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Dependence of neutral red negative area on laser power

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A screenshot of thermography of a sample dish after 30 sec. irradiation at average power of 200 mW

Ammonium Sulfate Improves Detection of Hydrophilic Quaternary Ammonium Compounds through Decreased Ion Suppression in Matrix-Assisted Laser Desorption/Ionization Imaging Mass Spectrometry

Hydrophilic quaternary ammonium compounds (QACs) include derivatives of carnitine (Car) or choline, which are known to have essential bioactivities. Here we developed a technique for improving the detection of hydrophilic QACs using ammonium sulfate (AS) in matrix-assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS). In MALDI mass spectrometry for brain homogenates, the addition of AS greatly increased the signal intensities of Car, acetylcarnitine (AcCar), and glycerophosphocholine (GPC) by approximately 300-, 700-, and 2500-fold. The marked improvement required a higher AS concentration than that needed for suppressing the potassium adduction on phosphatidylcholine and 2,5-dihydroxybenzoic acid. Adding AS also increased the signal intensities of Car, AcCar, and GPC by approximately 10-, 20-, and 40-fold in MALDI-IMS. Consequently, the distributions of five hydrophilic QACs (Car, AcCar, GPC, choline, and phosphocholine) were simultaneously visualized by this technique. The distinct mechanism from other techniques such as improved matrix application, derivatization, or postionization suggests the great potential of AS addition to achieve higher sensitivity of MALDI-IMS for various analytes

Clinicopathological features.

<p>Clinicopathological features.</p

Tandem mass spectrometry for <i>m/z</i> 732.5, <i>m/z</i> 706.5, <i>m/z</i> 806.5, and <i>m/z</i> 734.5.

<p>Precursor ions for each spectrum were (A) <i>m/z</i> 732.5, (B) <i>m/z</i> 706.5, (C) <i>m/z</i> 806.5, and (D) <i>m/z</i> 734.5. The product ion spectra show a common peak corresponding to phosphocholine.</p

Ion distributions of non-recurrence and recurrence groups.

<p>Characteristic distributions of ions are shown in samples of non-recurrence (upper) and recurrence (lower) groups. Regions circled by black and yellow dashed lines represent the cancer epithelial area and surrounding stroma, respectively. Signal intensities at <i>m/z</i> 706.5 and <i>m/z</i> 732.5 in the cancer epithelial area of the recurrence group were higher than those of the non-recurrence group. Both groups showed higher signal intensities at <i>m/z</i> 734.5 in surrounding stroma. Scale bar = 1000 μm. MALDI-IMS: matrix-assisted laser desorption/ionization-imaging mass spectrometry; H&E: hematoxylin and eosin.</p

The changes of microglia and astrocyte in the spinal cord sections after SNI in comparison with [PC(diacyl-16:0/20:4)+K]⁺.

<p>The intensity of Iba-1 in the ipsilateral dorsal horn increased from day 3 (maximum at day 7) <b>(A~C)</b>, while the GFAP did not show any difference at each time period <b>(J~L)</b>. Magnified images of Iba1 <b>(D~F)</b> and [PC(diacyl-16:0/20:4)+K]⁺ <b>(G~I)</b> in the ipsilateral dorsal horn. Scale bar: 300μm. Significant increase of [PC(diacyl-16:0/20:4)+K]⁺ was observed in the ipsilateral dorsal horn at day 7, which resembled the change of microglia. Scale bar: 1mm</p