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1.
The REGDIA regression diagnostics algorithm in S-Plus is introduced in order to examine the accuracy of pK
a predictions made with four updated programs: PALLAS, MARVIN, ACD/pKa and SPARC. This report reviews the current status of
computational tools for predicting the pK
a values of organic drug-like compounds. Outlier predicted pK
a values correspond to molecules that are poorly characterized by the pK
a prediction program concerned. The statistical detection of outliers can fail because of masking and swamping effects. The
Williams graph was selected to give the most reliable detection of outliers. Six statistical characteristics (F
exp, R
2, , MEP, AIC, and s(e) in pK
a units) of the results obtained when four selected pK
a prediction algorithms were applied to three datasets were examined. The highest values of F
exp, R
2, , the lowest values of MEP and s(e), and the most negative AIC were found using the ACD/pK
a algorithm for pK
a prediction, so this algorithm achieves the best predictive power and the most accurate results. The proposed accuracy test
performed by the REGDIA program can also be applied to test the accuracy of other predicted values, such as log P, log D, aqueous solubility or certain physicochemical properties of drug molecules. 相似文献
2.
Amal Halder Dulal C. Mukherjee Sumanta Bhattacharya 《Journal of solution chemistry》2010,39(9):1327-1340
Ground state non-covalent interactions between a macrocyclic receptor, C-methylcalix[4]resorcinarene (1) and fullerenes (C60 and C70) have been studied in benzonitrile by an absorption spectrophotometric method. Absorption bands are located in the visible
region due to the charge transfer (CT) transition between 1 and various electron acceptors (including fullerenes), namely, 2,3-dichloro-5,6-dicyano-p-benzoquinone, tetracyanoquinodimethane and p-chloranil. Utilizing the CT absorption bands, various important physicochemical parameters, including oscillator strength,
resonance energy, transition dipole strength of all the acceptor-1 complexes and vertical ionization potential of 1 are determined. Job’s method of continuous variation reveals 1:1 stoichiometry between fullerenes and 1. The most fascinating feature of the present study is that 1 binds selectively to C70 compared to C60 as obtained from binding constant (K) data of C60-1 (KC60-1K_{\mathrm{C}60\mbox{-}\mathbf{1}}) and C70-1 (KC70-1K_{\mathrm{C}70\mbox{-}\mathbf{1}}) complexes, i.e., KC60-1=190K_{\mathrm{C}60\mbox{-}\mathbf{1}}=190 dm3⋅mol−1 and KC70-1=5,800K_{\mathrm{C}70\mbox{-}\mathbf{1}}=5{,}800 dm3⋅mol−1 and selectivity (KC70-1
/KC60-1
) ∼30. Quantum chemical calculations based on hybrid density functional theory estimate the enthalpies of formation of the
fullerene-1 complexes in vacuo and provide very good support for selectivity in the K values of the C70 and C60 complexes of 1. The exchange and correlation energies have been calculated using a hybrid DFT functional method. We have opted to use the
hybrid DFT functional over the Hartree-Fock method, as it can account for correlation effects also. Molecular electrostatic
potential map calculations give a clear picture on the electronic structures of the fullerene-1 complexes. 相似文献
3.
Martínez-Cabot A Varela B Lloveras M Campos R Marco MP Messeguer A 《Analytical and bioanalytical chemistry》2008,391(2):617-624
The fatty acid esters of 3-(N-phenylamino)propane-1,2-diol (PAP) are biomarkers of toxic oil batches that caused toxic oil syndrome (TOS), an intoxication
that caused over 400 deaths and affected 20,000 people in Spain in 1981. PAP esters are converted into PAP by human pancreatic
lipase. The in vivo biotransformation of PAP in two mouse strains generated potentially toxic metabolites. Here we report
an enzyme-linked immunosorbent assay (ELISA) for PAP detection incorporating antibodies generated using PAP-hapten derivatives
1 and 2. The immunizing haptens were designed to recognize the phenylamino and hydroxymethylene moieties of the PAP structure. The
antisera raised against 1-HCH showed greater affinity for free PAP, as demonstrated in competitive experiments using either 1-BSA or 2-BSA as coating antigens. The developed ELISA detects PAP at a threshold of 130 μg L−1 and can be used over a wide range of pH and ionic strength values. The assay can be applied to human urine samples, after
a simple treatment method, with good recovery according to the correlation obtained when analyzing blind spiked urine samples.
