Detection of natural abundance 1H-13C correlations of cholesterol in its membrane environment using a gradient enhanced HSQC experiment under high resolution magic angle spinning

The quality and signal to noise ratio of a J-based HETCOR performed on a standard MAS probe have been compared with a gradient enhanced HSQC performed on a HR-MAS probe at 500 MHz. The sample selected was cholesterol, inserted at 30 mol% in acyl chain deuterated phospholipids (DMPC-d54), at a temperature where the bilayer is in a liquid crystalline phase (310 K). It is representative of any rigid molecule undergoing fast axial diffusion in a bilayer as the main movement. After optimization of the spinning rate and carbon decoupling conditions, it is shown that the ge-HSQC/MAS approach is far superior to the more conventional J-HETCOR/MAS in terms of signal to noise ratio, and that it allows the detection of all the natural abundance cross peaks of cholesterol in a membrane environment. Clear differences between the 1H and 13C chemical shifts of cholesterol in a membrane and in chloroform solution were thus revealed.     

硫酸交联壳聚糖湿膜的13C CP MAS NMR研究

首次采用¹³C CP MAS NMR技术对接近膜分离状态时的湿膜进行研究.结果表明:温膜的分子构象和分子运动能较全面地反映出膜的分离特性,弱的交联以及过快或过慢的分子运动均不利于膜的分离.     

硫酸交联壳聚糖干膜的13C CP MAS NMR研究

以不同浓度硫酸交联的壳聚糖干膜为研究对象,在国内首次采用¹³C CP MAS NMR技术从分子水平上对壳聚糖膜的结构进行研究,结果表明干膜壳聚糖分子的构象能直观地反映出膜的交联状况,交联状况与膜的分离性能密切相关,但仅对干膜的考察还不够全面.     

雷公藤精（Wilforgine）的2D NMR研究

用２Ｄ ＮＭＲ（＾１Ｈ－＾１ＨＣＯＳＹ，＾１Ｈ－＾１３Ｃ ＣＯＳＹ，ＴＯＣＳＹ，ＮＯＥＳＹ和ＣＯＬＯＣ）技术研究了从雷公藤中分离到的雷公藤精，对＾１Ｈ和＾１３Ｃ谱进行了归属。     

1H-1H double-quantum CRAMPS NMR at very-fast MAS (nuR=35 kHz): a resolution enhancement method to probe 1H-1H proximities in solids

A High-resolution two-dimensional (2D) (1)H double-quantum (DQ) homonuclear recoupling experiments, combined with smooth amplitude-modulation (SAM) homonuclear decoupling is presented. The experiment affords highly resolved and clean (1)H DQ-SQ 2D spectra at very-fast MAS rates (nu(R)=35 kHz). The method is well suited to probe (1)H-(1)H distances in powdered solids and demonstrations are applied on a NaH(2)PO(4) powdered sample, an inorganic compound having hydrogen bonding networks.     

2D(13)C-(13)C MAS NMR correlation spectroscopy with mixing by true (1)H spin diffusion reveals long-range intermolecular distance restraints in ultra high magnetic field

An improved 2D (13)C-(13)C CP(3) MAS NMR correlation experiment with mixing by true (1)H spin diffusion is presented. With CP(3), correlations can be detected over a much longer range than with direct (1)H-(13)C or (13)C-(13)C dipolar recoupling. The experiment employs a (1)H spin diffusion mixing period tau(m) sandwiched between two cross-polarization periods. An optimized CP(3) sequence for measuring polarization transfer on a length scale between 0.3 and 1.0 nm using short mixing times of 0.1 ms < tau(m) < 1 ms is presented. For such a short tau(m), cross talk from residual transverse magnetization of the donating nuclear species after a CP can be suppressed by extended phase cycling. The utility of the experiment for genuine structure determination is demonstrated using a self-aggregated Chl a/H(2)O sample. The number of intramolecular cross-peaks increases for longer mixing times and this obscures the intermolecular transfer events. Hence, the experiment will be useful for short mixing times only. For a short tau(m) = 0.1 ms, intermolecular correlations are detected between the ends of phytyl tails and ring carbons of neighboring Chl a molecules in the aggregate. In this way the model for the structure, with stacks of Chl a that are arranged back to back with interdigitating phytyl chains stretched between two bilayers, is validated.     

TRANILAST ^1H^13CNMR谱分析及其结构的鉴定

本文用COSY,CHCOR等二维核磁共振技术对TRANILAST,2[]3-(3.4-二甲基苯基)1-氧代-2-丙烯基]氨基]苯甲到进行了~1H、~(13)C NMR谱数据分析及归属,并结合~(13)C弛豫时间T_1 及变温实验对合成产品进行了结构鉴定.     

