STUDIES ON THE STRUCTURE OF FORKED CONJUGATIVE SYSTEMS——THE CRYSTAL STRUCTURE AND CONFORMATION OF 2-BENZOYLTHIOPHENE

The crystal structure and the conformational properties of the title compound have been investigated by means of X-ray single diffraction and the PCILO methods. C_(11)H_8OS belongs to the orthorhombic system, the space group is P2_12_12_1, a=11.945(4), b 10.236(7), c=7.649(4), Z=4, D_c-1.37g/cm~3. The molecule is not planar structure because of steric hindrance. The thiophene ring and the phenyl ring make dihedral angles of 21°(θ_1) and 32°(θ_2) with the carbonyl frame plane, respectively. The lowestenergy conformation obtained by PCILO calculation is in agreement with the crystallinestatc conformation. In this paper, the molecular structure, the influence of steric hindrance and the groups' abilities to conjugate upon the conformation and the variations of the potential energy of the isolated molecule in the whole conformational space are discussed.     

LAMELLAR STRUCTURE OF THERMOTROPIC LIQUID CRYSTALLINE POLYMERS

The lamellar structure of a thermotropic aromatic polyester with flexible spacer has beenstudied by using transmission electron microscopy. It was found that the lamellar structure couldbe observed in the crystalline samples of this semirigid polymer crystallized from different states.The thickness of lamellae is around 10 nm, which is similar to that of the conventional polymersof flexible chain molecules. The molecular chains in the lamellae are oriented in the thicknessdirection as determined by electron diffraction. The possibility of molecular chains folding in the lamellae has been discussed.     

THE CRYSTALLOGRAPHIC STRUCTURE OF THE PHOTOOXIDIZED PRODUCT OF HYPOCRELLIN A AND THE STUDY OF THE PHOTODYNAMIC ACTION MECHANISM

In attempting to study the phototherapeutic action and the photosensitized oxygenation mechanism, we have determined the crystal structure of the main oxidized product of hypocrellin A (HA). It was crystallized in monoclinic system with space group P2_1. The cell data are: a=10.030(3), b=8.877(3), c=15.764(5), β=104.50(2)°, Z=2. The crystal structure has been determined by direct method and refined to a final R of 0.055 based on the 1408 observed reflections with l>2.5σ(Ⅰ). The photooxidized product is composed of a heptacyclic aliphatic hydrocarbon connecting with two α-naphthoquinone derivatives as its skeletal molecule. No peroxidic linkage has been found. On the basis of the crystal structure determined, we have deduced part of the process of formation of the oxide, ⅰ. e. firstly, the peroxide was formed by photocycloaddition of oxygen molecule to Hypocrellin A, then thermodissociation took place to form a stable oxide.     

THE PRIMARY STRUCTURE OF ARROWHEAD PROTEINASE INHIBITOR

After the reduction and carboxymethylation of disulfide bonds, arrowhead proteinase inhibitors A and B were cleaved either by proteinases or by cyanogen bromide, the fractionated and purified peptides were then subjected to sequencing by a gas phase automatic sequencer, the primary structures were completed by the alignment of the peptides sequenced with overlapping peptides. Both inhibitors A and B consist of 150 amino acid residues with three pairs of disulfide bonds, share 90% homology in structure, and are markedly different from all other Ser proteinase inhibitors so far known. Hence, the arrowhead inhibitor may belong to a new inhibitor family. Based on their structure characteristics, it was deduced that both their two reactive sites might be located in the positions of Lys-Ser (45-46) and Arg-Tyr-Lys (77-79), respectively. Among 13 mutated residues in inhibitors A and B, the substitution of residue Arg in position 87 of inhibitor B for residue Leu in A might be the main cause of leading to diffe     

THE SOLID SOLUTION PHASE DIAGRAM OF THE MIXTURE OF ORTHO- AND PARACHLOROTOLUENES

The complete miscible solid solution with a minimum freezing point (-50.75℃; 26.88% para-) of the ortho- and para-chlorotoluene has been proved in this paper by many methods as the thermal analysis method, the X-ray matter phase analysis, the fractional crystallized separation method and the solidified separation method of solid solution, and by the Fel'dman's experiential productivity formula compared with the theoretical productivity formula which was obtained from the solidified separation according to the solid solution phase diagram. Therefore, the international official conclusion of simple eutectic type phase diagram of ortho- and para-chlorotoluene mixture does not agree with the experimental facts.The powder diffraction files of ortho- and para-chlorotoluenes are given in this paper.     

