title: Quick quantification of proteins by MALDI.
abstract: Previously, we reported that the matrix-assisted laser desorption ionization spectrum of a peptide became reproducible when an effective temperature was held constant. Using a calibration curve drawn by plotting the peptide-to-matrix ion abundance ratio versus the peptide concentration in a solid sample, a peptide could be quantified without the use of any internal standard. In this work, we quantified proteins by quantifying their tryptic peptides with the aforementioned method. We modified the digestion process; e.g. disulfide bonds were not cleaved, so that hardly any reagent other than trypsin remained after the digestion process. This allowed the preparation of a sample by the direct mixing of a digestion mixture with a matrix solution. We also observed that the efficiency of the matrix-to-peptide proton transfer, as measured by its reaction quotient, was similar for peptides with arginine at the C-terminus. With the reaction quotient averaged over many such peptides, we could rapidly quantify proteins. Most importantly, no peptide standard, not to mention its isotopically labeled analog, was needed in this method.
authors: Department of Chemistry, Seoul National University, Seoul, 151-747, Korea.
authors: Sung Hee
authors: SH
authors: Ahn
authors: Jeong Won
authors: JW
authors: Kang
authors: Jeong Hee
authors: JH
authors: Moon
authors: Kwang Pyo
authors: KP
authors: Kim
authors: Seong Hoon
authors: SH
authors: Lee
authors: Myung Soo
authors: MS
authors: Kim
mesh_terms: D000818:Animals; D002417:Cattle; D006801:Humans; D010446:Peptide Fragments / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D011506:Proteins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D020539:Sequence Analysis, Protein; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D014357:Trypsin / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D011506:Proteins; D014357:Trypsin
keywords: MALDI; protein quantificaton; quantification of hGH; quantification of myoglobin; tryptic digestion