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1.
Late diagnosis of hepatocarcinoma (HCC) is one of the most primary factors for the poor survival of patients. Thereby, identification
of sensitive and specific biomarkers for HCC early diagnosis is of great importance in biological medicine to date. In the
present study, serum metabolites of the HCC patients and healthy controls were investigated using the improved liquid chromatography–mass
spectrometry (LC/MS). A wavelet-based method was utilized to find and align peaks of LC–MS. The characteristic peaks were
selected by performing a two-sample t test statistics (p value <0.05). Clustering analysis based on principal component analysis showed a clear separation between HCC patients and
healthy individuals. The serum metabolite, namely 1-methyladenosine, was identified as the characteristic metabolite for HCC.
Moreover, receiver–operator curves were calculated with 1-methyladenosine and/or alpha fetal protein (AFP). The higher area
under curve value was achieved in 1-methyladenosine group than AFP group (0.802 vs. 0.592), and the diagnostic model combining
1-methyladenosine with AFP exhibited significant improved sensitivity, which could identify those patients who missed the
diagnosis of HCC by determining serum AFP alone. Overall, these results suggested that LC/MS-based metabonomic study is a
potent and promising strategy for identifying novel biomarkers of HCC. 相似文献
2.
Glutathione peroxidase (isolated from bovine erythrocytes) and its behaviour during alkylation and enzymatic digestion were
studied by various hyphenated techniques: gel electrophoresis–laser ablation (LA) inductively coupled plasma (ICP) mass spectrometry
(MS), size-exclusion liquid chromatography–ICP MS, capillary high-performance liquid chromatography (capHPLC)–ICP MS, matrix-assisted
laser desorption/ionization (MALDI) time-of-flight (TOF) MS, electrospray MS, and nanoHPLC–electrospray ionization (ESI) MS/MS.
ESI TOF MS and MALDI TOF MS allowed the determination of the molecular mass but could not confirm the presence of selenium
in the protein. The purity of the protein with respect to selenium species could be evaluated by LA ICP MS and size-exclusion
chromatography (SEC)–ICP MS under denaturating and nondenaturating conditions, respectively. SEC–ICP MS and capHPLC–ICP MS
turned out to be valuable techniques to study the enzymolysis efficiency, miscleavage and artefact formation during derivatization
and tryptic digestion. For the first time the parallel ICP MS and ESI MS/MS data are reported for the selenocysteine-containing
peptide extracted from the gel; capHPLC–ICP MS allowed the sensitive detection of the selenopeptide regardless of the matrix
and nanoHPLC–electrospray made possible its identification.
Figure Eye catching image
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
The significance of forensic arson analysis accelerates the applications of new technologies in this area. Based on the previously
reported application of differential mobility spectrometry (DMS) as a detection method for gas chromatography (GC) in arson
analysis, the performances of DMS and mass spectrometry (MS) were compared using a novel chemometric tool, projected difference
resolutions (PDRs). The PDR results show that one-way mass spectra data exhibit higher resolution than DMS data, while total
ion chromatograms from GC–DMS show higher resolution than that from GC/MS for differentiating seven kinds of ignitable liquids.
Combining the information from both chromatography and spectra, two-way data always have higher resolution than one-way data
for these two detection methods, and GC/MS would exhibit better performance than GC–DMS according to the minimum resolution
value. To verify the PDR results, a fuzzy rule-building expert system was applied for classifying these seven kinds of ignitable
liquids from fire debris based on GC–DMS and GC/MS data, respectively. The prediction accuracies were consistent with PDR
results, which proved that PDR is a powerful tool in comparing the performances of different analysis methods for pattern
recognition.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
Declan Williams Suzanne Ackloo Peihong Zhu Peter Bowden Kenneth R. Evans Christina L. Addison Chris Lock John G. Marshall 《Analytical and bioanalytical chemistry》2010,396(3):1223-1247
The endogenous peptides of human serum may have regulatory functions, have been associated with physiological states, and
their modifications may reveal some mechanisms of disease. In order to correlate levels of specific peptides with disease
alongside internal standards, the polypeptides must first be reliably extracted and identified. Endogenous blood peptides
can be effectively enriched by precipitation of the serum with organic solvents followed by selective extraction of peptides
using aqueous solutions modified with organic solvents. Polypeptides on filter paper were assayed with Coomasie brilliant
blue binding. The polypeptides were resolved by detergent tricine polyacrylamide electrophoresis and visualized by diamine
silver staining. Peptides in the extracts were collected by C18 and analyzed by matrix-assisted laser desorption/ionization
and liquid chromatography–electrospray ionization–tandem mass spectrometry (MS/MS) quadrupole time-of-flight MS/MS. Peptides
were resolved as multiple isotopic peaks in MS mode with mass deviation of 0.1 Da or less and similar accuracy for fragments.
