A New Expert System for Structural Interpretation of IR Spectra

A new expert system has been developed which can be used to aid chemists in structural interpretation of infrared spectra. The system consists of five essential portions: knowledge-base , inference engine, database, knowledge-acquisition module and explanatory interface. The system is implemented in Turbo PROLOG artificial intelligence language. Compared with other spectral interpretation systems this system is of the following advantages, i. e. the system has a friendly user interface, two kinds of methods for managing toowledge-base, several useful explanatory facilities such as why and how should explanation be made, etc. ; in addition, it can be run on the IBM PC/XT and its compatible microcomputers. Another important feature of the system is that it can simulate the reasoning procedure by which experienced chemists may interpret spectra as well as deduce complete molecular structures. So the system can also be used as a helpful learning tool for training chemistry students in IR spectrum interpreta     

Proton Nuclear Magnetic Resonance Studies on Conformation of Native Rat Liver Cd＿5Zn＿2－metallothionein Isoforms

The present paper describes proton nuclear magnetic resonance studies on native rat liver metallothionein isoforms (MT-I and-I). The two isoforrns were isolated and purified from rat liver after induced by cadmium chloride. 1D NMR spin-decoupling and 2D-COSY techniques were employed in this study for the iden-tification of individual methyl resonances in metallothionein- I and一I. a-domain of metallothionein-I containing four cadmium ions was also prepared and studied by NMR to aid domain specific assignment of these resonsnces. MT was studied extensively at various pH, temperatures and ionic strengths on the basis of these resonances assignment. It is stable in the range of pH 5-9 and also at higher temperatures. The flexible part of MT is near Ala8, Va139.     

Absorption Spectra and Resonance Rayleigh Scattering Spectra of Cu(Ⅱ)-Fluoroquinolone Chelates with Tetrachlorotetraiodo-fluoresceindisodium Salt System and Their Analytical Applications

在pH 4.2～4.8的B-R缓冲介质中,莫西沙星(MXFX)和加替沙星(GTF)等氟喹诺酮类抗生素(FLQs)能与铜(Ⅱ)形成螯合阳离子,进一步与虎红(Tf)阴离子通过静电引力和疏水作用形成FLQs∶Cu(Ⅱ)∶Tf为1∶1∶1的离子缔合物,体系反应导致共振瑞利散射(RRS)显著增强并出现新的RRS光谱.两种药物的反应产物具有相似的光谱特征,最大RRS峰位于373 nm处,并在590 nm处有1个较小的散射峰.在373 nm处一定浓度的抗生素与散射增强(△I)成正比,MXFX和GTF的线性范围分别为0.031 ～7.8 mg/L和0.029～9.0 mg/L.据此建立了测定氟喹诺酮类药物的新方法,方法用于胶囊和人尿液中FLQs的测定并取得满意结果.同时对反应机理及RRS增强原因进行了讨论.     

Multinuclear Nuclear Magnetic Resonance Studies of 〔VS_4 (CuPPh_3)_5 (CuCl) Br_2〕

11NTRoDUCTIONThecomplexchemistryofthetetrathiometallatestMS,j"-(M=Mo,W,n==2lM=V,n=3)hasbeenextensivelyinvestigatedbecauseofitspotentialutilityinimi-tationofbiologicalsystems"'.Especially,vanadium-containingheterometallicsulfurcomplexesareofinterestasmodelsoftheactivesitesinmetalloenzymestobiomimeticchemistst2'33.Studiesonthiometalateandrelatedmultimetalcomplexeshavebeenmain1yaboutsynthesesandcrystalstructures,butNMRinvestigationswereraret43.SinceNMRspectroscopyrespondstothemagneticpro…     

Using Nuclear Magnetic Resonance and MS/MS Spectroscopy for the Identification of Brodimoprim Metabolites in Rat Urine

Brodimoprim,a trimethoprim analogue diaminopyrimidine, 2,4-diamino-5-(4'-bromo-3',5'-dimethoxybenzyl) pyrimidine, is a new inhibitor of bacterial dihydro folate reductases (OHFRs), it shows activity against a broad spectrum of Gram-positive and negative-bacteria. Recently we reported the results of the study on the metabolites of brodimoprim in vivo with SPE-NMR method (solid phase extraction coupled with nuclear magnetic resonance), five metabolites were detected in rat urine1. They were …     

Synthesis and Characterization of One-dimensional and Two-Dimensional Porphyrin Polymers (Ⅰ)

