Co-reporter:Bin Yuan, Yiming Ding, Ghulam M. Kamal, Limin Shao, Zhiming Zhou, Bin Jiang, Peng Sun, Xu Zhang, Maili Liu
Journal of Magnetic Resonance 2017 Volume 278(Volume 278) pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.jmr.2017.03.004
•A new method for effectively reconstructing diffusion-ordered spectroscopy.•It can give a good estimate of the number of chemical components.•It can resolve more chemical components than widely used multivariate methods.•It’s good at analyzing a mixture of mono- and poly-disperse species.2D diffusion-ordered NMR spectroscopy (DOSY) has been widely recognized as a powerful tool for analyzing mixtures and probing inter-molecular interactions in situ. But it is difficult to differentiate molecules with similar diffusion coefficients in presence of overlapped spectra. Its performance is susceptible to the number of chemical components, and usually gets worse when the number of components increases. Here, to alleviate the problem, numerical simultaneous inversion of Laplace transform (SILT) of many related variables is proposed for reconstructing DOSY spectrum (SILT-DOSY). The advantage of the proposed method in comparison to other methods is that it is capable of estimating the number of analytes more accurately and deriving corresponding component spectra, which in turn leads to the more reliable identification of the components.Download high-res image (62KB)Download full-size image
Co-reporter:Gang-Jin Yu, Xiao-Ying Chen, Shi-Zhen Mao, Mai-Li Liu, You-Ru Du
Chinese Chemical Letters 2017 Volume 28, Issue 7(Volume 28, Issue 7) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.cclet.2017.04.013
The critical aggregation concentration (CAC) of four with three kinds of conventional surfactants, namely, two cationic surfactants [hexadecyltrimethyl ammonium bromide (CTAB) and tetradecyltrimethyl ammonium bromide (TTAB)], one anionic surfactant [sodium dodecyl sulfate (SDS)], and a nonionic surfactant [Triton X-100 (TX-100)], were determined by variation of 1H chemical shifts with surfactant concentrations. Results show that the CAC values of protons at different positions of the same molecule are different, and those of the terminal methyl protons are the lowest, respectively, which suggests that the terminal groups of the alkyl chains aggregates first during micellization. Measurement of the transverse relaxation time (T2) of different protons in SDS also show that the terminal methyl protons start to decrease with the increase in concentration first, which supports the above mentioned tendency.Download high-res image (86KB)Download full-size imageTerminal methyl groups (in blue) aggregate firstly during micellization, they initiate the micelle formation.
Co-reporter:Sen Wang;Peng Sun;Rongrong Zhang;Ang Lu;Lina Zhang
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 11) pp:7486-7490
Publication Date(Web):2017/03/15
DOI:10.1039/C6CP08744B
As a breakthrough to the traditional 1H diffusometry, the interaction of cations with cellulose is investigated via7Li and 23Na PFG-SE NMR. The diffusion coefficient of Li+ decreases more than that of Na+ with the addition of cellulose, which indicates a stronger binding of LiOH with the macromolecule. Therefore, a new, facile, accurate and repeatable method to characterize ion/polymer interactions is established.
Co-reporter:Yan Fang, Rongrong Zhang, Bo Duan, Maili Liu, Ang Lu, and Lina Zhang
ACS Sustainable Chemistry & Engineering 2017 Volume 5(Issue 3) pp:
Publication Date(Web):January 20, 2017
DOI:10.1021/acssuschemeng.6b03055
Chitin and chitosan are enticing natural polymers derived from seafood wastes, and their applications mostly depend on the degree of acetylation (DA). For their efficient utilization, a series of universal solvents for the direct dissolution from chitin to chitosan with various DA ranged from 5 to 94% were designed, and robust hydrogels were constructed from their solution via a physical regeneration, for the first time. The NMR results demonstrated that K+ of KOH interacted easily with C═O group to break the NH...O═C intermolecular hydrogen bonds of chitin, whereas Li+ of LiOH could bound with NH2 group to promote the destruction of NH...O6 hydrogen bonds of chitosan. Thus, a series of LiOH/KOH/urea aqueous solutions with weight ratios of LiOH to KOH from 0 to 2.5 were developed to directly dissolve these biomacromolecules with DAs ranging from 5 to 94%. Subsequently, a series of coagulants were also exploited for the regeneration of these chitin/chitosan solutions to construct the robust hydrogels with different DAs. These chitin/chitosan hydrogels exhibited homogeneous network structure consisting of nanofibers with a mean diameter of ∼30 nm as well as excellent mechanical properties and high transparency. By adding a fluorescent agent with strong affinity with only the -NH2 group, the resulting fluorescent hydrogels with different DAs could be visually recognized because the intensity reflected the different contents of the active amino group. Furthermore, the wastewater after regeneration could be easily recycled via reduced pressure distillation to reuse without consuming any chemicals or producing byproducts, leading to a thoroughly green process. This work opens a new avenue for dissolving biomacromolecules from chitin to chitosan via universal solvents and to construct new materials via green transformation, which would be beneficial for global sustainable development.Keywords: Chitin; Chitosan; Green transformation; Recycling of wastewater; Universal solvents;
Co-reporter:Ghulam Mustafa Kamal, Xiaohua Wang, Bin Yuan, Jie Wang, Peng Sun, Xu Zhang, Maili Liu
Talanta 2016 Volume 158() pp:89-99
Publication Date(Web):1 September 2016
DOI:10.1016/j.talanta.2016.05.033
•13C NMR spectroscopy facilitates the assignment and deconvolution.•Sucrose, glucose and glutamate are the main cause of the discrimination.•The addition of caramel and monosodium glutamate was found.Soy sauce a well known seasoning all over the world, especially in Asia, is available in global market in a wide range of types based on its purpose and the processing methods. Its composition varies with respect to the fermentation processes and addition of additives, preservatives and flavor enhancers. A comprehensive 1H NMR based study regarding the metabonomic variations of soy sauce to differentiate among different types of soy sauce available on the global market has been limited due to the complexity of the mixture. In present study, 13C NMR spectroscopy coupled with multivariate statistical data analysis like principle component analysis (PCA), and orthogonal partial least square-discriminant analysis (OPLS-DA) was applied to investigate metabonomic variations among different types of soy sauce, namely super light, super dark, red cooking and mushroom soy sauce. The main additives in soy sauce like glutamate, sucrose and glucose were easily distinguished and quantified using 13C NMR spectroscopy which were otherwise difficult to be assigned and quantified due to serious signal overlaps in 1H NMR spectra. The significantly higher concentration of sucrose in dark, red cooking and mushroom flavored soy sauce can directly be linked to the addition of caramel in soy sauce. Similarly, significantly higher level of glutamate in super light as compared to super dark and mushroom flavored soy sauce may come from the addition of monosodium glutamate.The study highlights the potentiality of 13C NMR based metabonomics coupled with multivariate statistical data analysis in differentiating between the types of soy sauce on the basis of level of additives, raw materials and fermentation procedures.