The sensitivity of MS and MS/MS analysis was estimated to be in the picomolar range or less. The peptide composition of the
extracts was dependent on solvent formulation. Multiple peptides from apolipoproteins, complement proteins, coagulation factors,
and many others were identified by X!Tandem with high mass accuracy of peptide ions and fragments from collision-induced dissociation.
Many previously unreported posttranslational modifications of peptides including phosphorylations, oxidations, glycosylations,
and others were detected with high mass accuracy and may be of clinical importance. About 4,630 redundant peptides were identified
with 99% confidence separately, and together some 1,251 distinct proteins were identified with 99% confidence or greater using
the Paragon algorithm. 相似文献
5.
Minute amounts of tissue supernatants from mouse neonates bearing a mutation in the copper (Cu)-transporter gene, Atp7a, were
injected into narrow-bore HPLC coupled with an inductively coupled plasma–mass spectrometer (ICP–MS) to examine Cu metabolism.
In the 14-day-old mutant neonates, Cu accumulated in the intestine in the metallothionein (MT)-bound form, and mRNA expression
of the two MT isoforms was increased. Meanwhile, Cu in the MT-bound form (Cu-MT) was depleted in the liver and mRNA expression
decreased in comparison with wild-type mice. These results suggest that Cu is not secreted by intestinal microvillus cells
into bloodstream due to the defect of Atp7a, and systemic depletion of Cu occurred. On the other hand, in the kidneys of mutant
mice, Cu accumulated in the MT-bound form despite the fact that mRNA expression of the two MT isoforms was low. Part of Cu-MT
in microvillus cells may be released into bloodstream at turnover and be preferably taken up by the kidneys. Consequently,
the mRNA expression of MT isoforms was not always coincident with the amounts of MT proteins binding Cu, and narrow bore HPLC–ICP–MS
used for MT protein determination is a complementary technique to real-time RT-PCR used for MT mRNA determination in Cu speciation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
Polyphenols belonging to the class of secondary metabolites of plants and microorganisms play an important role as bioactive
food constituents as well as contaminants. Structure elucidation of polyphenols in plant extracts or polyphenol metabolites,
especially those arising during biotransformation, still represents a challenge for analytical chemistry. Various approaches
have been proposed to utilize fragmentation reactions in connection with mass spectrometry (MS) for structural considerations
on polyphenolic targets. We compiled and applied specific liquid chromatography (LC)–electrospray ionization in positive mode
[ESI(+)]–tandem MS (MS/MS) and gas chromatography (GC)–(electron impact, EI)–MS/MS fragmentation reactions with a special
focus on the analysis of isoflavones, whereby this technique was also found to be extendable to determine further polyphenols.
For ESI(+)-MS the basic retro-Diels–Alder (rDA) fragmentation offers information about the substitution pattern in the A-
and B-rings of flavonoids and the elimination of a protonated 4-methylenecyclohexa-2,5-dienone (m/z = 107) fragment can be used as a diagnostic tool for many isoflavanones. For GC-(EI)-MS/MS analysis after derivatization
of the analytes to their trimethylsilyl ethers, the elimination of methyl radicals, tetramethylsilane groups or the combined
loss of two methyl groups can be shown to be specific for certain substitution patterns in polyphenols. The applicability
of the fragmentation reactions presented is demonstrated exemplarily for three derivatives of the isoflavone irilone. With
the help of these fragmentation reactions of the two MS techniques combined, a reliable identification of polyphenols is possible.
