DETERMINATION OF LINKING NUMBER OF pBR322 DNA

Do the two chains of the DNA molecule coil round one another plectonemically! If so. the linking number of relaxed circular DNA containing N base pairs, expected from the classical double helix, should be roughly equal to N/10.pBR322 DNA is a covalently closed circular DNA duplex containing 4362 base pairs. When it is in supereoiled state, its linking number calculated from B-DNA should be of the order of 4×10~2We have determined the linking number or relaxed pBR322 DNA Ⅰ' with electron microcopy. With the help of gel electrophoresis, it is proved that when DNA Ⅰ' has the writhing number Wr=2 2, its linking number L=1, 2, 3, 4. A further deduction is that the linking number of native pBR322, Lk《 4362/10.The difference between our experimental results and the estimates from the classical double helix structure is tremendous. The phenomena cannot be explained if there is only one form of DNA structure. Probably the tertiary structure of DNA is intrinsically determined by its primary structure, influen     

HEAT-STABLE DNA POLYMERASE I LARGE FRAGMENT RESOLVES HAIRPIN STRUCTURE IN DNA SEQUENCING

A heat-stable large fragment was obtained by subtilisin digestion of DNA polymerase, prepared fromBacillus stearothermophilus. The dideoxy sequencing method~([1]), combined with the use of M13 vector~([2,3])has proved to be the most powerful one for obtaining the sequences of large genomes. However, the hair-pin structure formed along the single-stranded DNA template often prevents the DNA polymerase frommoving on, with the result that no sequence information can be obtained. The heat-stable large fragmentthat we have obtained has proved to be the most active at 65℃. When the sequencing reaction was car-ried out at this temperature, the hairpin structure was resolved and the sequencing gels obtained weresatisfactory.     

STUDIES ON THE PHOTOCHEMICAL REACTION OF TERTIARY AROMATIC AMINES AND ALIPHATIC HALIDES——STRUCTURE OF THE PRODUCT AND MECHANISM OF THE REACTION

The photochemical reaction of aromatic amines in the presence of aliphatic halides and molecular oxygen were studied. There is a very obvious structural effect of amines on the photoreactions, and the purple products, formed only in the tertiary aromatic amines system, were proved to be amiuium radical salts, e. g. CH_3—(CH_3)_2Cl-by moans of UV, NMR and ESR spectroscopies electronic conductivity and chemical analysis. The purple product can oxidize the adrenaline to adrenochrome. The mechanism of the photoreaction and the oxidation were discussed.     

A Novel Toxicological Evaluation of TiO2 Nanoparticles on DNA Structure0

TiO2 has been tested to be toxic to DNA under the photo-irradiation of ultraviolet A （UVA）. However, in the dark conditions, after several days of treatment with TiO2 in aqueous solution, the interaction between TiO2 and two types of DNA was detected and the mechanisms were studied by the methods of gel-electrophoresis, IR spectroscopy and TEM. The results showed that the DNA would be bound to TiO2; the ratio of binding was related to the concentration and the treating time; the mechanism of binding is related to phosphate groups of DNA. Besides, DNA with different structure showed different degree of binding. These findings showed a new possible way through which the TiO2 nanoparticles interact with DNA.     

THE MECHANISM OF CURE REACTION OF 4,4''''-DIAMINODIPHENYL METHANE WITH TETRAGLYCIDYL 4,4''''-DIAMINODIPHENYL METHANE EPOXY

The cure reaction of tetraglycidyl 4,4'-diaminodiphenyl methane (TGDDM) epoxy resin with 4,4'-diaminodiphenyl methane (DDM) has been studied by using DSC. Instead of one exothermic peak, two exothermic peaks, indicative of a complex reaction mechanism, are shown in the DSC curve of TGDDM-DDM mixtures in nonisothermal cure experiments when the content of DDM is lower than stoichiometric ratio. The result of the kinetic analysis of the cure reaction shows that the activation energy of the lower temperature exotherm peak is about 56 kJ/mol and that of the higher temperature exotherm peak is about 136 kJ/mol. The lower temperature cure reaction peak can be attributed to the primary amine-epoxide and secondary amine-epoxide reactions, and the higher temperature cure reaction peak can be attributed to the epoxide-hydroxy reaction under catalysis of tertiary amine in the TGDDM epoxy resin. Because the network density of the cured epoxy resin is determined by these two reactions, the content of DDM has little effect on the glass transition temperature of cured epoxy resin.     

