Desorption atmospheric pressure photoionization (DAPPI) is an ambient mass spectrometry (MS) technique that allows the analysis of both polar and nonpolar compounds directly from the surfaces of various sample types. Here, DAPPI was used to study the chemical profiles in different parts of birch and alder tree barks. Four distinct fractions of Betula pendula (silver birch) bark were collected from three different developmental stages of the stem, after which the chemical profiles of the different tissue types were measured. Of special interest were triterpenoids, a class of important defensive substances, which are found in the bark of the silver birch. Additionally, the chemical profiles of lenticels and the surrounding surfaces in the phellem of B. pendula (silver birch), Alnus glutinosa (black alder), and Alnus incana (gray alder) were screened with DAPPI. Another ambient MS technique, laser ablation atmospheric pressure photoionization (LAAPPI), was further used for the mass spectrometry imaging of lenticels on the B. pendula phellem. All the studied birch bark fractions showed individual chemical profiles in DAPPI. The mass spectra from the young apical stem and the transition zone resembled each other more than the mature stem. Instead, the phellem was found to contain a high amount of triterpenoids in all the developmental stages of the stem. The most intense peaks in the DAPPI mass spectra of the birch bark fractions were those of betulin and lupeol. Betulinic and betulonic acid peaks were intense as well, and these compounds were detected especially in the lenticels of the tree samples.
The emission spectra of the lanthanide chelates enable them to act as a donor for several acceptors emitting at different
wavelengths. Fluorescence resonance energy transfer between terbium(III) chelate labeled antibody Fab fragment (donor) and
a 17β-estradiol conjugated to Alexa Fluor 488, 555, 594 or 680 (acceptor) was employed to study the functionality of the terbium(III)
chelate as an efficient donor for several acceptors emitting from green to far-red. During measurement, the sensitized emission
of the acceptor was measured at acceptor specific wavelength. All the tested dyes proved to be efficient acceptors, and they
were successfully used in the competitive homogeneous E2 assay. The highest signal to background ratio and the best assay
performance was obtained with Alexa Fluor 680, due to the very low donor emission background at the far-red area. In addition,
the sensitized emission of both Alexa Fluor 488 and 680 could be measured simultaneously without significant cross talk. 相似文献
Monolithically integrated, polymer (SU-8) microchips comprising an electrophoretic separation unit, a sheath flow interface and an ESI emitter were developed to improve the speed and throughput of proteomics analyses. Validation of the microchip method was performed based on peptide mass fingerprinting and single peptide sequencing of selected protein standards. Rapid, yet reliable identification of four biologically important proteins (cytochrome C, β-lactoglobulin, ovalbumin and BSA) confirmed the applicability of the SU-8 microchips to ambitious proteomic applications and allowed their use in the analysis of human muscle cell lysates. The characteristic tryptic peptides were easily separated with plate numbers approaching 10(6), and with peak widths at half height as low as 0.6 s. The on-chip sheath flow interface was also exploited to the introduction of an internal mass calibrant along with the sheath liquid which enabled accurate mass measurements by high-resolution Q-TOF MS. Additionally, peptide structural characterization and protein identification based on MS/MS fragmentation data of a single tryptic peptide was obtained using an ion trap instrument. Protein sequence coverages exceeding 50% were routinely obtained without any pretreatment of the proteolytic samples and a typical total analysis time from sampling to detection was well below ten minutes. In conclusion, monolithically integrated, dead-volume-free, SU-8 microchips proved to be a promising platform for fast and reliable analysis of complex proteomic samples. Good analytical performance of the microchips was shown by performing both peptide mass fingerprinting of complex cell lysates and protein identification based on single peptide sequencing. 相似文献
The performance of desorption electrospray ionization (DESI) in the analysis of a group of pharmaceuticals and their glucuronic acid conjugates is reported. The suitability of different sprayer solvents and different surfaces was examined. In the positive ion mode, water/methanol/trifluoroacetic acid performed best, whereas, in the negative ion mode, water/methanol/ammonium hydroxide was found to be the most suitable spray solvent. Of the surfaces investigated, polymethylmethacrylate (PMMA) was found to give the best performance in terms of sensitivity. Spray solution flow rate and the distance of the sprayer tip from the surface were also found to have significant effects on the signal intensity. Analytes with basic groups efficiently formed the corresponding protonated molecules in the positive ion mode, whereas acidic analytes, such as the glucuronic acid conjugates, formed intense signals due to the deprotonated molecules in the negative ion mode. Ionization of neutral compounds was less efficient and in many cases it was achieved through adduct formation with simple anions or cations. 相似文献
