NUCLEAR MAGNETIC RESONANCE STUDIES OF THE INTERACTION OF Ca~(2+) WITH SIALIC ACID~*

The interaction of Ca~(2+) with sialic acid has been investigated by 500 MHz proton nuclear magnetic resonance spectroscopy. The changes of chemical shifts were observed for all sialic acid protons at different Ca~(2+) concentrations, and these spectral observations were also accompanied by changes in the J-coupling constants between the H_7 and H_8 protons and between the H_8 and H'_9 potens. Analysis of these Ca~(2+)-induced changes indicated that three oxygen atoms among (OH)_7, (OH)_8 and (OH)_9 of sialie acid formed a geometrical space suitable for Ca~(2+) coordination As a consequence, sialic acid provided a high-affinity binding site for Ca~(2+), the binding constant was about 104.72m~(-1).     

STUDY ON THE PROTONATION MECHANISM OF 2,6-DIMETHYL NAPHTHALENE DICARBOXYLATE

By the study of absorption and fluorescence spectra and the lifetime of fluorescence at room and low temperatures of 2,6-dimethyl naphthalene dicarboxylate (DMN) in different concentrations of sulfuric acid, different interactions between molecules of DMN and sulfuric acid have been observed. These interactions have been revealed by the absorption spectra of charge transfer complex in the ground state, emission of exciplex, absorption spectra of hydrogen bonding interaction, absorption and emission spectra after proton transfer and different lifetimes before and after protonation. The interaction mechanism of DMN and sulfuric acid through first the CT complex and exciplex then hydrogen bonding and finally proton transfer is proposed.     

Computer-aided Interpretation of Proton Nuclear Magnetic Resonance Spectra (Ⅰ)——An Artificial Intelligence System for Interpretation of Proton NMR Spectra of Polymers

An artificial intelligence system for interpretation of proton NMR spectra of polymers is reported in this paper. The system, including spectra data base, knowledge data base and reasoning engine, is based on the characteristics of the proton NMR spectra of polymers and the spectra interpretation experiences of specialist. The system can partly simulate human thinking and interpret proton NMR spectra of polymers at different levels of sophistication. The program in the system was written in Turbo Prolog 2.0 and translated into machine language by computer compiler. It has been tested on an IBM PC/XT computer and a satisfactory result was given.     

THE CALCULATION OF CHEMICAL SHIFTS IN DISUBSTITUTED NAPHTHALENES

<正> The principle and method for calculating the chemical shifts of substituted benzenes have been extended to the calculation of chemical shifts in disubstituted naphthalenes. We have set up a series of empirical parameters for the calculation of chemical shifts. The calculated results of 439 8 values from 78 compounds show that the standard deviation between the calculated and the experimental values is 0.08 ppm. The combination of this calculation with that of the coupling constants can be used to provide a criterion .for the determination of molecular structure in disubstituted naphthalenes as well as to assign NMR parameters for the experiment of proton simulated spectra of disubstituted naphthalenes.     

THE POSSIBLE MECHANISM OF BINDING INTERACTION OF INSULIN MOLECULE WITH ITS RECEPTOR

Detailed structural comparisons and investigation of DPI, 2Zn insulin and some other derivatives of insulin were performed by the least-squares superimposition technique and the graphics technique. It is pointed out in this paper that the binding interaction with the receptor molecule should take place mainly on an amphipathic surface of the insulin molecule. In the middle, there is a hydrophobic surface with an area of about 150 consisting of many hydrophobic residues; while the polar or charged groups distributing around the hydro. phobic surface construct a hydrophilic zone. The hydrophobic surface is usually covered by the extended B-chain C-terminal peptides with great mobility and protected from the solvent molecules. The angle between the amphipathic surface and the surface of dimerization is about 20 degrees. The results from the detailed structural comparison between A1-(L-Trp) insulin and A1-(D-Trp) insulin have provided a very good explanation to their great difference in biological activity,     

THE CALCULATIOM OF CHEMXCAL SHIFTS IN SUBSTITOTED PYRIDINES

<正> The principle and method for the calculation of chemical shifts of substituted benzenes have been extended to calculation of the cheiiical shifts in substituted pyridines. We have set up a series of empirical parameters for calculation of the chemical shifts. The calculated results of 154 δ values frou 54 compounds show that the standard deviation between the calculated and the experimental values is 0 . 09 ppm. The combination of the coupling constants can be used to provide a criterion for the determination of molecular structure in substituted pyridines and to assign NMR parameters for the experiment of proton simulated spectra of substituted pyridines.     