Especially in such cases where NMR cannot be utilized owing to low analyte amounts being available or prior to purification,
valuable information can be obtained.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Ronald Maul and Nils Helge Schebb contributed equally to this work. 相似文献
7.
Liquid chromatography–tandem mass spectrometry (LC-MS/MS) and gas chromatography–mass spectrometry (GC-MS) have been compared
for the analysis of 2-isopropyl thioxanthone (ITX) and 2-ethylhexyl-4-dimethylaminobenzoate (EHDAB). Pressurized liquid extraction
(PLE) was applied for the extraction of ITX and EHDAB from milk and milk-based beverages. Samples were homogenized with sea
sand and anhydrous sodium sulfate, and were extracted with ethyl acetate at 100 °C and 10.3 × 106 Pa in one cycle of 10 min at 90% flush. Both, GC-MS and LC-MS/MS were suitable to determine these photoinitiators in the
PLE extracts, providing appropriate identification and quantification. The recoveries obtained ranged from 70 to 99% for ITX
and from 70 to 95% for EHDAB. These recoveries were equal as those obtained by a conventional liquid–liquid partitioning with
acetonitrile and tert-butyl methyl ether–hexane. The quantification limits using GC-MS, based on a signal-to-noise ratio of 10, were 0.5 μg/L for
ITX and 1 μg/L for EHDAB. The repeatability of the method, as indicated by the relative standard deviations, was within the
range 0.9–16.1%. The same parameters calculated using LC-MS/MS result in quantification limits of 0.1 μg/L for ITX and 0.02 μg/L
for EHDAB and repeatability within the range 5.2–19.4%. These results pointed out that both techniques are appropriate to
determine these compounds in food samples. The method was applied to milk and milk-based beverages from different supermarkets.
The ITX and EHDAB contents ranged from 2.5 to 325 μg/L and from 8 to 126 μg/L, respectively.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Quintana JB Rodil R López-Mahía P Muniategui-Lorenzo S Prada-Rodríguez D 《Analytical and bioanalytical chemistry》2007,388(5-6):1283-1293
A selective analytical method for the determination of nine organophosphate triesters and triphenylphosphine oxide (TPPO)
in outdoor particulate matter is presented. It involves a fully automated pressurised liquid extraction (PLE) step, integrating
an alumina clean-up process, and subsequent determination by large-volume injection gas chromatography–positive chemical ionisation–tandem
mass spectrometry (LVI-GC–PCI–MS/MS). The extraction variables (solvent, amount of adsorbent, temperature, time and number
of cycles) were optimised using a multicriteria strategy which implements a desirability function that maximises both extraction
and clean-up efficiencies while searching for the best-compromise PLE conditions. The final method affords quantification
limits of between 0.01 and 0.3 μg g−1 and recoveries of >80%, with the exceptions of the most polar analytes, TCEP and TPPO (~65%) for both urban dust and PM10
samples. Moreover, the method permitted the levels of these compounds in dust deposited outdoors (between LOD and 0.5 μg g−1 for TEHP) and PM10 samples (between LOD and 2.4 μg m−3 for TiBP) to be measured and reported for the first time.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
9.
Lutz F. Tietze Birgit Krewer Holm Frauendorf 《Analytical and bioanalytical chemistry》2009,395(2):437-448
One of the main problems of anti-cancer therapy is an insufficient differentiation between normal and malignant cells by the
known anti-proliferant agents. The antibody-directed enzyme prodrug therapy is a promising approach for a selective treatment
of cancer, in which a non-toxic prodrug is enzymatically converted into a highly cytotoxic drug at the surface of malignant
cells by a targeted antibody–enzyme conjugate. The transformations and the stability of a very promising novel prodrug and
its corresponding cytotoxic derivative were now investigated in detail by high-performance liquid chromatography (HPLC)–mass
spectrometry (MS). In order to determine the time-dependent DNA alkylation efficiency and the sequence selectivity of the
novel compounds, DNA binding studies using direct electrospray–Fourier transform ion cyclotron resonance–MS (ESI–FTICR–MS)
have been performed. These measurements were accompanied by HPLC analyses followed by MS of the separated species to confirm
the results of the direct ESI–FTICR–MS measurements. The sites of DNA alkylation could be identified unambiguously by the
mass spectrometric fragmentation pattern of the alkylated oligodeoxynucleotides as well as by the results of HPLC followed
by MS. A combination of all techniques applied led to a better understanding of the mode of action of the new therapeutics
and might be used for an estimation of the cytotoxicity of different prodrugs and drugs since the alkylation efficiency correlates
with the bioactivity of the compounds in cell culture investigations.