NUCLEAR PORE COMPLEX IN SPERMATOGENESIS OF BEIJING DOMESTIC DUCK——ELECTRON MICROSCOPE OBSERVATION OF FREEZE-ETCHING

The nuclear pore complex in spermatogenesis of Beijing domestic duck has been studiedby means of electron microscopic observation of freeze-etching. The structure of the poreobserved proves to be in accord with the model of the nuclear pore complex proposed respec-tively by Franke (1970) and Roberts et al. (1970). But its central granule may be present(1--3 granules) or absent. The granules are considered to be material in transit. The sizeand frequency of the pore vary with different types of reproductive cells, which is believedto be related to the cells' function. The pores concentrate on the side of nucleus near Golgizone in primary spermatocyte and near the proacrosome of spermatid, and this shows thefunctional variety of parts in the nucleus.     

CHROMATIN AND DNA OF YOLK GRANULES BENEATH "BLASTODERM REGION" OF UNFERTILIZED CHICKEN EGG

Electron microscopic study shows that the chromatin structure of yolk granules beneath the "blastoderm region" of the unfertilized chicken egg is identical to that of yolk granules beneath the blastoderm of the fertilized and unincubated chicken egg, and both chromatin structures are very similar to those of blastoderm nuclei. Furthermore the molecular shapes of DNA of both yolk granules are also very similar to those of the blastoderm nuclei, being all linear. Based on these observations, we have come to the conclusion that chromatin and DNA widely exist in the yolk when yolk granules have reached their development-specified competence. The results indicate further that the yolk granules are capable of synthesizing DNA, and provide the condition for the interaction of DNA with histones to form chromatin through self-organization.     

Enantioselective Alkynylation of Ketones Promoted by β-Sulfonamide Alcohol-Titanium Complexes

A readily available β-sulfonamide alcohol-titanium complex was found to be effective on promoting the asymmetric addition reaction of an alkynylzinc reagent to unactivated simple ketones under very mild conditions. And the corresponding chiral tertiary propargylic alcohols were obtained with enantiomeric excesses of up to 86%, which provided a simple, practical and inexpensive method to generate chiral tertiary propargylic alcohols.     

A SPIN LABELING STUDY OF CALF THYMUS DNA

2,2,6,6-Tetramethyl-4-(bis-ethyteneimino) triazinamino-piperidine-1-oxyl was used as the spin label. In ESR spectra of the product obtained (SL-DNA), the strongly immobilized peak greatly prevailed over the weakly immobilized component and a significant difference existed between their microwave saturation characteristics. The spin labeling reaction was investigated in some details. With the aid of beat denaturation (100℃, 15 min) of SL-DNA in conjunction with acid degradation (pH 1.5, 37℃, 23h), the quantity of labels bound to DNA was determined. Namely, the number of labels bound to 1000 nucleotides was found to be 4.0—12.6. The structural transition temperature of SL-DNA attained from variable temperature measurements was about 63℃ and a rise in this temperature was observed with increasing salt concentration.     

Endonuclease-based Method for Detecting the Sequence Specific DNA Binding Protein on Double-stranded DNA Microarray

The double-stranded DNA (dsDNA) probe contains two different protein binding sites. One is for DNA- binding proteins to be detected and the other is for a DNA restriction enzyme. The two sites were arranged together with no base interval. The working principle of the capturing dsDNA probe is described as follows: the capturing probe can be cut with the DNA restriction enzyme (such as EcoR I) to cause a sticky terminal, if the probe is not bound with a target protein, and the sticky terminal can be extended and labeled with Cy3-dUTP by DNA polymerase. When the probe is bound with a target protein, the probe is not capable to be cut by the restriction enzyme because of space obstruction. The amount of the target DNA binding proteins can be measured according to the variations of fluorescent signals of the corresponding probes.     