Co-reporter:Guifang Wang;Ze-Ting Zhang;Bin Jiang;Xu Zhang
Analytical and Bioanalytical Chemistry 2014 Volume 406( Issue 9-10) pp:2279-2288
Publication Date(Web):2014 April
DOI:10.1007/s00216-013-7518-5
Nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography are the two main methods for protein three-dimensional structure determination at atomic resolution. According to the protein structures deposited in the Protein Data Bank, X-ray crystallography has become the dominant method for structure determination, particularly for large proteins and complexes. However, with the developments of isotope labeling, increase of magnetic field strength, common use of a cryogenic probe, and ingenious pulse sequence design, the applications of NMR spectroscopy have expanded in biological research, especially in characterizing protein dynamics, sparsely populated transient structures, weak protein interactions, and proteins in living cells at atomic resolution, which is difficult if not impossible by other biophysical methods. Although great advances have been made in protein NMR spectroscopy, its applications in protein therapeutics, which represents the fastest growing segment of the pharmaceutical industry, are still limited. Here we review the recent advances in the use of NMR spectroscopy in studies of large proteins or complexes, posttranslation modifications, weak interactions, and aggregation, and in-cell NMR spectroscopy. The potential applications of NMR spectroscopy in protein therapeutic assays are discussed.
Co-reporter:Bin Jiang, Fan Luo, Yiming Ding, Peng Sun, Xu Zhang, Ling Jiang, Conggang Li, Xi-an Mao, Daiwen Yang, Chun Tang, and Maili Liu
Analytical Chemistry 2013 Volume 85(Issue 4) pp:2523
Publication Date(Web):January 22, 2013
DOI:10.1021/ac303726p
As a powerful tool for biological analysis, especially protein structure and dynamic studies, nuclear magnetic resonance (NMR) spectroscopy suffers from intrinsic low signal to nose ratio (SNR) and long acquisition time required for multidimensional (nD) experiments. Nonuniform sampling (NUS) can effectively speed up the experiment but often introduces artifacts into the spectrum. In addition to the development of highly sensitive hardware and NMR pulse sequences, data postprocessing is a relative simple and cost-effective method to improve the SNR and suppress the artifacts. In this work, we propose an effective approach for simultaneously suppressing noise and artifacts based on the resampling principle. The method is named NASR for short and tested using one-, two-, and three-dimensional (1D, 2D, and 3D) NMR spectra that were acquired using ether conventional or NUS (spiral and random, for 3D) approaches. The results reveal that the NASR is fast and applicable for improving the quality of 1D to nD NMR spectra with all kinds of sampling schemes.
Co-reporter:Yuanyuan Du, Wenxian Lan, Zhusheng Ji, Xu Zhang, Bin Jiang, Xin Zhou, Conggang Li, and Maili Liu
Analytical Chemistry 2013 Volume 85(Issue 18) pp:8601
Publication Date(Web):August 19, 2013
DOI:10.1021/ac401738z
Although blood plasma has been used to diagnose diseases and to evaluate physiological conditions, it is not easy to establish a global normal concentration range for the targeting components in the plasma due to the inherent metabolic diversity. We show here that NMR spectroscopy coupled with principal component analysis (PCA) may provide a useful method for quantitatively characterizing the metabolic diversity of human blood plasma. We analyzed 70 human blood plasma samples with and without addition of ibuprofen. By defining the PC score values as diversity index (Idiv) and the drug-induced PC score value change as interaction index (Idist), we find that the two indexes are highly correlated (P < 0.0001). Triglycerides, choline-containing phospholipids, lactate, and pyruvate are associated with both indexes (P < 0.0001), respectively. In addition, a significant amount of lactate and pyruvate are in the NMR “invisible” bound forms and can be replaced by ibuprofen. The diffusion and transverse relaxation time weighted NMR approaches gave rise to a better characterization of the diversity and the interaction than that of the one acquired using NOESYPR1D with 100 ms mixing time. These results might be useful for understanding the blood plasma–drug interaction and personalized therapy.
