Gel-free sample preparation for the nanoscale LC-MS/MS analysis and identification of low-nanogram protein samples

In-solution digestion; Nanoscale LC-MS/MS; Proteomics; Sample preparation; Animals; Caseins; Cattle; Chromatography, Liquid; Myoglobin; Nanotechnology; Peptide Fragments; Proteins; Serum Albumin, Bovine; Tandem Mass Spectrometry; Trypsin; Analytical Chemistry; Filtration and Separation