STUDIES ON THE CRYSTAL STRUCTURE OF Al-(D-TRYPTOPHAN) INSULIN

We have determined the crystal structure of Al-(D-Trp) insulin and discovered that it belongs to the trigonal system with space group R3. The parameters of the unit cell are a=b=78.6, c=50.0. A set of data for half a sphere reciprocal space to a spacing of 2.2 were collected. The model was adjusted and refined by using a step-by-step approach and a stereochemically-restrained least squares program, assisted by manual revision based on the difference Fourier maps, to a final R-factor of 0.218. The main and side chains of both Al-D-Trp residues in the asymmetric unit are well ordered. The packing of Al-(D-Trp) insulin in the unit cell, the conformational differences with other insulin structures and its structure and function relationship bave also been discussed.     

STUDY OF DEPENDENCE OF LIQUID CHROMATOGRAPHIC PERFORMANCE UPON PORE STRUCTURE OF POROUS POLYDIVINYLBENZENE MICROSPHERES

Pore structure of the porous polydivinylbenzene microspheres is controlled by the degreeof crosslinkage and the diluent used. It is proved by chromatographic results that the higher thedegree of crosslinkage is, the more the micellar pores will be formed, and the nature as wellas the quantity of the diluent determine the real pore structure. Among the structural para-meters of the microspheres, the size and the pore diameter affect the performance in HPLCmostly. The linear sample capacity of the microspheres in 1--2 order of magnitude larger thanthat of the Silica-ODS. According to this result, it could be confirmed that the solute mole-cules penetrate deeply into the skeleton of the polymer network. Based on the polymeric struc-ture with the same chemical composition but different in pore structure, the contribution tothe retention of several organic compounds by Henry's and/or adsorption coefficient has beenstudied. The results obtained show that Henry's coefficient is approximately 80% of thetotal contribution, i. e. dissolution mechanism plays the main role in the chromatographicprocess, especially in case of polar compounds. The experimental result that the chroma-tographic separation relatively slightly depends upon the sueface area of the polymer isanother ovidence. It is better to define this kind of polymeric stationary phase as a sorbentrather than an adsorbent. From the point of view of dissolution mechanism, it is suggestedthat a homogeneous porous polymeric stationary phase constructed with chemically rigid ske-letal structure and sufficiently thin bulk polymeric phase inside the microspheres should bean ideal packing for chromatography.     

RULE OF DISTRIBUTION OF PHASE POINTS OF POLY-UNIT MOLECULES AND HOMOLOGOUS LINEAR LAW

The chain M-(A)_n-N or ring obtained by bonding n number of A's with the same chemical structure in the same way is called the poly-unit molecule. Jiang Mingqian has discovered the famous homologous linear law for the poly-unit chain. Xu Guangxian and Li Lemin have studied its quantum-chemical basis and put forward the new linear factor.In order to study further the basic quantum chemistry of the homologous linear law, it is necessary to have first a thorough knowledge of the orbital characteristics of the polyunit molecules. The author studied the orbitals and the energy levels of poly-unit molecules by using difference equations. Based on the past work the concept of phase points of orbital was established, and the rule of distribution of phase points was developed as well. It is found that the phase points of similar orbitals in the molecules of a homologous series appear to condense around a certain point. Based on this fact a theoretical proof of the homologous linear law was made.     

STUDIES ON THE CRYSTAL STRUCTURE OF Al-(L-TRYPTOPHAN) INSULIN AT 2.1RESOLUTION

In order to study the biological effect of alterations to the N-terminus of the insulin A-chain, we have determined the crystal structure of Al-(L-Trp) insulin and discovered that it belongs to the trigohal system with space group R3. The parameters oof the unit cell are a=b=80.3A, c=37.5A. The model was adjusted and refined by using a stereochemically-restrained least squares program, assisted by manual revision of the model based on the difference Fourier map, to a final R-factor of 0.195. The main and side chains of both Al-(L-Trp) residues in the asymmetric unit are well ordered. It was found that the Al-Trp residue of molecule I occupied two distinct positions. We have proposed from the results of the three-dimensional structure that the 4-zinc insulin hexameric form is a stored state of insulin molecules in a conformation of low activity. The structural details of the insulin molecule and its structure and function relationship have also been discussed.     

THE MECHANISM OF COPOLYMERIZATION OF VINYL AND DIVINYL MONOMER Ⅵ: A STUDY ON THE MECHANISM OF THE STRUCTURE FORMATION OF CROSSLINKED POLYSTYRENE

In order to study the mechanism of the formation of maeroporous copolymer, the overall reaction kinetics, phase separation and gelation of the S/EGDM in the presence of inert solvents and the physical properties of the eopolymer were investigated and compared with the corresponding system of S/DVB and S/DVB/MMA. The formation of the network structure of the macroreticular polymer was studied and a model of the mechanism suggested.     