Mg~(2+)-MEDIATED CHANGES IN FLUIDITY OF PHOSPHOLIPID DECREASE THE SLOW MOTION OF THE INCORPORATED H~+-ATPase IN LIPOSOMES

The effect of Mg~(2+) on the slow motion of H~+-ATPase in proteoliposome was studied. The ST-ESR spectra of H~+-ATPase labeled with maleimide and incorporated in liposomes at various Ma~(2+)concentrations with incubation method were measured. The relationship between the diagnostic param-eters L"/L, C'/C derived from ST-ESR spectra and Mg~(2+) concentrations or temperatures was com-pared with that of the order parameter S derived from 5NS-ESR spectra under the same conditions. Obtain-ed results clearly showed that the increase of Mg~(2+) concentration or the decrease of temperature maycause the increase of the rotational correlation time of H~+-ATPase in proteoliposome. And the rota-tional diffusion rate of H~+-ATPase in membrane lipid is related to the activation energy of the sur-rounding lipid. The change of Mg~(2+) concentration in proteoliposome leads to a change of activarionenergy and influence in turn the slow motion of H~+-ATPase in 1ipid.     

THE STUDY OF SPECTRA AND X-RAY CRYSTAL STRUCTURE OF A NOVEL BIONICS INSECTICIDE——(CH_3)_2NHCH(CH_2S_2O_3)_2Na·H_2O

IR and NMR spectra of novel bionics insecticide—C_5NS_4O_6H_(12)Na·H_2O have been studied. The molecular and crystal structures of the compound also have been determined. The compound crystallizes in the monoclinic space group C_(2h)~5, - P2_1/n with α= 8.0972. (9) , b =16.262(4), c = 10.370(3), β= 94.26(2)° and z = 4.The result shows that N atom in this compound captures a proton to form HN~ group, Na~ is in statistical disorder. Therefore, the structural formula of tho compound is (CH_3)_2HN~ —CH(CH_2S_2O_3~-)_2·1/2 (Na~ )_2·H_2O.     

FOURIER TRANSFORM INFRARED SPECTROSCOPIC STUDY OF EFFECT OF LANTHANIDE IONS ON PHOSPHOLIPID MULTIBILAYERS

The molecular interactions between Nd~(3+), Gd~(3+)and Yb~(3+) and DPPC in multibilayer have been studied by Fourier transform infrared spectroscopy. The results show that incorporations of the lanthanide ions considerably shift the gel to liquid-crystal phase transition to higher temperatures. The incorporations of Gd~(3+) and Yb~(3+) obviously reduce the cooperations of the transition. The phosphate region of the spectra indicates that the Ln~(3+) binding to DPPC forms DPPC-Ln~(3+)complex and the Lna~(3+)binding is not dependent on the phase state of DPPC. The C-H stretching region of the spectra suggests that the incorporation of Ln~(3+)increases the conformational order of DPPC both in gel and in liquid-crystal phase as a result of the reduction of gauche rotamers.     

Studies on the Interaction of 12-Tungstophosphoric Acid and Diethylene Glycol

The homogeneous system of 12-tungstophosphoric acid and diethylene glycol was studied using IR and NMR spectra. It was found that the protons in 12-tungstophosphoric acid formed proton oxonium ions with the hydroxyl oxygen in diethylene glycol by hydrogen-bonds, and the formed proton oxonium ions could react with the terminal oxygens of heteropoly anions. The dehydration-cyclization mechanism of diethylene glycol in the presence of heteropoly acid was also proposed.     

Interactions of acetylcholinesterase with salvianolic acid B and rosmarinic acid from Salvia miltiorhiza water extract investigated by NMR relaxation rate

In order to understand whether the ameliorating effect on old ages memory disorder by the root of Salvia miltiorhiza is related to the acetylcholinesterase （ACHE） inhibition, two main ingredients, salvianolic acid B （1） and rosmarinic acid （2）, which were isolated from S. miltiorhiza water extract, were investigated in vitro by NMR relaxation rate in this work. The results showed that the proton selective relaxation rates and the molecular rotational correlation time of proton pairs for compounds 1 and 2 increased significantly by adding of AChE in mixing solution. The study reveals that the two compounds might bind to the enzyme and have ACHE inhibitory effect, which could contribute to the ameliorating effect at some extent on old ages memory disorder.     