Co-reporter:Conggang Li;Chun Tang
Protein & Cell 2013 Volume 4( Issue 10) pp:726-730
Publication Date(Web):2013 October
DOI:10.1007/s13238-013-3912-1
Co-reporter:Jun Liu, Yan Jiang, Hong Chen, Shi Zhen Mao, You Ru Du, and Mai Li Liu
The Journal of Physical Chemistry B 2012 Volume 116(Issue 51) pp:14859-14868
Publication Date(Web):November 29, 2012
DOI:10.1021/jp3082694
In this Article, we investigated effects of different types of conventional surfactants on exchange dynamics of quaternary ammonium dimeric surfactants, with chemical formula C14H29N+(CH3)2– (CH2)s–N+(CH3)2C14H29·2Br–, or 14-s-14 for short. Two nonionic surfactants, TritonX-100 (TX-100) and polyethylene glycol (23) laurylether (Brij-35), and one cationic surfactant, n-tetradecyltrimethyl ammonium bromide (TTAB), and one ionic surfactant, sodium dodecyl sulfate (SDS) were chosen as typical conventional surfactants. Exchange rates of 14-s-14 (s = 2, 3, and 4) between the micelle form and monomer in solution were detected by two NMR methods: one-dimensional (1D) line shape analysis and two-dimensional (2D) exchange spectroscopy (EXSY). Results show that the nonionic surfactants (TX-100 and Brij-35), the cationic surfactant (TTAB), and the ionic surfactant (SDS) respectively accelerated, barely influenced, and slowed the exchange rate of 14-s-14. The effect mechanism was investigated by the self-diffusion experiment, relaxation time measurements (T2/T1), the fluorescence experiment (I1/I3) and observed chemical shift variations. Results reveal that, nonionic conventional surfactants (TX-100 and Brij-35) loosened the molecule arrangement and decreased hydrophobic interactions in the micelle, and thus accelerated the exchange rate of 14-s-14. The cationic conventional surfactant (TTAB) barely changed the molecule arrangement and thus barely influenced the exchange rate of 14-s-14. The ionic conventional surfactant (SDS) introduced the electrostatic attraction effect, tightened the molecule arrangement, and increased hydrophobic interactions in the micelle, and thus slowed down the exchange rate of 14-s-14. Additionally, the two-step exchange mechanism of 14-s-14 in the mixed solution was revealed through interesting variation tendencies of exchange rates of 14-s-14.
Co-reporter:Xi-an Mao, Ning Li, Jiezhen Mao, Qiurong Li, Nan Xiao, Bin Jiang, Ling Jiang, Xu-xia Wang, Maili Liu
Journal of Magnetic Resonance 2012 214() pp: 352-359
Publication Date(Web):
DOI:10.1016/j.jmr.2011.11.019
Co-reporter:Yan Jiang, Hong Chen, Shizhen Mao, Pingya Luo, Youru Du, and Maili Liu
The Journal of Physical Chemistry B 2011 Volume 115(Issue 9) pp:1986-1990
Publication Date(Web):February 14, 2011
DOI:10.1021/jp107858y
The dynamics of mixed surfactants in aqueous solution has been studied at a molecular level by nuclear magnetic resonance (NMR) spectroscopy. The line widths and line shapes of the resonance peaks of two types of binary mixed surfactant systems, ionic/nonionic mixed solutions (12-2-12/TX-100, 14-2-14/TX-100, 14-2-14/Brij-35, and SDS/TX-100) and ionic/ionic mixed solutions (12-2-12/TTAB and 14-2-14/TTAB), in the 1H NMR spectra offered semiquantitative results about the influence of mixing on the surfactant exchange dynamics between monomers in aqueous solution and those in the micelles. The results showed that the exchange rates of the mixed surfactants were enhanced by each other for the three cationic/nonionic mixed solutions, while the exchange rates were lowered by each other for the two cationic/cationic mixed solutions. As for SDS/TX-100 mixed systems, the addition of SDS made the exchange rate of TX-100 in solution faster, while TX-100 made the exchange rate of SDS slower. These results provide some information about surfactant interaction in mixed solutions.
Co-reporter:Bin Jiang, Xianwang Jiang, Nan Xiao, Xu Zhang, Ling Jiang, Xi-an Mao, Maili Liu
Journal of Magnetic Resonance 2010 Volume 204(Issue 1) pp:165-168
Publication Date(Web):May 2010
DOI:10.1016/j.jmr.2010.02.009
For multidimensional NMR method, indirect dimensional non-uniform sparse sampling can dramatically shorten acquisition time of the experiments. However, the non-uniformly sampled NMR data cannot be processed directly using fast Fourier transform (FFT). We show that the non-uniformly sampled NMR data can be reconstructed to Cartesian grid with the gridding method that has been wide applied in MRI, and sequentially be processed using FFT. The proposed gridding-FFT (GFFT) method increases the processing speed sharply compared with the previously proposed non-uniform Fourier Transform, and may speed up application of the non-uniform sparse sampling approaches.
Co-reporter:Jingjing Wang, Xu Zhang, Peng Sun, Xianwang Jiang, Bin Jiang, Chunyang Cao, Maili Liu
Journal of Magnetic Resonance 2010 Volume 206(Issue 2) pp:205-209
Publication Date(Web):October 2010
DOI:10.1016/j.jmr.2010.07.007
As an effective method for solvent suppression, WATERGATE is widely used in high resolution NMR spectroscopy. It is usually composed of a number of pulses separated by constant intervals. However, theoretical and experimental analyses indicate that narrower bandwidth and lower intensities around the secondary suppression points occur in the excitation profile of the composite WATERGATE. The excitation profile distortion is caused by the chemical shift evolution during the RF pulses. The higher the ratio of pulse duration to the inter-pulse delay is, the severer the profile distorts. Therefore, in high magnetic fields, the effect will be serious when WATERGATE is applied to some biological samples whose resonances distribute over a wide range. As can be seen obviously by applying WATERGATE to detect a RNA–protein mixture sample in an 800 MHz spectrometer, the resonances of the imino protons were partially suppressed by showing decreased intensities, though the intended secondary suppression points were set far away from them. In this article, we proposed an optimized WATERGATE that could effectively compensate the chemical shift evolution during the RF pulses, and relieve the excitation profile distortion. The optimized experiment will be a good way to retain the imino signal intensities when WATERGATE is applied to detect the RNA samples in high magnetic field.