Figure Development of an ELISA for PAP in human urine 相似文献
4.
Lisowski W Keim EG Kaszkur Z van den Berg AH Smithers MA 《Analytical and bioanalytical chemistry》2007,389(5):1489-1498
Using a combination of scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction and X-ray photoelectron
spectroscopy (XPS), we made a comparative study of the high-temperature annealing impact on thin titanium deuteride (TiD
y
) films covered by an ultrathin Pd layer, and on Ti/Pd bilayer films. The bilayer films were prepared under ultrahigh vacuum
conditions and were in situ annealed using the same annealing procedure. It was found that the surface and the bulk morphology
of both films undergo different annealing-induced transformations, leading to an extensive intermixing between the Ti and
Pd layers and the formation of a new PdTi2 bimetallic phase. Energy-filtered TEM imaging and energy-dispersive X-ray spectrometry analysis, as well as XPS depth profiling
all provided evidence of a different distribution of Pd and Ti in the annealed TiD
y
/Pd film compared with the annealed Ti/Pd film. Our results show that thermal decomposition of TiD
y
, as a consequence of annealing the TiD
y
/Pd film, modifies the intermixing process, thereby promoting Ti diffusion into the Pd-rich top layer of the TiD
y
film and thus providing a more likely path for the formation of the PdTi2 phase than in an annealed Ti/Pd film.
Figure Figure Microstructural and chemical characterisation of thin TiDy/Pd film after annealing 相似文献
5.
Ma X Zhu T Xu H Li G Zheng J Liu A Zhang J Du H 《Analytical and bioanalytical chemistry》2008,390(4):1133-1137
A chemical prototype sensor was constructed based on nanofiber-structured TiO2 and highly sensitive quartz resonators. The gas-sensing behavior of this new sensor to selected simulant warfare agents was
investigated at room temperature. Results showed rapid response and good reversibility of this sensor when used with high-purity
nitrogen. This provides a simple approach to preparation of materials needed as chemical sensors for selected organic volatiles
or warfare agents.
Figure Sensing behavior of TiO2 nanofiber sensor to chemical vapors 相似文献
6.
Magnetic Fe3O4-C18 composite nanoparticles of approximately 5–10 nm in size were synthesized and characterized by IR spectroscopy, atomic
absorption spectroscopy, X-ray diffraction, and transmission electron microscopy. The magnetic Fe3O4-C18 composite nanoparticles were applied for cleanup and enrichment of organophosphorous pesticides. Comparative studies
were carried out between magnetic Fe3O4-C18 composite nanoparticles and common C18 materials. Residues of organophosphorous pesticides were determined by gas chromatography
in combination with a nitrogen/phosphorus detector. The cleanup and enrichment properties of magnetic Fe3O4-C18 composite nanoparticles are comparable with those of common C18 materials for enrichment of organophosphorous pesticides,
but the cleanup and enrichment are faster and easier to perform.
Figure Presumed mechanism for the adhesion of the OPs to the Fe3O4-C18 magnetic nanoparticles 相似文献
7.
