Direct Profiling of Phytochemicals in Tulip Tissues and In Vivo Monitoring of the Change of Carbohydrate Content in Tulip Bulbs by Probe Electrospray Ionization Mass Spectrometry

Probe electrospray ionization (PESI) is a recently developed ESI-based ionization technique which generates electrospray from the tip of a solid needle. In this study, we have applied PESI interfaced with a time of flight mass spectrometer (TOF-MS) for direct profiling of phytochemicals in a section of a tulip bulb in different regions, including basal plate, outer and inner rims of scale, flower bud and foliage leaves. Different parts of tulip petals and leaves have also been investigated. Carbohydrates, amino acids and other phytochemicals were detected. A series of in vivo PESI-MS experiments were carried out on the second outermost scales of four living tulip bulbs to monitoring the change of carbohydrate content during the first week of initial growth. The breakdown of carbohydrates was observed which was in accordance with previous reports achieved by other techniques. This study has indicated that PESI-MS can be used for rapid and direct analysis of phytochemicals in living biological systems with advantages of low sample consumption and little sample preparation. Therefore, PESI-MS can be a new choice for direct analysis/profiling of bioactive compounds or monitoring metabolic changes in living biological systems

Probing Acid-Induced Compaction of Denatured Proteins by High-Pressure Electrospray Mass Spectrometry

Further increase in the acidity in the most denaturing acidic solution is known to induce compaction of the fully unfolded protein into a compact molten globule. The phenomenon of “acid-induced folding of proteins” takes place at pH ∼1 in strong acid aqueous solutions with high electrical conductivity and surface tension, a condition that is difficult to handle using conventional electrospray ionization methods for mass spectrometry. Here, high-pressure electrospray ionization (HP-ESI) is used to produce well-resolved mass spectra for proteins in strong acids with pH as low as 1. The compaction of protein conformation is indicated by a large shift in the charge state from high charges to native-like low charges. The addition of salt to the protein in the most denaturing condition also reproduces the compaction effect, thereby supporting the role of anions in this phenomenon. Similar compaction of proteins is also observed in organic solvent/acid mixtures. The charge state of the compacted protein depends on the type of anions that formed ion pairs with a positive charge on the protein. The dissociation of ion pairs during the ionization process forms neutral acids that can be observed by HP-ESI using a soft ion introduction configuration

Online electrospray ionization mass spectrometric monitoring of protease-catalyzed reactions in real time

Although there are a lot of well established methods for monitoring enzyme-catalyzed reactions, most of them are based on changes in spectroscopic properties during the conversion of substrates to products. However, reactions without optical changes are common, which are inapplicable to these spectroscopic methods. As an alternative technique for enzymologic research, mass spectrometry (MS) is favored due to its specificity, sensitivity, and the ability to obtain stoichiometric information. In this work, probe electrospray ionization (PESI) source coupled with a time of flight mass spectrometer was employed to monitor some typical proteasecatalyzed reactions, including pepsinolysis and trypsinolysis of cytochrome c in real time. Due to the high electrical conductivity of each reaction system, corona discharges are likely to occur, which would decrease intensities of mass spectrometric signals. An ultra-fine sampling probe and an auxiliary vapor spray were adopted to prevent corona discharges. Experimental results from peptic and tryptic digestions of cytochrome c showed different and characteristic catalytic pathways. With the data presented in this study, PESI-MS can be considered as a potential tool for real-time monitoring of enzymatic reactions because of its simplicity in instrumental configuration, wide applicability under harsh conditions, and flexibility in combination with other techniques.Fil: Yu, Zhan. Shenyang Normal University; China. University Of Yamanashi; JapónFil: Chen, Lee Chuin. University Of Yamanashi; JapónFil: Mandal, Mridul Kanti. University Of Yamanashi; JapónFil: Nonami, Hiroshi. Ehime University; JapónFil: Erra Balsells, Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Hiraoka, Kenzo. University Of Yamanashi; Japó

Identification of Copper(II)-Lactate Complexes in Cu₂O Electrodeposition Baths: Deprotonation of the alpha-Hydroxyl Group in Highly Concentrated Alkaline Solution

This was Paper 1628 presented at the Honolulu, Hawaii, Meeting of the Society, October 2–7, 2016.Unveiling dissolved species in electrodeposition baths helps our understanding of electrodeposition behavior, such as growth orientation. A highly concentrated aqueous alkaline copper(II)–lactate solution is used for the electrodeposition of copper(I) oxide (Cu₂O) thin films with orientations; the semiconductor properties of these films facilitate their use in solar-cell materials, photocathodes, and photocatalysts. However, the dissolved species, presumably copper(II)–lactate complexes, cannot be deduced on the basis of known thermodynamic data, and have not been convincingly determined yet. In this work, we determine these cupric complexes by pH titration, ultraviolet–visible spectroscopy, and electrospray-ionization mass spectrometry (ESI-MS), including probe-ESI-MS (PESI-MS). Using PESI-MS, we successfully analyzed a highly concentrated solution without sample dilution. The determined complexes are Cu(H₋₁L)L⁻ and Cu(H₋₁L)₂²⁻ (CH₃CH(O⁻)COO⁻) is a lactate ion with a deprotonated α-hydroxyl group. As far as we know, this is the first direct experimental observation of H₋₁L²⁻ ions in a highly concentrated aqueous alkaline copper(II)–lactate solution. We also propose that H₋₁L²⁻ is stabilized by the high concentration and through coordination to copper(II) ions