Co-reporter:Haipeng Jiang;Hanjun Fang;Ling Jiang;Limin Zheng;Nian Wang;Anmin Zheng;Feng Deng; Dr. Maili Liu
Chinese Journal of Chemistry 2010 Volume 28( Issue 11) pp:2281-2286
Publication Date(Web):
DOI:10.1002/cjoc.201090377
Abstract
Resveratrol (3,5,4′-trihydroxylstilbene), a phytoalexin in response to injury or fungal attack, is found in grapes and other food products. It has been well documented that the compound has beneficial effects as hypolipidemic, anticancer, antiviral, neuroprotective, antiaging, and anti-inflammatory natural active principle. It was observed that both trans- and cis-resveratrols undergo hydrogen-deuterium (H/D) exchange at H-2,6 and H-4 positions of the A-ring. The exchange rates were determined by 1H NMR spectroscopy. The results reveal that the exchange rates are configuration and pH dependent. Derivative of 2-O-β-D-glucoside can significantly speed up the H/D exchange reactions for both isomers. The trans-resveratrol experiences faster H/D exchanging than the cis-resveratrol. Such isomeric effect is possibly due to the factor that the trans-resveratrol is in favor of forming larger/super conjugative system and has less spatial interference. Theoretical calculation shows that electronegativity at these positions is in the order of H-2,6>H-4, which is in consistent with the exchange rates observed by NMR. The results may be of help in understanding the properties of resveratrol, and in analysis of resveratrol in natural products or body fluids using mass spectroscopy that occasionally requires stable deuterium isotope labeling.
Co-reporter:Xiaohong Cui, Yan Jiang, Chunsheng Yang, Xingyu Lu, Hong Chen, Shizhen Mao, Maili Liu, Hanzhen Yuan, Pingya Luo and Youru Du
The Journal of Physical Chemistry B 2010 Volume 114(Issue 23) pp:7808-7816
Publication Date(Web):May 19, 2010
DOI:10.1021/jp101032z
This article provides a full description of the mixed micelle formation process at a molecular level. The mechanism of mixed micelle formation in binary surfactant aqueous solution systems, ionic/nonionic mixed systems (12-2-12/TX-100, 14-2-14/TX-100, and SDS/TX-100), and ionic/ionic mixed systems (12-2-12/TTAB, 14-2-14/TTAB, and SDS/CTAB), in heavy water solutions was studied by 1H NMR spectroscopy. The critical micellization concentrations of each individual component in the mixed surfactant solutions were gained by analyzing changes in chemical shift and intensities of resonance peaks. The chemical shift changes indicated that in the 12-2-12/TX-100 and SDS/TX-100 systems, micelles of TX-100 formed first, and then 12-2-12 or SDS molecules were fused in the micelles, respectively, which has been proved by 2D NOESY experiments. In contrast, 14-2-14 was the first component to form the micelles in the 14-2-14/TX-100 system. Although 12-2-12 and 14-2-14 are analogs and differ only in the length of the hydrophobic chain by two methylene groups, they showed different behaviors in the micellization processes in the mixture with TX-100. The observation suggests that in the binary surfactant system under current study, the component with lower cmc in the mixed solution aggregates first; then, the other one fuses, resulting in the mixed micelles as the total concentration increases. The same results were obtained for the ionic/ionic solutions, 12-2-12/TTAB, 14-2-14/TTAB, and SDS/CTAB. The above results suggest that the two mixed surfactants do not aggregate synchronously. It obviously demonstrates that the so-called “cmc of the mixed surfactant solution” needs reconsideration.
Co-reporter:Xin Zhou, Xianping Sun, Jun Luo, Mingsheng Zhan, Maili Liu
Journal of Magnetic Resonance 2009 Volume 196(Issue 2) pp:200-203
Publication Date(Web):February 2009
DOI:10.1016/j.jmr.2008.11.006
A theoretical approach to quantitatively estimate the spin polarization enhancement via spin polarization-induced nuclear Overhauser effect (SPINOE) in solid state is presented. We show that theoretical estimates from the model are in good agreement with published experimental results. This method provides a straightforward way to predict the enhanced factor of nuclear magnetic resonance signals in solid state experiments.
Co-reporter:Shengan XIA;Huilang LIU;Hang ZHU;Zhiming ZHOU;Xu ZHANG
Chinese Journal of Chemistry 2009 Volume 27( Issue 4) pp:751-758
Publication Date(Web):
DOI:10.1002/cjoc.200990124
Abstract
An NMR-based metabonomic approach was used to examine rat's urinary response to dosage of triptolide (TP), a major component responsible for the immunosuppressive and anti-inflammatory effects of Tripterygium wilfordii Hook F (TWHF). The urine samples of Wistar rats were collected at various time intervals before and after dosage of TP (i.p.) and measured using conventional 1H NMR spectroscopy. The data were statistically analyzed using a principle component analysis (PCA). The results showed that biochemical variation induced by TP was time-related, and the maximal alteration in the metabolites appeared at 16 h, and partially recovered 56 h later after dosage. Increment in relative concentrations of taurine, creatine, trimethylamine N-oxide and decrement in citrate, succinate, 2-oxoglutarate and hippurate were observed in the urine after dosage of TP. In addition, 2'-deoxycytidine appeared 0–16 h later after the dosage, which may be considered as another biomarker for the acute hepatotoxicity. It suggested that TP may disturb the metabolism of energy and gut microflora, and may cause acute liver lesion and a slight renal impair. These results were also supported by the conventional analysis of clinical plasma chemistry and histopathology. The information observed in this article may be useful for giving insight into mechanism of liver injury induced by TP.
