, thyroxine, in serum, involving quantitation of the released signal group by gas chromatography with electron capture detection.
A method for determining three-dimensional structural information of a protein which involves producing the protein in a form substantially labeled with .sup.13 C of .sup.15 N or both substantially labeled with .sup.15 N and .sup.13 C and partially labeled with .sup.2 H and subjecting the protein to nuclear magnetic resonance spectroscopic analysis. The isotopically labeled protein is produced by a method which involves producing a substantially labeled microbial protein hydrolysate, subjecting the protein hydrolysate to cation exchange chromatography to produce a partially purified labeled amino acid mixture, subjecting the partially purified labeled amino acid mixture to anion exchange chromatography to produce a purified labeled amino mixture and supplementing the purified labeled amino acid mixture with isotopically labeled cysteine and optionally with isotopically labeled glutamine and asparagine.
