This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Methods: Protein rich powder was prepared from each type of kidneys as described in previous report. N-glycans were released enzymatically by PNGase F and the released N-glycans were permethylated and profiled by mass spectrometry. The detailed procedures are shown below. Preparation of protein rich powder from kidneys Kidneys were homogenized and de-lipidated followed by the method of Aoki.et.al (2007). Briefly, kidneys were homogenized by homogenizer on ice. Lipids were extracted by adjusting the solvent mixture to give a final ratio of chloroform/methanol/water equal to 4:8:3. The extract was incubated at room temperature with end-over-end agitation. The insoluble proteinaceous material was collected by centrifugation and re-extracted three times. The final pellet of insoluble protein was further washed with cold-acetone/water (4:1, v/v) four times and dried under a stream of nitrogen. N-linked glycan preparation The dried sample was dissolved in 0.1 M Tris-HCl buffer, pH 8.2 containing 0.01 M CaCl2. The sample then was denatured by heating for 5 minutes at 100?C. After cooling, the sample was digested with the trypsin (37oC, overnight). The sample was then heated at 100? C for 5 min to inactivate trypsin and spun at 3000 rpm in a refrigerated centrifuge for 15 minutes. The supernatant was collected and dried. The sample was then passed through a C18 sep-pak cartridge and washed with 5% acetic acid to remove contaminants (salts, free sugar, etc.). Peptides and glycopeptides were eluted in series with 20% iso-propanol in 5% acetic acid, 40% iso-propanol in 5% acetic acid and 100% iso-propanol and dried in a speed vacuum concentrator. The dried samples were combined and incubated with PNGase F at 37?C overnight to release N-glycans. After digestion, the sample was passed through a C18 sep-pak cartridge and the released N-glycans was eluted with 5% acetic acid and dried by lyophilization, and then permethylated based on the method of Anumula and Taylor (Anumula and Taylor, 1992) and profiled by mass spectrometry. Mass spectrometry MALDI/TOF-MS was performed in the reflector positive ion mode using ?-dihyroxybenzoic acid (DHBA, 20mg/mL solution in 50%methanol:water) as a matrix. The spectrum was obtained by using a Microflex LRF (Bruker). For the purpose of comparison of peak intensity of each N-glycan component, at least three spectra were obtained for each sample and then intensity % of each N-glycan components among total N-glycans observed in individual spectra were calculated then averaged from the three spectra for each sample.
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