THE PRIMARY STRUCTURE OF THE LACTATE DEHYDROGENASE ISOZYME M. FROM GIANT PANDA

The amino acid sequences of tryptic, chymotryptic and cyanogen bromide cleavage peptides of the lac-tate dehydrogenase isozyme M4 from giant panda have been determined. Based on the overlapping peptidesand by a comparison with the known sequence of porcine lactate dehydrogenase isozyme M subunit, thecomplete primary structure of the giant panda lactate dehydrogenase isozyme M subunit has been estab-lished. The polypeptide chain of giant panda lactate dehydrogenase isozyme M subunit consists of 331amino acid residues. There is a variance of 17 amino acid residues between the porcine and the giantpanda lactate dehydrogenase isozyme M subunits. Most of the variable residues are substitutions bychemically similar amino acids and take place at residues not related to the active center of the enzyme.     

THE RING OPENING REACTION OF AN EPOXY COMPOUND ON THE TOP OF CHEMISORBED CYSTAMINE STUDIED BY THE SERS TECHNIQUE

Metal foils for Raman scattering were prepared by HNO_3 etching method. These foils werefound to exhibit a strong SERS effect and excellent thermal stability. SERS spectra of cystaminehave been taken to illustrate the usefulness of this sample preparation method in the studies ofchemisorption. The ring opening reactions of an epoxy compound have been observed on the topof chemisorbed cystamine on silver foils.     

NITROSYL FERROUS CHELATES——FTIR STUDY ON THE COORDINATION OF NITRIC OXIDE TO FERROUS CHELATES IN AQUEOUS SOLUTIONS

Fourier transform infrared spectroscopic studies of coordination compounds of a series of ferrous aminopolyphosphonates and aminopolyacetates with nitric oxide in aqueous solutions have been described for the first time. The polydentate ligands considered include: nitrilotrimethylenephosphonic acid (NTMP), ethylenediaminetetramethylenephosphonic acid (EDTMP), triethylenetetraaminehexaacetic acid (TTHA), diethylenetriaminepentaacetic acid (DTPA), trans-1,2-cyclohexylenedinitrilotetraacetic acid (CyDTA), ethylenedioxydiethylenedinitrilotetraacetic acid (EGTA) and nitrilotriacetic acid (NTA).By examining the spectra of ~(14)NO and ~(15)NO complexes in both D_2O and H_2O solutions, the characteristic frequencies of N-O vibration in the nitrosyls were assigned. A "red" shift of N-O stretching vibration frequency in the chelates was observed as compared with the aquacomplex [Fe(H_2O)_5(NO)]~(2+). With the aid of FTIR technique, the redox reaction of the nitrosyls with sulfite and oxygen were studied. The coor     

FLASH PHOTOLYSIS STUDY OF INSULIN

The transient absorption spectra of the initial UV-photolysis products of insulin and des-pentapeptide (B26--30)-insulin (DPI) were determined and compared with that of freetyrosine. The far-UV band of the spectra (<300 nm) has not been reported before. Theirmain initial photoproducts are p-alanylphenoxyl radical (λ_(max)=410,390nm) and an uniden-tified radical (λ_(max)=270 nm). The photolysis yields are closely correlative with the disso-ciation rate of hydroxyl group on phenol ring of tyrosine residues, which in turn dependson the exposed degree of these residues. The quantum yields of the phenoxyl radicals form-ed in photolysis of insulin and DPI were determined and compared with that of free tyro-sine. Based on the comparison, the number of light accessible tyrosine residue in insulin andDPI can be calculated, which provides more quantitative information on the exposed degreeof tyrosine residues in these two proteins.     

