A computer-based method was used to predict ¹³C NMR chemical shifts. The method involves computation of molecular descriptors from topological and geometrical representations of molecules and selection of variables. Multiple regression analysis was used to calculate coefficients relating the descriptors to observed chemical shifts. We predicted the ¹³C chemical shifts of 45 secondary carbon centers in our data set of 22 cyclohexanes with a standard error of 1.4ppm.

Two dammarane-type triterpenoid saponins, 20(R)-ginsenoside Rg₂ and 20(S)-ginsenoside Rg₂, were isolated from stems-leaves of Panax ginseng C.A.Mey.. In this paper, all of the ¹H and ¹³C NMR chemical shifts of the two compounds were assigned through 1D NMR and 2D NMR with Pulse Field Gradient (PFG) techniques (GCOSY,GHMQC and GHMBC).

When being put into CDCl₃ (slightly acidic condition), the double bond of steroid drug (LIVIAL) will rearrange 24 hours. This paper shows that the 2D NMR techniques were successfully performed to determine the structures of compound 1 and compound 2. All of the ¹H and ¹³C NNR chemical shifts were assigned by 1D and 2D NMR. Their stereochemistry was discussed, too. The structures of compound 1 and compound 2 were simulated by computer molecular modeling. Their results agree with those of 2D NMR.

A toxin isolated from waterbloom of the colonial cyanobacterium Microcystis aeruginosa collected in a fish pond was studied by one-dimensional and two-dimensional nuclear magnetic resonance techniques. Combined with other analytical techniques, it is shown that this toxin is just microcystin-LR, the most common cyclo-heptapeptide. The connectivity of amino acids in the cyclic part of this toxin is determined.

Solid complexes of Amoxycillin with d¹⁰ configuration metal ions have been synthesized. IR,UV, and fluorescence spectra of complex compounds have been studied. The complex and the complexing mechanism have been studied by means of NMR.

The structure of β-benzene carbonic-γ-substituted benz-γ-butyrolactone was defined by means of ¹H NMR, ¹³C NMR and 2D NMR. The spectral behaviour of β benzene carbonic-γ-substituted benz-γ-butyrolactone was discussed and the reaction progress in this reaction system was also proposed.

A new triterpene saponin, arilloside D was isolated from roots of Polygala arillata and studied by the two dimensional NMR spectra including ¹H-¹1H COSY, ¹³C-¹H COSY, TOCSY and HMBC. The chemical shifts of arilloside D were assigned.

Raman magnetic resonance experiment is a useful tool for direct detection of multiple-quantum signals in one-dimensional mode. It has been shown that all possible order quantum transitions in a spin system may be detected by the method using excitation radiofrequency field with proper offset and strengths. Among these quantum transition signals the single-quantum transition signals are usually strongest. The strong single-quantum signals may cause problems in dynamic range of receiver, spectral baseline roll and phase artifacts. Thus, suppression of strong single-quantum signals is necessary to obtain a high quality Raman magnetic resonance spectrum. Here we report an RMR experiment to suppress the strong single-quantum signals by alternatively accumulating FID signals with positive and negative irradiation offsets. It follows from the analysis of the product operator formalism that the strong single-quantum signals are symmetrical about offset, that is, when irradiation offset changes from positive value to negative, the strong single-quantum signals also invert their intensities for a heteronuclear spin system. Therefore, the accumulation of FID with positive and negative irradiation offset can suppress strong single-quantum signals in RMR experiments. The RMR experiments with alternative positive and negative offset accumulation acquisition on heteronuclear AX_n(n=1,2,3) spin systems (CHCl₃,CH₂Cl₂,CH₃OH) are carried out on an ARX-500MHz spectrometer, where proton is irradiated and canbon-13 is detected. The experimental results show that the strong single-quantum signals are suppressed effectively and the multiple-quantum signals with intensity similar to those of the single-quantum signals are acquired. This is in a good agreement with the above theoretical prediction.

