EFFECTS OF L-PHENYLALANINE ON THE RADIATION SYNTHESIS OF POLY(N,N''''-METHYLENEBISACRYLAMIDE-co-4-VINYLPYRIDINE)(MICRO)GELS

The effects of L-phenylalanine(L-Phe)on the synthesis of poly(N,N'-methylenebisacrylamide-co-4-vinylpyridine) (poly(Bis-co-4-VP))(micro)gels by γ-ray irradiation were studied.The addition of L-Phe could not only decrease the gelation dose(D_g)of the synthesis obviously,but also transform the morphology of copolymer from microgel to gel.In addition,the swelling ability of the(micro)gels was also affected in the presence of L-Phe.The decrease of D_g was ascribed to the effect of pH,while the transformation of the morphology was ascribed to the effect of L-Phe on the stability of the poly(Bis-co-4-VP)microgel.Such an effect was confirmed further as compared with the effects of L-alanine,L-glutamic acid,L-arginine,sulfuric acid and aqueous ammonia.     

Hel photoelectron spectroscopic (PES) and quantum chemistry study on the dimeric compound of 2(5H) furanone

The HeI photoelectron (PE) spectra of both 2(5H) furanone and its trans-chair-dimenc-compound (t-c-DFN) are reported.The assignment of the PES bands is made on the basis of band shapes,the PES results of the molecules which have the similar atomic groups,and the restricted Hartree-Fock (RHF) calculations for the molecules studied.From the results of both PES experimental and theoretical calculations,it is proved that the ionization potential (IPs) of the HOMO for the dimenc-compound is lower than that of the HOMO for the monomer.And the total energy computed for the t-c-DFN is the lowest in the four possible configurations of dimeric-compounds of 2(5H) furanone Therefore the synthesis of t-c-DFN is also the easiest.     

A THEORETICAL APPROACH TO P_(co_2) EVOLUTION IN THE ATMOSPHERE BASED ON ASSOCIATIONS OF SEDIMENTARY MINERALS

Based on the theory of pH evolution of sea water and the balance between the seawater and the atmosphere the authors discussed the problems about (i) the method ofcalculating P_(CO_2) in the ancient atmosphere with the associations of sedimentary miner-als; (ii) the evolution of P_(CO_2) values in the geologic history; (iii) the relations of thepH evolution of sea water with carbonate precipitations; and (iv) calculation of the pHlimit for some associations of sedimentary minerals and its corresponding P_(CO_2) valuesin the atmosphere. The authors pointed out that though carbonates had deposited little in the Archaean,the content of CO_2 gas in the Archaean atmosphere was very high and was gradually go-ing up to form a thick CO_2 atmosphere. Up to 2600 Ma ago, the P_(CO_2) had reached a gradeof 10- 50 atm. There was a general trend of evolution that from the early Proterozoicera to the present the depositional horizon of carbonate layers was gradually risingand finally surpassed the horizons of clay min     

STUDIES ON CHIRAL THIOPHOSPHORIC ACIDS AND THEIR DERIVATIVES [ⅤⅢ]——THE STEREOCHEMISTRY OF SOME REACTIONS OF THE MIXED ANHYDRIDE OF O-ETHYL PHENYLPHOSPHONOTHIOIC AND O-ETHYL O-PHENYL PHOSPHOROTHIOIC ACIDS

In this paper, (1) alkaline methanolysis, (2) acid methanolysis, (3) alkaline hydro-lysis, (4) aminolysis of (+)-(R)-(R)-mixed anhydride 1 of O-ethyl phenylphosphonothioic:and O-ethyl O-phenylphosphorothioic acid, (5) its reactions with KSH and (6) with PCl_5have been studied. The cleavage of P-O-P bonds in all the reactions studied has beenfound. In reactions (1)-(4), attacks of nucleophiles occur to the phosphorus atoms of phos-phonyl groups forming the products with inversion of configuration, while the configurationof the phosphorus atoms of phosphoryl groups which are not attacked is retained. Inreaction (5), the uncleophile -SH attacks the phosphorus atom of the phosphonyl group,but a racemic product results because of the formation of ph(EtO)P(S)~- which loseschirality; the configuration of the phosphorus atom of the phosphoryl group which is notattacked is still retained. In reaction (6), both the phosphonyl and phosphoryl groups arechlorinated giving as products (-)-(R)-thiophophonyl chloride 1     