Co-reporter:Yan Jiang, Xing-Yu Lu, Hong Chen, Shi-Zhen Mao, Mai-Li Liu, Ping-Ya Luo and You-Ru Du
The Journal of Physical Chemistry B 2009 Volume 113(Issue 24) pp:8357-8361
Publication Date(Web):May 14, 2009
DOI:10.1021/jp902419u
Three kinds of conventional surfactants, namely, two nonionic surfactants [polyethylene glycol (23) lauryl ether (Brij-35) and Triton X-100 (TX-100)], one cationic surfactant [n-tetradecyltrimethyl ammonium bromide (TTAB)], and an anionic surfactant [sodium n-dodecyl sulfate (SDS)}, were mixed into the quaternary ammonium gemini surfactant [C14H29N+(CH3)2]2(CH2)2·2Br− (14−2−14) in aqueous solution. The exchange rate constants between 14−2−14 molecules in the mixed micelles and those in the bulk solution were detected using two nuclear magnetic resonance (NMR) methods: one-dimensional (1D) line shape analysis and two-dimensional (2D) exchange spectroscopy (EXSY). The results obtained from these two methods were consistent. Both showed that mixing a nonionic conventional surfactant, either Brij-35 or TX-100, enhanced the exchange process between the 14−2−14 molecules in the mixed micelles and those in the bulk solution. In contrast, the anionic surfactant SDS and the cationic surfactant TTAB slowed the process slightly.
Co-reporter:Bin Jiang, Nan Xiao, Huili Liu, Zhiming Zhou, Xi-an Mao and Maili Liu
Analytical Chemistry 2008 Volume 80(Issue 21) pp:8293
Publication Date(Web):October 9, 2008
DOI:10.1021/ac8015455
In quantitative analysis, inverse gated 1H decoupled 13C NMR provides higher resolution than 1H NMR. However, due to the lower sensitivity and longer relaxation time, 13C NMR experiment takes much longer time to obtain a spectrum with adequate signal-to-noise ratio. The sensitivity can be enhanced with DEPT and INEPT approaches by transferring polarization from 1H (I) to 13C (S), but since the enhancements depend on coupling constants (1JSI) and spin systems (SI, SI2, SI3), the enhancements for different spin systems are not uniform and quantitative analyses are seriously affected. To overcome these problems, Henderson proposed a quantitative DEPT (Q-DEPT) method by cycling selected read pulse angles and polarization-transfer delays (Henderson, T. J. J. Am. Chem. Soc. 2004, 126, 3682−3683), and satisfactory results for SI system are achieved. However, the optimization is incomplete for the SI2 and SI3 systems. Here, we present an improved version of Q-DEPT (Q-DEPT+) and a quantitative POMMIE (Q-POMMIE) where the cyclic delays and read pulse phases are applied. The improved methods prove to be suitable for all spin systems over a large J-coupling range (90−230 Hz), and the 13C signals are nearly equally enhanced with standard deviation less than 5%.
Co-reporter:Bin Jiang, Huili Liu, Maili Liu, Chaohui Ye, Xian Mao
Chemical Physics 2008 Volume 351(1–3) pp:33-36
Publication Date(Web):3 July 2008
DOI:10.1016/j.chemphys.2008.03.027
Abstract
It has been well accepted that the double quantum (DQ) correlated-spectroscopy revamped by asymmetric z-gradient echo detection (CRAZED) signal is enveloped in the profile function t2 exp [−(t2 + 2t1)/T2], but this function is too simple to describe the spin echo characteristics of the CRAZED free induction decay signal. In this paper the DQ CRAZED experiment is analyzed by including the homogeneous and inhomogeneous broadening effects, and a formula for the time domain DQ CRAZED signal is obtained. This formula includes the chemical shift echo and the inhomogeneous echo, both appearing at t2 = 2t1. Experiments have confirmed the theory.
Co-reporter:Xiao-Yan Yang;Hong Chen;Gong-Zhen Cheng;Shi-Zhen Mao
Colloid and Polymer Science 2008 Volume 286( Issue 6-7) pp:639-646
Publication Date(Web):2008 June
DOI:10.1007/s00396-007-1804-8
The characteristics of N,N′-bis(cetyldimethyl)-α,ω-alkane (propane and butane) diammonium dibromide (16-3-16 and 16-4-16) aqueous solutions were studied by one- and two-dimensional 1H nuclear magnetic resonance (NMR). The measurements of self-diffusion coefficient and inter-proton distance at 318 K suggest that 16-3-16 spherical micelles are formed in the dilute solution at a concentration of 0.26 mmol/l and the polar head groups of the surfactant are in a saw-toothed form staying at the surface of the micelle to overcome the strong electrostatic repulsion force. Relaxation measurements obviously show that the spacer chain is rigid in the surface layer of the hydrophobic micellar core, and the side alkyl chains of 16-3-16 are packed more tightly than those of 16-4-16 in the micellar core. The line-shape analysis of the methyl protons at the end of the side alkyl chain of 16-3-16 and 16-4-16 suggests that two possible momentary morphologies of their side alkyl chains are situated in the micelle, respectively.
Co-reporter:Xiaohong Cui, Shizhen Mao, Maili Liu, Hanzhen Yuan and Youru Du
Langmuir 2008 Volume 24(Issue 19) pp:10771-10775
Publication Date(Web):August 26, 2008
DOI:10.1021/la801705y
The mechanism of micelle formation of surfactants sodium dodecyl sulfate (SDS), n-hexyldecyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) in heavy water solutions was studied by 1H NMR (chemical shift and line shape) and NMR self-diffusion experiments.1H NMR and self-diffusion experiments of these three surfactants show that their chemical shifts (δ) begin to change and resonance peaks begins to broaden with the increase in concentration significantly below their critical micelle concentrations (cmcʼs). At the same time, self-diffusion coefficients (D) of the surfactant molecules decrease simultaneously as their concentrations increase. These indicate that when the concentrations are near and lower than their cmcʼs, there are oligomers (premicelles) formed in these three surfactant systems. Carefully examining the dependence of chemical shift and self-diffusion coefficient on concentration in the region just slightly above their cmcʼs, one finds that the pseudophase transition model is not applicable to the variation of physical properties (chemical shift and self-diffusion coefficient) with concentration of these systems. This indicates that premicelles still exist in this concentration region along with the formation of micelles. The curved dependence of chemical shift and self-diffusion coefficient on the increase in concentration suggests that the premicelles grow as the concentration increases until a definite value when the size of the premicelle reaches that of the micelle, i.e., the system is likely dominated by the monomers and micelles. Additionally, the approximate values of premicelle coming forth concentration (pmc) and cmc were obtained by again fitting chemical shifts to reciprocals of concentrations at a different perspective, and are in good accordant with experimental results and literature values and prove the former conclusion.
