X-RAY STUDIES ON THE STRUCTURE OF DES-PENTAPEPTIDE INSULIN AT 2.4  RESOLUTION——SOLUTION OF THE PHASE PROBLEM USING THE ANOMALOUS SCATTERING OF CADMIUM AND THE DERIVATION OF A MODEL STRUCTURE

The three dimensional structure of des-pentaptide insulin has been solved at a resolu-tion of 2.4A. The structure determination was achieved without the use of heavy atom de-rivatives, by using only the phase information obtained from the seattering (both real andimaginary) of X-rays by cadmium ions present in the native crystal. Using this phase in-formation, a map, with figure of merit 0.56, was produced which enabled an initial modelof the protein to be constructed. Because of the novelty of this approach to the solutionof the phase problem the procedures used are explained in some detail.     

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.     

REFINED CRYSTAL STRUCTURE OF INSULIN AT 1.8A RESOLUTION——CRYST

The structure of insulin has been refined by difference Fourier method at 1.8A resolu-tion. A set of computer programs calculating the mF_o-nF_c Fourier synthesis and the cor-rections of parameters automatically has been set up. With the programs to refine theinsulin model obtained from MIR map at 1.8A resolution for 11 cycles, the R index(R=∑|KF_o- F_c|/∑KF_o) is reduced to 0.210 from the initial value of 0.388. Duringthe refinement the stereochemistry of the insulin molecules is constantly detected andadjusted to fit the reasonable geometry. The refinement has greatly improved the structuremodel of insulin and provided more detailed structure information. On the basis of this thesystems of hydrogen bond in an insulin dimer are determined and the interaction betweenwater and insulin molecules in the crystal is investigated.     

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.     

THE SPHERULITE-LIKE STRUCTURE OF MAIN CHAIN THERMOTROPIC AROMATIC COPOLYESTERS

A new spherulite-like structure of main chain thermotropic aromatic copolyesters formed insolution cast specimens was observed and was studied by means of polarizing microscopy, X-ray diffraction,SEM and IR spectrometry. Results indicate that the spherulite-like structure of main chain thermotropicaromatic copolyesters formed from the casting solution (phenol/Cl_2CH_2CH_2Cl_2) is not a real crystal but only ahigh oriented arrangement of the macromolecular chains as a spherulite. This resulted from the interactionbetween the needle-like crystal of phenol and the rigid mesomorphic groups of molecular chain. The parallelpacking of extended copolyester molecules along the needle-like crystal of phenol leads to the formation ofthe spherulite-like structure.     

THE CRYSTAL STRUCTURE OF THE ADDITION COMPOUND OF DECAVANADIC ACID AND 5,7-DIMETHYL-2, 3-DIHYDRO-1, 4-DIAZEPINIUM

The title compound crystallizes in the space group C_(2h)~5-P2_1/n with unit cell constantsa=10.938 A, b=19.189 A, c=13.384 A and β=105.09°. Intensities of 4022 independent reflec-tions were collected with four-circle diffractometer using MoKa radiation. After reduction fordiffractometer data, we derived first the position parameters of all the V atoms by directmethod using SHELXTL program. The coordinates of all the non-hydrogen and hydrogenatoms were obtained from successive Fourier and difference sytheses. The block-diagonalleast-squares refinement for all atoms gave a final discrepancy weighted factor R_w=0.050. The result of structure analysis shows that four protons of each decavanadic acid arecaptured by the nitrogen atoms involved in the azepine molecules which are condensation pro-ducts of ethylenediamine with acetylaceton. In crystal, the isopoly-decavanadate anion, 7-member heterocyclic azepium and the crystal water are linked together by ionic forces andhydrogen bonding and the chemical content within a unit cell has been identified as 2[H_2V_(10)O_(28)]~(-4)·8[C_7N_2H_(13)]~( 1)·12H_2O.     

MOLECULAR STRUCTURE AND ABSOLUTE CONFIGURATION OF SUBEROGORGIN

In the present paper it is reported that the molecular structure and absolute configuration of poisonous suberogorgin are determined by using X-ray diffraction method. The crystal of suberogorgin belongs to orthogonal system with space group D_2~4-P2_12_12_1. The crystallographic parameters are: a=16.135, b=13.189, c=12.901, Z=8. The initial model of the crystal structure was solved by the direct method. The refinement of the strueture parameters was carried out by using the least square method and led to a final R-factor of 0.056. In accordance with the molecular structure of suberogorgin mentioned above, the solvent effect of NMR has been further discussed and the relationship between the molecular structure of suberogorgin and its toxicity has also been preliminarily investigated.     