The performance of nanoporous silicon (pSi) and ultra-thin layer chromatography (UTLC) plates as surfaces for desorption electrospray ionization (DESI) was compared with that of polymethyl methacrylate (PMMA) and polytetrafluoroethylene (PTFE), both popular surfaces in previous DESI studies. The limits of detection (LODs) and other analytical characteristics for six different test compounds were determined using all four surfaces. The LODs for the compounds were in the fmol-pmol (pg-ng) range. The LODs with the pSi surface were further improved for each of the compounds when heat was applied to the surface during sample application which gave LODs as low as or lower than those achieved with PMMA and PTFE. The UTLC plates were successfully used as a rapid means of chromatographic separation prior to DESI-MS analysis. Another advantage achieved using the newer pSi and UTLC surfaces was increased speed of analysis, associated with drying of solution-phase samples. This took place immediately at the UTLC surface and it could be achieved rapidly by gently heating the pSi surface. The presence of salts in the sample did not cause suppression of the analyte signal with any of the surfaces. 相似文献
Novel synthesis methods for the preparation of quaternary piperazine derivatives of chitosan were developed. Quaternary ammonium moiety can be selectively inserted into either one or both of the piperazine nitrogens, yielding structurally uniform chitosan derivative structures. Water-soluble end products were thoroughly characterized with FT-IR, 1H NMR, 13C NMR and 2D 1H-13C HSQC NMR. The molecular weights of the end products were determined by GPC with triple detection. 相似文献
The ligninolytic enzyme system ofPhanerochaete chrysosporiun is able to decolorize several recalcitrant dyes. Three lignin peroxidase isoenzymes, LiP 3.85, LiP 4.15, and LiP 4.65, were
purified by preparative isoelectric focusing from the carbon-limited culture medium ofP. chrysosporium. Based on amino terminal sequences, the purified isoenzymes correspond to the isoenzymes H8, H6, and H2, respectively, from
theN-limited culture. The purified isoenzymes were used for decolorization of an azo dye, Crocein Orange G (COG). According to
the kinetic data obtained, the oxidation of COG by lignin peroxidase appeared to follow Michaelis-Menten kinetics. Kinetic
parameters for each isoenzyme were determined. The inactivating effect of ascending H2O2 concentrations on COG oxidation is shown to be exponential within the used concentration range. The best degree of decolorization
of 100 μM COG was obtained when the H2O2 concentration was 150 μM. This was also the lowest H2O2 concentration for maximal decolorization of 100 μM COG, regardless of the amount of lignin peroxidase used in the reaction. 相似文献
Nanofibrillated cellulose (NFC) is increasingly utilized in materials and biomedical applications consequently increasing
interest in the modification of its surface properties. Besides modification using polyelectrolytes and polysaccharides, NFC
can be combined with solid particles enabling formation of fibril network loaded with particles. Use of particles enabling
easy functionalization could be beneficial for the development of hybrid structures, and lead to preparation of nanocomposites
and functional materials. In order to explore interactions related to preparation of such structures, the interactions between
nanosized precipitated calcium carbonate (nanoPCC) and nanoclay particles and NFC were examined by observing adsorption of
the particles on NFC substrate using a quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy
(AFM) imaging. By a treatment with carboxymethylated cellulose (CMC), the anionicity of the NFC substrate could be increased,
providing an additional tool to affect the interplay between NFC and the inorganic particles. For slightly cationic nanoPCC
particles an increase in the anionicity of the NFC by the CMC treatment increased the affinity, while the opposite was true
for anionic nanoclay. Additionally, for interactions between nanoclay and NFC, dispersion stability was an important factor.
QCM-D was successfully used to examine the adsorption characteristics of nanoparticles although the technique is commonly
used to study the adsorption of thin polymer layers. Distinct adsorption characteristics were observed depending on the nanoparticle
used; nanoclay particles deposited as a thin layer, whereas nanoPCC particles formed clusters. 相似文献
The kinetic resolution of 1-(3-pyridyl)buten-3-ylamine with activated and non-activated acyl donors and Burkholderia cepacia lipase (lipase PS-D) under dry conditions has been studied. The N-acylation in isopropyl acetate (E >100) and the acidic hydrolysis of the (R)-amide produced gave the corresponding enantiomerically enriched amines. 相似文献