共查询到20条相似文献,搜索用时 31 毫秒
1.
Naik PK Lopus M Aneja R Vangapandu SN Joshi HC 《Journal of computer-aided molecular design》2012,26(2):233-247
Our screen for tubulin-binding small molecules that do not depolymerize bulk cellular microtubules, but based upon structural
features of well known microtubule-depolymerizing colchicine and podophyllotoxin, revealed tubulin binding anti-cancer property
of noscapine (Ye et al. in Proc Natl Acad Sci USA 95:2280–2286, 1998). Guided by molecular modelling calculations and structure–activity relationships we conjugated at C9 of noscapine, a folate
group—a ligand for cellular folate receptor alpha (FRα). FRα is over-expressed on some solid tumours such as ovarian epithelial
cancers. Molecular docking experiments predicted that a folate conjugated noscapine (Targetin) accommodated well inside the
binding cavity (docking score −11.295 kcal/mol) at the interface between α- and β-tubulin. The bulky folate moiety of Targetin
is extended toward lumen of microtubules. The binding free energy (ΔG
bind) computed based on molecular mechanics energy minimization was −221.01 kcal/mol that revealed favourable interaction of Targetin
with the receptor. Chemical synthesis, tubulin-binding experiments, and anti-cancer activity in vitro corroborate fully well
with the molecular modelling experiments. Targetin binds tubulin with a dissociation constant (K
d value) of 149 ± 3.0 μM and decreases the transition frequencies between growth and shortening phases of microtubule assembly
dynamics at concentrations that do not alter the total polymer mass. Cancer cells in general were more sensitive to Targetin
compared with the founding compound noscapine (IC50 in the range of 15–40 μM). Quite strikingly, ovarian cancer cells (SKOV3 and A2780), known to overexpress FRα, were much
more sensitive to targetin (IC50 in the range of 0.3–1.5 μM). 相似文献
2.
S. S. Deshmukh M. Dutta Choudhury V. Shankar 《Applied biochemistry and biotechnology》1993,42(2-3):95-104
Partially purified glucose isomerase fromStreptomyces thermonitrificans when coupled to glutaraldehyde-activated Indion 48-R, retained 30–40% activity of the soluble enzyme. However, an approximately
twofold increase in the activity could be achieved by binding the enzyme in the presence of glucose. Binding the enzyme to
matrices presaturated with either glucose or fructose and influence of lysine modification on the activity of the soluble
enzyme revealed that the comparatively low activity observed in case of the enzyme bound in the absence of substrate is the
result of the nonspecific binding of either substrate or product to the matrix. Immobilization did not affect the pH and temperature
optima of the enzyme, but it lowered the temperature stability. Immobilization resulted in a marginal increase in theK
m
and a threefold decrease in theV
max
. Substrate concentrations as high as 36% glucose could be converted to 18.5% fructose in 5 h, at pH 7.0 and 70‡C. The bound
enzyme, however, showed inferior stability to repeated use and lost approx 40% of its initial activity after five cycles of
use. Indion 48-R bound glucose isomerase could be stored, in wet state, for 30 d without any apparent loss in its initial
activity. 相似文献
3.
Nina I. Giricheva Georgiy V. Girichev Yulia S. Medvedeva Sergey N. Ivanov Anna V. Bardina Vyacheslav M. Petrov 《Structural chemistry》2011,22(2):373-383
A combined gas-phase electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pvtz, MP2/cc-pvtz) study of molecular
structure of 2-nitrobenzenesulfonamide (2-NBSA) was carried out. Quantum chemical calculations showed that 2-NBSA has four
conformers, two of which are stabilized by intramolecular hydrogen bond. The latter (with the S–N bond in a close to orthogonal
position around the phenyl ring and differing from each other by staggered or eclipsed positions of the N–H and S=O bonds
in the SO2NH2 group) presented in a saturated vapor over 2-NBSA at T = 433 (3) K in commensurable amounts. Experimental internuclear distances (Ǻ) for the staggered conformer are (?): r
h1(C–H)av. = 1.071(9), r
h1(C–C)av. = 1.390(4), r
h1(C–S) = 1.789(8), r
h1(S=O)av. = 1.427(6), r
h1(S–N) = 1.644(6), r
h1(N–O)av. = 1.221(4), r
h1(C′–N) = 1.487(8), r
h1(N–H)av. = 1.014. Calculations at B3LYP/cc-pvtz level were performed to determine the structure and the energies of the transition
states between conformers. It was shown that the conformer structures of free molecule differ from those of a molecule stabilized
by intermolecular hydrogen bonds in a crystal. Influence of a substituent X (X = –CH3, –NO2) on conformational features of the ortho-substituted benzenesulfonamide was established. 相似文献
4.
