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121.
To explore the molecular mechanism of the matrix metalloproteinases (MMPs) in tumor processes, two photoaffinity trimodular probes were designed and synthesized based on the structure activity relationship and the following photoaffinity labelling experiments afforded positive results. 相似文献
122.
123.
Roel De Mondt Luc Van Vaeck Andreas Heile Heinrich F. Arlinghaus Frank Vangaever Jens Lenaerts 《Analytical and bioanalytical chemistry》2009,393(8):1917-1921
Recent publications on static secondary ion mass spectrometry (S-SIMS) focus on molecular depth profiling by using polyatomic
or ultra-low energy monoatomic projectiles. Since their applicability depends on the relationship between the ion yield and
the depth, which is hard to obtain without extensive studies, a combination of a wear test method with S-SIMS surface analysis
was performed in the current study. Using this non-sputtering procedure, the relation between the signal intensity and the
local concentration remains in principle the same as that at the surface (which is easy to determine). Mechanical erosion
was successfully applied to expose sub-surface material from organic multilayers. Through surface analysis with S-SIMS on
the gradually exposed deeper planes, molecular depth profiles could be obtained. The study was conducted on a model system
relevant to offset printing, consisting of two polymer layers, containing dyes and a surfactant, cast on an Al substrate.
Figure Concept of mechanical erosion followed by S-SIMS surface analysis to obtain molecular depth profiles 相似文献
124.
P. Vega J. Pisonero N. Bordel A. Tempez M. Ganciu A. Sanz-Medel 《Analytical and bioanalytical chemistry》2009,394(1):373-382
A compact magnetically boosted radiofrequency glow discharge (GD) has been designed, constructed and its analytical potential
evaluated by its coupling to a mass spectrometer (MS). Simple modifications to the original source configuration permitted
the insertion of permanent magnets. Small cylindrical Nd–Fe–B magnets (∅ = 4 mm, h = 10 mm) were placed in an in-house-modified GD holder disc that allows easy and fast exchange of the magnets. The different
processes taking place within the GD plasma under the influence of a magnetic field, such as sputtering, ionisation processes
and ion transport into the MS, were studied using different GD operating conditions. Changes to the ionisation and ion transport
efficiency caused by the magnetic field were studied using an rf-GD-TOFMS setup. A magnetic field of 60–75 gauss (G) was found
not to affect the sputtering rates but to enhance the analyte ion signal intensities while decreasing the Ar species ion signals.
Moreover, magnetic fields in this range were shown not to modify the crater shapes, enabling the fast and sensitive high depth
resolved analysis of relatively thick coated samples (micrometre) by using the designed compact magnetically boosted rf-GD-TOFMS.
相似文献
M. GanciuEmail: |
125.
Sasidhar Maddula Lars Mathias Blank Andreas Schmid Jörg Ingo Baumbach 《Analytical and bioanalytical chemistry》2009,394(3):791-800
Detection and immediate quantification of microbial metabolic activities is of high interest in fields as diverse as biotechnology
and infection biology. Interestingly, the most direct signals of microbial metabolism, the evolution of volatile metabolites,
is largely ignored in the literature, and rather, metabolite concentrations in the microbial surrounding or even disruptive
methods for intracellular metabolite measurements (i.e., metabolome analysis) are favored. Here, the development of a multi
capillary column coupled ion mobility spectrometer (MCC-IMS) was described for the detection of volatile organic compounds
from microbes and the MCC-IMS was used for characterization of metabolic activity of growing Escherichia coli. The MCC-IMS chromatogram of the microbial culture off-gas of the acetone-producing E. coli strain BL21 pLB4 revealed four analytes that positively correlated with growth, which were identified as ethanol, propanone
(acetone), heptan-2-one, and nonan-2-one. The occurrence of these analytes was cross-validated by solid-phase micro-extraction
coupled with gas chromatography mass spectrometry analysis. With this information in hand, the dynamic relationship between
the E. coli biomass concentration and the metabolite concentrations in the headspace was measured. The results suggest that the metabolic
pathways of heptan-2-one and nonan-2-one synthesis are regulated independent of each other. It is shown that the MCC-IMS in-line
off-gas analysis is a simple method for real-time detection of microbial metabolic activity and discussed its potential for
application in metabolic engineering, bioprocess control, and health care. 相似文献
126.
John S. Fletcher Xavier A. Conlan Nicholas P. Lockyer John C. Vickerman 《Applied Surface Science》2006,252(19):6513-6516
Atomic depth profiling using secondary ion mass spectrometry, SIMS, is common in the field micro-electronics; however, the generation of molecular information as a function of sample depth is difficult due to the accumulation of damage both on and beneath the sample surface. The introduction of polyatomic ion beams such as SF5 and C60 have raised the possibility of overcoming this problem as they deposit the majority of their energy in the upper surface of the sample resulting in increased sputter yields but with a complimentary reduction in sub-surface damage accumulation. In this paper we report the depth profile analysis of the bio-polymer polycaprolactone, PCL, using the polyatomic ions and and the monoatomic Au+. Results are compared to recent analysis of a similar sample using . depth profiling of cellulose is also demonstrated, an experiment that has been reported as unsuccessful when attempted with implications for biological analysis are discussed. 相似文献
127.