Porphyrin polymers are of interest in relation to conductive materials[1, 2], catalysts for photosynthetic charge separation[3], or the fundamental features in biological systems[4]. There have been many versatile studies about them[5.6]. The one-dimensional "Shish Kebab"porphyrin polymers synthesized with a new method different from those reported and Schiff-base porphyrin polymers with two-dimensional nano-structure have provided a new field of study. The present paper covers highly ordered…     

Synthesis,Structure and Fluorescence of Olefin-Copper(Ⅰ) Coordination Polymers

The organic olefin ligand 2,5-dimethyl-1-(4-vinyl-benzyl)-piperazine reacts with CuX(X = Cl, Br) to obtain two novel olefin-copper(I) coordination polymers [C_(15)H_(22)N_2Cu_2Cl_3]n(1) and [C_(15)H_(20)N_2Cu_2Br_2]n(2). There are two types of CuX warp structures that have never been seen before in the presence of methanol under solvothermal conditions. The new olefin-copper(I) coordination complex crystallizes in the monoclinic space group P21/c to obtain compounds 1 and 2. Its unique green fluorescence effect can be applied to the LED field.     

Structural Determination of Bis-histidinopeptide Zinc Complexes by 15N NMR (HMBC) Spectra

Polynitrogen receptors such as bis-histidine peptides possess strong ability to bind metals, which play much important roles in medicinal, bioinorganic, bioorganic, biomimetic and supramolecular chemistry. In order to investigate the interaction of these hosts with a variety of neutral, cationic and anionic guests, several techniques, for example, NMR,potentiometric tirations and monocrystal X-ray diffraction have been employed. Among them NMR is a powerful technique for unraveling the structure of polynitrogen receptors as long as they are in solution where the rapid tumbling of molecules averages out the anisotropies such as chemical shift and dipole-dipole interactions. General 1H NMR approach has been widely used for the study of host-guest interaction, but it is difficult for the accurate measurement in complexes structures, particularly metal complexes structures in which how the polynitrogen receptors bind metal, and which nitrogen binds metal and so on.     

Resonance Rayleigh Scattering Spectra of Thorium(IV)-bisazo Dye of Chromotropic Acidprotein Systems and Their Analytical Applications

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Studies of Molecular Motions of Ocotillol-Type Saponins in Solution by ~(13)C Nuclear Magnetic Relaxation

In this paper, the fully anisotropicoverall tumbling motions and side groups internal rotation of ocotillol-type saponins separated from the leaves of Panax Quidquefolium L. are investigated by ~(13)C nuclear magnetic relaxation. The fully anisotropic overall tumbling motion model with methyl conformation jumps internal rotation among three equivalent sites is presented, and the spectral density function of this model is derived. The rotation rates for overall tumbling motions to ocotillol-type saponins (OTS) are computed by Woessner's fully anisotropic overall tumbling motion model, and the internal rotation rate and barrier for side groups in OTS are calculated using free diffusion internal rotation model, restriction diffusion internal rotation model and conformation jumps internal rotation model, respectively.     

Synthesis and Evaluation of Aromatic DTPA-bis(amide) Gadolinium Complexes as Magnetic Resonance Imaging Contrast Agents

ＳｙｎｔｈｅｓｉｓａｎｄＥｖａｌｕａｔｉｏｎｏｆＡｒｏｍａｔｉｃＤＴＰＡ┐ｂｉｓ（ａｍｉｄｅ）ＧａｄｏｌｉｎｉｕｍＣｏｍｐｌｅｘｅｓａｓＭａｇｎｅｔｉｃＲｅｓｏｎａｎｃｅＩｍａｇｉｎｇＣｏｎｔｒａｓｔＡｇｅｎｔｓＺＨＵＯＲｅｎ－Ｘｉ＊＊，ＷＥＮＪｉｅ...     

Influence of Different Organic Carboxylate Anions on the Crystal Structure of Silver(Ⅰ)Coordination Polymers

The reaction of AgNO3 , 4,4′-bipyridine (bpy) and 2,2′-bipyridine-3,3′-dicarboxylic acid (H2bpdc)/2,2′-biquinoline-4,4′-dicarboxylic acid (H2bqdc)/1,3-benzenedicarboxylic acid (H2bdc) gave rise to block-like crystals of [Ag4(bpy)2(bpdc)2]·13H2O(1), [Ag2(bpy)(bqdc)(H2O)]·4.5H2O(2) and [Ag2(bpy)2(H2O)2](bdc)·3H2O(3) by slow evaporation. All the three complexes contain sandwich-like crystal structures, in which anionic sheets built up from different anions (bpdc2- , bqdc2- and bdc2- ) and lattice water molecules via rich hydrogen-bonding interactions are inserted between the cationic silver complex layers, and the abundant Ag···Ag, Ag···N and π-π stacking interactions further strengthen the 3D frameworks. The lattice water molecules are situated among the framework of crystal structure and stabilized by rich hydrogen-bonding interactions, and lattice water molecules may play a role in the orientation of organic anions in the crystal packing. Additionally, the thermal properties of 1, 2 and 3 were also discussed in detail.     