STRUCTURE OF PLASMA-POLYMERIZED OCTAFLUOROCYCLOBUTANE

Plasma-polymerization of octafluorocyclobutane was carried out in a capacitively coupled tubu-lar reactor with external electrodes. The number-average molecular weight, melting temperature,decomposition temperature and solubility in te trafluorodibromoethane of the products was mea-sured and the polymer structure was characterized by ESR. IR and ~(1)9F-NMR methods. The experi-mental results show the absence of the highly crosslinked structure but a fluorine-deficient structurecaused by free-radicals, carbonyl groups. double bonds and multicage-like segments in the polymer.     

THE CRYSTAL STRUCTURE OF BAYLEYITE

The bayleyite crystallizes in monoclinic space group C_2~5h-P2_1/c with a=6.499(1), b=15.235(5), c=26.513(6), β= 92.92(2)°, Z=4. Intensities of 3430 independent reflections are collected with diffractometer using MoKα radiation. The crystal structure has been solved by the Patterson method and refined by block least square refinement for positional parameters and isotropic temperature factor of non-hydrogen atoms. The final R factor is 0.038.The result of crystal structure analysis shows that the structure consists of discrete [UO_2(CO_3)_3]~(4-) ions and Mg~(2 ) cations are between slab-like units, but they are not in a slablike unit. Its crystal struture is different from that of liebigite which was determined by Appleman. Complexes and cations between slab-like units and in a slab-like unit are connected by hydrogen bonds formed by water molecules.     

X-RAY STUDIES ON THE STRUCTURE OF DES-PENTAPEPTIDE INSULIN AT 2.4 RESOLUTION——THE REFINEMENT OF THE STRUCTURE

The determination of an initial model for the crystal structure of des-pentapeptide in-sulin, using only the phase information obtained from the scattering of cadmium ions inthe native crystal, has been described. This paper describes the refinement of this modelagainst both the experimental X-ray observations and the a priori stereochemical observationsusing the method of restrained parameter least squares. The corrected and extended modelincluded not only all the non-hydrogen atoms of the protein and one cadmium ion, but alsosome 49 water molecules. Fourier syntheses using amplitudes of 2F_o-F_c, phase angles prob-abilistically combined from the anomalous scattering and model phase information, witheach term weighted according to its reliability gave clear results without detectable bias to-wards the current model. The final model has acceptable stereochemistry (root mean squaredeviation from ideal bond lengths 0.027 A), and predicts the observed X-ray scattering sat-isfactorily (R = 0.182 for all dat     

ELECTRONIC ENERGY BAND STRUCTURE OF MOLECULAR CRYSTAL TTF-TCNQ——CHANGE OF ENERGY BAND STRUCTURE DURING PEIERLS PHASE TRANSITION

In this paper, the electronic energy bands of the molecular crystal TTF-TCNQ have been calculated. The results demonstrate that the positions and the widths of the energy bands of this crystal conform to the rules given by our previous paper exactly, i.e. the positions of the energy bands of crystal orbitals are determined by the energy levels of corresponding molecular orbitals of the isolated molecules, and the widths of the energy bands are determined by the interaction between the molecular orbitals belonging to different molecules in the crystal. The results also demonstrate that the dimerization which appears after Peierls phase transition has a considerable effect on band widths. The dimerization causes the band widths of TTF and TCNQ columns to become narrow sharply. According to the relationship between the mobility of charge carriers and the band width given by Frhlich and Sewell, the sharp change of electrical conductivity of TTF.TCNQ crystal during Peierls phase transition can be explained p     

X-RAY STUDIES ON THE STRUCTURE OF DES-PENTAPEPTIDE INSULIN AT 2.4 RESOLUTION——THE DPI MOLECULE AND ITS STRUCTURAL RELATIONSHIP WITH INSULIN

The structure of the monomeric insulin analogue des(B26—B30) insulin is presented.; A detailed comparison with the 2Zn insulin structures shows that while there are some large changes in the structure, the basic secondary structural units maintain their integrity. The DPI structure is broadly similar to molecule Ⅰ in the 2Zn structure, and in this respect is like other crystal forms of insulin. In addition to changes on the surface of the structure there are some subtle but extensive changes in the heart of the molecule. The molecules are closely packed in the crystal with many and varied contacts, including a complex network of protein-cadmium interactions and a considerable number of water mediated contacts. The molecular surface has an unusually large number of hydrophobic groups which tend to cluster in a thick band running around the protein. The crystal structure is well ordered, indeed the clarity of some side chains and the definition of the water molecules is superior to that found in the mor     

EFFECT OF DRAWING ON MORPHOLOGY,STRUCTURE AND MECHANICAL PROPERTIES OF BLENDS OF A LIQUID CRYSTALLINE POLYMER AND MODIFIED POLY(PHENYLENE OXIDE)

