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1.
Huang R Pomin VH Sharp JS 《Journal of the American Society for Mass Spectrometry》2011,22(9):1577-1587
Improved methods for structural analyses of glycosaminoglycans (GAGs) are required to understand their functional roles in
various biological processes. Major challenges in structural characterization of complex GAG oligosaccharides using liquid
chromatography-mass spectrometry (LC-MS) include the accurate determination of the patterns of sulfation due to gas-phase
losses of the sulfate groups upon collisional activation and inefficient on-line separation of positional sulfation isomers
prior to MS/MS analyses. Here, a sequential chemical derivatization procedure including permethylation, desulfation, and acetylation
was demonstrated to enable both on-line LC separation of isomeric mixtures of chondroitin sulfate (CS) oligosaccharides and
accurate determination of sites of sulfation by MS
n
. The derivatized oligosaccharides have sulfate groups replaced with acetyl groups, which are sufficiently stable to survive
MS
n
fragmentation and reflect the original sulfation patterns. A standard reversed-phase LC-MS system with a capillary C18 column
was used for separation, and MS
n
experiments using collision-induced dissociation (CID) were performed. Our results indicate that the combination of this
derivatization strategy and MS
n
methodology enables accurate identification of the sulfation isomers of CS hexasaccharides with either saturated or unsaturated
nonreducing ends. Moreover, derivatized CS hexasaccharide isomer mixtures become separable by LC-MS method due to different
positions of acetyl modifications. 相似文献
2.
Yu. K. Grishin I. P. Gloriozov S. M. Gerdov V. A. Roznyatovsky L. L. Frolova A. V. Kuchin Yu. A. Ustynyuk 《Russian Chemical Bulletin》2008,57(8):1689-1696
The selectivity of deuterium distribution between the nonequivalent positions in 3-carene (1), 4-α-acetyl-2-carene (2), and 4-(1-hydroxyethyl)-2-carene (3) has been measured by 2H-{1H} NMR spectroscopy at the natural abundance of deuterium. These “H/D-isotope portraits” were shown to be typical of terpenes
and terpenoids produced in plants via the biosynthetic DXP pathway. The mechanism of acylation of 1 was studied by the density functional theory method (PBE functional, TZ2p basis set). The six-membered ring in compound 1 is planar. However, the endo attack of electrophiles on this ring is more favorable both kinetically and thermodynamically. It was shown both experimentally
and theoretically that the elimination of a hydrogen atom in the second reaction step proceeds stereoselectively at the C(2)
atom from the anti position with respect to the three-membered ring and occurs with pronounced nucleophilic assistance from the carbonyl group.
For Part 2, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1657–1664, August, 2008. 相似文献
3.
Complexation behavior of NpO2
+ with ortho-silicic acid (o-SA) has been studied using solvent extraction at ionic strengths varying from 0.10 to 1.00M (NaClO4) at pcH 3.68±0.08 and 25 °C with bis-(2-ethylhexyl) phosphoric acid (HDEHP) as the extractant. The stability constant value
(log β1) for the 1:1 complex, NpO2(OSi(OH)3), was found to decrease with increase in ionic strength of the aqueous phase [6.83±0.01 at I=0.10M to 6.51±0.02 at I = 1.00M]. These values have been fitted in the SIT model expression and compared with similar values of complexation of the
metal ions Am3+, Eu3+, UO2
2+, PuO2
2+, Np4+, Ni2+ and Co2+. The speciation of NpO2
+-o-silicate/carbonate system has been calculated as a function of pcH under ground water conditions.
On leave from Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085, India. 相似文献
4.
Summary. The structure of 2-amino-4-aryl-1-arylideneaminoimidazoles in DMSO-d6 solution was investigated by means of NMR spectroscopic methods (1H, 13C, 15N). From these data the (E)-configuration at the excocyclic C=N bond and a strong preference for the conformer with the imidazole H-5 and the N=CH proton being spatially close (s-trans regarding the N–N bond) can be concluded. Reaction of the title compounds with acetic anhydride leads to mono and diacylation at the 2-amino group, whereas treatment with pivalic anhydride exclusively affords the corresponding monoacyl product. The mono- and diacylation products exhibit similar configurational and conformational properties as the parent compounds. 相似文献
5.