A Thermochemical Study on Complex Nickel（Ⅲ）L—α—Histidine

The formation enthalpy ofcomplex nickel(Ⅱ）-histidine(His)in water was determined by means of microcalorimetry in the temperature range of 298.15-323.15K.The standard enthalpy of the formation of Ni(His)2^2 (aq) was calculated.On the basis of the experimental and the calculated results,three thermodynamic parameters(the activation enthaly,the activation entropy and the activation free energy),the rate constants,three kinetic parameters(the apparent activation energy,the pre-exponential constant and the reaction order)of the formation reaction of the title complex were obtained.     

Synthesis of α-Bromine- Terminated Polystyrene Macroinitiator and Its Initiation of MMA Polymerization by ATRP

In the present paper the synthesis of block copolymers via the transformation from living anionic polymerization (LAP) to atom transfer radical polymerization (ATRP) was described. Α-Bromine-terminated polystyrenes(PStBr) in the LAP step was prepared by using n-BuLi as initiator, tetrahydrofuran (THF) as the activator, α-methylstyrene (α-MeSt) as the capping group and liquid bromine (Br2) as the bromating agent. The effects of reaction conditions such as the amounts of α-MeSt, THF, and Br2 as well as molecular weight of polystyrene on the bromating efficiency (BE) and coupling extent (CE) were examined. The present results show that the yield of PStBr obtained was more than 93.8% and the coupling reaction was substantially absent. PStBr was further used as the macroinitiator in the polymerization of methyl-methacrylate(MMA) in the presence of copper(Ⅰ) halogen and 2,2-bipyridine(bpy) complexes. It was found that the molecular weight of the resulted PSt-b-PMMA increased linearly with the increase of the conversion of MMA and the polydispersity was 1.2-1.6. The structures of PStBr and P(St-b-MMA) were characterized by 1H NMR spectra.     

Investigation of the Photosensitized Mechanisms of PCBs in the Presence of Natural Organic Matter

The structures of 26 different congeners of polychlorinated biphenyls(PCBs, including monothrough deca-chlorinated) were optimized using density functional theory(DFT) calculations with the 6-31+G(d,p) basis set. The activation energies for the dechlorination of these systems were calculated for direct photodegradation and photosensitized degradation reaction pathways in the presence of natural organic matter(NOM). The dechlorination mechanism of these PCBs and the ring-opening reaction mechanisms(using QST3 method) of the photosensitive degradation products were analyzed. The results showed that(i) the activation energy for the photosensitized degradation of PCBs was much lower than that of direct photodegradation;(ii) the degradation activities(i.e., C–Cl bond cleavage energies) were the same for both degradation pathways and followed the order ortho meta para;(iii) the degradation activities of asymmetric PCBs were higher than those of the corresponding symmetrical PCBs for the direct photodegradation and it was completely opposite in the photosensitive degradation;(iv) there was no correlation between the dissociation energy and the number of C–Cl bonds for the direct photodegradation and dechlorination products were all biphenyl;(v) the degradation activity of PCBs decreased as the number of C–Cl bonds increased in the presence of NOM; and(vi) even when the dechlorination reaction was incomplete, it produced chlorophenol. Furthermore, the free radicals of NOM led to the ring-opening reactions of PCBs via an initial addition step. The main site of these ring-opening reactions was the ortho position. Notably, the likelihood of ring-opening reactions occurring involving the degradation products increased as the degradation degree of PCBs increased.     

