共查询到20条相似文献,搜索用时 93 毫秒
1.
W. Y. Choy S. C. F. Au-Yeung S. Y. Fan W. L. A. K. Chiu C. S. Cockram 《Fresenius' Journal of Analytical Chemistry》1998,361(5):500-503
Glucose in 5% D2O/95% H2O solution was successfully determined quantitatively by measurements of the 1H NMR peak height (intensity) of the single peaks at δ(1H) = 5.22 and 4.64 ppm corresponding to the α-D and the β-D-glucose spectrum, respectively. The single peaks were obtained
from decoupling of the high field part of the AX spectrum of the α-D- or the β-D-glucose by incorporation of time shared homonuclear
decoupling in the WATR-CPMG method (WATR-HDCPMG) without re-attenuation of the water peak. The method was applied to the determination
of total glucose in blood plasma from human subjects undergoing oral glucose tolerance test (OGTT) in the teaching hospital.
The results compared favorably with those obtained from the standard glucose oxidase method obtained in a hospital pathology
laboratory. The accuracy of the results obtained using the WATR-HDCPMG method was within 3.5% of the glucose oxidation method.
Received: 5 January 1998 / Revised: 23 February 1998 / Accepted: 26 February 1998 相似文献
2.
Philip E. Pfeffer Kevin B. Hicks Michael H. Frey Stanley J. Opella William L. Earl 《Journal of carbohydrate chemistry》2013,32(2):197-217
Abstract NMR spectra of crystalline α-D-glucose DH2O (1), α-D-glucose (2), and β-D-glucose (3) were examined by 13C cross polarization magic angle spinning (CPMAS) methods. Each of the three forms of glucose exhibited a distinctly different spectrum. Chemical interconversion of 2 and 3 as well as the in situ dehydration of 1 during the course of the CPMAS NMR experiment was monitored in the 13C spectra. Samples of 1, 2, and 3 specifically enriched at C-1 and C-6 with 13C yielded 13C spectra in which the resonances corresponding to the adjacent C-2 and C-5 carbons were not visible due to strong homonuclear 13C dipolar interactions with the high abundance label. Spectra of these analogues as well as the C-2 and C-3 labeled materials provided the complete 13C chemical shift assignments of crystalline 1 2, and 3. A comparison of the solid state and solution 13C spectra revealed substantial resonance shifts for each of the three structures examined. 相似文献
3.
Anderson O. Ribeiro Osvaldo A. Serra 《Journal of inclusion phenomena and macrocyclic chemistry》2010,67(3-4):281-285
The solubilization of an europium (III) β-diketonate chelate in aqueous medium and the changes in its photophysical properties upon its inclusion into an α-cyclodextrin hydrophobic cavity are described. The complex [Eu(tta)3·(H2O)2] (tta = 4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dione) was synthesized, characterized, and incorporated into the hydrophobic cavity by stirring in an α-cyclodextrin aqueous solution. The inclusion was confirmed by 1H NMR, and the stoichiometry of association was obtained by the Job method. The maximum in the excitation spectrum of the α-CD inclusion compound in aqueous solution was shifted 28 nm compared with the maximum of non α-CD complex. The emission spectrum of the association is similar to that of the free solid complex and displays the characteristic 5D0 → 7F0-4 Eu3+ transitions. 相似文献
4.
The 13C NMR spectrum (at natural abundance) of monomeric chlorophyll α in acetone-d6 has been recorded to re-examine the assignments of the low field (aromatic-olefinic) region of the spectrum. The assignments, made by the examination of the fully coupled spectrum and by the use of long-range selective 1H decoupling (LSPD) with low-power irradiation, were compared with those of the previous reports. The results of the present work clarify the ambiguities previously encountered in the assignment of the 10a-ester, 7c-propionyl, P-2-phytyl, 2b-vinyl, γ- and β-methine carbon atoms, as well as the β-pyrrolic carbon-6 and α-pyrrolic carbons ?16 and ?17 of chlorophyll α. Reassignment of the three last carbons was found necessary. Knowledge of the chemical shifts of these carbon atoms was considered to be particularly valuable, as it yields relevant information on the delocalized π electron system which is crucial for the function of chlorophyll in photosynthesis. 相似文献
5.