The 1H NMR spectra (working frequencies of 500 and 600 MHz) of polychloroprenes are studied. The spin systems of protons for monomer
units of different configurations (1,2, 3,4, 1,4-cis-and 1,4- trans- units), as well as for dyad and triad combinations of 1,4 units, are classified. A high working frequency, the method of
double resonance, and the calculation of chemical shifts by empirical increments make it possible to refine the assignment
of 1H NMR signals. 相似文献
6.
A. V. Belyaev M. A. Fedotov S. N. Vorob’eva 《Russian Journal of Coordination Chemistry》2009,35(8):577-581
It was shown that the monomeric rhodium sulfate complexes [Rh(H2O)4(SO4)]+, trans-[Rh(H2O)2(SO4)2]?, cis-[Rh(H2O)2(SO4)2]?, and [Rh(SO4)3]3? were not predominant forms in aqueous solutions. The 103Rh NMR chemical shifts of the complexes were assigned, and the conditions for their formation in solutions, concentration parameters, and acidity at which the fraction of the monomers was maximal were determined. The constants of formation of the complexes and ion pair (IP) were estimated: K IP = 8 ± 3.5, K 1 ≈ 8, K 2trans ≈ 1, K 2cis ≈ 1, and K 3 ≈ 2. 相似文献
7.
T. A. Mastryukova O. I. Artyushin M. P. Pasechnik E. V. Sharova I. L. Odinets V. P. Morgalyuk I. G. Tananaev G. V. Myasoedova B. F. Myasoedov 《Russian Chemical Bulletin》2005,54(11):2540-2544
The composition of complexes formed upon the extraction of UVI and ThIV nitrates with O-n-nonyl(N,N-dibutylcarbamoylmethyl) methyl phosphinate (L) from solutions of nitric acid without additional solvent was determined by 31P NMR spectroscopy. The structures of the complexes formed were studied by IR spectroscopy. Uranium(VI) is extracted from 3 and 5 M solutions of HNO3 as the [UO2(L)2(NO3)2] complex, while thorium(IV) is extracted from 5 M HNO3 as the [Th(L)3(NO3)3]+·NO
3
−
complex. In both cases, ligand L has bidentate coordination. Ligand L contacts with 3 and 5 M nitric acid to form adducts L·HNO3 and L· (HNO3)2, respectively.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2460–2464, November, 2005. 相似文献
8.
L. O. Nindakova N. N. Chipanina V. K. Turchaninov M. V. Ustinov B. A. Shainyan 《Russian Chemical Bulletin》2005,54(10):2343-2347
The reaction of di-μ-chlorobis(1,5-cyclooctadiene)dirhodium with (4S, 5S)-2,2-dimethyl-4,5-bis(methylaminomethyl)-1,3-dioxolane (1) gave the complex [Rh(cod)(1)]Cl (cod is 1,5-cyclooctadiene). The composition of the complexes CoCl2 · L2 and [Rh(cod)(L2)]X (L2 = 1, (4S,5S)-2,2-dimethyl-4,5-bis(aminomethyl)-1,3-dioxolane, and (4S, 5S)-2,2-dimethyl-4,5-bis(dimethylaminomethyl)-1,3-dioxolane; X = Cl, TfO) was studied using IR and 1H NMR spectroscopy. In the RhI cyclooctadienediamine complexes, the diene molecule forms a stronger bond with the metal atom than that in the cyclooctadienediphosphine
analogs.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2270–2274, October, 2005. 相似文献
9.
