Enhanced Visualization of Small Peptides Absorbed in Rat Small Intestine by Phytic-Acid-Aided Matrix-Assisted Laser Desorption/Ionization-Imaging Mass Spectrometry

Abstract

Enhanced visualization of small peptides absorbed through a rat intestinal membrane was achieved by matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-IMS) with the aid of phytic acid as a matrix additive. Penetrants through intestinal peptide transporter 1, i.e., glycyl-sarcosine (Gly-Sar, 147.1 m/z) and antihypertensive dipeptide, Val-Tyr (281.2 m/z), were chosen for MALDI-IMS. The signal-to-noise (S/N) ratios of dipeptides Gly-Sar and Val-Tyr were seen to increase by 2.4- and 8.0-fold, respectively, when using a 2',4',6'-trihydroxyacetophenone (THAP) matrix containing 5.0 mM phytic acid, instead of the THAP matrix alone. Owing to the phytic-acid-aided MALDI-IMS method, Gly-Sar and Val-Tyr absorbed in the rat intestinal membrane were successfully visualized. The proposed imaging method also provided useful information on intestinal peptide absorption; to some extent, Val-Tyr was rapidly hydrolyzed to Tyr by peptidases located at the intestinal microvillus during the absorption process. In conclusion, the strongly acidic additive, phytic acid, is beneficial for enhancing the visualization of small peptides using MALDI-IMS, owing to the suppression of ionization-interfering salts in the tissue.

Elution Profile of Di-peptides on a Sulfonated Ethylstyrene-Divinylbenzene Copolymer Resin Column by High-performance Liquid Chromatography

“…3 Our studies regarding peptide-induced physiological functions also revealed that basic and/or hydrophobic small peptides, such as Trp-His, exerted vasorelaxation effects in the aorta through the retardation of intracellular Ca 2+ -signaling pathways, [4][5][6] and could be absorbed intact into the blood system via intestinal peptide transporter 1. [7][8][9] Peptides, which are condensed amino acids, have many members in their polymeric series, e.g., >400 di-peptides and >8000 tri-peptides, and simple and convenient assays for bioactive small peptides in food hydrolysates or natural materials are required in the food industry. It is difficult to separate small peptides in hydrolysates in a one run-in assay 10 in reversed-phase high-performance liquid chromatography (HPLC), because of their similar polarities and hydrophobicities.…”

Visualization of Tocopherol Acetate Absorbed Inside Laminated Films by a Matrix-assisted Laser Desorption/Ionization-imaging Mass Spectrometry

“…of THAP matrix onto the target section (Hong et al, 2013). In the present study, a marked MS signal of tocopherol acetate with Na…”

Foodomics and Food Safety: Where We Are

“…This technique gives information about both the molecular size of the substance and its localization in tissue samples (44,155). However, this potentially powerful strategy was seldom used in foodomics (44,(156)(157)(158). Hong et al (156) used MALDI imaging mass spectrometry for enhanced visualization of small peptides in rat intestine, presenting only the optimization of the method.…”

“…However, this potentially powerful strategy was seldom used in foodomics (44,(156)(157)(158). Hong et al (156) used MALDI imaging mass spectrometry for enhanced visualization of small peptides in rat intestine, presenting only the optimization of the method. An example of the application of imaging mass spectrometry in the fi eld of food safety is the detection of procymidone, a frequently used fungicide in cucumber samples by nanoparticle-assisted laser desorption-ionization mass spectrometry imaging (157).…”