Toshinobu Higashimura Mitsuru Hoshino Yoshitsugu Hirokawa Kei Matsuzaki Toshiyuki Uryu 《Journal of polymer science. Part A, Polymer chemistry》1977,15(11):2691-2700
Benzyl, ethyl, and deuterated ethyl propenyl ethers (BzPE, EPE, and EPE-d5, respectively) with different cis/trans isomer ratios were polymerized by BF3O(C2H5)2 at ?78°C in toluene, methylene chloride, and nitroethane solvents. Poly(propenyl alcohol) [poly(PA)] was also prepared by treating poly(BzPE) with HBr gas. The steric structure of these polymers was studied by 1H- and 13C-NMR spectroscopy. The poly(EPE-d5) obtained from a trans-rich monomer mixture was crystalline, while one from a cis-rich monomer mixture was amorphous. Poly(BzPE) was always amorphous. Poly(BzPE), poly(PA), and poly(EPE-d5) gave 1H-NMR spectra with two β-methine peaks, relative intensities of which depended on the geometric structure of the monomers. Their spectra of β-methyl protons decoupled from β-methine proton were also split into two peaks, relative intensities of which corresponded to those of the two α-methine peaks. 13C-NMR spectra of α-OCH2 and β-CH3 of poly(EPE), respectively, consisted of two peaks. These observations show that the poly(propenyl ethers) examined, whether crystalline or amorphous, have only two dyad structures (probably threo or erythro-meso and racemic), and that their α- and β-carbons have the same dyad structure, irrespective of the kind of the alkoxyl groups. 相似文献
6.
The mechanisms of formation of m/z 73 ions in the mass spectrum of the ionized title compound were investigated by deuterium substitution and by examining the decompositions of metastable ions. Two routes to the [C4H9O]+ ions were found in the normal spectrum. The ethyl lost by the major pathway contains the α- and β-hydrogens and a γ-hydrogen from the butyl group. The minor route involves the loss of ethylene from the [M? H]+ ion. There were metastable peaks for losses of ethyl, ethanol and methyl from the molecular ion. The ethyl contains the α- and β-methylenes and a γ-hydrogen, while the methyl is the δ-methyl of the butyl group. The labeling data rule out a previous mechanistic proposal for the loss of ethyl and support a mechanism involving stepwise isomerization to the sec-butyl ethyl ether molecular ion. However, the metastable ion chemistries of the molecular ions from the n- and sec-butyl ethyl ethers are highly dissimilar, perhaps due to decompositions from different electronic states. The n-pentyl methyl ether ions loses both ethyl and propyl, apparently following rearrangements to the 3-pentyl and 2-pentyl ether ions. Di n-butyl and n-butyl methyl ethers also give metastable peaks for loss of methyl, ethyl and the shorter chain alcohol. 相似文献
7.
Jason B. Bialecki Josef Ruzicka Carl S. Weisbecker Meena Haribal Athula B. Attygalle 《Journal of mass spectrometry : JMS》2010,45(3):272-283
Collision‐induced dissociation (CID) mass spectra of differently substituted glucosinolates were investigated under negative‐ion mode. Data obtained from several glucosinolates and their isotopologues (34S and 2H) revealed that many peaks observed are independent of the nature of the substituent group. For example, all investigated glucosinolate anions fragment to produce a product ion observed at m/z 195 for the thioglucose anion, which further dissociates via an ion/neutral complex to give two peaks at m/z 75 and 119. The other product ions observed at m/z 80, 96 and 97 are characteristic for the sulfate moiety. The peaks at m/z 259 and 275 have been attributed previously to glucose 1‐sulfate anion and 1‐thioglucose 2‐sulfate anion, respectively. However, based on our tandem mass spectrometric experiments, we propose that the peak at m/z 275 represents the glucose 1‐thiosulfate anion. In addition to the common peaks, the spectrum of phenyl glucosinolate (β‐D ‐Glucopyranose, 1‐thio‐, 1‐[N‐(sulfooxy)benzenecarboximidate] shows a substituent‐group‐specific peak at m/z 152 for C6H5‐C(?NOH)S?, the CID spectrum of which was indistinguishable from that of the anion of synthetic benzothiohydroxamic acid. Similarly, the m/z 201 peak in the spectrum of phenyl glucosinolate was attributed to C6H5‐C(?S)OSO2?. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
8.