After enzymatic cleavage of the sugar moiety, the untoxic prodrug is converted rapidly into the corresponding highly cytotoxic
drug that alkylates DNA with high efficiency
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Lutz F. TietzeEmail: |
10.
A screen-printed (SP) microarray is presented as a platform for the achievement of multiparametric biochips. The SP platform
is composed of eight (0.28-mm2) working electrodes modified with electroaddressed protein A-aryl diazonium adducts. The electrode surfaces are then used
as an affinity immobilisation support for the orientated binding of capture monoclonal antibodies, having specificity against
four different point-of-care related proteins (myoglobin, cardiac troponin I, C-reactive protein and brain natriuretic peptide).
The immobilised capture antibodies are involved in sandwich assays of the four proteins together with biotinylated detection
antibodies and peroxidase-labelled streptavidin in order to permit a chemiluminescent imaging of the SP platform and a sensitive
detection of the assayed proteins. The performances of the system in pure buffered solutions, using a 25-min assay duration,
were characterised by dynamic ranges of 0.5–50, 0.1–120, 0.2–20 and 0.67–67 μg/L for C-reactive protein, myoglobin, cardiac
troponin I and brain natriuretic peptide, respectively. The four different assays were also validated in spiked 40-times-diluted
human sera, using LowCross buffer, and were shown to work simultaneously in this complex medium.
Figure Principle of the screen-printed POC microarray and a schematic representation of the assay architecture.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
11.
Determination of evodiamine and rutecarpine in human serum by liquid chromatography–tandem mass spectrometry 总被引:1,自引:0,他引:1
Evodiamine and rutecarpine are two kinds of indole alkaloids contained in the fruit of Evodiae fructus, which have been shown to exhibit various bioactivities in humans. A liquid chromatography–tandem mass spectrometric method
(LC–MS/MS) was developed for the determination of evodiamine and rutecarpine in human serum. The serum was extracted by solid-phase
extraction (SPE) and analyzed using a C18 column and a mobile phase consisting of methanol–water (85:15) solution containing
5 mmol/L ammonium formate at a flow rate of 0.5 mL/min. The mass spectrometer was operated in positive mode, employing the
extracted ion chromatogram (EIC) for detection and quantitation of evodiamine (m/z 288) and rutecarpine (m/z 304). Good linear relationships between the peak area and the concentration were obtained in the ranges of 5.2–1040 ng/mL
and 10.2–1020 ng/mL, with correlation coefficients (r) of 0.999 and 0.998, for evodiamine and rutecarpine, respectively. The repeatabilities (RSD, n=6) of quantitation for evodiamine and rutecarpine were 2.18–4.00% and 2.99–5.67%, respectively, and the recovery ranged from
90.5% to 98.1%. A comparative study of the different ionization and quantitation modes, including ESI–MS, ESI–MS/MS, APCI–MS
and APCI–MS/MS, was also accomplished. The MS/MS fragmentation mechanism of the base peak ([M+H]+, m/z 304) of evodiamine was investigated in order to identify the analytes in more complicated body fluid samples.
相似文献
12.