Kawthar Bouchemal Patrick Couvreur Samia Daoud-Mahammed Jacques Poupaert Ruxandra Gref 《Journal of Thermal Analysis and Calorimetry》2009,98(1):57-64
In this study, the entrapment of benzophenone (BZ) into supramolecular nanoassemblies prepared by mixing two water-soluble
associative polymers (i.e. polymerized β-CD (pβ–CD) and dextran grafted with lauryl-side chains (MD)) has been investigated
by using isothermal titration microcalorimetry (ITC) and molecular modeling. ITC experiments have been performed at various
temperatures (4 °C (277 K), 25 °C (298 K), and 37 °C (310 K)) to evaluate the interaction of BZ with pβ–CD in comparison with
β-CD. The inclusion complexation for both β-CD/BZ and pβ–CD/BZ interactions was entropy-driven (|ΔH| < |TΔS|) when the temperature of the experiment was low (4 °C) and enthalpy-driven (|ΔH| > |TΔS|) with minor entropic contribution when the temperature was increased (25 and 37 °C). Using all the thermodynamic data obtained
for β-CD/BZ and pβ–CD/BZ interactions when the temperature of the experiment was varied, the
\Updelta H = f(T\Updelta S ) \Updelta H\; = \;f(T\Updelta S ) plot was perfectly linear, which reflected an enthalpy–entropy compensation process. Finally, the combination of ITC data
with molecular modeling provided consistent information in regard to the location of MD side chains and BZ inside the cyclodextrin
cavity, as well as concerning the stability of the nanoassemblies loaded with BZ. 相似文献
5.
E. A. Belousova V. V. Koval N. I. Rechkunova S. Kh. Degtyarev O. S. Fedorova O. I. Lavrik 《Russian Chemical Bulletin》2005,54(5):1306-1310
The interaction of DNA polymerase Tte from Thermus thermophilus B35 with dUTP analog containing a fluorescein residue bound to C(5) of the base (Flu-dUTP) was studied by fluorescence titration.
The dissociation constants of the enzyme—substrate complexes in the absence and in the presence of a DNA duplex containing
an extended template and bivalent metal ions and the kinetic parameters of polymerization by DNA polymerase Tte in the presence of Flu-dUTP were determined.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1268–1272, May, 2005. 相似文献
6.
Juozas Kulys Zilvinas Dapkunas Robert Stupak 《Applied biochemistry and biotechnology》2009,158(2):445-456
Many industrial pollutants, xenobiotics, and industry-important compounds are known to be oxidized by peroxidases. It has
been shown that highly efficient peroxidase substrates are able to enhance the oxidation of low reactive substrate by acting
as mediators. To explore this effect, the oxidation of two N-hydroxy derivatives, i.e., N-hydroxy-N-phenyl-acetamide (HPA) and N-hydroxy-N-phenyl-carbamic acid methyl ester (HPCM) catalyzed by recombinant Coprinus cinereus (rCiP) peroxidase has been studied in presence of efficient substrate 3-(4a,10a-dihydro- phenoxazin-10-yl)-propane-1-sulfonic
acid (PPSA) at pH 8.5. The bimolecular constant of PPSA cation radical reaction with HPA was estimated to be (2.5 ± 0.2)·107 M−1 s−1 and for HPCM was even higher. The kinetic measurements show that rCiP-catalyzed oxidation of HPA and HPCM can increase up
to 33,000 times and 5,500 times in the presence of equivalent concentration of high reactive substrate PPSA. The mathematical
model of synergistic rCiP-catalyzed HPA–PPSA and HPCM–PPSA oxidation was proposed. Experimentally obtained rate constants
were in good agreement with those calculated from the model confirming the synergistic scheme of the substrate oxidation.