Milan Meloun Zuzana Ferenčíková Hana Málková Tomáš Pekárek 《Central European Journal of Chemistry》2012,10(2):338-353
Risedronate inhibits bone resorption in diseases like osteoporosis, Paget’s disease, tumor bone diseases or the malfunction
of phosphocalcium metabolism. The acid-base properties of risedronate in an aqueous solution have been studied in a pH range
from 2 to 12 and can be described in terms of four dissociation steps: pK
a,2, pK
a,4, pK
a,5 (related to the dissociation of POH groups) and pK
a,3 related to the dissociation of protonated amino group NH3
+. The mixed dissociation constants were determined at different ionic strengths I = 0.02 to 0.20 mol dm−3 KCl and of 25°C and 37°C using pH-spectrophotometric and pH-potentiometric titration methods. Determination of group parameters L
0, H
T might lead to false estimates of common parameters
p
K
a;therefore, the computational strategy employed is important. A comparison between the two programs ESAB and HYPERQUAD demonstrated
that the ESAB program provides a better fit of potentiometric titration curve. The thermodynamic dissociation constants pK
aT were estimated by a nonlinear regression of (pK
a, I) data and a Debye-Hückel equation at 25°C and 37°C, pK
a,2T = 2.37(1) and 2.44(1), pK
a,3T = 6.29(3) and 6.26(1), pK
a,4T = 7.48(1) and 7.46(2) and pK
a,5T = 9.31(7) and 8.70(3) at 25°C and 37°C using pH-spectroscopic data and pK
a,2T = 2.48(3) and 2.43(1), pK
a,3T= 6.12(2) and 6.10(2), pK
a,4T = 7.25(2) and 7.23(1) and pK
a,5T = 12.04(5) and 11.81(2) at 25°C and 37°C. The ascertained estimates of three dissociation constants pK
a,3, pK
a,4, pK
a,5 are in agreement with the predicted values obtained using PALLAS
相似文献
8.
Nanostructured electrochemical DNA biosensors for detection of the effect of berberine on DNA from cancer cells 总被引:2,自引:0,他引:2
Ovádeková R Jantová S Letasiová S Stepánek I Labuda J 《Analytical and bioanalytical chemistry》2006,386(7-8):2055-2062
Multi walled carbon nanotubes (MWNT) in dimethylformamide (DMF) or aqueous sodium dodecyl sulfate (SDS) solution, colloidal
gold nanoparticles (GNP) in phosphate buffer solution (PBS), and a GNP–MWNT mixture in aqueous SDS solution have been investigated
for chemical modification of a screen-printed carbon electrode used as the signal transducer of a dsDNA-based biosensor. Differential
pulse voltammetry of the DNA redox marker and the guanine moiety anodic oxidation and cyclic voltammetry with K3[Fe(CN)6] as indicator revealed substantial enhancement of the response of the biosensor, particularly when MWNT in SDS solution was
used. The biosensor was used in testing of berberine, an isoquinoline plant alkaloid with significant antimicrobial and anticancer
activity. Berberine had a very strong, concentration-dependent, effect on the structural stability of DNA from the human cancer
cells (U937 cells) whereas non-cancer cells were changed only when berberine concentrations were relatively high 75 and 50 μg
mL−1.
Figure Schematic illustration of preparation of the nanostructured films: (a) layer-to-layer coverage (DNA/nanomaterial/SPE); (b) mixed coverage (DNA-nanomaterial/SPE) 相似文献
9.
10.
Tahereh Khajvand Olia Alijanpour Mohammad Javad Chaichi Majid Vafaeezadeh Mohammad Mahmoodi Hashemi 《Analytical and bioanalytical chemistry》2015,407(20):6127-6136
The effects of six synthetic imidazolium-based ionic liquids (ILs) on the CuII-catalyzed chemiluminescence of lucigenin (Luc-CL) in the pH range 6.0–11 were investigated. Preliminary experiments found that the CL emission was strongly enhanced or inhibited in the presence of the ILs. The degree of enhancement or inhibition of the CL intensity in the presence of each IL was related to the molecular structure of the IL, the medium used, and the pH. The maximum enhancement of the CL intensity was observed at pH 9.0 (amplification factor?=?443). This decrease in the pH at which maximum CL enhancement occurred and the substantial signal amplification of the Luc-CL may be related to a strong interaction between CuII and the imidazolium ring of superior ILs at this pH. Additionally, the formation of IL microdomains in semi-aqueous media permitted more solubility of the product yielded by the Luc-CL reaction (N-methylacridone), which could increase the CL intensity. To obtain consistent data on the catalytic efficiency of CuII in the presence of various ILs as well as the corresponding CL emission intensities, fluorescence quantum yields (Φ F) of lucigenin were measured under the same conditions. Comparison of the data pointed to the mechanism that controls the properties of Luc-CL in the presence of the CuII/IL complexes. Based on the catalytic effect of the CuII/IL complex and the measurement of the enzymatically generated H2O2, a novel, simple, and sensitive CL method for determining glucose with a detection limit (LoD) of 6.5 μM was developed. Moreover, this method was satisfactorily applied to the determination of glucose in human serum and urine samples. 相似文献
11.
