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The structure of the nucleosome core particle at low ionic strenth (10-0.04 mM Na + ) has been studied by small angle neutron scattering in various H 2 O/D 2 O mixtures. At 0.04 mM Na + ,the radius of gyration obtained at 39% D 2 O where scattering from the DNA dominates was 32 A, and at 65% D 2 O where scattering from the histones dominates, 40 A. An abrupt increase in the radius of gyration from 35 to 40 A was observed at about 1 mM ionic strength at 65% D 2 O, with decreasing the ionic strength from 10 mM. No loss of the histone secondary structure was detected by circular dichroism over the range of the ionic strength examined. These results suggest that at low ionic strength (⪅1 mM) the histones are located outside of the nucleosome core particle accompanied by an alteration of the tertiary and/or quaternary structure of the histone octamer, with the DNA in a folded conformation.

The elastic tensile modulus of the crystalline regions parallel to the chain axis E1 for poly(isobutylene oxide) (PIBO) was determined by an x-ray diffraction method. The stress-strain (σ—e) curve calculated from the meridional reflection of (002) shows an inflection point at about 75 MN/m2 or an extension of 0.25%. The observed moduli below and above this point are 29 and 47 GN/m2, respectively, at room temperature. The initial lower modulus agrees well with the value, 29.7 GN/m2, calculated on the basis of the double zigzag structure of PIBO chain determined by Kaji and Sakurada. The higher modulus may be due to an intrachain steric hindrance between the hydrogen atoms of the methylenic group in the main chain and those of the two side methyl groups.

Etude de solutions de polyhydrogenesulfate de vinyle et de ses sels de lithium, sodium et potassium

The elastic moduli Et of crystal lattices of polymers perpendicular to molecular chain axis are dependent on the intermolecular forces, and can be determined by an X-ray diffraction method. At first, the assumption of “homogeneous stress distribution” used in the evaluation of Et was confirmed experimentally. The Et values of a number of well known polymers were compared and discussed from the viewpoint of intermolecular forces. Hydrogen bonding and dipole forces increased Et, whereas disorders in the crystal lattices and linear side chains decreased Et. As a particular application of Et it can be employed to discriminate whether a comonomer component of a copolymer can enter the crystal lattice or not. Die Elastizitatsmoduln Et der Kristallgitter von Polymeren senkrecht zur Molekulkettenachse hangen von den zwischenmolekularen Kraften ab und konnen mit Hilfe einer Rontgenstrahlenbeugungs-Methode bestimmt werden. Zuerst wurde die Annahme der «homogenen Spannungsverteilung», die zur Berechnung von Et benutzt wurde, experimentell bestatigt. Die Et-Werte einer Anzahl gut bekannter Polymere wurden miteinander verglichen und vom Standpunkt der zwischenmolekularen Krafte diskutiert. Wasserstoffbruckenbindung und Dipol-Wechselwirkungskrafte erhohten Et, wahren Fehlordnungen im Kristallgitter und lineare Seitenketten Et erniedrigten. Eine spezielle Anwendung des Et-Wertes ist die Unterscheidung, ob eine Comonomer-Komponente eines Copolymeren in das Kristallgitter eingebaut werden kann oder nicht.

Neutron inelastic scattering measurements were carried out on semicrystalline and highly crystalline polyethylenes with degrees of crystallinity of 0.46 and 0.96, respectively, at 10 K to investigate low-energy excitations below 10 meV. It was found that the density of states G (ω) of the crystalline phase can be described by the Debye model but that of the amorphous phase shows an excess excitation peak at ≈2.5 meV. The calculated heat capacity C ( T ) of the amorphous phase shows a peak at ≈ 6 K in the plot of C ( T )/ T 3 versus T , while C ( T )/ T 3 for the crystalline phase is constant at low temperatures.

In order to evaluate the conformation of a single chain in mixed solutions of sodium salts of hydrogenated and deuterated poly(vinyl sulfuric acid) (PVSNa(H) and PVSNa(D)) without added salts, measurements of time-of-flight neutron small angle scattering (NSAS) were performed while making use of a wide band chopper. By means of the deuterium labeling, the scattering law, S(Q) , of the polymer solution can be separated into two parts: the intrapolymer scattering law, S 1 ( Q ), and the interpolymer one, S 2 ( Q ). Using the Kratky plot, it is concluded that at Q values larger than 0.04 A −1 , the polyelectrolyte can be regarded as a rod-like molecule. It has also been shown that the wide band chopper could be useful for NSAS studies of polymer solutions as well as crystalline aggregates of metals.

Two crystal analyser type quasielastic neutron spectrometers, a conventional resolution device with high efficiency, and a high resolution one with a wide energy window, have been installed at a spallation pulsed cold neutron source (a 20 K methane moderator). A data reduction program using a technique of statistical data analysis has also been developed. These spectrometers combined with the data reduction program have demonstrated their usefulness in profile analysis studies for low energy diffusive phenomena in molecular liquids, polymers and other materials.