In order to explain the different reactivity of substrates, the docking of substrates in the active site of the enzyme was
calculated. Molecular dynamic calculations show that the enzyme–substrate complexes are structurally stable. The high reactive
PPSA exhibited higher affinity to enzyme active site than HPA and HPCM. Furthermore, the orientation of HPA and HPCM was not
favorable for proton transfer to the distal histidine, and different substrate reactivity was explained by these diversities. 相似文献
7.
Issa Yavari Nasir Iravani S. Zahra Sayyed-Alangi Rahimeh Hajinasiri 《Monatshefte für Chemie / Chemical Monthly》2009,35(1):1199-1204
Abstract
An efficient synthesis of alkyl acylcarbamodithioates by reaction of acid chlorides with ammonium thiocyanate in the presence of thiols is described. The unusually large values of 5 J FH = 12–15 Hz, observed for alkyl (2-fluorobenzoyl)carbamodithioates provide information about Ar–C–N–H torsion in these compounds. 相似文献8.
Myung Ho Lee Euo Chang Jung Kyuseok Song Yun Hee Han Hyun Sang Shin 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(2):639-645
This work investigates the sorption of americium [Am(III)] onto kaolinite and the influence of humic acid (HA) as a function
of pH (3–11). It has been studied by batch experiments (V/m = 250:1 mL/g, C
Am(III) = 1 × 10−5 mol/L, C
HA = 50 mg/L). Results showed that the Am(III) sorption onto the kaolinite in the absence of HA was typical, showing increases
with pH and a distinct adsorption edge at pH 3–5. However in the presence of HA, Am sorption to kaolinite was significantly
affected. HA was shown to enhance Am sorption in the acidic pH range (pH 3–4) due to the formation of additional binding sites
for Am coming from HA adsorbed onto kaolinite surface, but reduce Am sorption in the intermediate and high pH above 6 due
to the formation of aqueous Am-humate complexes. The results on the ternary interaction of kaolinite–Am–HA are compared with
those on the binary system of kaolinite–HA and kaolinite–Am and adsorption mechanism with pH are discussed. Effect of different
molecular weight of HA, with three HA fractions separated by ultrafiltration techniques, on the Am sorption to kaolinite were
also studied. The results showed that the enhancement of the sorption of Am onto kaolinite at the acidic pH conditions (pH
3–4) was higher with HA fractions of higher molecular weight. Also, the Am sorption over a pH range from 6 to 10 decreased
with decreasing molecular weight of HA. 相似文献
9.
Sara Goñi Francisca Puertas María Soledad Hernández Marta Palacios Ana Guerrero Jorge S. Dolado Bruno Zanga Fulvio Baroni 《Journal of Thermal Analysis and Calorimetry》2010,102(3):965-973
This research is part of a European project (namely, CODICE project), main objective of which is modelling, at a multi-scale,
the evolution of the mechanical performance of non-degraded and degraded cementitious matrices. For that, a series of experiments
were planned with pure synthetic tri-calcium silicate (C3S) and bi-calcium silicate (C2S) (main components of the Portland cement clinker) to obtain different calcium–silicate–hydrate (C–S–H) gel structures during
their hydration. The characterization of those C–S–H gels and matrices will provide experimental parameters for the validation
of the multi-scale modelling scheme proposed. In this article, a quantitative method, based on thermal analyses, has been
used for the determination of the chemical composition of the C–S–H gel together with the degree of hydration and quantitative
evolution of all the components of the pastes. Besides, the microstructure and type of silicate tetrahedron and mean chain
length (MCL) were studied by scanning electron microscopy (SEM) and 29Si magic-angle-spinning (MAS) NMR, respectively. The main results showed that the chemical compositions for the C–S–H gels
have a CaO/SiO2 M ratio almost constant of 1.7 for both C3S and C2S compounds. Small differences were found in the gel water content: the H2O/SiO2 M ratio ranged from 2.9 ± 0.2 to 2.6 ± 0.2 for the C3S (decrease) and from 2.4 ± 0.2 to 3.2 ± 0.2 for the C2S (increase). The MCL values of the C–S–H gels, determined from 29Si MAS NMR, were 3.5 and 4 silicate tetrahedron, for the hydrated C3S and C2S, respectively, remaining almost constant at all hydration periods. 相似文献
10.