New far-visible absorbing anilino-cyanine dyes have been synthesised for future application as chromoionophores in integrated
waveguide absorbance optodes based on bulk optodes. The effect of the heterocycle, of the substitution of the heterocyclic
nitrogen and of the type of heptamethine central ring on the pK
a
values (4.3–8.2 in ethanol–water solutions and 9.5–11.0 in plasticised PVC membranes), on the spectroscopic characteristics
of the dye and on photostability is discussed. pH-selective bulk optodes have been formulated as a first approach to develop
ion-selective optodes, and sensitivity, repeatability, lifetime and response time have been determined. The dyes show good
analytical behaviour for use as chromoionophores for the development of ion-selective optodes. Reversible (80–87%), fast (tr90% = 0.94–2.28 min) and pH-sensitive membranes (slopes of 0.09–0.23 ΔAbs·pHdec–1, absorbance range 0.19–0.53) have been obtained. Moreover, they exhibit good spectroscopic features for employment with integrated
optochemical sensors: absorption maxima of the acidic species in plasticised PVC membranes matched those of 650–670-nm LEDs,
high molar absorption coefficients ( L mol–1 cm–1 and L mol−1 cm−1) and fluorescence.
Absorption spectra of the acidic and basic structures of one of the synthesised chromoionophores at different pKa values.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
12.
The simultaneous determination of three isomers of phenylenediamines (o, m, and p-phenylenediamine) and two isomers of dihydroxybenzenes (catechol and resorcinol) in hair dyes was performed by capillary
zone electrophoresis coupled with amperometric detection (CZE–AD). The effects of working electrode potential, pH and concentration
of running buffer, separation voltage, and injection time on CZE–AD were investigated. Under the optimum conditions the five
analytes could be perfectly separated in 0.30 mol L−1 borate–0.40 mol L−1 phosphate buffer (pH 5.8) within 15 min. A 300 μm diameter platinum electrode had good responses at +0.85 V (versus SCE)
for the five analytes. Their linear ranges were from 1.0 × 10−6 to 1.0 × 10−4 mol L−1 and the detection limits were as low as 10−7 mol L−1 (S/N = 3). This working electrode was successfully used to analyze eight kinds of hair dye sample with recoveries in the range
91.0–108.0% and RSDs less than 5.0%. These results demonstrated that capillary zone electrophoresis coupled with electrochemical
detection using a platinum working electrode as detector was convenient, highly sensitive, highly repeatable and could be
used in the rapid determination of practical samples.
Figure Electropherograms obtained from 10 mg mL−1 hair dye sample solutions at a platinum working electrode under optimum CZE–AD conditions: (a) natural black (I), (b) golden: (1) p-phenylenediamine, (2) m-phenylenediamine, (3) o-phenylenediamine, (4) resorcinol, and (5) catechol 相似文献
13.
D. A. Loginov A. A. Pronin L. S. Shul’pina E. V. Mutseneck Z. A. Starikova P. V. Petrovskii A. R. Kudinov 《Russian Chemical Bulletin》2008,57(3):546-551
The mononuclear arene complexes [Cb*Co(arene)]+ (3a–g; Cb* = C4Me4; arene is biphenyl (a), diphenylmethane (b), 1,2-diphenylethane (c), diphenyl ether (d), p-terphenyl (e), 1,2-dimesitylethane (f), or 1,3-dimesitylpropane (g)) were synthesized by the reactions of arenes either with the benzene complex [Cb*Co(C6H6)]+ (1) under visible light irradiation or with the acetonitrile derivative [Cb*Co(MeCN)3]+ (2) in refluxing THF. The reactions of 2 with 1,2-diphenyle-thane, 1,3-dimesitylpropane, and p-terphenyl in a ratio of 2: 1 afforded the dinuclear complexes [Cb*Co(μ-η:η-arene)CoCb*]2+ (4c,e,g). The stability of the dinuclear arene complexes was estimated by DFT calculations. The structures of the complexes [3a]PF6 and [3e]PF6 ere established by X-ray diffraction.