Poly(iminoborane)s: An Elusive Class of Main‐Group Polymers?

The significance of inorganic main‐group polymers is demonstrated most clearly by the commercial relevance of polysiloxanes (silicones). Organoboron‐based materials such as π‐conjugated organoborane polymers and BN‐doped polycyclic aromatic hydrocarbons are currently attracting considerable attention. Surprisingly, poly(iminoborane)s (PIBs; [BRNR′]_n), that is, the parent unsaturated BN polymers, which are formally isoelectronic to polyacetylene, have not been convincingly characterized thus far. Herein, we present the synthesis and comprehensive characterization of a linear oligo(iminoborane), which comprises a chain of 12–14 BN units on average. With our synthetic approach, unwanted side reactions that result in borazine formation are effectively suppressed. Supporting DFT and TD‐DFT calculations provide deeper insight into the microstructure and the electronic structure of the oligomer.     

The Study of the Reaction Mechanism for the Dehydrogenation of Ethylbenzene on Iron Oxide Catalysts (Ⅰ)——IR Spectra of Adspecies and Kinetic Isotope Effects

In situ PT-IR spectroscopy was used to examine ethylbenzene adspecies on iron-oxide-besed catalysts,and the method of kinetic isotope effects was used to investigate the rate determining step of the dehydrogenation.A possible reaction mechanism is proposed.     

Syntheses,Crystal Structures,and Magnetic Properties of Mn(Ⅱ) and Co(Ⅱ) Coordination Polymers Constructed from Pyridine-tricarboxylate Ligand

Two coordination polymers, namely {[Mn(HL_1)(phen)]·4H_2O}_n(1) and [Co_2(HL_2)_2(H_2O)_2]_n(2) have been constructed hydrothermally using H_3L_1 and H_3L_2(H_3L_1 = 2-(5-carboxypyridin-2-yl)terephthalic acid, H_3L_2 = 2-(4-carboxypyridin-3-yl)terephthalic acid), phen, MnCl_2×4H_2O and CoCl_2×6H_2O. The products were isolated as stable crystalline solids and were characterized by IR spectroscopy, elemental, thermogravimetric(TGA), powder(PXRD) and single-crystal X-ray diffraction analyses. Compound 1 features a 3D framework structure, which was topologically classified as a trinodal 4,6,6-connected net with the unique topology defined by the point symbol of(3~(10).5.6~4)4(3~(10).6.7~4)2(5.6~2.8~2.9). Compound 2 possesses a 2D metal-organic layer, which was topologically classified as a binodal 4,4-connected layer defined by the point symbol of(4~3.6~2.8). The layers are further extended into a 3D supramolecular framework via hydrogen bonds. The magnetic properties for both compounds were also investigated, indicating antiferromagnetic interactions between the adjacent metal ions.     

Studies on the Properties of Schiff Base Type of Aryl mercury Compounds( Ⅰ )——~1H NMR Spectra of Some Schiff Base Type Aryl mercury Compounds and Substituted Benzyl ideneanilines

1H NMR spectra of 16 Schiff base type of arylmercury compounds and 4 -substituted benzylideneanilines have been studied. It was found that the p-substituents of the N-phenyl ring do not affect the δ values of methine proton, whereas the o-substitutents influence the δ values of methine proton, whereas the o-substituents influence the δ values of methine proton significantly. These changes can be reasonably interpreted in terms of the steric inhibition of o-substituents and intramolecular coordination of imino nitrogen with mercury. The influence of the m-or p-substituent of the C-phenyl ring on the δ values of methine proton exhibited a linear correlation with Hammett constants σp or σm. It was also confirmed that in the molecules of Schiff base type of arylmercury compounds there exists an intramolecular coordination via a four-membered ring.     

3d-RADIAL WAVE FUNCTION AND ITS APPLICATION (Ⅰ)——Semi-Empirical Radial Wave Function and Spectra for Free Cations of The First Transition Series

THE double-ζ function form of radial wave function is discussed,and the semi-empirical double-ζ radial wave functions of 3d-orbitsfor the free divalent and trivalent cations of the first transi-tion series are suggested.The overlap integrals between thesewave functions and the corresponding Hartree-Fock results ofWatson are greater than 0.99.The deviation for Racah para-meters and spin-orbit coupling constant calculated from the ex-perimental fitting results is,in general,less than 6%.It istherefore likely that for free ions the spectra calculated bymeans of radial wave functions are expected to be in agreementwith the experimental results.     