Nina I. Giricheva Georgiy V. Girichev Yulia S. Medvedeva Sergey N. Ivanov Vyacheslav M. Petrov 《Structural chemistry》2012,23(3):895-903
A combined gas-phase electron diffraction and quantum chemical (B3LYP/cc-pVTZ, MP2/cc-pVDZ) study of molecular structure of
2,4,6-trinitrobenzenesulfonic acid (2,4,6-tri-NBSA) was carried out. Quantum chemical calculations showed that 2,4,6-tri-NBSA
possesses six conformers, which form three pairs of enantiomers with the relative energy of 0, 4.4/3.9, and 2.5/2.5 kcal/mol.
It was experimentally established that at T = 444(5) K a saturated vapor over 2,4,6-tri-NBSA is, predominantly (up to 93 mol.%), represented by a low-energy enantiomers
II and II′ characterized by intramolecular hydrogen bond between an H atom of the hydroxyl group and one of the O atoms of
the NO2 group. Experimental internuclear distances for the low-energy enantiomers are (?): r
h1(C–C)av. = 1.387(4), r
h1(C–S) = 1.811(6), r
h1(S=O)av. = 1.424(4), r
h1(S–O) = 1.579(4), r
h1(N–O)av. = 1.214(3), r
h1(C–N)av. = 1.491(5). Geometry of the conformer II points on existance of strong steric interactions between SO2OH group and two ortho-nitro groups. Analysis of the orbital interactions between the substituents and benzene ring was carried out. Geometric parameters
and energies of transition states between conformers were calculated (B3LYP). 相似文献
11.
The reaction of [PtMe3(bpy)(Me2CO)](BF4) (2) (prepared from [PtMe3I(bpy)] (1) plus Ag(BF4)) with MeSSMe resulted in the formation of [PtMe3(bpy)(MeSSMe-κS)](BF4) (3). A single-crystal X-ray diffraction analysis revealed in the octahedral Pt(IV) complex (configuration index: OC-6-33), a conformation of the monodentately κS bound MeSSMe ligand (C–S–S–C 92.7(4)°) being very close to that in non-coordinated MeSSMe, thus allowing some hyperconjugative
interaction stabilizing the S–S bond. The reaction of [K(18C6)][(PtMe3)2(μ-I)(μ-pz)2] (4; 18C6 = 18-crown-6, Hpz = pyrazole) with Ag(BF4) and MeSSMe resulted in the formation of dinuclear complexes [(PtMe3)2(μ-pz)2(μ-MeSSMe)] existing at room temperature in acetone solution as different fast interconverting isomers. At –40 °C, two isomers
with a μ-1κS:2κS (5a) and a μ-1κS:2κS′ (5b) coordinated MeSSMe ligand in the ratio 2:1 could be identified 1H NMR spectroscopically. DFT calculations of type 5 complexes revealed the existence of two conformers with a μ-MeSSMe-1κS:2κS ligand, which differ mainly in the C–S–S–C dihedral angle (66.4 vs. 180.0° 6a/6a′). They have essentially the same energy and a very low activation barrier in acetone as solvent (1.3 kcal/mol) for their
mutual interconversion. A further equilibrium structure was identified to be an isomer having a μ-MeSSMe-1κS:2κS′ ligand (6b) that proved to be only 1.9 kcal/mol higher in energy than 6a/6a′. 相似文献
12.
