The Cu²⁺-tussah silk protein complexes have been studied by ESR, UV and IR. On the basis of these spectra and ligand field theory calculation, the ligands at the Cu²⁺, the oxidation state of Cu²⁺ and the structure model of these complexes were proposed. MoreBack

The series expansions of operator functions are discussed. The product operator formulism for high-spin systems with weakly coupling is given and applied to DEPT experiments of In S (1/2) systems. The general formula of enhancement factors for I (1)_n S (1/2) (e. g. CD_n) systems is given. The structure of DEPT spectra is figured.

The quality of ISIS localized spectroscopy is improved by a combination of DIGGER and ISIS spatial locali/ation techniques.

2D INADEQUATE sequence is one of the most important 2D NMR techniques in current use. By the use of 2D INADEQUATE spectra and DEPT, hetero and homonuclear shift-correlated 2D spectra, the peaks of ¹³Cspectrum of δ-V_E have been assigned. The chemical shifts of each proton were evaluated by C-H correlate 2D spectra. Some peaks of ¹³C spectrum of δ-V_E and 2D INADEQUATE spectra were discussed, and the data in literature^[1] should be amended.

The work in this paper is one of the attempts to obtain more structural information from powder or frozen solution samples. The copper (Ⅱ) complexes with nitrogen as donor atoms in the form of N₄, cis N₂O₂, trans-N₂O₂ and NO₃ donor sets on the equatorial plane is treated. In this paper we will show that the magnitudes of the nitrogen hypcrfine couplings have some correlation with the donor sets as well as types of nitrogens, and the found correlation is useful for estimation or confirmation of coordination structure of copper (Ⅱ) complexes with unknown or uncertain structure.

¹H and ¹³C NMR spectra of ethyl benzenecarboximidates (Ⅰ) and ethyl N-(ethoxycarbonylmethyl) benzenecarboximidates (Ⅱ) were determined. The resonance lines of these compounds were assigned, and the empirical substituent increments of -C-OEt=NH and -C-OEt=NCH₂ CO₂ Et were obtained. It was found that therewere some linear relationships between chemical shifts and Hammett constants σ.

Three kinds of ethylene-dimethylaminocthyl methacrylatc copolymers (E-DAM) were analyzed using COM and APT ¹³C NMR methods. Correction parameters to the chemical shifts of ¹³C were obtained. The sequence distribution of copolymers were discussed.

The paramagnetic induced shifts of the coordination compounds of lanthanide with L-histidinc have been measured in weak-acidic condition by XL-200 NMR spectrometer. The induced shifts were separated into compound formation shifts, contact shifts and pseudo-contact shifts. The structures of coordination compounds were simulated based on the pseudo-contact shifts and some structure parameters have thus been obtained. In addition, the magnetic characteristics of lanthanides were discussed in this paper.

The pharmacological results indicate that the N-monoalkyl substituted (E)-and (Z)-α-halocinnamamidcs display different actions on the central nervous system (CNS-depressant or CNS-stimulant activity). According to the results determined by NMR, the difference in the coupling constants of two olefinic protons (J_E > J_Z) between the two geometrical forms can be used for isomeric assignment for the unsubstituted compounds on the olefinic protons. The value of chemical shifts of β-olefinic H, (δ_H (Z) > δ_H (E)), and NH (δ_H (Z) > δ_H (E)), the difference of which are more than 1 ppm, can be used to distinguish the configuration of α-halocinnamamides^[10]. The coupling constants and β-olefinic proton can be utilized to distinguish α-halocinnamoyl piperidines, because there is no proton on the nitrogen of piperidine ring and the chemical shift difference of β-olefinic H between Z and E form is very small. Because determination is not very easy and has so many interfering factors, these piperidine Z or E compounds can be distinguished by conformation variation of piperidine^[11].
Comparing the aromatic parts of ¹H-NMR spectra of the whole series of α-halocinnamamides, we discovered that the chemical shifts and spectral patterns of aromatic protons are very different between Z and E, due to the difference in stcric-hindrance. Thus this method can be used to distinguish Z or E configuration of α-halocinnamamides.

