Provided herein are Amyotrophic lateral sclerosis (ALS) biomarkers and methods of using these ALS biomarkers to diagnose and treat ALS.

Compositions and methods have been developed for the detection of homocysteine. For example, a fluorescent probe can selectively detect homocysteine based on the redox reaction between the azido group and homocysteine. The fluorescent response is selective for homocysteine over other biologically abundant thiols such as cysteine and glutathione. In addition, a linear calibration curve can be obtained for quantitative analysis in phosphate buffer and plasma.

Provided are methods for detecting protein interactions in a sample, the methods comprising: (a) detecting two or more polypeptides that when associated emit a first detectable signal in a first light emission spectrum; (b) contacting the two or more polypeptides with a third polypeptide conjugated to a dipole acceptor moiety that has a second light emission spectrum when excited within a light excitation spectrum, wherein the light excitation spectrum overlaps with the first light emission spectrum; and (c) detecting a second detectable signal emitted in the second light emission spectrum by the dipole acceptor moiety. Also provided are bioluminescent complexes comprising: (a) a first polypeptide conjugated to a dipole acceptor moiety, wherein the emits a first detectable signal in a first light emission spectrum.

In various embodiments a capture surface for capturing high velocity and hypervelocity dust and ice particles is provided. In certain embodiments the capture surface is comprised of a soft metal that is chosen to optimize particle capture efficiency, to minimize thermal degradation of chemicals and biochemical in the particles, and to present the captured particles to an analyzer for chemical and biochemical analysis of the particles and their contents. In various embodiments capture chambers comprising one or more such capture surfaces are provided as well as methods of use thereof.

A fast and accurate reverse-phase high pressure liquid chromatography (“RP-HPLC”) method for detecting amino acids in small volumes (e.g. less than 50 .Math.L) of a biological sample, such as plasma. An assay for the simultaneous determination of ammonium and primary amino acids using RP-HPLC in samples such as plasma. A method for calculating intercellular volumes from a cell lysate to which a known volume and concentration of a non-naturally occurring amino acid is added.

The invention relates to an activated form of procaine, and the use of the activated procaine, or salts or solvates thereof, to label amine-containing compounds. In some embodiments, the amine-containing compound is an N-glycan.

The invention relates to an activated form of procaine, and the use of the activated procaine, or salts or solvates thereof, to label amine-containing compounds, such as N-glycans, amine-containing amino acids, amine-containing peptides, amine-containing proteins, or other amine-containing compounds in a sample. Use of activated procaine as a label allows for sensitive detection of compounds labeled with it both by fluorescence and by mass spectrometry.

A sensor can include a nanostructure in a housing configured to contact a sample.

Provided are methods for detecting protein interactions in a sample, the methods comprising: (a) detecting two or more polypeptides that when associated emit a first detectable signal in a first light emission spectrum; (b) contacting the two or more polypeptides with a third polypeptide conjugated to a dipole acceptor moiety that has a second light emission spectrum when excited within a light excitation spectrum, wherein the light excitation spectrum overlaps with the first light emission spectrum; and (c) detecting a second detectable signal emitted in the second light emission spectrum by the dipole acceptor moiety. Also provided are bioluminescent complexes comprising: (a) a first polypeptide conjugated to a dipole acceptor moiety, wherein the emits a first detectable signal in a first light emission spectrum.

The present invention pertains to a method for determining the biological activity of a neurotoxin, the method comprising the steps of: (a) expressing a fusion protein comprising (i) an anchor protein, (ii) a reporter protein and (iii) a neurotoxin cleavage site intervening the anchor protein and the reporter protein, in neurotoxin-sensitive cells; (b) incubating the neurotoxin-sensitive cells of (a) with a neurotoxin and cultivating the cells under conditions which allow the neurotoxin to exert its biological activity; (c) permeabilizing the neurotoxin-sensitive cells of (b) under conditions which allow the release of the reporter protein but not the release of the anchor protein from the permeabilized neurotoxin-sensitive cells; and (d) quantifying the activity of the reporter protein released from the cells, thereby determining the biological activity of the neurotoxin. In addition, the invention relates to a fusion protein comprising (i) an anchor protein, (ii) a reporter protein, and (iii) a neurotoxin cleavage site intervening the anchor protein and the reporter protein, for determining the biological activity of a neurotoxin, in neurotoxin-sensitive cells. Further encompassed by the present invention is a kit comprising the fusion protein of the invention. Finally, the invention pertains to the use of a fusion protein of the invention for determining the biological activity of a neurotoxin, in neurotoxin-sensitive cells.