We have developed a neutron quasielastic scattering spectrometer with conventional energy resolution. The spectrometer operates at the spallation cold neutron source in the KENS spallation source at the National Laboratory for High Energy Physics. High efficiency was achieved by adopting large analyser mirrors and the spallation cold nuetron source. The spectrometer has demonstrated considerable usefulness in spectral profile analysis studies of molecular liquids and polymers.

La transition entre la region diluee et la region semidiluee se produit a une masse moleculaire critique. Etude avec du polystyrenesulfonate de sodium sans addition de sel

The crystallite sizes of α and β forms of nylon 6 along the chain axis were determined by Wallner's method. First the shifts of the maximum positions of meridional reflections from their ideal reciprocal-lattice positions were calculated for the various crystallite sizes. Second, using these relationships, crystallite sizes were estimated from the observed maximum positions of reflections. The estimated values agree well with those from the integral widths of reflections by the method of Hosemann and Wilke.

Studies were carried out to determine the crystalline elastic modulus E1 along the chain axis for the α-form of nylon-6 [poly(e-caprolactam)] by X-ray diffraction. To obtain an inherent E1 value of this polymer the problem was solved that different orders of meridional reflections give different E1 values. Thus the disagreement was found to be due to the increase of the crystallite size by the applied stress. When corrected for this effect, the values from the 040 and 0.14.0 reflections agreed well with each other. The resulting modulus was 183 GN/m2 at 23°C, which was much lower than a theoretically calculated value of 262,8 GN/m2 for the fully extended structure model by Manley and Martin. This seems to be due to the slight shortening at the amide group of the molecular chain because it was confirmed from the intensity changes of the 040 and 0.14.0 reflections of this polymer by the applied stress that the amide part is more extensible than the polymethylene section. Judging from similar considerations the previously reported E1 values for nylon-66 and nylon-6,10 are valid.

The change of the crystallite size in the chain-axial direction by application of tensile stress was investigated for highly oriented nylon 6 (α and γ) fibers. The crystallite sizes were determined from the line widths of the X-ray meridional reflections using the method of HOSEMANN and WILKE. In both, the α- and γ-forms the crystallite size increases with the applied stress and levels off when it approaches the initial long spacing. This result can be interpreted by the fringed micell fibrillar model with crystalline regions alternating between amorphous regions; the crystallites grow at the expense of the amorphous regions retire into the intercrystallite regions in the fibril with the applied stress. In fact this was supported by the analysis of the small angle X-ray scattering intensities. Die Anderung der Kristallitgrose in Kettenrichtung durch Anwendung von Zugspannung wurde bei hochorientierten Fasern von Polycaprolactam (α- und γ-Nylon 6) untersucht. Die Kristallitgrosen wurden aus Messungen der Linienbreite von Rontgenmeridianreflexen mittels der Methode von HOSEMANN und WILKE bestimmt. In den beiden Formen (α und γ) nimmt die Kristallitgrose mit der angelegten Zugspannung zu und nivelliert sich, wenn sie sich der anfanglichen Langperiode nahert. Dieser Befund kann mit Hilfe des Modells der „fibrillaren Fransenmizelle” erklart werden, in welchem kristalline Bereiche mit amorphen Bereichen abwechseln; und zwar wachsen die Kristallite einfach auf Kosten des amorphen Materials. Weiter legt dieses Modell die Vermutung nahe, das herausragende Teile der amorphen Bereiche sich unter der angelegten Zugspannung in die interkristallinen Bereiche in der Fibrille zuruckziehen. Tatsachlich wurde diese Annahme durch die Analyse der Rontgenkleinwinkelstreuungsintensitaten bestatigt.

Low density polyethylene film is drawn at room temperature four times the original length and subjected to thermal annealing at 60, 80, and 100 °C keeping the film length constant. Long spacing measured by SAXS increased with increasing temperature of annealing; the increase of the long spacing is presumed to be due to the decrease of the number of micelles through relaxation during the annealing. Simultaneous measurement of the changes of the long spacing and the film length by stretching is carried out and stress-extension curves are obtained. The values of the initial moduli of the long spacingE 1 and the film lengthY are very near to each other. Elastic modulus of the crystal latticeE c is known to be 235 GN/m2 and that of the amorphous regionE a is found to be 0.15 GN/m2. When higher stress is applied than in the case of the initial modulus, the percentage of extension of film is much greater than that of the long spacing. The discrepancy is explained by the increase of the number of micelles through stress crystallization.