Gero P. Hooff Nina Patel W. Gibson Wood Walter E. Müller Gunter P. Eckert Dietrich A. Volmer 《Analytical and bioanalytical chemistry》2010,398(4):1801-1808
The isoprenoids farnesyl-(FPP) and geranylgeranylpyrophosphate (FPP and GGPP) are two major lipid intermediates in the mevalonate
pathway. They participate in post-translational modification of members of the superfamily of small guanosine triphosphatases
(GTPases; Ras, Rab, Rac, etc.) via prenylation reactions. Due to the important role of these proteins in a number of cell
processes, in particular cell growth, division, and differentiation, investigation of the involvement of isoprenoids in these
processes is of great interest. In a previously published report, we described a fully validated assay for the quantitation
of the two isoprenoids using a high-performance liquid chromatography (HPLC)–fluorescence detection (FLD) method. The current
work expands on the previous method and enhances it greatly by using a much faster state-of-the-art ultrahigh-performance
liquid chromatography (UHPLC) technique coupled to tandem mass spectrometry (MS/MS). The method exhibited a linear concentration
range of 5–250 ng/mL for FPP and GGPP in human brain tissue; it was shown to be unaffected by ion suppression and provided
results almost six times faster than the HPLC–FLD assay. Comparison of UHPLC–MS/MS and HPLC–FLD yielded excellent comparability
of the two assays for both isoprenoids. Based on the UHPLC–MS/MS assay, a novel in vitro test system was implemented to study
enzyme specificity for distinct amino acid CAAX motifs, which is potentially useful for investigating target interactions
of new therapeutics for diseases involving pathological regulation of isoprenoids and/or small GTPases. 相似文献
13.
Poulsen ME Christensen HB Sørensen MT Leffers H Andersen JH 《Analytical and bioanalytical chemistry》2007,389(6):1799-1804
Chlormequat is a plant growth regulator widely used on cereals, and there is general concern that it may impair human fertility.
A LC–MS/MS method for the analysis of chlormequat in milk and serum was developed and validated in connection with an investigation
on the effect of chlormequat on pig reproduction. Validation of the method was based on recovery tests at three spiking levels,
determined as double determinations and repeated at least four times. Samples were extracted with methanol–water–acetic acid,
centrifuged, filtrated and determined by LC–MS/MS. The mean recoveries were in the range 80–110%, and the LOD was 0.2 ng/g
for serum and 0.3 ng/g for milk. The values for repeatability and reproducibility were within 2/3 of the limits given by the
Horwitz equation. Samples of pig serum (59) and sow milk (27) were analyzed using the method. Chlormequat was determined in
four milk samples in the range of 0.4 ng/g to 1.2 ng/g and in all serum samples in the range of 0.2 ng/g−4.0 ng/g. 相似文献
14.
We previously showed for the proteins BCL-XL, IL-2, and MDM2 that transient pockets at their protein–protein binding interfaces can be identified by applying the PASS
algorithm to molecular dynamics (MD) snapshots. We now investigated which aspects of the natural conformational dynamics of
proteins induce the formation of such pockets. The pocket detection protocol was applied to three different conformational
ensembles for the same proteins that were extracted from MD simulations of the inhibitor bound crystal conformation in water
and the free crystal/NMR structure in water and in methanol. Additional MD simulations studied the impact of backbone mobility.