Asakawa D Moriguchi S Takayama M 《Journal of the American Society for Mass Spectrometry》2012,23(1):108-115
The influence of arginine (Arg), lysine (Lys), and phenylalanine (Phe) residues and phosphorylation on the molecular ion yields
of model peptides have been quantitatively studied using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry
in both positive- and negative-ion mode. The results obtained from these experiments have been interpreted from the standpoint
of two different components, namely, desorption and ionization, on the basis of the physicochemical properties of constituent
amino acids of the model peptides. The presence of basic residues such as Arg and Lys enhanced the ion yields of protonated
molecules [M + H]+. An N-terminal rather than a C-terminal Arg residue was advantageous for the formation of both [M + H]+ and [M – H]–. The presence of the Phe residue resulted in the increase of the ion yields of both [M + H]+ and [M – H]–. In contrast, the presence of phosphate group(s) contributed to the suppression of the yields of both [M + H]+ and [M – H]– due to the loss of phosphate group. The detection limits for both [M + H]+ and [M – H]– of model peptides have been evaluated. 相似文献
13.
Ar and Kr matrix effect on the geometry and Cl–H stretching (ν
s
(Cl–H)) and librational (ν
l
(Cl–H)) frequencies of the hydrogen-bonded complex Cl–H···NH3 are simulated within the framework of polarizable continuum model with integral equation formalism (IEF-PCM) at B3LYP and
MP2 levels of theory with the basis set 6-311++G(2df,2pd). Within the framework of B3LYP and IEF-PCM, the simulated gas phase,
Ar, and Kr matrix ν
s
(Cl–H) of the complex are 2140, 1684, and 1550 cm−1, respectively, which deviate from the experimental values (~2200, 1371, and 1218 cm−1) by −60, 313, and 332 cm−1. Within the framework of MP2 and IEF-PCM, the gas phase, Ar, and Kr matrix ν
s
(Cl–H) are calculated as 2366, 2037, and 1957 cm−1 by the harmonic approximation, and as 2177, 1876, and 1665 cm−1 by the full-dimensional anharmonic correction. The matrix effect modeling is of greater importance than the anharmonic correction
in accounting for the large experimental gas phase to Ar or Kr matrix shift of the ν
s
(Cl–H) (−829 or −982 cm−1). Our calculations do not support the assignment of the 733.8 and 736.9 cm−1 bands to the Ar and Kr matrix ν
l
(Cl–H). 相似文献
14.
Naik PK Chatterji BP Vangapandu SN Aneja R Chandra R Kanteveri S Joshi HC 《Journal of computer-aided molecular design》2011,25(5):443-454
Noscapine and its derivatives are important microtubule-interfering agents shown to have potent anti-tumor activity. The binding
free energies (ΔG
bind) of noscapinoids computed using linear interaction energy (LIE) method with a surface generalized Born (SGB) continuum solvation
model were in agreement with the experimental ΔG
bind with average root mean square error of 0.082 kcal/mol. This LIE–SGB model guided us in designing a novel derivative of noscapine,
amino-noscapine [(S)-3-((R)-9-amino-4-methoxy-6-methyl-5,6,7,8-tetrahydro [1, 3] dioxolo[4,5-g]isoquinolin-5-yl)-6,7-dimethoxy isobenzo-furan-1(3H)-one] that has higher tubulin binding activity (predicted ΔG
bind = −6.438 kcal/mol and experimental ΔG
bind = −6.628 kcal/mol) than noscapine, but does not significantly change the total extent of the tubulin subunit/polymer ratio.
The modes of interaction of amino-noscapine with the binding pocket of tubulin involved three hydrogen bonds and are distinct
compared to noscapine which involved only one hydrogen bond. Also the patterns of non-bonded interactions are albeit different
between both the lignads. The ‘blind docking’ approach (docking of ligand with different binding sites of a protein and their
evaluations) as well as the reasonable accuracy of calculating ΔG
bind using LIE–SGB model constitutes the first evidence that this class of compounds binds to tubulin at a site overlapping with
colchicine-binding site or close to it. Our results revealed that amino-noscapine has better anti-tumor activity than noscapine. 相似文献
15.
