Abstract
Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is one of the most powerful methods to analyze biomolecules in biological tissues and cells because it provides detailed chemical structure information and chemical images with a high spatial resolution. However, in terms of quantitative analysis, there are issues such as matrix effects that often cause secondary ion intensity changes regardless of the actual concentration in a sample. For instance, the intensity of secondary ions related to peptides is generally suppressed when lipids coexist. Since the evaluation of biomolecules is crucial to understand biological phenomena, it is required to analyze peptides or lipids without matrix effects. Therefore, the mechanism of matrix effects regarding peptides and lipids in TOF-SIMS was investigated in this study. Leu-enkephalin (YGGFL, molecular weight of 555.3 Da) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC, C44H84NO8P, molecular weight 785.6 Da) were employed to prepare model samples. Model samples contain different weight ratios of these two molecules. The intensity of secondary ions related to the peptide or the lipid was compared with control samples containing pure leu-enkephalin or DOPC. As a result, it is indicated that the intensity of DOPC related secondary ions is strongly enhanced by coexisting leu-enkephalin, while the intensity of leu-enkephalin related secondary ions is suppressed by coexisting DOPC especially in a low concentration range of the peptide.
Highlights
In this study, the matrix effects between peptides and lipids were studied because their influences are so large that quantitative analysis of them is very difficult both are important components in biological samples
It is indicated that the intensity of DOPC related secondary ions is strongly enhanced by coexisting leuenkephalin, while the intensity of leu-enkephalin related secondary ions is suppressed by coexisting DOPC especially in a low concentration range of the peptide
The magnified spectra are shown in the supplementary material (Fig. S1).15. These results indicate that the matrix effects of leuenkephalin and DOPC enhance the intensity of the lipid
Summary
The matrix effects between peptides and lipids were studied because their influences are so large that quantitative analysis of them is very difficult both are important components in biological samples. The influence between leu-enkephalin (LE), a peptide secreted from specific neurons, and a lipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), was mainly investigated in this study. The matrix effects between the peptide and the lipid in TOF-SIMS spectra and images were evaluated
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