Formation of cyclic ions in the electron impact induced fragmentation of 1,n-bis-(alkylthio) alkanes
Elke Anklam 《Research on Chemical Intermediates》1990,13(1):17-29
Fragmentation of molecular ions of 1,n-bis(alkylthio)alkanes (R1-S-(CH2)n-S-R2) occurs mainly by α- or β-cleavage to a sulphur atom. The ratio of fragments derived by α- or β-cleavage depends on the number of methylene groups (n) between the two sulphur atoms and on the alkyl groups R1 and R2. Generally β-cleavage induced fragmentation dominates for 1,2-bis(alkylthio)ethanes (n=2) leading to formation of thiiranium ions. Fragmentations derived by α-cleavage are predominant for all compounds with n=3; base peaks corresponding to [M-(R)]+ or [M-(2R)+(H)]+ are found which gives evidence for formation of five membered cyclic ions. Such fragmenss are less intense in compounds with n=4 whereas m all other compounds β-cleavage predominates if R = methyl, ethyl, n-propyl. 相似文献
9.
The application of ultrasound for the synthesis of ternary oxide AgMO2 (M=Fe, Ga) was investigated. Crystalline α-AgFeO2 was obtained from the alkaline solutions of silver and iron hydroxides by sonication for 40 minutes. α-AgFeO2 was found to absorb optical radiation in the 300-600 nm range as shown by diffuse reflectance spectroscopy. The Raman spectrum of α-AgFeO2 exhibited two bands at 345 and 638 cm−1. When β-NaFeO2 was sonicated with aqueous silver nitrate solution for 60 minutes, β-AgFeO2 possessing orthorhombic structure was obtained as the ion-exchanged product. The Raman spectrum of β-AgFeO2 showed four strong bands at 295, 432, 630 and 690 cm−1. Sonication of β-NaGaO2 with aqueous silver nitrate solution for 60 minutes resulted in olive green colored, α-AgGaO2. The diffuse reflectance spectrum and the EDX analysis confirmed that the ion-exchange through sonication was complete. The Raman spectrum of α-AgGaO2 had weak bands at 471 and 650 cm−1. 相似文献
10.
The heat required to release and vaporize bound H2O from crystalline α-lactose monohydrate and from lactose glass, as determined by differential scanning calorimetry is 12.3±0.7 and 10.8±0.5 kcal·mole−1 of H2O, respectively. Water vapor sorption by anhydrous α-lactose leads to the formation of the α-monohydrate. The isotherm, obtained gravimetrically for this process is Langmuir type. β-Lactose is completely non-hygroscopic below 97% relative humidity. Thereafter, it sorbs H2O rapidly to form a concentrated solution wherein the lactose is capable of mutarotation. Densites of lactose forms determined pycnometrically by helium displacement are: 1.535 g/cm3 for α-lactose·H2O; 1.547 g/cm3 for anhydrous α-lactose; and 1.576 g/cm3 for β-lactose. 相似文献
11.
F. Bawa D. G. Cameron C. S. Creaser H. R. Hudson M. Pianka O. O. Shode 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract Fast atom bombardment mass spectrometry has been applied to a range of ionic, zwitterionic, and thermally labile organophosphorus compounds and has been shown to be a potentially valuable aid to identification and characterisation. Results are presented for the positive ion spectra of quasiphosphonium salts, aminophosphonic, aminophosphonous, and aminophosphinic acids, phosphonopeptides, and a number of heat sensitive derivatives. The quasiphosphonium intermediates derived from alkyl esters of phosphorus (III) acids and halogeno compounds generally show base peaks corresponding to the phosphonium ion which fragments to give the protonated form of the Arbuzov product. Strong characteristic peaks are also obtained from various phosphonic and phosphinic derivatives. α- and ω-aminoalkanephosphonic acids and their guanidino analogues give base peaks corresponding to [M+H]+ ions and show simple fragmentations arising mainly from the loss of HPO3 and H3PO3 Phosphonous derivatives give peaks corresponding to [M+H]+ and [2M+H]+ with the base peak apparently resulting from the elimination of HPO3 from the dimeric structure. Elimination of H3PO2 is also indicated. Examples of phosphonopeptides are also shown to give base peaks at [M+H]+ and to exhibit characteristic fragmentations that are of potential value as aids to identification. Fast atom bombardment mass spectra have also been recorded for a number of pesticidal phosphorodithioates, their principal metabolites, and some related esters. Although [M+H]+ peaks are clearly present in all cases, the intensity is variable and fragmentations are generally more complex than those obtained for the compounds referred to above. O,O-Diethyl phosphorodithioates, for example, frequently give rise to (EtO)2PS+, which fragments further by stepwise elimination of ethylene as is also observed in electron impact mass spectrometry. We are grateful to SERC for support of this work and for FAB mass spectrometry facilities at the Physico-Chemical Measurements Unit, Harwell. 相似文献
12.