EPR STUDIES OF CUBANE-LIKE TETRANUCLEAR MOLYBDENUM CLUSTER COMPOUNDS

<正> The polycrystalline EPR spectra of three cubane-type tetranuclear molybdenum cluster compounds Mo4S4(μ-OAc)2(dtp)4(1), Mo4S4(μ-OAc)2(dtp)4-·H (2), Mo4OS3(μ-dtp)3(dtp)3(3) are reported. By comparison of the EPR parameters at room temperature and at 77K, it is found that the EPR spectra of (1) and (2) should be attributed to the whole molecule of the cluster compounds while that of (3) to the molybdenum atoms under two different local environments. According to the results of quantum chemistry calculations by means of SCC-EHMO method and the data of X-ray crystal structure analysis, it is shown that the frontier orbital (HOMO), which is composed mainly of the multiple centre d-pπ bonds botween the metal atoms and the bridge (or terminal) groups and occupied by the unpaired electrons of the clusters, is similar to that of the π-conjugated system of free radicals. In many circumstances, the local environment around the Mo atom in cluster distors from ideal Td symmetry to a lower symmetry as to make th     

STUDY OF TPD AND KINETICS ON NO+CO OVER COPPER-SUBSTRATE CATALYSTS

The kinetics of the CO+NO reaction and the adsorption of CO,NO,CO_2 and N_2O over Cu-M-O(Ⅰ)(M=Fe or Mn)and Cu-M-Ce-O(Ⅱ)catalystswere studied in a micro reactor system with TPD technique.The results showthat the catalytic activity of(Ⅱ)is higher than that of(Ⅰ)for the CO+NO re-action,and the higher the conversion of NO,the greater the activity differencebetween(Ⅰ)and(Ⅱ)is.Over(Ⅰ)the rate of NO elimination is dependent onthe partial pressures of NO,CO,CO_2 with the kinetics orders of0.75～0.71,0.95～0.96,-0.28～-0.30,respectively.The TPD study shows that thepresence of Ce in(Ⅱ)may promote the adsorption of NO,CO on the surface,that is to say,increase the coverage(θ)_(NO),(θ)_(CO),which results in the reaction or-ders with respect to NO,CO down in the kinetics equation.For CO_2 and N_2Othe situation is opposed,the presence of Ce makes the(θ)_(CO_2),and(θ)_(NO)on(Ⅱ)de-crease,which weakens the inhibition of CO_2 for the topic reaction.     

Study on the Photophysical Process in N-Phenyl Phenothiazine and N-(2-Pyridine) Phenothiazine

By the measurements of the solvent and temperature effects of the fluorescence emission spectra and lifetime of N-phenyl phenothiazine (PHZ) and N-(2-pyridine) phenothiazine (PYZ),the existence of strongly twisted intramolecular charge transfer (TICT) state in PYZ emission spectra is proved.The exciplex formed by PHZ, PYZ and dimethyl terephthalate (DMTP) is investigated, and moreover, the transient absorption spectra of positive and negative ions as the results of the dissociation of the exciplex in the polar solvents is observed through the flash photolysis.     

A New Kinetic Method of Processing TA Data

A new method of investigating the kinetic parameters and mechanism functions of a solid phase reaction is presented. This method is to analyze the data based on the use of these data at the same temperature and the same degree of conversion on a series of TA curves with different heating rates, so that the kinetic triplet--the activation energy E, the pre-exponential factor A and the analytical form of the function of conversionf(α) can be obtained. The main advantage of this method is that the values of E and f(α) are obtained respectively, and the determination of f(α) is not under the influence of the value of E and the calculation of the value of E is not influenced by thef(α) either.     

Investigation of aggregation in solvent extraction of lanthanides by acidic extractants (organo-phosphorus and naphthenic acid)

Three acidic extractants (Ⅰ) di(2-ethylhexyl) phosphoric acid (HDEHP),(Ⅱ) 2-ethylhexyl phos-phonic acid mono-2-ethylhexyl ester (KEHPEHE) and (Ⅲ) naphthenic acid were employed in preparing the samples for the characterization of the coordination structure of lanthanlde-extractant complexes and the physicochemical nature of aggregates formed in the organic diluent of the solvent extraction systems.Photo correlation spectroscopy (PCS) re-suits on the aggregates formed by the partially saponified HDEHP in n -heptane showed that the hydrodynamic radius of the aggregates was comparable to the molecular dimensions of HDEHP.The addition of 2-octanol into the diluent,by which the mixed solvent was formed,increased the dimensions of the corresponding aggregates.Aggregates formed from the ianthamde ions and HDEHP in the organic phase of the extraction systems were found very unstable.In the case of naphthenic acid,PCS data showed the formation of w/o microemulsion from the saponified naphthenic acid in the mix     