The more efficient CONCOORD or normal mode analysis (NMA) techniques gave significantly smaller pockets than MD simulations,
whereas tCONCOORD generated pockets comparable to those observed in MD simulations for two of the three systems. Our findings
emphasize the influence of solvent polarity and backbone rearrangements on the formation of pockets on protein surfaces and
should be helpful in future generation of transient pockets as putative ligand binding sites at protein–protein interfaces.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Aronov PA Hall LM Dettmer K Stephensen CB Hammock BD 《Analytical and bioanalytical chemistry》2008,391(5):1917-1930
Biologically active forms of vitamin D are important analytical targets in both research and clinical practice. The current
technology is such that each of the vitamin D metabolites is usually analyzed by individual assay. However, current LC-MS
technologies allow the simultaneous metabolic profiling of entire biochemical pathways. The impediment to the metabolic profiling
of vitamin D metabolites is the low level of 1α,25-dihydroxyvitamin D3 in human serum (15–60 pg/mL). Here, we demonstrate that liquid–liquid or solid-phase extraction of vitamin D metabolites
in combination with Diels–Alder derivatization with the commercially available reagent 4-phenyl-1,2,4-triazoline-3,5-dione
(PTAD) followed by ultra-performance liquid chromatography (UPLC)–electrospray/tandem mass spectrometry analysis provides
rapid and simultaneous quantification of 1α,25-dihydroxyvitamin D3, 1α,25-dihydroxyvitamin D2, 24R,25-dihydroxyvitamin D3, 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 in 0.5 mL human serum at a lower limit of quantification of 25 pg/mL. Precision ranged from 1.6–4.8 % and 5–16 % for 25-hydroxyvitamin
D3 and 1α,25-dihydroxyvitamin D3, respectively, using solid-phase extraction.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
Wetterhall M Shevchenko G Artemenko K Sjödin MO Bergquist J 《Analytical and bioanalytical chemistry》2011,400(9):2827-2836
In this study, a temperature-induced phase fractionation known as cloud-point extraction (CPE) with the non-ionic surfactant
Triton X-114 was used to simultaneously extract, concentrate, and fractionate hydrophobic and hydrophilic proteins from mouse
brain tissue. Two bottom-up proteomic techniques were used to comprehensively identify the extracted proteins. The first “shotgun”-based
approach included tryptic digestion of the proteins followed by reversed-phase nanoliquid chromatography (RP-nanoLC) in combination
with electrospray ionization (ESI) tandem mass spectrometry (MS/MS). In the second approach, the extracted intact proteins
were first separated by one-dimensional (1D) gel electrophoresis and then in-gel digested with trypsin and analyzed with nanoLC-MS/MS.
In total, 1,825 proteins were unambiguously identified and the percentage of membrane proteins was 26% which is at the reported
genome expression levels of 20–30%. The protein overlap between the two approaches was high. The majority (77%) of the identifications
in the first approach was also found by the second method. The protein overlap between the CPE-extracted hydrophilic and hydrophobic
fractions was rather small (16–23%) for both methods, which indicates a good phase separation. A quantitative evaluation of
the CPE with iTRAQ labeling and nanoLC-ESI-MS/MS analysis gave iTRAQ ratios at the expected levels and an overall variation
of the entire method at 17–31%. The results indicate very reproducible sample preparation and analysis methods that readily
can be applied on large-scale sample sets. 相似文献
17.
Qian Y Preston K Krokhin O Mellish J Ens W 《Journal of the American Society for Mass Spectrometry》2008,19(10):1542-1550
We have performed a detailed characterization and identification of wheat gluten proteins obtained from the Teal variety of
Canadian hard red spring wheat. RP-HPLC separation of the sample into 35 fractions has reduced the spectral complexity; this
was followed by MALDI mass spectrometry (MS), which showed the presence of six or fewer resolved protein components above
20 kDa in each RP-HPLC fraction, giving a total of 93 MS resolved peaks. These included 17 peaks in the ω-gliadin fractions (F1–4), 12 in the high molecular weight (HMW) glutenin subunit fractions (F5–8), 59 in the α- and β-gliadins and low molecular weight (LMW) glutenin subunit fractions (F9–31) and 5 peaks in the γ-gliadin fractions (F32–35). Peptide maps of tryptic digests of HPLC fractions were obtained from a tandem quadrupole time-of-flight
mass spectrometer (MALDI QqTOF MS) and were submitted to the ProFound search engine. HMW glutenin subunits including Ax2*,
Dx5, Bx7, and Dy10 (consistent with the known profile of Teal), and LMW glutenin subunits including six from group 3 type
II and 1 from group 2 type I, were identified with reasonable sequence coverage from HPLC fraction 5, 7, 17, and 18. The identities
of the peptides attributed to selected gluten proteins were confirmed using MS/MS with BioMultiView to match the predicted
and measured partial amino acid sequences. Because of incomplete wheat DNA databases, many wheat gluten proteins could not
be identified. These results suggest that the combination of RP-HPLC with MS and MS/MS techniques is a promising approach
for the characterization of wheat gluten proteins. 相似文献
18.