Samina Rubnawaz Waqas Khan Kayani Nosheen Akhtar Rashid Mahmood Asif Khan Mohammad K. Okla Saud A. Alamri Ibrahim A. Alaraidh Yasmeen A. Alwasel Bushra Mirza 《Molecules (Basel, Switzerland)》2021,26(16)
Ajuga bracteosa Wall. ex Benth. is an endangered medicinal herb traditionally used against different ailments. The present study aimed to create new insight into the fundamental mechanisms of genetic transformation and the biological activities of this plant. We transformed the A. bracteosa plant with rol genes of Agrobacterium rhizogenes and raised the regenerants from the hairy roots. These transgenic regenerants were screened for in vitro antioxidant activities, a range of in vivo assays, elemental analysis, polyphenol content, and different phytochemicals found through HPLC. Among 18 polyphenolic standards, kaempferol was most abundant in all transgenic lines. Furthermore, transgenic line 3 (ABRL3) showed maximum phenolics and flavonoids content among all tested plant extracts. ABRL3 also demonstrated the highest total antioxidant capacity (8.16 ± 1 μg AAE/mg), total reducing power, (6.60 ± 1.17 μg AAE/mg), DPPH activity (IC50 = 59.5 ± 0.8 μg/mL), hydroxyl ion scavenging (IC50 = 122.5 ± 0.90 μg/mL), and iron-chelating power (IC50 = 154.8 ± 2 μg/mL). Moreover, transformed plant extracts produced significant analgesic, anti-inflammatory, anticoagulant, and antidepressant activities in BALB/c mice models. In conclusion, transgenic regenerants of A. bracteosa pose better antioxidant and pharmacological properties under the effect of rol genes as compared to wild-type plants. 相似文献
128.
Maja Friščić Franz Bucar Kroata Hazler Pilepić 《Journal of mass spectrometry : JMS》2016,51(12):1211-1236
Plants produce a great number of metabolites with potentially useful biological activities. Species from the genus Globularia (Plantaginaceae) are known as sources of different phenolic and iridoid compounds. Globularia alypum L. is a medicinal plant used as a healing agent in many Mediterranean countries. Similarities in phytochemical composition are often observed for related species. For Globularia spp., such findings were mostly based on identification of several isolated compounds from distinct species. To our knowledge, this is the first study that enables simultaneous comparison of phytochemical profiles from several members of the genus Globularia. Liquid chromatography‐photodiode array detection‐electrospray ionization‐tandem mass spectrometry was used for the analysis of methanolic extracts of aerial parts obtained from four Globularia species (G. alypum, G. punctata, G. cordifolia and G. meridionalis). In total, 85 compounds were identified or tentatively identified based on comparison of their retention time, UV and MSn (up to MS4) spectra to those of standard compounds and/or to literature data. Among these, high relative amounts of bioactive molecules such as globularin, globularifolin, asperuloside and verbascoside (acteoside) were found. Apart from providing new insights into the phytochemistry and chemotaxonomy of selected Globularia species, results of this study complement existing MS/MS spectral data and could enable easier mass spectrometric profiling of certain bioactive compounds such as iridoids and phenylethanoids in related plant species, genera and families. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
129.
《Surface Science Reports》2014,69(4):196-295
This review introduces hydrogen depth profiling by nuclear reaction analysis (NRA) via the resonant 1H(15N,αγ)12C reaction as a versatile method for the highly depth-resolved observation of hydrogen (H) at solid surfaces and interfaces. The technique is quantitative, non-destructive, and readily applied to a large variety of materials. Its fundamentals, instrumental requirements, advantages and limitations are described in detail, and its main performance benchmarks in terms of depth resolution and sensitivity are compared to those of elastic recoil detection (ERD) as a competing method. The wide range of 1H(15N,αγ)12C NRA applications in research of hydrogen-related phenomena at surfaces and interfaces is reviewed.Special emphasis is placed on the powerful combination of 1H(15N,αγ)12C NRA with surface science techniques of in-situ target preparation and characterization, as the NRA technique is ideally suited to investigate hydrogen interactions with atomically controlled surfaces and intact interfaces. In conjunction with thermal desorption spectroscopy, 15N NRA can assess the thermal stability of absorbed hydrogen species in different depth locations against diffusion and desorption. Hydrogen diffusion dynamics in the near-surface region, including transitions of hydrogen between the surface and the bulk, and between shallow interfaces of nanostructured thin layer stacks can directly be visualized. As a unique feature of 15N NRA, the analysis of Doppler-broadened resonance excitation curves allows for the direct measurement of the zero-point vibrational energy of hydrogen atoms adsorbed on single crystal surfaces. 相似文献
130.
For practical purposes the calculation of rate constants is not particularly valuable, since their physical significance is not clear. Of greater practical use are metabolic control coefficients and elasticities. Given the definition of the flux control coefficients C(E)(J), concentration control coefficient C(E)(X) and elasticity epsilon (X)(v(1)). We can calculate symbolic formulae for these using computer algebra-techniques. These are then functions of V(max), K(m), K(i) enzyme and concentrations. Having derived estimates of V(max), K(m), K(i) using the fitting method we can then calculate values of the control coefficients and elasticities. Furthermore we can calculate the metabolic control parameters using symbolic values for the conventional kinetic parameters. Using these we have verified the summation and connectivity theorems. This is a useful cross check on the reliability of the calculations. 相似文献