For Part 6, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 535–539, March, 2008. 相似文献
14.
Various levels of calculations are carried out~for exploring the potential energy surface (PES) of triplet SiC3O, a molecule of potential interest in interstellar chemistry. A total of 38 isomers are located on the PES including chain-like,
cyclic and cage-like structures, which are connected by 87 interconversion transition states at the DFT/B3LYP/6-311G(d) level.
The structures of the most relevant isomers and transition states are further optimized at the QCISD/6-311G(d) level followed
by CCSD(T)/6-311+G(2df) single-point energy calculations. At the QCISD level, the lowest lying isomer is a linear SiCCCO 1 (0.0 kcal/mol) with the 3 ∑ electronic state, which possesses great kinetic stability of 59.5 kcal/mol and predominant resonant structure
. In addition, the bent isomers CSiCCO 2 (68.3 kcal/mol) and OSiCCC 5 (60.1 kcal/mol) with considerable kinetic stability are also predicted to be candidates for future experimental and astrophysical
detection. The bond natures and possible formation pathways in interstellar space of the three stable isomers are discussed.
The predicted structures and spectroscopic properties for the relevant isomers are expected to be informative for the identification
of SiC3O and even larger SiC
n
O species in laboratory and interstellar medium.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Ortega-Algar S Ramos-Martos N Molina-Díaz A 《Analytical and bioanalytical chemistry》2008,391(2):715-719
A single optosensing device based on lanthanide-sensitized luminescence was developed for determination of p-aminobenzoic acid (PABA). The method is based on the formation of a complex between PABA and Tb(III) immobilized on the solid
phase (QAE A-25 resin) placed inside the flow cell. NaCl (1 M) was used as carrier solution and HCl (0.05 M) as eluent. The
sample solutions of PABA (100 μL) containing Tb(III) and buffered at pH = 6.0 were injected into the carrier stream and the
luminescence was measured at λ
ex = 290 nm and λ
em = 546 nm. The method shows a linear range from 0.2 to 6.0 μg mL−1 with an RSD of 1.2% (n = 10) and a sampling frequency of 22 h−1. A remarkable characteristic of the method is its high selectivity which allows it to be satisfactorily applied to the analysis
of PABA in pharmaceutical samples without prior treatment.
Figure Typical emission bands of Tb(III) in a solid-phase PABA–Tb(III) luminescence spectrum 相似文献
16.
Xiaoyu Liu Xuejiao Feng Xiaoning Xu Fei Wang Yanming Wang 《Journal of Sol-Gel Science and Technology》2018,86(2):343-350
Herein, porous Li3V2(PO4)3/C microspheres made of nanoparticles are obtained by a combination of sol spray-drying and subsequent-sintering process. Beta-cyclodextrin serves as a special chelating agent and carbon source to obtain carbon-coated Li3V2(PO4)3 grains with the size of ca. 30–50?nm. The unique porous structure and continuous carbon skeleton facilitate the fast transport of lithium ion and electron. The Li3V2(PO4)3/C microspheres offer an outstanding electrochemical performance, which present a discharge capacity of 122?mAh?g?1 at 2?C with capacity retention of 96% at the end of 1000 cycles and a high-rate capacity of 113?mAh?g?1 at 20?C in the voltage window of 3.0–4.3?V. Moreover, the Li3V2(PO4)3/C microspheres also give considerable cycling stability and high-rate reversible capacity at a higher end-of-charge voltage of 4.8?V. 相似文献
17.