SYNTHETIC STUDIES ON BLOOD COMPATIBLE BIOMATERIALSⅡ. SYNTHESIS OF POLY(ETHYLENEGLYCOL MONOMETHYLLTHER ) METHACRYLATE AND ANTITHROMBOGENICITY OF ITS COPOLYMERS

Poly (ethyleneglycol monomethylether) methacrylate (PEGMM)was synthesized by means of the reaction of methacrylyl chloride with sodium monomethylpolyethyleneglycoxide and was characterized by FTIR, ~1H-NMR,and ultraviolet spectrometries. A series of poly (vinyl alcohol)-graft-PEGMM (PVA-g-PEGMM )and methyl methacrylate-PEGMM copolymer (PMMA-PEGMM) were prepared and tested for antithrombogenicity in vitro. The results indicate that the antithrombogenicity of the copolymers basically increases with the increasing of the DP of polyoxyethylene (POE) chain and tends to a plateau after the DP around 114,i.e. the long chain structure of POE is favourable to the antithrombogenicityof its copolymers ;moreover, the extent of the improvement ofantithrombogenicity also relates to the PEGMM content of the copolymers and the kind of the matrix that the POE chains are located on. These results are consistent with the anticipation of the hypothesis of maintaining proteins normal conformations for blood compatible bioraaterials.     

Investigation of radionuclide 63Ni(II) sequestration mechanisms on mordenite by batch and EXAFS spectroscopy study

The sorption behavior and microscopic sequestration mechanisms of radionuclide 63Ni(II) on mordenite as a function of aging time,ionic strength,initial 63Ni(Ⅱ) concentrations,solid content and coexistent electrolyte ions were investigated by the com-bination of batch and EXAFS techniques.Macroscopic experiment results show that the sorption of 63Ni(Ⅱ) is dependent on ionic strength at pH<7,and independent of ionic strength at pH>7.The sorption percentage of 63Ni(Ⅱ) on mordenite increases with increasing solid content,while the sorption capacity decreases as solid content increases.The presence of different elec-trolyte ions can enhance or inhibit the sorption of Ni(II) on mordenite in various degrees.EXAFS analysis results of the sam-ples under three different ionic strengths suggest that the retained 63Ni(Ⅱ) in these samples exists in an octahedral environment with six water ligands.In the initial period of rapid uptake,the sorption of 63Ni(Ⅱ) is dominated by the formation of in-ner-sphere surface complexes.As aging time increases,63Ni(Ⅱ) sequestration behavior tends to be mainly controlled by the formation of Ni phyllosilicate co-precipitates and/or Ni(OH)2(s) precipitates.Results for the second shell fit of the sample pre-pared at an initial 63Ni(Ⅱ) concentration of 100 mg/L indicate the possible formation of Ni polynuclear surface complexes.Both the macroscopic sorption data and the molecular level evidence of 63Ni(Ⅱ) surface speciation at the mordenite/water in-terfaces should be factored into better predictions of the mobility and bioavailability of 63Ni(Ⅱ) in environment mediums.     

Spectrophotometric Determination of Trace Chromium(VI) in Mass Chromium(III)

There is little conclusive evidence of the toxic effects of Cr(III) so far, but Cr(VI) has carcinogenic activity, so the analysis of the chromine ions is very important in environmental research and the quality control of industry products. Usually Cr(III) and Cr(VI) interfere with each other in the species analysis, the measurement of Cr(VI) of numerous previous papers is related to the Cr(VI) samples, which contain a little Cr(III). When the amount of trivalent chromine exceeds ten …     