PREPARATION,IDENTIFICATION AND INTERFACIAL ACTIVITIES OF PETROLEUM CARBOXYLATE AS SURFACTANT FOR CHEMICAL FLOODING

Petroleum carboxylate that may be suitable for tertiary oil recovery have been producedinexpensively from the fractions of Daqing crude oil by a two step process.The feed stock was firstoxidized in the vapor phase,followed by reaction of the oxidized products with sodiumhydroxide.Dilute solutions of sodium carboxylates were produced and showultralow(10~(-2)mN/m)interfacial tensions(IFTs)against a variety of hydrocarbons with a widerange of ACN(Alkane Carbon Number).Infrared spectroscopy was used to identify the functionalgroups in the oxidized and the saponified products.     

ASSIGNMENT OF ~(13)C NMR SPECTRA OF POLYMER WITH SEMIEMPIRICAL METHOD——SURVEY OF SPECTRUM OF SECONDARY CARBON OF 1, 2-PBD

In chain molecules of 1, 2-PBD, there are two kinds of gauche arrangements, which is the cause of making the spectrum of the secondary carbon in main chain of the polymer split. In such a complex system, the gauche arrangements of the secondary carbon and the tertiary carbon occupy an important position. Hence, the contribution of the tertiary carbon to the chemical shifts of the secondary carbon has a decisive effect on the sequence structure distribution. In comparison the contribution of vinyl groups is much less. The γ values are: γ_1=-6.37～-6.41 ppm represents the effect of the tertiary carbon and γ_2=0.0～-1.56 ppm the contribution of vinyl. The mean square errors are 0.364 and 0.166×10~(-2) ppm~2, respectively in the two cases of considering the effect of vinyl and vice versa. In this paper, we discuss the effects of model chain type, chain length and temperature on the bond probability. Meanwhile, it is pointed out that there exist a few cases, which are not in accord with the usual distrib     

SYNTHESIS AND PROPERTIES OF POTASSIUM 11-TUNGSTONIOBATE

The anion of tungstoniobate was synthesized for the first time as KqNbW″O40 2H_2O by the reaction of soluble potassium niobate and porous white tungstic acid in aqueous solution. The structure of the anion may be proposed reasonably to be similar to that of dodecameric anion of paratungstate, resulting from substituting of one WO_6 group in paratungstate anion by one NbO_4 group and leading to the formation of tungstoniobate anion according to the extreme similarity of IR and UV spectra of these two different anions. Potassium 11-tungstoniobate is soluble in wator and unstable in alkaline medium while the structure of the anion may be considered to keep unchanged in acidic medium according to the spectrophotometrical results.     

Homocoupling of Aryl Iodides Catalyzed by Cyclopalladated Complexes of Tertiary Arylamines

Homocoupling of aryl iodides catalyzed by cyclopalladated complexes of tertiary arylamines gives symmetric biaryls with good yields in DMA or ionic liquid [Bmim]BF4. This catalytic alternative of the Ullmann reaction has proved to be sensitive to both electronic and steric factors of substrates.     

INTRODUCING EXOGENOUS DNA INTO PLANTS AFTER POLLINATION——DNA TRAVERSE PATHWAY OF POLLEN TUBE TO REACH EMBRYONIC SAC

The technique of introducing exogenous DNA into plants through the pathway of pollen tube after pollination has been applied since 1978 for transformation of the egg, zygote or carly embryonic cells. By introducing the erogenous DNA containing the goal gene(s) into cotton and rice, several new varieties with economic value and genetic stability are obtained. Thus molecular breeding of crops can be realized by this biotechnique.The pollen tube pathway is demonstrated by tritium-labelled cotton DNA (> 50kb). The labelled DNA is injected into cotton ovaries from the center of the top 24 h after selfing. 30 min to 8 h later, the ovaries are removed. It is clearly shown that the exogenous DNA can only pass from the micrnphyle to the opened nucellus, and then reach the embryonic sac. ~3H-DNA can be found in the embryonic sacs 30 min after injection. In more than 80％ of the embryonic sacs ~3H-DNA can be seen between 2 and 4 h after injection. No ~3H-DNA is found inside the pollen tubes. Therefore it is not th     