Kavosh Majlesi Clemente Bretti Rosalia Maria Cigala Concetta De Stefano Kimia Majlesi Silvio Sammartano 《Journal of solution chemistry》2018,47(3):528-543
A potentiometric method has been used for the determination of the protonation constants of N-(2-hydroxyethyl)iminodiacetic acid (HEIDA or L) at various temperatures 283.15?≤?T/K?≤?383.15 and different ionic strengths of NaCl(aq), 0.12?≤?I/mol·kg?1?≤?4.84. Ionic strength dependence parameters were calculated using a Debye–Hückel type equation, Specific Ion Interaction Theory and Pitzer equations. Protonation constants at infinite dilution calculated by the SIT model are \( \log_{10} \left( {{}^{T}K_{1}^{\text{H}} } \right) = 8.998 \pm 0.008 \) (amino group), \( \log_{10} \left( {{}^{T}K_{2}^{\text{H}} } \right) = 2.515 \pm 0.009 \) and \( \log_{10} \left( {{}^{T}K_{3}^{\text{H}} } \right) = 1.06 \pm 0.002 \) (carboxylic groups). The formation constants of HEIDA complexes with sodium, calcium and magnesium were determined. In the first case, the formation of a weak complex species, NaL, was found and the stability constant value at infinite dilution is log10KNaL?=?0.78?±?0.23. For Ca2+ and Mg2+, the CaL, CaHL, CaL2 and MgL species were found, respectively. The calculated stability constants for the calcium complexes at T?=?298.15 K and I?=?0.150 mol·dm?3 are: log10βCaL?=?4.92?±?0.01, log10βCaHL?=?11.11?±?0.02 and \( \log_{10} \beta_{\text{Ca{L}}_{2}} \)?=?7.84?±?0.03, while for the magnesium complex (at I?=?0.176 mol·dm?3): log10βMgL?=?2.928?±?0.006. Protonation thermodynamic functions have also been calculated and interpreted. 相似文献
10.
This paper is focused on a characterization of bacterial contamination in pool water of the interim spent fuel storage (JAVYS Inc.) in Slovak Republic and on bioaccumulation of 137Cs and 60Co by isolated bacteria. Bacterial community in pool water is kept on very low level by extremely low concentration of solutes in deionized water and by the efficient water filtration system. Based on standard methods and sequencing of 16S rDNA four pure bacterial cultures were identified as Kocuria palustris, Micrococcus luteus, Ochrobactrum spp. and Pseudomonas aeruginosa. Isolated aerobic bacteria were able to bioaccumulate 137Cs and 60Co in laboratory experiments. The mechanism of Co and Cs binding involve rapid interactions with anionic groups of the components of cell surface and in the case of Cs+ ions is followed by transport processes across cytoplasm membranes and by intracellular distribution. The maximum specific uptake of Cs+ after 48 h cultivation in mineral medium (MM) reached 7.54 ± 0.48 μmol g?1 dw (Ochrobactrum spp.), 19.6 ± 0.1 μmol g?1 dw (M. luteus) and 20.1 ± 2.2 μmol g?1 dw (K. palustris). The maximum specific uptake of Co2+ after 24 h cultivation in MM reached 31.1 ± 3.5 μmol g?1 dw (Ochrobactrum spp.), 86.6 ± 12.2 μmol g?1 dw (M. luteus) and 16.9 ± 1.2 μmol g?1 dw (K. palustris). These results suggest that due to the long lasting uptake of 137Cs, 60Co and other radionuclides by biofilm in pool water high specific radioactivities (Bq m?2) can be expected on stainless steel walls of pools. 相似文献
11.
Two isomeric dibenzofuran carboxaldehydes, namely 2-methoxydibenzo[b,d]furan-1-carbaldehyde (4) and 2-methoxydibenzo[b,d]furan-3-carbaldehyde (5), were synthesized. Formylation of 2-methoxydibenzo[b,d]furan (3) with α,α-dichloromethyl methyl ether and tin(IV) chloride gave a mixture of aldehydes 4 and 5 in 95 % yield and in a 35:65 ratio. Their 1H and 13C NMR spectral signals were not sufficiently resolved in CDCl3 solution to achieve their complete assignment, but this was possible in DMSO-d 6 with the help of 2D-NMR techniques: NOESY for 1H–1H interactions and HSQC and HMQC experiments for 1H–13C correlations. These aldehydes were used in the synthesis of novel β-phenylethylamines and NBOMe derivatives, which are undergoing biological evaluation. 相似文献
12.
Ashok Behera Kakali De Susmita Chandra Sankha Chattopadhyay Mridula Misra 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(1):123-129
In vivo imaging of tumours using radiolabelled somatostatin (SST) analogues has become an accepted clinical tool in oncology.