EFFECT OF STRUCTURE ON DEFECT FORMATION IN CRYSTAL OF LITHIUM BORIC OXIDE (LBO)

<正> The effect of structure on the defective formation in non-linear optical crystal of lithium boric oxide(LBO)was studied by X-ray topography.Only a few dislocations with the density less than 50/cm2 occur in the specimen cut far from the seed.Most inclusive formed in the late growth stage show a regular orthorhombic shape with a definite orientation,which are due to the negative crystal growth happened further in the inclusioned melt.The grown-in dislocation takes nearly the screw character with the Burgers vector b almost all in the low index directions,however,the inclusion-induced dislocation is distributed much closely in a network parallel only to the plane of(010)and also takes the screw type with b all in the lowest diretions of this plane.The high movability of lithium ions in open structure and the loosely atmic packings on certain planes were taken into account for the defect formation in addition to for some other crystal properties.     

THE CRYSTAL STRUCTURE OF 1-CYANOPROPYLSILATRANE

The crystal structure of 1-cyanopropylsilatrane [NC(CH_2)_3 Si(OCH_2CH_2)_3N] has been determined by X-ray diffraction method. It's crystallized in orthorhombic, space group Pna2_1, with a=12.797(3), b=11.843(2), c= 8.163(2), and Z=4. The structure is solved by the direct method and refined by the block-diagonal least-squares. The initial R value is 0.379 and the final one is 0.078 for 1040 observable reflections. The result of the structure analysis indicates the presence of pentaeoordinate silicon. The molecular geometry of silicon is a distorted trigonal bipyramid. The transannular dative bond length between silicon and nitrogen is 2.164(4), the Si—C is 1.884(5). The angle of N—Si—C is 178.9(4)°.All the calculations are carried out using the (GC-80) (ALGOL 60) system of programs which were developed by one of the authors over the computer TQ-16 (32K, 48 bits)madein China.     

RELAXATION IN DOMAINS:STRUCTURE AND SEGMENTAL DYNAMICS OF LC/I DIBLOCK COPOLYMERS

A series of block copolymers consisting of an isotropic (polystyrene) block and a side-chain liquid crystallineblock (LC) have been studied using small-angle X-ray scattering and dielectric spectroscopy. The triblock copolymer (PS-LC-PS) displays an order-to-order transition (OOT) together with the isotropic/nematic transition of the LC phase. The seriesof diblock copolymers show no clear OOT but the phase diagram differs from that of non-LC block copolymers. Thesegmental dynamics as measured with dielectric spectroscopy is dominated by the α and δ relaxation of the LC block. Bothdisplay a WLF like temperature dependence. The relaxation times are influenced by the constraints of the nanoscale domains.They are decreased for the LC confined in the domain as compared to the LC in the continuous matrix.     

STUDIES ON THE CRYSTAL STRUCTURE OF (D-Ala)-B0 PORCINE INSULIN AT 1.9 RESOLUTION

The crystal structure of (D-Ala)-B0 porcine insulin has been determined, using data to 1.9 and atomic parameters of 2 Zn porcine insulin as a starting model, and through the use of the difference method and the restrained least square method, to a final R-factor of 0.211 and r. m. s. deviation of 0.057 for the bond lengths. The electron densities of B0 residues were very clear. Introduction of B0 residues into the molecules had reduced the thermal vibration of the N-terminus of B-chain for both molecules Ⅰ and Ⅱ and made the molecules pack closer in the crystal The obvious differences between the crystal structures of 2 Zn and (D-Ala)-B0 porciue insulin were the conformations of partial polar groups around the possible receptor binding surface and the assembly mode of two helixes of A-chain in molecule I. In the local environment of the N-terminus of Bchain there were great differences between the crystal structures of(D-Ala)-B0 porcine insulin, (Trp)-B1 porcine insulin and Des B1(Phe) bovine insulin.     

A RAMAN-SPECTROSCOPIC STUDY OF PHASE STRUCTURE OF DRAWN POLYETHYLENE

A drawn high density polyethylene(HDPE)has been measured by Raman spectroscopy and differential scanning calorimetry (DSC). The crystalline structure of drawn HDPE is analysed by the Raman internal modes in terms of mass fractions of the crystalline orthorhombic phase, the liquid- like amorphous phase and the disordered anisotropic phase. The mass fractions depend on draw temperature T_d and draw ratio R_d . The fraction of disordered anisotropic amorphous phase changes very little with, the T_d and increases with increasing R_d. Sum of the mass fractions of crystalline orthorhombic phase and the disordered anisotropic phase increases linearly as the same slope as the crystallinity W_c determined from DSC measurements with increasing T_d or R_d and it is higher than the W_c for all the samples. The results show that the mass fraction of disordered anisotropic phase is partially devoted by the taut tie molecules (TTM s) in the amorphous state. The dependence of the disordered anisotropic phase on T_d and R_d supports the mechanism of plastic deformation of fibre structure.     

THE DEGREE OF CRYSTALLINITY OF NYLON-1010 BY WAXD

Based on the X-ray scattering intensity theory and using the atomic scattering factorapproximate expression,the correction factors for three main crystalline peaks and an amorphouspeak of Nylon-1010 were calculated and the formula of degree of crystallinity of Nylon-1010 wasderived by graphic multipeak resolution method. The results calculated are compatible with the density measurement and calorimetry.     