Co-reporter:Zhiming Zhou, Wenxian Lan, Weinong Zhang, Xu Zhang, Sheng’an Xia, Hang Zhu, Chaohui Ye, Maili Liu
Journal of Chromatography A 2007 Volume 1154(1–2) pp:464-468
Publication Date(Web):22 June 2007
DOI:10.1016/j.chroma.2007.04.018
Directly coupled HPLC-NMR has become a powerful tool for separation and structural elucidation of unknown compounds. However, there are only a few reports on application of on-flow two-dimensional (2D) NMR in HPLC-NMR. Here we present an alternative method for recording real-time 2D-NMR spectrum (total correlation spectroscopy, TOCSY) on a commercial HPLC-NMR system. The method is based on well-established Hadamard matrix for 2D-NMR frequency encoding. In addition, a modified/improved solvent suppression approach is incorporated. This makes it possible to carry out the experiment with both polar and gradient eluents, the widely used chromatographic conditions. The method is exampled using a synthesized mixture of three amino acids (His, Phe and Try) and a human urine sample. The method demonstrated here may be utilized for high-throughput structural or unknown component identification and fast dynamic study in a variety of applications.
Co-reporter:Wenxian Lan, Hang Zhu, Zhiming Zhou, Chaohui Ye, Maili Liu
Chemistry and Physics of Lipids 2007 Volume 148(Issue 2) pp:105-111
Publication Date(Web):August 2007
DOI:10.1016/j.chemphyslip.2007.04.012
A large number of studies indicate that oxidative modification of plasma lipoproteins, especially low-density lipoprotein (LDL), is a critical factor in initiation and progression of atherosclerosis. We have previously found that ibuprofen (IBP), a potential antioxidant drug to inhibit LDL oxidation, interacted with lipoproteins in intact human plasma. In the present study, we compare the binding affinities of IBP to LDL and HDL (high-density lipoprotein) by 1H NMR spectroscopy. When IBP is added into the HDL and LDL samples, the N+(CH3)3 moieties of phosphatidylcholine (PC) and sphingomyelin (SM) in lipoprotein particles experience the chemical shift up-field drift. Intermolecular cross-peaks observed in NOESY spectra imply that there are direct interactions between ibuprofen and lipoproteins at both hydrophobic and hydrophilic (ionic) regions. These interactions are likely to be important in the solubility of ibuprofen into lipoprotein particles. Ibuprofen has higher impact on the PC and SM head group (N+(CH3)3) and (CH2)n group in HDL than that in LDL. This could be explained by either IBP has higher binding affinity to HDL than to LDL, or IBP induces orientation of the phospholipid head group at the surface of the lipoprotein particles.
Co-reporter:Yuan-Yuan Du;Guo-Yun Bai;Xu Zhang;Mai-Li Liu
Chinese Journal of Chemistry 2007 Volume 25(Issue 7) pp:
Publication Date(Web):16 JUL 2007
DOI:10.1002/cjoc.200790181
A combination of 1H nuclear magnetic resonance (NMR) spectroscopy and principal component analysis (PCA) has shown the potential for being a useful method for classification of type, production origin or geographic origin of wines. In this preliminary study, twenty-one bottled wines were classified/separated for their location of production in Shacheng, Changli and Yantai, and the types of the blended, medium dry, dry white and dry red wines, using the NMR-PCA method. The wines were produced by three subsidiary companies of an enterprise according to the same national standard. The separation was believed to be mainly due to the fermentation process for different wines and environmental variations, such as local climate, soil, underground water, sunlight and rainfall. The major chemicals associated with the separation were identified.
Co-reporter:Fang Li;Ling Jiang;Jing Nie;Yuqi Feng;Weinong Zhang;Huiting Zhang;Minghui Yang
Magnetic Resonance in Chemistry 2007 Volume 45(Issue 11) pp:929-936
Publication Date(Web):18 SEP 2007
DOI:10.1002/mrc.2072
Valsartan (1), an antihypertensive drug of the sartan family, and three related compounds, 3-methyl-2-((2′-(1-methyl-1H-tetrazol-5-yl)biphenyl-4-ylmethyl) pentanoylamino)butyric acid (2), 3-isopropyl-6-propyl-4-(2′-(1H-tetrazol-5-yl)biphenyl-4-ylmethyl) morpholine-2,5-dione (3), and 3-isopropyl-6-propyl-4-(4′-(1H-tetrazol-5-yl)biphenyl4-ylmethyl) morpholine-2,5-dione (4), were studied by nuclear magnetic resonance (NMR) spectroscopy. Assignment of 1H and 13C NMR resonances for the compounds were completed using COSY, HSQC and HMBC techniques. It was found that each of the compounds 1, 2, and 4 had two sets of 1H and 13C resonances, suggesting the presence of two conformers in solution. Based on NOESY experiments at different temperatures, thermodynamic parameters of the conformational exchange process were deduced for these compounds. The exchange barrier was found to be 17.9 ± 0.7, 18.5 ± 0.8, and 17.7 ± 0.6 kcal mol−1 with the corresponding free energy difference (ΔG) of 0.32 ± 0.04, 0.23 ± 0.01, and 0.13 ± 0.04 kcal mol−1 for 1, 2, and 4, respectively, at 298 K. Two conformations of valsartan were elucidated by NMR spectroscopy and quantum chemistry calculation. The results showed that two conformers of valsartan interchange via rotation about the C(O)N bond. Copyright © 2007 John Wiley & Sons, Ltd.