植物油的1H NMR和13C NMR的测定

油酸和亚油酸,是人体必需的营养成份,具有抗癌,防止动脉硬化,降脂减压等作用,因而它们在治疗一些癌症及减肥降血脂等方面取得了较好的疗效^[1-3]。通常油酸,亚油酸和其他脂肪酸以甘油酯的形式,大量地存在于植物油中。本文用¹H NMR测定了5种植物油各组峰面积积分,按文献[4]扣除法,整理了各组峰的积分值,计算出油脂中每摩尔所含各功能团的个数,不饱和度,酯化度等数据。此外,还记了豆油和茶油的¹³C NMR谱,从这两种谱图相关谱线积分值推算出各功能团与甲基基团的比率与¹H NMR谱所得结果接近。并计算出,上述两种油中所含脂肪酸甘油酯和各种不饱和脂肪酸甘油酯的克分子百分数。对测得CCH₂C基团质子自旋晶格弛豫时间T₁进行分析后,给出一经验公式来予以拟合,计算结果与测定值吻合。这一事实说明,油脂中各种组分克分子百分数的计算是可以信赖的。     

雷公藤内酯酮的2D NMR研究

从雷公藤根皮中分离出一种含三个环氧基的二萜内酯酮化合物(Ⅰ),利用一维和二维NMR技术,通过对¹H和¹³C NMR谱的分析,归属了所有和¹H和¹³C化学位移。     

Optimization of three-dimensional TROSY-type HCCH NMR correlation of aromatic (1)H-(13)C groups in proteins.

Improved methods for three-dimensional TROSY-Type HCCH correlation involving protons of negligible CSA are presented. The TROSY approach differs from the conventional approach of heteronuclear decoupling in evolution and detection periods by not mixing fast and slowly relaxing coherences and usually suppressing the former. Pervushin et al. (J. Am. Chem. Soc. 120, 6394-6400 (1998)) have proposed a 3D TROSY-type HCCH experiment where the TROSY approach is applied only in one of the (13)C dimensions. A new pulse sequence applying the TROSY approach in both indirect dimensions is advantageous when the TROSY effect of the carbons is large or when a relatively high resolution is required. For lower resolutions or moderate TROSY effects we show that it is possible to combine the best of both worlds, namely to suppress heteronuclear couplings without mixing fast and slowly relaxing coherences while at the same time superimpose the two components and thus have both contribute to the detected signal. That is possible using the novel technique of Spin-State-Selective Time-Proportional Phase Incrementation (S(3) TPPI). The new 3D S(3) TPPI TROSY HCCH method is demonstrated on a (13)C,(15)N-labeled protein sample, RAP 18-112 (N-terminal domain of alpha(2)-macroglobulin receptor associated protein), at 750 MHz and average sensitivity enhancements of 10% are obtained for the cross peaks in comparison to methods based on conventional decoupling on one of the carbons or on TROSY on both carbons.     

一种环烯醚萜甙（8—O—acetyl—shanzhiside methylester）的2D NMR

利用二维核磁共振技术对从独一味植物中分离的的环烯醚萜甙化合物进行了＾１Ｈ和＾１３Ｃ ＮＭＲ的归属，并确定其糖与甙的接点。     

Removal of t(1) noise from metabolomic 2D (1)H-(13)C HSQC NMR spectra by Correlated Trace Denoising

The presence of t(1) noise artefacts in 2D phase-cycled Heteronuclear Single Quantum Coherence (HSQC) spectra constrains the use of this experiment despite its superior sensitivity. This paper proposes a new processing algorithm, working in the frequency-domain, for reducing t(1) noise. The algorithm has been developed for use in contexts, such as metabolomic studies, where existing denoising techniques cannot always be applied. Two test cases are presented that show the algorithm to be effective in improving the SNR of peaks embedded within t(1) noise by a factor of more than 2, while retaining the intensity and shape of genuine peaks.     

2(1H)喹啉酮化合物及其开环衍生物的13C NMR研究

本文报道了16种2(1H)喹啉酮及其开环衍生物的碳谱研究,归属了取代喹啉酮母核骨架及侧链上每个碳原子的化学位移,并就卤素取代对母核骨架碳的化学位移影响规律进行了探讨.文中所有化合物的核磁数据迄今未见文献报道.     