Dr. Rajeev Ramanan Sodiq O. Waheed Prof. Christopher J. Schofield Dr. Christo Z. Christov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(46):11827-11836
Arginine methylation is an important mechanism of epigenetic regulation. Some Fe(II) and 2-oxoglutarate dependent Jumonji-C (JmjC) Nϵ-methyl lysine histone demethylases also have N-methyl arginine demethylase activity. We report combined molecular dynamic (MD) and Quantum Mechanical/Molecular Mechanical (QM/MM) studies on the mechanism of N-methyl arginine demethylation by human KDM4E and compare the results with those reported for N-methyl lysine demethylation by KDM4A. At the KDM4E active site, Glu191, Asn291, and Ser197 form a conserved scaffold that restricts substrate dynamics; substrate binding is also mediated by an out of active site hydrogen-bond between the substrate Ser1 and Tyr178. The calculations imply that in either C−H or N−H potential bond cleaving pathways for hydrogen atom transfer (HAT) during N-methyl arginine demethylation, electron transfer occurs via a σ-channel; the transition state for the N−H pathway is ∼10 kcal/mol higher than for the C−H pathway due to the higher bond dissociation energy of the N−H bond. The results of applying external electric fields (EEFs) reveal EEFs with positive field strengths parallel to the Fe=O bond have a significant barrier-lowering effect on the C−H pathway, by contrast, such EEFs inhibit the N−H activation rate. The overall results imply that KDM4 catalyzed N-methyl arginine demethylation and N-methyl lysine demethylation occur via similar C−H abstraction and rebound mechanisms leading to methyl group hydroxylation, though there are differences in the interactions leading to productive binding of intermediates. 相似文献
16.
The alkynylation of nitrones catalyzed by chiral zinc(II)-complexes was studied by means of the density functional theory
(DFT). All the intermediates and transition states were optimized completely at B3LYP/6-31G(d,p) level. Calculation results
confirm that this alkynylation of nitrones was endothermic and the total absorbed energy was about 14 kJ/mol. The formation
of the M5 complexes was the rate-determining step and the chirality-limiting step for this alkynylation. The transition states TS3-re involve a H(8)–O(2)–Zn(6)–C(9)–C(14)–N(13)–O(12) 7-membered ring, and thus the transition states TS3-si involve a Zn(6)–C(9)–C(14)–N(13)–O(12) 5-membered ring. The dominant reaction is the attack of nitrones from the re-surface of M4. The reactivity of anti-nitrones was stronger than that of syn-nitrones for zinc-catalyzed alkynylation of nitrones. The
dominant reaction channel was cata → TS1b → M1b → M2 → M3b → TS2b → M4b → TS3b1-anti-re → M5b1-anti-re → Pro-R. The dominant products predicted theoretically were of R-chirality, (2R)-N-hydroxy-N-methylpent-3-yn-2-amine.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
17.
Jigar Patel Qiong Zhang R. Michael L. McKay Robert Vincent Zhaohui Xu 《Applied biochemistry and biotechnology》2010,160(1):232-243
Hexa-histidine (6His) peptide was inserted to a permissive site of the surface layer (S-layer) protein RsaA of Caulobacter crescentus. The recombinant strain JS4022/p723–6H, expressing RsaA-6His fusion protein was examined for its ability to sequester Cd(II)
from the bacterial growth medium. When mixed with 1 ppm CdCl2, JS4022/p723–6H removed 94.3 ∼ 99.9% of the Cd(II), whereas the control strain removed only 11.4 ∼ 37.0%, depending on experimental
conditions. The effective contact time of the cells and Cd(II) was as short as 15 min. When higher concentrations of CdCl2 were tested, JS4022/p723–6H consistently demonstrated enhanced binding capacity over the control strain. At 15 ppm of Cd(II),
each gram of JS4022/p723–6H dry cells retrieved 16.0 mg of Cd(II), comparing to 11.6 mg g−1 achieved by the control strain. This work provides a potential cost-effective solution toward bioremediation of heavy metals
from aqueous systems. 相似文献
18.