Co-reporter:Ai-Hong Liu;Shi-Zhen Mao;Mai-Li Liu;Yu-Xi Zhang
Colloid and Polymer Science 2007 Volume 285( Issue 4) pp:381-388
Publication Date(Web):2007 January
DOI:10.1007/s00396-006-1580-x
A novel acrylamide/methacrylic acid template copolymer was prepared using polyallylammonium chloride (PAAC) as a template. This copolymer contains acrylamide (PAM), phenoxy acrylate (POA), and acylic acid (PAA) blocks. The investigation by high resolution nuclear magnetic resonance (1H NMR) shows that intramolecular hydrogen bonds between the PAM and PAA blocks lead to compact molecular arrangement at quite low pH values, and the motion of the phenoxy side chain of the POA blocks is somewhat restricted. With the increase in pH value of the solution, the carboxylic acid of the PAA block gradually dissociates, which weakens hydrogen bonds between the PAM and PAA blocks. The decrease in Dw, self-diffusion coefficient of water, indicates the growth in aggregate size of the template copolymer. The cross peaks between amide protons and backbone protons shown in 2D nuclear overhauser spectroscopy (NOESY) spectra imply the existence of the intermolecular hydrogen bonding interaction between PAM and PAA blocks. After the carboxylic acid of the PAA block is completely dissociated in alkaline solution, the electrostatic repulsion of the carboxylic ion makes the molecular chain of the copolymer exhibit more outstretched. Consequently, the phenoxy groups (the side chain of the POA block) have more space to move.
Co-reporter:Guoyun Bai, Yanfang Cui, Yunhuang Yang, Chaohui Ye, Maili Liu
Journal of Pharmaceutical and Biomedical Analysis 2005 Volume 38(Issue 4) pp:588-593
Publication Date(Web):15 July 2005
DOI:10.1016/j.jpba.2004.12.037
A competitive low-affinity binding model was proposed for determining the number of mutual (overlapped) and specific binding sites of two ligands (A, B) on a protein (P). To use the model, one needs to carry out a titration experiment by adding either ligand A or B into a three-component system (A–B–P), and to monitor the spectroscopic parameter changes. Fitting the titration curve to the proposed model, one can get the mutual and specific binding sites of the two ligands on the protein. The model was examined by using human serum albumin (HSA) as a receptor and tolmetin (TOL) and salicylic acid (SAL) as ligands. Proton longitudinal relaxation rates (R1) were measured on a 500-MHz NMR spectrometer during the titration and used to derive the mutual binding sites. It was found that among the binding sites of 32 ± 4 for SAL and 28 ± 2 for TOL on HSA, there were 17 ± 5 mutual sites for the two ligands. This result indicates that, although HSA has large binding capacities for most ligands, there are still a reasonable amount of the low-affinity binding sites that are structure selective.
Co-reporter:Yunhuang Yang, Guoyun Bai, Xu Zhang, Chaohui Ye, Maili Liu
Analytical Biochemistry 2004 Volume 324(Issue 2) pp:292-297
Publication Date(Web):15 January 2004
DOI:10.1016/j.ab.2003.10.002
Recent studies have suggested that ibuprofen inhibits low-density lipoprotein oxidation in a high dose-dependent manner and is a promising drug for treatment of the conditions associated with atherosclerosis. In this article, we present the NMR spectroscopic evidence for the interaction between ibuprofen and phospholipids in lipoprotein particles in intact human plasma. Ibuprofen caused chemical shift upfield drifts for the protons of –N+(CH3)3 moieties of phosphatidylcholine and sphingomyelin, olefinic chains (–CHCH–, –CHCHCH2CHCH–, –(CH2)nCH2CH), and (CH2)n and CH3 groups, from unsaturated lipids in lipoprotein particles. The ibuprofen may interact directly with the above-mentioned groups of phospholipids or induce structural changes in the lipoproteins. This may shed light on the mechanism by which the drug protects against oxidative modification of lipoproteins.
Co-reporter:Maili Liu;Jeremy K. Nicholson;John C. Lindon;Huiru Tang
Magnetic Resonance in Chemistry 2002 Volume 40(Issue 13) pp:S83-S88
Publication Date(Web):8 NOV 2002
DOI:10.1002/mrc.1121
The 1H NMR spectra of human blood plasma show, inter alia, prominent resonances from the methyl and methylene groups of the fatty acyl chains from the triglycerides, phospholipids and cholesteryl esters of lipoproteins. Each band shows some degree of peak resolution due to chemical shift differences between the lipoprotein fractions, namely very low-density lipoprotein (VLDL), low-density lipoprotein (LDL) and high-density lipoprotein (HDL). In order to assign resonances within the NMR bands to individual lipoproteins, previous studies relied upon the measurement of pure fractions obtained by ultracentrifugation. Here a new approach was used where the lipoprotein peaks in the NMR spectrum were deconvolved mathematically and the area of each sub-peak was monitored using an NMR pulse sequence to yield the diffusion coefficient relating to each sub-peak and hence to each type of lipoprotein. The validity of the deconvolution results was confirmed by comparison of 1H NMR spectra measured at 600 and 800 MHz. The diffusion coefficient is directly related to the hydrodynamic radius of the particle and hence provides an unambiguous assignment. The derived diffusion coefficients of the lipoprotein fractions therefore provide a direct assignment of the NMR bands and also give a measure of lipoprotein particle size, the results being in agreement with those from conventional measurements. Copyright © 2002 John Wiley & Sons, Ltd.