Molybdovanadophosphoric acid with Keggin structure and its salts are effective catalysts for oxidation reactions. Based on the NMR measurements of ³¹P, ⁵¹V,¹³⁹La, ¹⁷O and ¹H in these catalyst samples in combination with the correspondingIR and DTG determination, it is shown that the addition of lanthanum does not affect the formation of heteropolyacid with Keggin structure. However, lanthanum can exert strong action on water molecules, leading to the existence of more water molecules among the polyanions, which might probably affect catalytically oxidative activity.

The insulin nitroxide free radical was first prepared and used to study the kinetic changes of the spectral parameters in the process of combination between the insulit:probe and its receptor. The experiments show that before and after combination the conformation of membrane protein, rotational correlation time (τ_c) of insulin molecule and the amplitude (h₀) of ESR spectra of insulin nitroxide free radical have been obviously changed. These changes of parameter of ESR spectrum are related to the endocytose of insulin receptor complexes. The combination could rather be inhibited, when the sulfhydryl group, free amino group or hydroxide group of receptor were blocked.

The ¹H and ¹³C NMR spectra of the analgesic dihydroetophine (1) were studied by ¹H-¹H COSY-NOESY, ¹³C-¹H COSY and long range ¹³C-¹H COSY techniques. The chemical structure of the analgesic was furthur confirmed. In addition, from 2D NOE experimental result, C-7 configuration has been elucidated as (2). The result was confirmed by X-ray diffraction analysis.

In this paper, HomoCOSY and Hetero-CHCOR 2D NMR techniques were used to analyze and assign the ¹H and ¹³C NMR spectra of Tranilast, 2-[[3-(3, 4-Dinethoxy-phcnyl)-1-oxo-2-propenyl] amino] benzoic acid. ¹³C relaxation times (T₁) and variable temperature experiments were used also to identify the structure of the synthesized title compound. Simulated proton spectrum was used to confirm the results.

In order to determine the structure of alkyl aromatic ether of urushiol dimer, the model compound CH₃ CH₂ C-O-OHCH₃ was synthesized.The structue and the assignment of resonances were confirmed by 2D-NMR and MS. The results have shown that there is the same structural unit, 2-butyl phenyl ether, in the urushiol dimer.

The two-dimensional nuclear Overhauser effect correlated spectroscopy (NOESY) technique was successfully applied to investigate the structure and stereochemistry problems of some natural products, such as cephalotaxine, methyl gibberellate, ganwuweizic acid and rabdosinate. It is confirmed that NOESY is powerful and effective for the NMR chemical shift assignments which can hardly be done by conventional techniques, especially for the molecular configuration and conformation analysis.

The nitroxidc radicals produced from hydroxylamines in the radical polymerization of vinyl monomers have been studied by ESR technique. The results show that the nitroxidc radicals formed from their parent hydroxylamines can be detected in the presence of initiators BPO and AIBN. From these experimental results, the inhibition mechanism for the polymerization is proposed and discussed.

The effect of proton homonuclcus coupling modulation on the polarization transfer signals is studied theoretically and experimentally using the INEPT pulse sequence as a demonstrative example The simultaneous polarization transfer from two proton groups having different coupling constants will the measured spin -(1)/2 nucleus is also investigated.

In this paper, a design of TE₀₁₁ mode right cylindrical ESR sample cavity and the author's designed example are introduced.

HMBC is a sensitive method for determining long-range ¹H-¹³C connectivity. It is suitable for conelating methyl protons with carbon atoms through two-and three-bond, especially.
HOHAHA provides relay information over all protons in spin coupling network.
In this paper HMBC and HOHAHA, in combination with ¹H COSY and ¹³C-¹H COSY have been used to unambiguously assign ¹³C and ¹H resonances for Quillaic Acid-3-O-giucuronic acid.