Polymer strands with various draw ratios of a thermotropic liquid crystalline polymer(LCP) and modified poly(phenylene oxide) were prepared by drawing the melts leaving aslit die in open air. The morphology, structure and mechanical properties of the resultingstrands were studied as a function of LCP content and draw ratio. It was found that thethermal and mechanical properties of the matrix phase did not change dramatically withthe amount of LCP and draw ratio, but the orientation of LCP phase could be increasedwith draw ratio. The mechanical properties of the strands could be improved by moderatelydrawing the melts. Wide angle X-ray diffraction suggested that the improvement in tensilestrength of the strands was due to the resultant fibrillation of LCP phase and enhancedmolecular orientation. Morphological observation indicated that excessive drawing of thestrands could lead to the break down of the microfibrils of LCP and thus resulted in thedecrease of mechanical strength.     

ENVIRONMENTAL STABILITY OF THE POLYENE PREPARED BY DEHYDROCHLORINATION OF POLY(VINYL CHLORIDE)

A high-quality polyene can be obtained by exensive dehydrochlorination of poly(vinyl chloride) (PVC) in aliquid/solid two-phase system. The liquid phase is a tetrahydrofuran solution of PVC containing a small amount ofpoly(ethylene glycol) with molar mass of 400 g as a phase transfer catalys. The solid phase is potassium hydroxide particles.The structure of the polyene is polyacetylene-like and has a long conjugated C=C sequence and a narrow dispersity ofpolyene sequences according to its FT-infrared and Raman spectra. The environmental stability of the polyene was alsostudied by IR, Raman spectra and elemental analysis. Experimental results demonstrated that the polyene was susceptible toair and could be changed into a material containing high concentrations of hydroxyl and carbonyl groups. The polyenesequences were shortened and its dispersity became broader due to the effect of dioxygen.     

REFINEMENT OF THE STRUCTURE OF DESPENTAPEPTIDE (B26—30) INSULIN AT 1.5 RESOLUTION

The refinement of the structure of despentapeptide (B26-20) insulin (DPI) at 1.5 Aresolution is described in the present paper. Against the X-ray diffraction data of newlygrown crystals, the restrained parameter least-squares refinement of the structure alter-nated with model-rebuilding. The original 2.4A resolution model has been thoroughlyrefined and parts of it have been eonsiderably revised. The cadmium coordination struc-ture has been well determined, and appears to be a nearly ideal octahedron. After refine-ment 84 water oxygen atoms have been included in the final model; this gives us detailedinformation for studies on the water structure in the DPI crystal. The final crystal-lographic reliability index R value was 0.144 for 5678 unique observable reflexions (F_o great-er than 1.5σ (F_o)) in the 10-1.5A range; the refined model has a root-mean-squaredeviation from standard bond lengths of 0.04A.     

THE STRUCTURE BASIS OF THE POOR FIBRIN SPECIFICITY OF UROKINASE(Ⅱ)——THE INHIBITION OF UROKINASE A CHAIN 149--157 ON THE FIBRIN STIMULATED ACTIVATION OF PLASMINOGEN BY TISSUE TYPE PLASMINOGEN ACTIVATOR

In view of the similarity of the charge distribution between fibrin A_α148--161 and Achain 149--157 of urokinase,the latter might compete with fibrin A_α148--161 when singlechain pro-urokinase is converted to double chain urokinase.To test this, the stretch of uro-kinase A chain 135--157 was separated from the low molecular weight urokinase, a competi-tive binding between this stretch and fibrin to tPA kringle-2 was shown by radio-bindingassay. The inhibition of the stretch on the fibrin stimulated activation of plasminogen wasdemonstrated in the caseinolytic system. The synthesized novapeptide urokinase A chain 149--157 (R-peptide) showed a significant inhibition on the activation of plasminogen in the pres-ence of fibrin. By contrasting finely with R-peptide, a synthesized novapeptide in which Arg154and Arg156 were replaced by Asp (D-peptide) did not show any inhibition effect on the fi-brin stimulated activation of plasminogen by tPA. These results suggest that the positivelycharged residues in the     

DIGITAL IMAGE ANALYSIS OF PHASE STRUCTURE IN THE BLEND OF POLY(BUTYLENE TEREPHTHALATE-COCAPROLACTONE) WITH POLYCARBONATE

The digital image processing technique was used for the extraction of physical information from the temporal image of phase structure in the process of phase separation in the blend of poly (butylene terephthalate-co-caprolactone )with polycarbonate. The power spectrum images of the two-dimensional Fourier transformation (2DFT) of the temporal image of phase structure reflect the change of the phase size with time.