Yb3Al5O12 (YbAG) single crystals doped with different concentrations of Pr were synthesized by the Floating Zone (FZ) method. Then, we evaluated their basic optical and scintillation properties. All the samples showed photoluminescence (PL) with two emission bands appeared approximately 300–500 nm and 550–600 nm due to the charge transfer luminescence of Yb3+ and intrinsic luminescence of the garnet structure, respectively. A PL decay profile of each sample was approximated by a sum of two exponential decay functions, and the obtained decay times were 1 ns and 3–4 ns. In the scintillation spectra, we observed emission peaks in the ranges from 300 to 400 nm and from 450 to 550 nm for all the samples. The origins of these emissions were attributed to charge transfer luminescence of Yb3+ and intrinsic luminescence of the garnet structure, respectively. The scintillation decay times became longer with increasing the Pr concentrations. Among the present samples, the 0.1% Pr-doped sample showed the lowest scintillation afterglow level. In addition, pulse height spectrum of 5.5 MeV α-rays was demonstrated using the Pr-doped YbAG, and we confirmed that all the samples showed a full energy deposited peak. Above all, the 0.1% Pr-doped sample showed the highest light yield with a value of 14 ph/MeV under α-rays excitation. 相似文献
13.
13C NMR spectroscopy was used for the unequivocal analysis of the mixture of products of RuCl2[P(C6H5)3]3-catalysed transfer deuteriation of benzylideneacetophenone by (a) DCOONa/H2O, (b) HCOONa/D2O and (c) DCOONa/D2O. Signal assignments in the 13C spectra were obtained mainly from the deuterium-induced 13C isotope shifts. The geminal 13C? 2H shift of the β-carbon of deuteriated 1,3-diphenylpropan-1-one is almost twice that for the α-carbon. 相似文献
14.
Fmoc-AA-OPfp (AA=Tyr or Ser) (1 equiv) was reacted with β-d-Glc(OAc)5 (6 equiv) in the presence of BF3.Et2O (6 equiv) in CH2Cl2 at room temperature for 2 h, and the glycosylation reaction mixture was used directly to couple to the amino group of the peptide resin without isolation and purification of the Fmoc-AA[β-d-Glc(OAc)4]-OPfp. Moreover, the -OAc protecting groups of glucose was removed just prior to releasing the peptide from the resin using 6 mM NaOMe in 85% DMF-MeOH. The crude product obtained by TFA cleavage contained >90% of the target O-glycopeptide, and the 500 MHz 1H NMR analysis revealed that the glycosylation reaction was nearly stereoselective (>97% β-anomer). This method is rapid and stereoselective, and can now be exploited for the routine synthesis of O-glycopeptides. 相似文献
15.
Bruce Coxon 《Journal of carbohydrate chemistry》2013,32(4):525-543
Abstract The hydroxyl proton coupled 1H NMR spectra of solutions of β-d-digitoxopyranose and of an equilibrated mixture of the four ring forms of d-digitoxose in dimethylsulfoxide-d 6 have been assigned completely by two-dimensional, proton chemical shift correlated NMR spectroscopy and spin decoupling at 400 MHz. Analysis of resolution enhanced, one-dimensional 1H NMR spectra yielded an almost complete set of CH and OH proton-proton coupling constants for the four ring forms. The free aldehydo form of d-digitoxose in dimethylsulfoxide-d 6 solution has been detected by means of its characteristic H-l quartet at 6 9.687. Quantitative analysis of the equilibrated mixture of the five forms of d-digitoxose gave the composition:- α-pyranose, β-pyranose, α-furanose, β-furanose, aldehydo form, 11.2, 67.3, 8.4, 13.0, and 0.1%, respectively. The 4 C 1 chair conformations have been assigned to the α- and β-pyranose forms by analysis of the coupling constants and are discussed qualitatively in terms of their relative stabilities. 相似文献
16.