H. Namazi M. Adeli Z. Zarnegar S. Jafari A. Dadkhah A. Shukla 《Colloid and polymer science》2007,285(14):1527-1533
Benzyl alcohol and Rose Bengal were loaded and entrapped using linear–dendritic macromolecules by two procedures. In the first
procedure, benzyl alcohol was attached to the end functional groups of linear–dendritic macromolecules by ester bonds to afford
linear–dendritic–host conjugates. In the second procedure, entrapment was based on physical interactions between Rose Bengal
and linear–dendritic macromolecules; this procedure is known as complexation method. Loading and binding capacity of different
linear–dendritic macromolecules was investigated using 1H nuclear magnetic resonance (NMR) and UV spectroscopy methods. It was found the loading or binding capacity of linear–dendritic
macromolecules depends on their generation, so that higher generations have higher loading or binding capacity. Diameter of
nanocarriers was investigated using dynamic light scattering (DLS) experiments, and it was between 16 and 50 nm for different
nanocarriers. Release of guest molecules from nanocarriers was evaluated at pH 1, 7.4, and 10.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
Jung C 《Analytical and bioanalytical chemistry》2008,392(6):1031-1058
Cytochrome P450 proteins (CYPs) are a big class of heme proteins which are involved in various metabolic processes of living
organisms. CYPs are the terminal catalytically active components of monooxygenase systems where the substrate binds and is
hydroxylated. In order to be functionally competent, the protein structures of CYPs possess specific properties that must
be explored in order to understand structure–function relationships and mechanistic aspects. Fourier transform infrared spectroscopy
(FTIR) is one tool that is used to study these structural properties. The application of FTIR spectroscopy to the secondary
structures of CYP proteins, protein unfolding, protein–protein interactions and the structure and dynamics of the CYP heme
pocket is reviewed. A comparison with other thiolate heme proteins (nitric oxide synthase and chloroperoxidase) is also included.
Figure The protein secondary structure, protein unfolding, redox-partner protein–protein interaction, structural changes induced
by the reduction of the heme iron, and the structure and dynamics of the active site of cytochromes P450 (CYP) can be studied
using Fourier transform infrared spectroscopy (FTIR). FTIR spectroscopy is a good approach for gaining a deeper insight into
structure–function relationships in CYPs.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
J. García-Lavandeira C. Salgado-Petinal E. Blanco R. Cela 《Analytical and bioanalytical chemistry》2010,397(2):751-763
We have developed and validated a quantitative liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI
MS/MS) procedure for the simultaneous determination of seven natural and semisynthetic tropane alkaloids in plasma: atropine
(d-hyoscyamine/l-hyoscyamine), cocaine, homatropine, ipratropium, littorine, N-butylscopolamine, and scopolamine. Plasma and serum samples were precipitated for deproteinization (recovery 88–94%), followed
by reversed-phase-based liquid chromatography prior to positive electrospray ionization for detection by multiple reaction
monitoring using a linear ion trap quadrupole mass spectrometer. All analytes were quantified using cocaine-d3 as an internal standard suitable and reliable for robust, precise (coefficient of variation 2–13%), and accurate (87–122%)
measurement within a linear range of 3 orders of magnitude (0.05–50 ng/ml plasma). The method was exemplarily applied to stability
studies in phosphate-buffered saline, human serum, and rabbit serum. Each alkaloid was incubated separately and samples were
taken at distinct incubation time points. Supernatants of diverse alkaloids at corresponding time points were pooled and subjected
to simultaneous LC-ESI MS/MS quantification. This combinatorial analysis design allowed us to analyze the stability of samples
with a drastically reduced number of chromatographic runs. In the presence of rabbit serum, all tropane alkaloids tested were
degraded significantly within minutes to hours, with the exception of the stable semisynthetic compounds ipratropium and N-butylscopolamine. In contrast, in the presence of equal concentrations of human serum, no degradation was observed for any
of the compounds, with the exception of cocaine. Relevant enzymes involved in enzymatic degradation are discussed. 相似文献