Results (
Thai) 2:
[Copy]Copied!
3.3. Visualizing intact protein distributeon on PE-UHMW up to 204 kDa
Besides the finding that proteins adsorbon PE-UHMW aside from their post-translational modifications or hydrophobic quality, it is necessary to localize proteins adsorbing on PE- UHMW in order to correlate them to polymer qualities such as surface roughness or oxidation. For this the 15 _m PE-UHMW slices, incubated in SF for 24 h, were investigated concerning the adsorbed protein layer and the localization of certain proteins in a MSI approach. HCCA for the low or SA for the high molecular mass range were applied using the piezo printer at a lateral resolution of 100 _m covering the whole PE-UHMW sample homogeneously Fig.4 a shows an exemplary covered PE-UHMW sample after applying HCCA with the piezo printer. A rather thick matrix layer with fine crystal for mation is observed. Similar results were obtained for SA. The sameproteins as inprofiling experiments were detected, i.e. all highlya bundant species such as albumin, IgG and the apolipoprotein subclasses. Profile mass spectra were already presented in Fig.2a and 2b showing protein adsorption up to 204 kDa.Yet some proteins exhibited characteristic localization on the polymer material. Fig.4b shows the intensity distribution of apolipoprotein D[M+H]+ (m/z 22,301) and Fig.4e the distribution of the unknown protein at 204 kDa on GUR- 1050 PE-UHMW after total ion current(TIC) normalization. Molecules were almost homogeneously distributed on the polymer. The analyzed PE-UHMW sample showed a small folded area in the center, whereas the majority area was mounted completely planar to the conductive tape. On perfectly prepared samples all proteins were detected with a similar homogeneous lateral distributions. Interestingly that in the few areas not covered with Apo D especially albumin was found (Fig.4c). On both polymer variants, GUR-1050 and Vitamin E doped, m/z values correlating to[M+H]+ ions of human serum albumin (m/z 66,615) were detected in the center region of the polymer slice, with especially high intensities in folded area(Fig.4c and f).The area of high intensity on top of the sample results from protein adsorption on the conductive tape on which the polymer is mounted. Compared to the conventionally used GUR-1050PE-UHMW, Vitamin E doped material (Fig.4f) showed less signal intensities for all detected proteins. However, adsorbed proteins, IgG and an unidentified compound with m/z 204,000 (Fig.4d and e),revealed similar preferences for folded regions and sharp edges.To investigate the influence of protein degradation due to protease activity, MSI experiments were performed on samples removed from SF incubation after 15,30,60min and 3 h. It was found that homogeneous protein layers are formed already after 30 min of incubation and no loss of signal intensity or increased signal-to-noise ratio excelling biological variation was observed (data not shown).
Being translated, please wait..