In bioorganic analysis, abundant structural information can be provided by carbon-13 nuclear magnetic resonance (¹³C NMR) and more and more attentions have recently been paid on its molecular modelling and quantitative prediction which on the basis of the relationship of chemical shift of carbon nuclear magnetic resonance with descriptor variables of chemical structure. By using multiple linear regression (MLR) and latent factor analysis (LFA) techniques, quantitative ¹³C NMR models are achieved to accurately express correlation of ¹³C NMR chemical shifts with five structural parameters and to successfully predict the chemical shift (CS)of any other compounds optimally. First, the history and progress in quantitative structure spectra relationship (QSSR) were critically reviewed, and a set of novel descriptors consisting of 4 elements, called atomic electronegative distance edge vector (AEDV) were first developed by our laboratory and further investigated for the bioactive compounds. Next, MLR and LFA were simply introduced; Matlab and True Basic programs for quantitative molecular modelling (QMM) were designed and written by ourselves. Then, various chemical shifts of ¹³C NMR for 457 different chemically equivalent carbon atoms in 135 natural sugars were estimated and/or predicted with the atomic electronegative distance edge vector (AEDV) with 4 elements and the γ calibration parameter:The correlation coefficients R, roots of mean square error RMS, standard deviation SD, F-statistic value F, and explained variance being n=62, R=0.9910, RMS=1.9602 (SD=1.9762, R²=0.9821, F=502.3294, EV=0.9805); n=79, R=0.9886, RMS=2.5405 (SD=2.5567, R²=0.9773, F=515.6046, EV=0.9757); n=302, R=0.9514, RMS=3.6884 (SD=3.6945, R²=0.9051, F=468.8276, EV=0.9035)and n=14, R=0.5772, RMS=8.8626(SD=9.1972, R²=0.3331, F=0.5828, EV=-0.0837)for the primary, secondary, tertiary and quaternary carbons in all carbohydrates, respectively. Finally, cross validation with leave-one-out (LOO) procedure was made on the QSSR equations for all four types of carbon atoms. The good results were obtained for the first three types of carbon atoms except the quaternary carbon atoms, which indicated that there exists a simply multiple linear relationship between CS and AEDV for primary, secondary, tertiary carbon atoms of sugars.

The results of ¹H NMR investigation of α-cyclodextrin inclusions with p-and m-cresol in heavy water are reported in this paper. It was found that though there is difference in chemical shift of some protons in α-cyclodextrin cavity between after and before complexing with cresol, only singlet resonance peak had been detected by ¹H NMR, position of which was dependent upon the inclusive degree. The average geometrical structures of inclusion complexes and their equilibrium constants under different inclusive degrees had been calculated based on ¹H NMR data, and the situation of dynamic variation of entering depth of cresol into α-cyclodextrin cavity had been described. Meanwhile, the comparison of the above results of α-cyclodextrin with β-cyclodextrin are made in this paper.

The-mid-chain and end-chain peroxyl radicals are trapped in the samples irradiated in air at room temperature. They decay slowly at room temperature. It was indicated by means of DSC technique that melting temperature T_m of irradiated F-40 decreases with the increasing radiation dose. This fact was interpreted in terms of the general model of lamellar crystallites.

Combination of digital quadrature detection and over-sampling techniques is discussed in detail. It is demonstrated by theoretical analysis and experimental result that, through simultaneous changes of sampling frequency and the frequency difference between radio-frequency irradiation and reference signals, one can complete the NMR data processing procedure with performing digital filtration once. As a result, the whole data processing procedure may, in most cases, be accomplished within the time interval waiting for the recovery of the magnetization.

A novel spectral editing technique, which can be referred to as DEPT-(90+45), is described. It is modified from the DEPT-135 pulse sequence by substituting the 135° -pulse by a 90° -pulse and a 45° -pulse. By employing different phase cycles, one can obtain methyl-only spectrum and methylene-only spectrum. The methyl only spectrum is completely free of residual methine and methylene signals. However, the methine-only spectrum (DEPT-90) and the methylene-only spectrum are interfered with substantial residual signals from not-selected carbon-proton groups. As a consequence, DEPT-(90+45) can be very useful for spectral editing in one-dimensional NMR spectroscopy.

Comparing to a paramagnetic sample, the signal of magnetic resonance of a ferromagnetic sample not only is much stronger, but also reflects many characteristics of ferromagnetic resonance (FMR) spectra. Such as, the FMR spectra are different between virgin magnetization and magnetization with remanence M_r. Barkhausen jumps is characterized by FMR spectrum in virgin magnetization. The FMR can also be used to study anisotropy of magnetocrystal, shape anisotropy, and magnetic phase transition of ferromagnetism-high temperature paramagnetism, etc.