Polymeric Structure and Solid ~(31)P, ~(113)Cd NMR Spectra of Cadmium(II) Dialkyldithiophosphate (Alkyl = n-butyl and i-butyl)

Owing to the particular affinity toward metal ion and changeable dentation, dialkyldithiophosphates are commonly used ligands in preparation of the transition metal complexes with variable structures1. For instances relevant to this work, the IIB metal complexes defined crystallographically so far have provided the examples as follows2-12 (Scheme 1). Scheme 1 The frameworks of IIB metal complexes of dialkyldithiophosphate MMMMMMMMMM a b c d …     

An analytical approach for on-site analysis of breath samples for Δ9-tetrahydrocannabinol (THC)

Increased acceptance of cannabis containing the psychoactive component, Δ9-tetrahydrocannabinol (THC), raises concerns about the potential for impaired drivers and increased highway accidents. In contrast to the “breathalyzer” test, which is generally accepted for determining the alcohol level in a driver, there is no currently accepted roadside test for THC in a motorist. There is a need for an easily collectible biological sample from a potentially impaired driver coupled with an accurate on-site test to measure the presence and quantity of THC in a driver. A novel breath collection device is described, which includes three separate sample collectors for collecting identical A, B, and C breath samples from a subject. A simple one-step ethanol extraction of the “A” breath collector sample can be analyzed by UHPLC/selected ion monitoring (SIM) liquid chromatography/mass spectrometry (LC/MS) to provide qualitative and quantitative determination of THC in breath sample in less than 4 min for samples collected up to 6 h after smoking a cannabis cigarette. SIM LC/MS bioanalyses employed d3-THC as the stable isotope internal standard fortified in negative control breath samples for quantitation including replicates of six calibrator standards and three quality control (QC) samples. Subsequent confirmation of the same breath sample in the B collectors was then confirmed by a reference lab by LC/MS/MS analysis. Fit-for-purpose bioanalytical validation consistent with pharmaceutical regulated bioanalyses produced pharmacokinetic (PK) curves for the two volunteer cannabis smokers. These results produced PK curves, which showed a rapid increase of THC in the breath of the subjects in the first hour followed by reduced THC levels in the later time points. A simpler single-point calibration curve procedure with calibrators and QC prepared in ethanol provided similar results. Limitations to this approach include the higher cost and operator skill sets for the instrumentation employed and the inability to actually determine driver impairment.     

Some studies of the chromatographic properties of gels (‘Artificial antibodies/receptors’) for selective adsorption of proteins

Summary Although conventional imprinting involving the use of charged functional monomers has been used by many authors for selective adsorption of small molecules, it has not been very successful with high-molecular-weight substances, for example proteins (“...macromolecules, such as proteins are difficult to apply as templates...”; H. S. Andersson, Doctoral Thesis, Trycki H?gskolan Kalmar, 1999, p. 8.). Four years ago we therefore introduced an alternative method based on the polymerization ofnon-charged monomers (acrylamide andN,N′-methylenebisacrylamide) in the presence of the protein of interest. The selectivity of the gels for proteins was high (for instance, myoglobin from horse was adsorbed by a column designed to be selective for this protein, whereas, myoglobin from whale was not adsorbed) and they can therefore be regarded as ‘artificial antibodies’ (or ‘artificial receptors’). This paper deals with improvements of the chromatographic properties of these gels. For example, by modifying the polymerization conditions the protein (hemoglobin) capacity, as well as the flow rate were increased fouifold. This was achieved by entrapment of the selective soft polyacrylamide gel in the pores of a rigid inert gel by letting the monomers and the protein diffuse into the pores of agarose beads (Sepharose^TM) before starting the polymerization. The gel formed was cut into pieces. The agarose beads were freed from the surrounding polyacrylamide gel by stirring. This technique is universal and is recommended also for molecular imprinting studies of small molecules. Another universal method has been introduced for rapid screening of potential monomers and gels for the preparation of selective adsorbents. This very simple method is based on the assumption that the absorption maximum of a protein changes when the protein interacts with the free monomers or the adsorbent synthesized from the monomers (and does not change when the protein does not interact). Preliminary docking experiments indicate that selective adsorption of the protein by the polyacrylamide matrix is based primarily on hydrogen-bonding and dipole-dipole interactions. The strengths of these interactions can be varied by choosing different gel matrices (for removal of a given protein the interactions should be very strong, whereas they should be weaker for chromatographic analysis).