SYNTHESES OF ETHYL PERFLUOROACETYLENIC ESTERS AND STEREOCHEMISTRY OF A NOVEL ACETYLENIC ESTER-VINYL ETHER REARRANGEMENT

The intramolecular Wittig reaction has been applied to the syntheses of ethyl trifluoro-but-2-ynoate (2a) and ethyl heptafluoro-hex-2-ynoate (2b). Treatment of 2a and 2b withaqueous sodium hydroxide, followed by acidification, affords 3-ethoxy-4,4,4-trifluoro-2-bu-tenoic acid (3a) and 3-ethoxy-4,4,5,5,6,6,6-heptafluoro-2-hexenoic acid (3b) respectively. Anovel acetylenic ester to vinyl ether rearrangement takes place as thc corresponding methylestors. Their structures are ascertained by elemental analysis and IR and NMR spectra.The stereochemistry of this novel acetylenic ester to vinyl ether rearrangement has been studied.On the basis of ~1H NMR data, we find that the reaction is highly stereoseleetive and the Z-isomer predominated to the extent of above 94% in all cases. The results of the solventeffect of benzene and NOE enhancement in NMR spectroscopy further confirm the configura-tion of the Z- and E-isomer.     

STUDY ON THE TREATMENT AND REUSE OF WASTEWATER FROM THE PRODUCTION OF 2—NAPHTHANOL

Systematic studies on the treatment and reuse of the acid industrial watewater containing sodium 2-Naphthylsulfonate(β-salt)from 2-Naphthanol production process by ND-910 resin (made by self) is reported in this paper.Under the operation conditions of initial β-salt concentration of 10000-25000mg/L and initial CODCr of 20000-40000mg/L,the removal rates of Sodium 2-Naphthylsulfonate and CODCr are over 95% and over 89%,respectively.The effluent can be discharged directly after biological degradation.The working sorption capacity of ND-910 Resin for β-salt is over 230g/kg.An alkali-water wash procedure isutilized to regenerate resin and the reclaiming rate of β-salt is over 98%.     

PHOTOPHYSICS STUDIES OF ORCANIC COMPOUNDS (Ⅻ)——THE INVESTIGATION OF THE FLUORESCENCE SPECTRA OF N-SALICYLIDENE-p-(N,N-DIMETHYLAMINO)ANILINE

The fluorescence spectra of N--salicylidene-p-(N,N--dimethylamino)aniline have beeninvestigated in various solvents. Three kinds of fluorescence have been found in the solutionsof various concentrations. They are the excited intermediate (EI) which is formed when theproton transfer has occurred but essentially retains the geometry of the enol tautomer, theexciplex (EX) which consists of a ground monomer and an excited state intermediate and theexcited dimer (ED) which is caused by ground state aggregate. The fluorescence lifetimesof the fluorophores have been measured in tetrahydrofuran (THF). Luminescent mechanismhas been discussed based on the fluorescence spectra and the kinetic data of the compound.     

STRUCTURAL EFFECT IN FORKED CONJUGATIVE SYSTEMS——BIFURCATION-TYPE OF FORKED POLYENIC NITRILES,CARBOXYLIC ACIDS AND ESTERS

Five homologous series of bifurcate systems of aliphatic and aromatic polyenic cyano andcarboxylic compounds have been prepared and studied. The electronic absorption spectra forthe series and the NMR chemical shifts for the methyl-, methylene- and beta-protons havebeen found to conform very well to the rule of homologous linearity. The mass spectra forthe α-cyano polyenic ester series show strong peaks for the fragments of M-COOEt but noneof M-CN, indicating that the CN group seems to be in stronger conjugation with the poly-enic chain than the COOEt group does. In all the forked series studided, a red shift in electronic spectra is brought about upon theintroduction of an electron-attractive branching group, just like the case of introducing anelectron-repelling substituent. This has been taken as an indication of the predominance of themolecular integrality over the group characteristics. By means of the method of similar triangles between a homologous line for a linearseries and that for the corres     

Amide-Exchange-Rate-Edited NMR （AERE-NMR） Experiment： A Novel Method for Resolving Overlapping Resonances

This paper describes an amide-exchange-rate-edited （AERE） NMR method that can effectively alleviate the problem of resonance overlap for proteins and peptides. This method exploits the diversity of amide proton exchange rates and consists of two complementary experiments： （1） SEA （solvent exposed amide）-type NMR experiments to map exchangeable surface residues whose amides are not involved in hydrogen bonding, and （2） presat-type NMR experiments to map solvent inaccessibly buried residues or nonexchangeable residues located in hydrogen-bonded secondary structures with properly controlled saturation transfer via amide proton exchanges with the solvent. This method separates overlapping resonances in a spectrum into two complementary spectra. The AERE-NMR method was demonstrated with a sample of ^15N/^13C/^2H（70%） labeled ribosome-inactivating protein trichosanthin of 247 residues.