The preparation and characterization of heparin-immobilized microspheres which were used to bind acidic fibroblast growth
factor (aFGF), vascular endothelial growth factor (VEGF), monocyte chemoattractant protein 1 (MCP-1/CCL2), and regulation
upon activation normal T cell express sequence (RANTES/CCL5) is described. These beads were used as trapping agents in microdialysis
sampling experiments in a separate study. Both free heparin and a synthesized heparin–albumin conjugate were immobilized onto
microspheres and compared for their effectiveness. The heparin–albumin conjugate microspheres exhibited significant nonspecific
adsorption which appeared to be due to the albumin content. The prepared heparin-immobilized microspheres were stable for
3 months at 4 °C. A bead-based flow cytometric assay was developed to study the binding capacity and specificity of the heparin-immobilized
microspheres to cytokines. These heparin-immobilized microspheres exhibited broad dynamic ranges for binding to the four cytokines
(aFGF, 1.0–1,000 ng/mL; VEGF, 0.5–1,000 ng/mL; CCL2, 1.95–1,000 ng/mL; CCL5, 1.95–500 ng/mL). Fast binding kinetics of the
cytokines to the heparin-immobilized beads suggests that these beads may be useful as affinity agents in microfluidic flow
systems. 相似文献
19.
Wu R Marta RA Martens JK Eldridge KR McMahon TB 《Journal of the American Society for Mass Spectrometry》2011,22(9):1651-1659
The structure of the proton-bound lysine dimer has been investigated by infrared multiple photon dissociation (IRMPD) spectroscopy
and electronic structure calculations. The structures of different possible isomers of the proton-bound lysine dimer have
been optimized at the B3LYP/6-31 + G(d) level of theory and IR spectra calculated using the same computational method. Based
on relative Gibbs free energies (298 K) calculated at the MP2/aug-cc-pVTZ//B3LYP/6-31 + G(d) level of theory, LL-CS01, and
followed closely (1.1 kJ mol–1) by LL-CS02 are the most stable non-zwitterionic isomers. At the MP2/aug-cc-pVTZ//6-31 + G(d) and MP2/aug-cc-pVTZ//6-31 + (d,p)
levels of theory, isomer LL-CS02 is favored by 3.0 and 2.3 kJ mol–1, respectively. The relative Gibbs free energies calculated by the aforementioned levels of theory for LL-CS01 and LL-CS02
are very close and strongly suggest that diagnostic vibrational signatures found in the IRMPD spectrum of the proton-bound
dimer of lysine can be attributed to the existence of both isomers. LL-ZW01 is the most stable zwitterionic isomer, in which
the zwitterionic structure of the neutral lysine is well stabilized by the protonated lysine moiety via a very strong intermolecular
hydrogen bond. At the MP2/aug-cc-pVTZ//B3LYP/6-31 + G(d), MP2/aug-cc-pVTZ//6-31 + G(d) and MP2/aug-cc-pVTZ//6-31 + G(d,p)
levels of theory, the most stable zwitterionic isomer (LL-ZW01) is less favored than LL-CS01 by 7.3, 4.1 and 2.3 kJ mol–1, respectively. The experimental IRMPD spectrum also confirms that the proton-bound dimer of lysine largely exists as charge-solvated
isomers. Investigation of zwitterionic and charge-solvated species of amino acids in the gas phase will aid in a further understanding
of structure, property, and function of biological molecules. 相似文献
20.
An all-electron scalar relativistic calculation on Cu
n
H (n = 1–13) clusters has been performed by using density functional theory with the generalized gradient approximation at the
PW91 level. Our results reveal that the hydrogen atom prefers to occupy the two fold coordination site for Cu
n
H (n = 2, 4–6, 8, 10–13) clusters, the single fold coordination site for Cu
n
H (n = 1, 3, 7) and the three fold coordination site for Cu9H cluster. For all Cu
n
H clusters, only the Cu11 structure in Cu11H is distorted obviously. After adsorption, the Cu–Cu bond is strengthened and the Cu–H bond of odd-numbered Cu
n
H clusters is relatively stronger than that of adjacent even-numbered Cu
n
H clusters. The Cu–Cu bond-length and Cu–H bond-length for all Cu
n
H clusters of our work are significantly shorter than those of previous work. This discrepancy can be explained in terms of
the scalar relativistic effect. The most favorable adsorption between small copper clusters and hydrogen atom takes place
in the case that hydrogen atom is adsorbed onto an odd-numbered pure Cu
n
cluster and becomes Cu
n
H cluster with even number of valence electrons. The odd–even alteration of magnetic moments is observed in Cu
n
H clusters and may provide the material with tunable code capacity of “0” and “1” by adsorbing a hydrogen atom onto odd- or
even-numbered copper clusters. 相似文献