Shanmughasundaram Duraisamy Tirupathi Rao Penki Brij Kishore Prabeer Barpanda Prasant Kumar Nayak Doron Aurbach Nookala Munichandraiah 《Journal of Solid State Electrochemistry》2017,21(2):437-445
A porous, hollow, microspherical composite of Li2MnO3 and LiMn1/3Co1/3Ni1/3O2 (composition: Li1.2Mn0.53Ni0.13Co0.13O2) was prepared using hollow MnO2 as the sacrificial template. The resulting composite was found to be mesoporous; its pores were about 20 nm in diameter. It also delivered a reversible discharge capacity value of 220 mAh g?1 at a specific current of 25 mA g?1 with excellent cycling stability and a high rate capability. A discharge capacity of 100 mAh g?1 was obtained for this composite at a specific current of 1000 mA g?1. The high rate capability of this hollow microspherical composite can be attributed to its porous nature. 相似文献
18.
The proteomic characterization of proteins and protein complexes from cells and cell organelles is the next challenge for
investigation of the cell. After isolation of the cell compartment, three steps have to be performed in the laboratory to
yield information about the proteins present. The protein mixtures must be separated into single species, broken down into
peptides, and, finally, identified by mass spectrometry. Most scientists engaged in proteomics separate proteins by electrophoresis.
For characterization and identification of proteomes, mass spectrometry of peptides is the method of choice. To combine electrophoresis
and mass spectrometry, sample preparation by “in-gel digestion” has been developed. Many procedures are available for in-gel
digestion, which inspired us to review in-gel digestion approaches.
Figure Classical in-gel digestion process for a protein band stained with CBB. Protein bands are cut from the polyacrylamide gel
(1). CBB molecules (blue circles) bound to the protein are released by iterative incubation in a buffered organic solvent system (2). To increase digestion efficiency and sequence coverage proteins are reduced (3) and alkylated (4). Proteins are subsequently digested with proteolytic enzymes (scissors symbols), typically trypsin (5). Trypsin cleaves at the amino acid residues arginine (R) and lysine (K). The resulting peptides (A, B, and C) are extracted from the polyacrylamide matrix (6). The peptide solution can be further purified for analysis by mass spectrometry (Section “Concentration and desalting of peptides”) 相似文献
19.
After being treated by mixed acids, single-walled carbon nanotubes (SWNTs) were shortened and had negatively charged groups
on the surface. Positively charged hemoglobin or myoglobin at pH 5.0 was successfully assembled with SWNTs into layer-by-layer
films on solid surfaces, designated as {SWNT/protein}
n
. While only those proteins in the first few bilayers closest to the electrode surface exhibited electroactivity, the {SWNT/protein}
n
films demonstrated a much higher fraction of electroactive proteins and better controllability in film construction compared
with cast films of the proteins and carbon nanotubes. The proteins in the {SWNT/protein}
n
films retained their near-native structure at medium pH. The stable protein film electrode showed good electrocatalytic properties
toward reduction of oxygen and hydrogen peroxide, demonstrating the potential application of the {SWNT/protein}
n
films as a new type of biosensor based on the direct electrochemistry of proteins without using mediators.
Figure Cyclic voltammograms at 0.2 V s−1 in pH 7.0 buffers with different number of bilayers (n) for layer-by-layer {single-walled carbon nanotube/hemoglobin}
n
films. 相似文献
20.
Herschbach H Hosomizu K Hahn U Leize E Van Dorsselaer A Imahori H Nierengarten JF 《Analytical and bioanalytical chemistry》2006,386(1):46-51
The electrospray mass spectrometric characterization of neutral dendrons with a carboxylic acid function or a t-butyl ester moiety at the central point and up to eight peripheral C60 subunits has been performed and is described in detail. Molecules bearing a carboxylic acid group at the center turned out
to be preferentially ionized by deprotonation, whereas those with a t-butyl ester head group were ionized by reduction of the C60 units in the infusion capillary of the electrospray source.
Electronic supplementary material Supplementary material is available for this article at and is accessible for authorized users. 相似文献