HYNIC-Tyr3 octreotide and Tyr3 octreotide were synthesized by FMOC solid-phase peptide synthesis using a semi-automated synthesizer. These were analyzed
and purified by RP-HPLC, mass spectroscopy, IR spectroscopy, 1H NMR and 13C NMR. The prochelator 6-BOC-HYNIC was also synthesised and characterised indigenously. HYNIC-Tyr3 octreotide was labelled with 99mTc using Tricine and EDDA as coligand by SnCl2 method. Labelling with 99mTc was performed at 100 °C for 15 min and radiochemical analysis by ITLC and HPLC methods. The radiochemical purity of the
complex was over 98% and log p value was found to be −1.27 ± 0.12. The stability of radiolabelled peptide complex was checked at 37 °C up to 24 h. Blood
clearance and protein-binding study was also performed. In vivo biodistribution studies in rat showed uptake of 99mTc-HYNIC-TOC in kidney than any other organs. The blood clearance was faster with rapid excretion through kidneys and relatively
low uptake in liver. 相似文献
13.
A. A. Medzhidov P. A. Fatullaeva S. M. Peng R. G. Ismaiylov G. H. Lee S. R. Garaeva 《Russian Journal of Coordination Chemistry》2012,38(2):126-133
Reactions of N-(2-hydroxy-3,5-R1,R2-benzyl)-4-aminoantipyrines with copper acetate in ethanol gave complexes with Schiff bases (SBs) rather than the expected
complexes with reduced SBs; i.e., the starting ligands undergo oxidative dehydrogenation during the complexation reaction.
The corresponding complexes with reduced SBs were obtained from sodium salts of the ligands and cupric sulfate in aqueous
solutions. Kinetic measurements showed that oxidative dehydrogenation occurs in the heteroleptic complexes Cu(L
i
)(CH3COO)(X) (L
i
H are derivatives of N-(2-hydroxy-3,5-R1,R2-benzyl)-4-aminoantipyrines; i = 6–10; X = H2O, CH3OH, CH3CH2OH) but does not occur in the complexes CH3OH, CH3CH2OH. The absence of oxidative dehydrogenation of the ligands in Cu(L
i
)2 · H2O can be explained by the octahedral environment of the Cu2+ ion and, accordingly, the absence of the coordination site for molecular oxygen. The molecular structures of two Cu(II) complexes
with SBs were determined by X-ray diffraction. 相似文献
14.
H. Yuan L. Luo L. Zhang S. Zhao S. Mao J. Yu L. Shen Y. Du 《Colloid and polymer science》2002,280(5):479-484
1H NMR self-diffusion coefficient, spin–spin relaxation and two-dimensional nuclear Overhauser enhancement spectroscopy measurements
of sodium dodecyl sulfate (SDS) in poly(ethylene glycol) (PEG) aqueous solution show that SDS molecules start to self-aggregate
at a concentration of 3.3 mM, which is well below the normal critical micellar concentration (cmc). SDS micelles are formed
when the cmc is reached with PEG solubilized in their hydrophobic micellar cores.
Electronic Publication 相似文献
15.
V. Ya. Kavun I. A. Tkachenko N. A. Didenko A. B. Slobodyuk V. I. Sergienko 《Russian Journal of Inorganic Chemistry》2010,55(8):1179-1183
The ionic mobility in heptafluorozirconates (NH4)2.7Rb0.3ZrF7 and (NH4)2.75Cs0.25ZrF7 has been studied by 1H and 19F NMR in the temperature range 150–430 K. The types of ion motion were determined and their activation energies were estimated.
A phase transition results in a modification in which diffusion in the ammonium sublattice and orientational disorder of ZrF73− anions are observed. Owing to diffusion of ammonium ions, the compounds have relatively high ionic conductivity (σ ≥ 5 ×
10−5 S/cm at 420 K). 相似文献
16.