SYNTHESIS AND PROPERTIES OF ANILING ANILING AND 0-AMINOBENZENESULFONIC ACID COPOLYMER*

Poly(aniline- co-o-aminobenzenesulfonic acid) (PAOABSA) as a water soluble conducting polymerwas synthesized by chemical polymerization. The productivity and the room-temperature conductivity of thecopolymer were measured as a function of the reaction conditions, such as reaction temperature, the ratio ofoxidant to monomer and the degree of sulfonation defined as the ratio of sulfur to nitrogen atoms(S/N). Themain results obtained are summarized as follows : (1) lower reaction temperature (at about 0℃) is favorablefor the enhancement of the room-temperature conductivity of the copolymer; (2) higher content of oxidant isunfavorable for increasing the room-temperature conductivity of the copolymer; (3) both productivity androom-temperature conductivity of the copolymer decrease with increase of the degree of sulfonation whichwas always lower than 0.5 even an excess of o-aminobenzenesulfonic acid was added, probably because thereactivity ratio of aniline (γ=2.99± 0.05) is much higher than that of o-aminobenzenesulfonic acid (γ_2 = 0.06±0.02) estimated by using Fineman-Ross method and least square method.     

A Novel Optical Properties of Molecular “Light Switch” and its Analytical Application

Because of the high affinity (Ka≥ 10^6 L mol^-1) between Ru(phen)2(dppz)^2 and DNA, the adding of DNA in the solution of Ru(phen)E(dppz)^2 -SDS makes the dissociation of Ru(phen)E(dppz)^2 -SDS, and results in decrease of the resonance light scattering (RLS) signals andincrease of the absorbance. Based on this, a novel method is proposed for DNA assay.     

Influence of amphiphilic structures on the stability of polyphenols with different hydrophobicity

Autooxidation of five polyphenols representing range of different hydrophobicities(catechin gallate (CG),(-)catechin((-)C),epicatechin(EC),epigallocatechin gallate(EGCG)and epigallocatechin(EGC)) in three different aqueous solutions:molecular solution,micellar solution(Tween-20)and liposomal dispersion(soybean lecithin)was monitored by HPLC.The rate of oxidation of the five polyphenols was higher at pH 4.5 than at pH 3.5.Compared with the control,addition of Tween-20(micellar structure)and lecithin(liposomal structure)significantly decreased the degradation of polyphenols.In the presence of lecithin the autooxidation of all the five polyphenols was slower than in the presence of Tween-20. The effective protection of the colloidal structures was compared with the hydrophobicity of the poly- phenols estimated from the partitioning between octanol and water.The protection from oxidation in the presence of the colloidal structures(micellar or liposomal)increased with increasing partitioning of a polyphenol towards the hydrophobic environment.The protecting effect of the colloidal structures was more effective at pH 4.5 than at pH 3.5.     

FEATURES OF Pb ISOTOPIC COMPOSITION OF ORES AND EVOLUTION OF CONTINENTAL CRUST OF CHINA

Based on the Pb isotopic features, the ore leads in the continent of China can be dividedinto four types: (i) single-stage lead of low μ value derived from mantle, (ii) homogeneouslead of crustal source with high μ value, (iii) modern mixing lead between mantle andcrust, and (iv) residual lead of crustal source. As the leads from mantle had possessed single-stage features (μ = 7.8) before the Proterozoic, the ages of continental crust can be calculatedbased on the mixing Pb of type (iii). The results hidicate that the continental crust of Chinawas mainly generated during the Archaean, and the growth rates of crust reached the max-ima by the ages of 3.3-3.4, 2.6 and 1.6-1.7 b.y. The occurrences of residual crust Pbwith high ~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb anomalies were associated with the remelting andreconstruction of crust since 1.6 b.y. ago. The lead sources in the continent of China showhigher Th/U ratios (3.3-6.5) and ~(207)Pb anomalies than those in other continents, indicationthe conti     

Molecular Mechanism of High Energy Proton Radiation——Raman Spectroscopic Character of Microcosmic Damage in the Space Structure of DNA

High energy proton is an important type of the space radiation. The paper investigates the radiatione ffect of high energy proton (27.9 MeV) on DNA aqueous solution in the field of the molecular mechanism. The following information about the microcosmic damage to the space structure of DNA was obtained: (ⅰ) breakage of a part of interbase hydrogen bonds which maintained double helical structure of DNA; (ⅱ) damage on four bases, in which the damage on adenine ring was the most serious; (ⅲ) obvious change of deoxyribose; (ⅳ) serious damage on backbone phosphate ion (PO_2~-) and phosphate diester (PO_2) and the occurrence of scissions of double-stranded and single-stranded DNAs; (ⅴ) obvious decrease in the amount of B-form conformation.