Co-reporter:Mudasir Majeed, Abdullah I. Hussain, Shahzad A.S. Chatha, Muhammad K.K. Khosa, ... Maili Liu
Saudi Journal of Biological Sciences (May 2016) Volume 23(Issue 3) pp:389-396
Publication Date(Web):1 May 2016
DOI:10.1016/j.sjbs.2015.04.010
In the present work, the response surface methodology (RSM) based on a central composite rotatable design (CCRD), was used to determine optimum conditions for the extraction of antioxidant compounds from Origanum vulgare leaves. Four process variables were evaluated at three levels (31 experimental designs): methanol (70%, 80%, and 90%), the solute:solvent ratio (1:5, 1:12.5, 1:20), the extraction time (4, 10, 16 h), and the solute particle size (20, 65, 110 micron). Using RSM, a quadratic polynomial equation was obtained by multiple regression analysis for predicting optimization of the extraction protocol. Analysis of variance (ANOVA) was applied and the significant effect of the factors and their interactions were tested at 95% confidence interval. The antioxidant extract (AE) yield was significantly influenced by solvent composition, solute to solvent ratio, and time. The maximum AE was obtained at methanol (70%), liquid solid ratio (20), time (16 h), and particle size (20 micron). Predicted values thus obtained were closer to the experimental value indicating suitability of the model. Run 25 (methanol:water 70:30; solute:solvent 1:20; extraction time 16 h and solute particle size 20) showed highest TP contents (18.75 mg/g of dry material, measured as gallic acid equivalents) and DPPH radical scavenging activity (IC50 5.04 μg/mL). Results of the present study indicated good correlation between TP contents and DPPH radical scavenging activity. Results of the study indicated that phenolic compounds are powerful scavengers of free radical as demonstrated by a good correlation between TP contents and DPPH radical scavenging activity.
Co-reporter:He Deng, Xianping Sun, Maili Liu, Chaohui Ye, Xin Zhou
Pattern Recognition (January 2017) Volume 61() pp:66-77
Publication Date(Web):1 January 2017
DOI:10.1016/j.patcog.2016.07.036
•We present an adaptive entropy-based window selection scheme.•The novel local difference measure map can keep low false alarm rates under the same probability of detection.•The proposed method is simple and effective with regard to detection accuracy.Dim and small target detection in complex background is considered a difficult and challenging problem. Conventional algorithms using the local difference/mutation possibly produce high missed or mistaken detection rates. In this paper, we propose an effective algorithm for detecting dim and small infrared targets. In order to synchronously enhance targets and suppress complex background clutters, we adopt an adaptive entropy-based window selection technique to construct a novel local difference measure (LDM) map of an input image, which measures the dissimilarity between the current region and its neighboring ones. In this way, the window size can be adaptively regulated according to local statistical properties. Compared with the original image, the LDM map has less background clutters and noise residual. This guarantees the lower false alarm rates under the same probability of detection. Subsequently, a simple threshold is used to segment the target. More than 600 dim and small infrared target images against different complex and noisy backgrounds were utilized to validate the detection performance of the proposed approach. Extensive experimental results demonstrate that the proposed method not only works more stably for different target movements and signal-to-clutter ratio values, but also has a better performance compared with classical baseline methods. The evaluation results suggest that the proposed method is simple and effective with regard to detection accuracy.
Co-reporter:Sen Wang, Peng Sun, Rongrong Zhang, Ang Lu, Maili Liu and Lina Zhang
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 11) pp:NaN7490-7490
Publication Date(Web):2017/02/20
DOI:10.1039/C6CP08744B
As a breakthrough to the traditional 1H diffusometry, the interaction of cations with cellulose is investigated via7Li and 23Na PFG-SE NMR. The diffusion coefficient of Li+ decreases more than that of Na+ with the addition of cellulose, which indicates a stronger binding of LiOH with the macromolecule. Therefore, a new, facile, accurate and repeatable method to characterize ion/polymer interactions is established.
![Gadolinate(1-),[1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetato(4-)-kN1,kN4,kN7,kN10,kO1,kO4,kO7,kO10]-, sodium (9CI)](http://img.cochemist.com/ccimg/93000/92923-44-9.png)
![Gadolinate(1-),[1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetato(4-)-kN1,kN4,kN7,kN10,kO1,kO4,kO7,kO10]-, sodium (9CI)](http://img.cochemist.com/ccimg/93000/92923-44-9_b.png)
![3,5,8-Trioxa-4-phosphahexacos-17-en-1-aminium,4-hydroxy-N,N,N-trimethyl-9-oxo-7-[[(1-oxohexadecyl)oxy]methyl]-, inner salt,4-oxide, (7R,17Z)-](http://img.cochemist.com/ccimg/26900/26853-31-6.png)
![3,5,8-Trioxa-4-phosphahexacos-17-en-1-aminium,4-hydroxy-N,N,N-trimethyl-9-oxo-7-[[(1-oxohexadecyl)oxy]methyl]-, inner salt,4-oxide, (7R,17Z)-](http://img.cochemist.com/ccimg/26900/26853-31-6_b.png)
![Ferrate(2-), [7,12-diethenyl-3,8,13,17-tetramethyl-21H,23H-porphine-2,18-dipropanoato(4-)-κN21,κN22,κN23,κN24]-, hydrogen (1:2), (SP-4-2)-](/data/chemimg/522800/14875-96-8.png)
![Ferrate(2-), [7,12-diethenyl-3,8,13,17-tetramethyl-21H,23H-porphine-2,18-dipropanoato(4-)-κN21,κN22,κN23,κN24]-, hydrogen (1:2), (SP-4-2)-](/data/chemimg/522800/14875-96-8_b.png)