H. López-González M. Jiménez-Reyes M. Solache-Ríos A. Rojas-Hernández 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(1):103-108
Solubility product (Lu(OH)3(s)⇆Lu3++3OH−) and first hydrolysis (Lu3++H2O⇆Lu(OH)2++H+) constants were determined for an initial lutetium concentration range from 3.72·10−5 mol·dm−3 to 2.09·10−3 mol·dm−3. Measurements were made in 2 mol·dm−3 NaClO4 ionic strength, under CO2-free conditions and temperature was controlled at 303 K. Solubility diagrams (pLuaq vs. pC
H) were determined by means of a radiochemical method using 177Lu. The pC
H for the beginning of precipitation and solubility product constant were determined from these diagrams and both the first
hydrolysis and solubility product constants were calculated by fitting the diagrams to the solubility equation. The pC
H values of precipitation increases inversely to [Lu3+]initial and the values for the first hydrolysis and solubility product constants were log10
β*
Lu,H
= −7.92±0.07 and log10
K*sp,Lu(OH)3 = −23.37±0.14. Individual solubility values for pC
H range between the beginning of precipitation and 8.5 were S
Lu3+ = 3.5·10−7 mol·dm−3, S
Lu(OH)2+ = 6.2·10−7 mol·dm−3, and then total solubility was 9.7·10−7 mol·dm−3. 相似文献
17.
F. Alkan T. Small S. Bai A. Dominowski C. Dybowski 《Journal of Structural Chemistry》2016,57(2):369-375
The temperature and concentration dependences of 207Pb NMR chemical shifts of Pb(NO3)2 in D2O are reported. The results are analyzed in terms of exchange between a solvated lead ion and the Pb(NO3)+ contact-ion pair. Predictions of the chemical shift difference between the aquated ion and contact-ion pair are carried out for the gas-phase entities and for the solvated species with a DFT calculation. Previously reported data on 207Pb NMR chemical shifts of Pb(NO3)2 in H2O are reevaluated. From the analysis, the enthalpy of dissociation of the contact-ion pair is found to be–42.3±1.0 kJ/mol. 相似文献
18.
A. V. Afonin 《Russian Journal of Organic Chemistry》2009,45(12):1769-1771
Long-range 19F-1H spin-spin coupling with participation of vinyl group protons, observed in the 1H NMR spectra of fluoro-substituted aryl vinyl sulfides, indicates that these compounds exist as equilibrium mixtures of s-cis and s-trans rotational isomers. 相似文献
19.
195Pt, 1H, and 13C NMR spectroscopy was used to study the structure of binuclear platinum(III) acetamidate complexes with 1,10-phenanthroline and 2,2′-bipyridine ligands [Pt2(phen)2(acam)4](NO3)2 (1) and [Pt2(bipy)2(acam)4](NO3)2 (2) in aqueous solutions. The 195Pt NMR spectra of solutions of complexes 1 and 2 in D2O exhibit two signals with satellites due to the 195Pt–195Pt spin-spin coupling (1 J(Pt–Pt) ≈ 6345 Hz), whereas their 1H and 13C NMR spectra contain four sets of signals for the protons and the carbon atoms of the heterocyclic and acetamidate ligands. The signals were assigned using the COSY, NOESY, and HSQC/ HMBC experiments and comparing the coordination shifts of the signals for the protons of heterocycles. These data allowed us to draw a conclusion that binuclear complexes 1 and 2 in solution have a head-to-head structure with nonequivalent platinum(III) atoms (coordination cores PtN5 and PtN3O2), the axial-equatorial coordination of the bidentate heterocyclic molecules, and two bridging and two terminal acetamidate ligands. 相似文献
20.
A. V. Afonin 《Russian Journal of Organic Chemistry》2010,46(9):1313-1316
The analysis of long-range spin-spin coupling 19F-1H and the other conformation-dependent parameters of 1H NMR spectra shows that aryl vinyl selenides like aryl vinyl sulfides exist as mixtures of s-cis and s-trans rotational isomers. The combined data of 1H and 13C NMR spectra reveal the increase in the torsional angle ϑ at the bond X-CH=CH2 (X = S, Se) in selenides compared to sulfides due to diminished interaction energy of the unshared electron pairs of selenium
with the π*-orbitals of the double bond as compared to analogous interaction in sulfides. 相似文献