Electrospray ionization mass spectrometry of neat undiluted ionic liquid (IL) and the analysis of protein with the doping of IL were performed using high-pressure electrospray. The use of disposable micropipette tips as emitters eased the handling of viscous and easy-to-clog samples and improved the reproducibility of the measurement. A high-pressure operation enabled the stable electrospray of the highly conductive IL from these relatively large bore emitters. The measurement of the current–voltage relationship of 1-ethyl-3-methylimidazolium tetrafluoroborate (Emim BF₄) revealed an unusual negative differential resistance that has not been seen in the typical atmospheric or high-pressure electrospray. Mass spectrometric analysis of this IL also showed the characteristic response of various ion species with the emitter voltage. When added to the commonly used protein solution, the mass spectrum also showed protein peaks that correspond to the adduction of fluoroboric acid molecules (HBF₄).

Mass spectrometry (MS) is a valuable tool that enables label-free analysis and the ability to measure multiple molecules. The atmospheric pressure MS imaging (MSI) method usually requires tedious sample preparation. A simple ionization method with minimal sample preparation is needed for high-throughput analysis. We have developed an ion source that does not require sample preparation such as thinning, curing, planarization, or addition of matrix by the electrospray-assisted laser desorption/ionization with gas transportation (ELDI-GT). The sample is transported with nitrogen gas through a heated tube to the electrospray. The ion signal of protonated caffeine was measured under different transport conditions. The ion signal intensity was found to increase 11-fold by changing the flow rate and tube temperature from 2.8 cm³/s and 473 K to 25 cm³/s and 673 K. ELDI-GT was able to visualize the localization of caffeine crystals at a pixel size of 50 µm using MSI because of the effective GT using the heated tube. The dependence of the ion signal intensity was discussed on the amount of heat applied to the sample in the heated tube. ELDI-GT allowed accurate localization of caffeine at a pixel size of 50 µm without the need to apply thinning and matrix to a sample.

Aberrant glycosylation of membrane proteins is a hallmark of cancer and a useful molecular marker for the diagnosis of breast cancer (BC). However, the molecular mechanisms by which altered glycosylation affects the malignant transformations associated with BC are poorly understood. Accordingly, we performed comparative membrane N-glycoproteomics using the human BC cell line pair, Hs578T, and its syngeneic normal cell line, Hs578Bst. A total of 359 N-glycoforms derived from 113 proteins were identified in both cell lines, of which 27 were found only in Hs578T cells. Significant changes in N-glycosylation were found in the lysosome-associated membrane protein 1 (LAMP1), the integrin family, and laminin. Confocal immunofluorescence microscopy images revealed the accumulation of lysosomes in the perinuclear space in cancer cells, which could be associated with marked changes in LAMP1 glycosylation, such as a decreased level of polylactosamine chains. Overall, the alterations in glycosylation may be involved in changes in the adhesion and degradation of BC cells.

The negative ion at m/z 20 observed at atmospheric pressure corona discharge ionization mass spectra has been identified by supplying the vapors of deuterium oxide (D₂O) and H₂¹⁸O. From the mass shifts of the ion at m/z 20 observed with D₂O and H₂¹⁸O, it was suggested that the chemical composition of the ion at m/z 20 is to be H₄O. Further mass shift from m/z 20 to 22 was observed by supplying the vapor of perfluorokerocene, suggesting the chemical composition of H₃F. The chemical compositions of the negative ions H₄O⁻ and H₃F⁻ were consistence with the dipole-bound complex states between hydrogen H₂ and polar molecules such as H₂O and hydrogen fluoride (HF) having dipole moments beyond a critical dipole moment of 1.625 D, theoretically proposed by Skurski and Simons. The ionic chemical compositions and structures of H₄O⁻ and H₃F⁻ obtained with density functional theory calculations implied that both dipole-bound complex H₂O⁻…H₂ and HF⁻…H₂ can be formed by exothermic reactions by which H₂ molecule is complexing with negative ions H₂O⁻ and HF⁻, respectively.

“Retronasal aroma” refers to the aroma released from food during consumption and traveling through the nose after leaving the mouth. It is closely related to the behavior of odor compounds released from food into the mouth and plays a crucial role in our overall perception of flavor. As a result, research focusing on measuring the behavior of retronasal aroma has gained attention for exploring the relationship between sensory perception and flavor. We attempted to develop a data analysis method that specifically targets a time span of a few seconds to tens of seconds, starting from when food is placed in the mouth during eating and extending to just after swallowing. In this study, we observed a strong correlation between the periodic waveform data derived from performing the third derivative (jerk) on the detection intensity data obtained using a mass spectrometer and the behavior of the detection intensity. Furthermore, by performing a frequency analysis using a fast Fourier transform on the jerk data, it was possible to extract the frequencies that contribute to sensory perception during eating. Furthermore, the reconstructed jerk data derived from the extracted data using the inverse fast Fourier transform provided a clearer explanation of sensory perception during eating. Our algorithm suggests new short-term time-series data applications.