Abstract: Aspects of the present disclosure include methods for detecting a low abundance protein and methods for identifying a site of N-glycosylation on a protein. In practicing methods according to certain embodiments, a eukaryotic cell is contacted with an isotopic labeling composition and isotopically labeled N-glycosylated peptides obtained from the eukaryotic cell are assessed by liquid chromatography-tandem mass spectrometry. A predetermined isotopic pattern in the mass spectrum is identified and amino acid sequences of the peptides containing the predetermined isotopic pattern are determined. Systems for identifying a predetermined isotopic pattern in mass spectra and determining amino acid sequences of peptides containing the predetermined isotopic pattern are also described.

Abstract: Aspects of the present disclosure include methods for detecting a low abundance protein and methods for identifying a site of N-glycosylation on a protein. In practicing methods according to certain embodiments, a eukaryotic cell is contacted with an isotopic labeling composition and isotopically labeled N-glycosylated peptides obtained from the eukaryotic cell are assessed by liquid chromatography-tandem mass spectrometry. A predetermined isotopic pattern in the mass spectrum is identified and amino acid sequences of the peptides containing the predetermined isotopic pattern are determined. Systems for identifying a predetermined isotopic pattern in mass spectra and determining amino acid sequences of peptides containing the predetermined isotopic pattern are also described.

Abstract: The present invention provides a crystallized form of the E223Q Y365F mutant of the light chain of botulinum neurotoxin serotype A (BoNT/A) protein as well as the atomic structure of this mutant protein. The present invention also provides crystals of the E223Q Y365F mutant of the BoNT/A light chain in complex with the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) domain of the SNAP-25 (synaptosome-associated protein-25 kDa) protein as well as the atomic structure of this complex. The present invention further provides a method of determining whether an agent mimics a region of the SNAP-25 protein that interacts with BoNT/A. With this method, a three-dimensional representation of the SNAP-25 region is used to computationally compare the agent with the three-dimensional representation of the SNAP-25 region.

Abstract: The present invention provides a crystallized form of the E224Q Y336F mutant of the light chain of botulinum neurotoxin serotype A (BoNT/A) protein as well as the atomic structure of this mutant protein. The present invention also provides crystals of the E224 Y336F mutant of the BoNT/A light chain in complex with the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) domain of the SNAP-25 (synaptosome-associated protein-25 kDa) protein as well as the atomic structure of this complex. The present invention further provides a method of determining whether an agent mimics a region of the SNAP-25 protein that interacts with BoNT/A. With this method, a three-dimensional representation of the SNAP-25 region is used to computationally compare the agent with the three-dimensional representation of the SNAP-25 region.