ADSORPTION OF TANNIN ACID ONTO AN AMINATED MACROPOROUS RESIN FROM AQUEOUS SOLUTIONS

A macroporous polymeric adsorbent NG-8 was synthesized with divinylbenzene using conventional suspension polymerization technique.Its aminated product NG-9 was prepared by introducing tertiary amino groups into NG-8 for removal of tannin acid from aqueous solutions.NG-9 could be used directly without a wetting process and had higher adsorption capacity than NG-8,which might be attributed to the enhanced adsorbent-adsorbate interaction due to the tertiary amino groups on the polymeric matrix.The Langmuir equation was successfully employed to describe the adsorption process.The adsorption enthalpy change further validated the uptake of tannin acid on NG-9 to be an enhanced physical adsorption because of the Lewis acid-base interaction.In addition,adsorption kinetic studies testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate maybe for the hindrance of the tertiary amino groups and water clusters built up.     

Oxidation of glyoxal to glyoxylic acid by oxygen over V2O5/C catalyst

A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH regulation during the reaction. By using this catalyst, the conversion of glyoxal and the yield of glyoxalic acid were 29.2% and 13.6%, respectively at 313 K and oxygen flow 0.1 L/rain after reaction for 10 h.     

Metal-free reduction of tertiary phosphine oxides with Hantzsch ester简

The （COCl）2/Hantzsch ester is found to be an effective system for the metal-free reduction of tertiary phosphine oxides. The reaction proceeds under mild conditions, and is applicable to triarylphosphine oxides and alkyldiarylphosphine oxides to produce the corresponding tertiary phosphines in good to excellent yields. This new finding provides a practical, convenient and metal-free method for the reduction of tertiary phosphine oxides to tertiary phosphines, and shows potential application in organic synthesis.     

One—dimesional Infinite Chain Organotin Compounds： Synthesis and structural Characterization of Triphenyltin Thiazole—2—carboxylate and Triphenyltin 3—Pyridinylcarboxylate

Triphenyitin thiazole-2-carboxylate(1) and triphenyltin 3-pyridinylcar boxylate(2) were synthesized by the reaction of sodium thiazole-2-carboxylate or sodium 3-pyridinylcarboxylate with the triphenyltin chloride and their crystal structures were determined by single crystal X-ray diffraction analysis.In the structure of 1, the tin atom is five-coordinated in a distorted trigonal bipyramidal structure.Due to the presence of a close intermolecular Sn…S interaction distance of 0.3666nm,the structre can be described as a weakly-bridged on-dimensional chain compound.In the structure of 2,the tin atom is five-coordinated with bridging 3-pyridinylcarboxylate ligands N atom and resulting structure is one-dimensional chain compound.     

Reaction Mechanism,Synthesis and Characterization of Urea-glyoxal （UG） Resin

The reaction mechanism of glyoxal （G） with urea （U） under weak acid condition was theoretically investigated at PW91/DNP/COSMO of quantum chemistry using density functional theory （DFT） method. The results show that the addition reaction of G with U under the conditions mainly involves the reactions of U with protonated glyoxal （p-G）, protonated 2,2-dihy- droxyacetaldehyde （p-G 1） and protonated bis-hemdiol （p-G2） to form two important carbocation reactive intermediates of C-p-UG and C-p-UG1, and two important hydroxyl compounds of UG and UG1. These compounds play important roles in the formation of UG resin. According to the result of quantum chemical calculation, UG resin was synthesized successfully under weak acid conditions. The UG resin was characterized by matrix assisted laser desorption ionization time of flight mass spectrometry （MALDI-TOF-MS）, ultraviolet and visible spectroscopy （UV-vis）, Fourier transform infrared spectroscopy （FT1R） and nuclear magnetic resonance spectroscopy （13CNMR and 1HNMR）. These instrumental analytical results agree with each other and further confirm the addition reaction pathway of glyoxal with urea proposed by quantum chemical calculation.