DETERMINATION OF DEGREE OF CRYSTALLINITY OF NYLON 1212 BY WIDE-ANGLE X-RAY DIFFRACTION

Based on the X-ray scattering intensity theory and using the approximate expression for the atomic scattering factor, the correction factors for three crystalline peaks and an amorphous peak of Nylon 1212 were calculated and the formula of degree of crystallinity of Nylon 1212 was derived by a graphic multipeak resolution method. The degree of crystallinity calculated from the WAXD method is compatible with those obtained by density and calorimetry methods.     

STRUCTURAL PHASE TRANSITION OF ALIPHATIC NYLONS VIEWED FROM THE WAXD/SAXS AND VIBRATIONAL SPECTRAL MEASUREMENTS AND MOLECULAR DYNAMICS CALCULATION

The crystalline phase transition of aliphatic nylon 10/10 has been investigated on the basis of the simultaneous measurement of wide-angle and small-angle X-ray scatterings, the infrared spectral measurement and the molecular dynamics calculation. An interpretation of infrared spectra taken for a series of nylon samples and the corresponding model compounds was successfully made, allowing us to assign the infrared bands of the planar-zigzag methylene segments reasonably. As a result the methylene segmental parts of molecular chains were found to experience an order-to-disorder transition in the Brill transition region, where the intermolecular hydrogen bonds are kept alive although the bond strength becomes weaker at higher temperature. The small-angle X-ray scattering data revealed a slight change in lamellar stacking mode in the transition region. The crystal structure has been found to change more remarkably in the temperature region immediately below the melting point, where the conformationally disordered chains experienced drastic rotational and translational motions without any constraints by hydrogen bonds, and the lamellar thickness increased largely along the chain axis. These experimental results were reasonably reproduced by the molecular dynamics calculation performed at the various temperatures.     

MOLECULAR STRUCTURE AND ABSOLUTE CONFIGURATION OF THE DITERPENE LACTONE, PRAELOLIDE

Praelolide is a new compound which was isolated out from the gorgonian, Menella praelonga (Ridley), collected from the South Sea of China at Zhanjiang, Guangdong. The molecular formula is C_(28) H_(35) O_(12)C1. The research result by X-ray diffraction method on the crystal structure is presented. The compound is orthorhombic with space group P2_12_12, cell dimensions α=16.936, b=16.709, c=10.333, and Z=4. The structure has been solved by direct method and refined to R=0.055 for 2257 unique observable reflexions by least-squares. The molecule is composed of the major conformational isomer in which the three main rings(a six-membered ring, an eight-membered ring, a six-membered ring) take separately the form of chair-chairboat-chair, a five-membered actone ring, a C1 substitution, 4 acetate groups, and a three-membered epoxide ring. The absolute configuration of the molecule has also been determined by statistics (R factor ratio =1.012) and Bijvoet pairs observation. For 30 pairs of the greatest anomalo     

STATISTICS OF A NOVEL CLASS OF LIQUID CRYSTAL POLYMERS

A novel class of the liquid crystal polymers with mesogens laterally attached to flexible main chain backbones has been synthesized recently by us. While the flexible backbones tend to take configuration of maximum entropy the mesogenic side groups tend to orientate because of the anisotropie soft dispersion forces. A mean field theory is presented to describe the competition between these two trends which makes it possible for this class of polymers to show anisotropic (liquid crystal) phase within certain temperature range where the polymer main chains and the side chain mesogens will take approximately parallel arrangement, which is different from the normal side chain liquid crystal polymers. The temperature range of the liquid crystal phase, its ordering and phase transition all depend on the flexibility of the backbone, the strengthof the anisotropic forces of the side groups and the hinge elasticity. The results show that the liquid crystalisotropic phase transition is of the first order. The phase diagram, i. e. the dependence of the transition temperature on the structure of the polymers is also given.     

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.     

INVERSION OF A NONLINEAR DYNAMICAL MODEL FROM THE OBSERVATION

A technique for inversion of a nonlinear dynamical model from the observations has been developed, and examined by using the Lorenz system. The results show that the Lorenz system can be accurately inversed by using the observation data set. This technique will be broadly used in establishing the nonlinear dynamical model from an actual data set.     

THE CRYSTAL STRUCTURE OF YIMENGITE

Yimengite is a new species of mineral discovered in Shandong Province in 1980, with crystal chemical formula K(Cr, Ti, Fe, Mg, Al, Si)_(12)O_(19). It belongs to hexagonal system, and its cell parameters α_0=5.857 and c_0=22.940. 749 separate diffraction intensities of crystal were collected on RASA=IIS auto-four-circle single crystal diffractometer.All atomic coordination, temperature factor and degree of occupation were obtained by RASA-SAP interpretation system, and XTL crystallographic procedure, atomic distances and bond angles for each atom were calculated. Deviation factor R is 0.080.Through the medium of determination of the crystal structure of the new mineral yimengite, coordination form of monovaleace alkali metal element—potassium, etc. in high pressure have been cleared, a five fold coordination form of Fe cations—regular bipyramid has been established, and some new information on the geochemical state of some elements, such as Cr, Ti, etc. have been provided.