Sohan Lal 《International Journal of Polymer Analysis and Characterization》2014,19(7):625-636
The molecular dynamics of pristine and 100 MeV O7+ ion–modified liquid crystalline polyurethane (LCPU) was carried out using the thermally stimulated depolarization currents (TSDC) method. The TSDC spectra of pristine LCPU samples consist of current peaks appearing around 110,160, 210, and 260 K and are called the γ, β, α, and δ peaks respectively. The γ-peak is attributed to the crankshaft motion of the spacer group (but-2-ene group). The β-peak is due to the localized rotational fluctuations of C?O groups. The α-peak is associated with the dipolar orientation of imines group present in the urethane linkage, and the δ-peak has its origin in the space charge trapping mechanism. In the TSDC spectra of O7+ ion–irradiated LCPU samples the γ-peak almost disappears, which shows that the ion induced modification in the methylene linkage. A relaxation process owing to new sub-polar groups formed due to dehydrogenation of CH2 groups and occurring in the vicinity of β-relaxation is discussed. The radiation-induced chain scissioning at NH groups in LCPU is also confirmed from the fluence effect on the α-peak. The irradiation results in the production of a large number of defect sites and an increase in the same results in the enhancement of δ-relaxation. 相似文献
17.
The essential participation of agostic interactions in C−H bond activation, cyclometallation and other catalytic processes has been widely observed. To quantitatively evaluate the Mo−H−C agostic interaction in the Mo β/γ- agostomers [CpMo(CO)2(PiPr3)]+ ( Mo , 1 and Mo , 2 ) and the Mn−H−C agostic interaction in the Mn α/ϵ-agostomers [(C6H9]Mo(CO)3] ( Mn , 1 and Mn , 2 ), the comprehensive density functional theory (DFT) theoretical investigations were performed. Results indicated that the Mo β-agostomer 1 is only favorable by 0.5 kcal mol−1 than Mo γ-agostomer 2 , and the Gibbs barrier for their interconversion was 9.1 kcal mol−1. A slightly higher Gibbs barrier of 12.7 kcal mol−1 for the isomerization between the Mn α/ϵ-agostomers was also obtained. The relatively strong agostic interactions in Mo β-agostomer 1 and Mn α-agostomer 1 were further verified by the AIM (Atoms-In-Molecules) analyses and the NAdOs (natural adaptive orbitals) analyses. The findings on the agostic interaction presented in this study are believed to benefit the understandings of the agostic interaction involved catalytic processes and to promote the development of new organometallic complexes. 相似文献
18.
13C FT n.m.r. spectra were obtained from borates of methyl α-D -glucopyranoside, triethylboron, sodium tetraphenylboron and 1-butaneboronic acid employing a simultaneous 1H and 11B decoupling network. The effectiveness of the system was evident using the three latter organoboron compounds. Since no diminution in line broadening of signals occurred in the spectrum of the sugar borate, the absence of 13C? O? 11B coupling was indicated. This finding was confirmed by comparing the effects of varying the temperatures of sugar borates and triethylboron on their conventional 13C n.m.r. spectra. 相似文献
19.
Full analyses of the five-spin 1H n.m.r. spectra for the diene protons of isoprene, ethylbutadiene and β-myrcene under conditions of decoupling the sidechain α-protons are reported. The data are discussed in terms of spin–spin coupling mechanism and molecular conformation. The fully-coupled spectra of the compounds were also examined and coupling information obtained. 相似文献
20.
K. I. Popov N. M. Sultanova H. Rönkkömäki 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(10):1680-1682
The concentration dissociation constants pK c of the α and β D-glucose anomers were measured at pH 12–14 by the 13C NMR method. The pK c values for L ? H?1L + H equilibria at 25°C and an ionic strength of 1.0 mol/l (NaCl) were pK c α = 12.31 ± 0.03 and pK c β = 12.03 ± 0.01. Dissociation was found to shift all the spectrum lines downfield. The most probable hydroxyl group responsible for the dissociation of β-D-glucose was determined. 相似文献