Satellite transitions in natural abundance solid-state (33)S MAS NMR of alums--sign change with zero-crossing of C(Q) in a variable temperature study

Experiences obtained from recent improvements in the performance of solid-state (14)N MAS NMR spectroscopy have been used in a natural abundance (33)S MAS NMR investigation of the satellite transitions for this interesting spin I=3/2 isotope. This study reports the first observation of manifolds of spinning sidebands for these transitions in (33)S MAS NMR as observed for the two alums XAl(SO(4))(2) x 12H(2)O with X=NH(4) and K. For the NH(4)-alum a variable temperature (33)S MAS NMR study, employing the satellite transitions, shows that the (33)S quadrupole coupling constant (C(Q)) exhibits a linear temperature dependence (in the range -35 degrees C to 70 degrees C) with a temperature gradient of 3.1 kHz/ degrees C and undergoes a sign change with zero-crossing for C(Q) at 4 degrees C (277 K). For the isostructural K-alum a quite similar increase in the magnitude of C(Q) with increasing temperature is observed, and with a temperature gradient of 2.3 kHz/ degrees C. Finally, for optimization purposes, a study on the effect of the applied pulse widths at constant rf field strength on the intensity and variation in second-order quadrupolar lineshape for the central (1/2<-->-1/2) transition of the K-alum has been performed.     

Assignment of the 1H and 13C NMR Chemical Shifts of (3,4-Dihydro-2H-pyran-5-yl)-oxo-acetic Acid Methyl Ester Using the Two Dimensional HMBC Technique

The identification of (3, 4-dihydro-2H-pyran-5-yl)-oxo-acetic acid methyl ester has been realized by combination of two dimensional HETCOR and HMBC techniques. ¹³C and ¹H chemical shifts asignements are described.     

苯甲亚氨酸乙酯及N—乙氧基羰基亚甲基苯甲亚氨酯乙酯的~1H和~(13)C NMR的研究

本文测定了苯甲亚氨酸乙酯(Ⅰ)和N-乙氧基羰基亚甲基苯甲亚氨酸乙酯(Ⅱ)的~1H和~(13)C NMR谱,归属了共振谱线,得到了这两类化合物的官能团在苯衍生物中的经验增量,讨论了化学位移与Hammett常数的相关性.     

Proton dynamics in letovicite, (NH4)3H(SO4)2: a 1H and 14N NMR spectroscopic study

The improper ferroelastic phase letovicite (NH₄)₃H(SO₄)₂ has been studied by ¹H MAS NMR as well as by static ¹⁴N NMR experiments in the temperature range of 296–425 K. The ¹H MAS NMR resonance from ammonium protons can be well distinguished from that of acidic protons. A third resonance appears just below the phase transition temperature which is due to the acidic protons in the paraelastic phase. The lowering of the second moment M₂ for the ammonium protons takes place in the same temperature range as the formation of domain boundaries, while the signals of the acidic protons suffer a line narrowing in the area of T_c. The static ¹⁴N NMR spectra confirm the temperature of the motional changes of the ammonium tetrahedra. Two-dimensional ¹H NOESY spectra indicate a chemical exchange between ammonium protons and the acidic protons of the paraphase.     

Structure Elucidation and Assignment of 1H and 13C Spectra of the New Fused Cyclobutane-Naphthofuran Derivative by Two-Dimensional NMR in Different Solvents

One of the major product from the photodimerization of 2-[2-(2-methyl-phenyl)ethenyl)]naphtho[2. 1-b]furan (1) is a new fused cyclobutane-naphthofuran derivative, 6-(2-methylphenyl)-1-[2-(2-methylphenyl)ethenyl]-7-(2-naphtho-[2,1-b]furyl)-3-[2,1]naphtho-2-oxabicyclo[3.2.0]hept-3-ene (2). Its ¹H and ¹³C NMR spectra were fully assigned by the application of COSY, LR COSY, NOESY, APT and HETCOR experiments in deuterated chloroform, acetone and benzene solutions.     

NOE和二维NMR技术在倍半萜化学位移归属中的应用

本文用NOE和二维核磁共振技术-COSY,C-H化学位移相关,C-H远程化学位移相关(COLOC),DEPT对二个倍半萜分子的立体化学结构进行了研究,并对其¹H和¹³C化学位移进行了归属。     

Sensitivity enhancement in (13)C solid-state NMR of protein microcrystals by use of paramagnetic metal ions for optimizing (1)H T(1) relaxation

We discuss a simple approach to enhance sensitivity for (13)C high-resolution solid-state NMR for proteins in microcrystals by reducing (1)H T(1) relaxation times with paramagnetic relaxation reagents. It was shown that (1)H T(1) values can be reduced from 0.4-0.8s to 60-70 ms for ubiquitin and lysozyme in D(2)O in the presence of 10 mM Cu(II)Na(2)EDTA without substantial degradation of the resolution in (13)C CPMAS spectra. Faster signal accumulation using the shorter (1)H T(1) attained by paramagnetic doping provided sensitivity enhancements of 1.4-2.9 for these proteins, reducing the experimental time for a given signal-to-noise ratio by a factor of 2.0-8.4. This approach presented here is likely to be applicable to various other proteins in order to enhance sensitivity in (13)C high-resolution solid-state NMR spectroscopy.