The crystal structure of poly(isobutylene oxide) has been determined by X-ray diffraction methods. The unit cell is orthorhombic with lattice constants a = 10.76 A, b = 5.76 A, and c = 7.00 ± 0.03 A (chain axis); the space group is P212121. The unit cell contains four monomeric units; the calculated density is 1.104 g/ccm, in agreement with the observed value of 1.040 g/ccm. The chain is nonplanar and has a double zigzag structure; this conformation has been confirmed by comparing calculated and observed values of the elastic modulus of this polymer in the chain axial direction. To determine the chain packing, structure factors for reflections were calculated for all possible positions in the unit cell, and a satisfactory result was obtained. Die Kristallstruktur von Polyisobutylenoxid wurde mittels Rontgenstreuung bestimmt. Die Elementarzelle ist orthorhombisch mit den Gitterkonstanten a = 10,76 A, b = 5,76 A, c = 7,00 ± 0,03 A (Kettenachse); die Raumgruppe ist P212121. Die Elementarzelle enthalt vier monomere Einheiten; die berechnete Dichte ist 1,104 g/ccm, die mit dem beobachteten Wert von 1,040 g/ccm befriedigend ubereinstimmt. Die Kette ist nicht eben und hat eine doppelte Zick-Zack-Struktur; diese Konformation wurde durch den Vergleich von den berechneten und beobachteten Werten des Elastizitatsmoduls in der Richtung der Kettenachse dieses Polymeren bestatigt. Um die Kettenpackung zu bestimmen, wurden Strukturfaktoren fur Reflexionen aller moglichen Lagen in der Elementarzelle berechnet, und ein befriedigendes Resultat wurde gewonnen.

ポリェチレンテレフタレート (PET) およびその共重合物-ポリェチレンテレフタレート/8.3mol%アジベート (PET/PEA) およびポリェチレンテレフタレート/8.3mol%イソフタレート (PET/PEI)-について, 鎖軸に対し直角方向の結晶弾性率 (Et) を測定した。その結果, つぎの値を得た。PET…(100): Et=4.7×104kg/cm2 (110): Et=3.8×104kg/cm2 (010): Et=4.2×104kg/cm2 (23±1℃)PET/PEA…(100): Et=4.7×104kg/cm2 (110): Et=3.7×104kg/cm2 (010): Et=4.2×104kg/cm2 (20±1℃)PET/PEI…(100): Et=4.2×104kg/cm2 (110): E2=3.4×104kg/cm2 (010): Et=3.8×104kg/cm2 (20±1℃)PETの値は, ポリェチレンのEt (3.8-4.3×104kg/cm2) とほぼ同程度であり, したがって, PETの分子鎖間には特に強い結合力は働いていない。しかし,(100) 面に対するEtは他の方向に比して若干高い。これはおそらく, ベンゼン核どうしのπ電子相互作用が働いているためと思われる。また, 共重合物のEt値をPETと比較すると, PET/PEAではほとんど等しいが, PET/PEIではいずれの面についても約10%ほど小さくなっている。このことは, イソフタレート成分はアジペート成分に比べてPETの結晶格子中により入りやすく, そのためPET/PEIの揚合には結晶格子が乱されてEtが低下したことを示しているものと思われる。

Molecular chain conformations of poly-γ-methyl-L-glutamate, poly-γ-methyl-D-glutamate, and poly-γ-methyl-D,L-glutamate in membranes prepared by using mainly trifluoroacetic acid and formic acid as solvents were investigated by infrared, X-ray diffraction, and optical rotatory dispersion measurements. It was pointed that these polymers exist in the α-helix form in membranes cast from trifluoroacetic acid solutions, but in the β-chain form in membrances swollen in formic acid. The β-chain structure was also observed in crystals precipitated from dilute solutions including formic acid. The formation of the β-chain structure was discussed.

要旨本報告ではポリエチレンォキシベンゾエート [PEOB:〓] を試料とし鎖軸方向に関する結晶弾性率を測定した結果について述べる。PEOBの結晶構造には繊維周期 (FIP) の異なる2種類の変態 (α, β) が存在し, α型のFIPは15.60Åであり, これは伸び切ったジグザグ構造に比べて19.2%短縮した値である。一方, β型のFIPは19.1Åであり, これはほぼ伸び切った構造の分子鎖から成っている。α型結晶のみから成る試料1ならびにα型およびβ型結晶の共存する試料2を用いてα型結晶の鎖軸方向に関すを弾性率を測定し次の値を得た。PEOB: α型 (試料1) Et=6.0×104kg/cm2 (20±1℃)PEOB: α型 (試料2) Et=7.4×104kg/cm2試料2により得られたEt値は試料1による値よりも幾分大きいが両者はほぼ等しい結果を与える。PEOBのα型結晶に関する上に示したEt値は, 高分子の鎖軸方向に関する結晶弾性率の値としては非常に小さな値である。この結果は主鎖にみられる著しい構造の短縮から理解できる。さらに, 試料1と2においてα型結晶のEt値が等しく得られた事実からβ型結晶の存在はα型結晶の弾性率測定に影響を与えないことが示された。試料1, 2のいずれの場合にも試料の弾性率は結晶弾性率に等しく得られた。

We have succeeded in growing Saccharomyces cerevisiae (baker's yeast) on media containing 2H2O and isolating the core histones highly deuterated in the non-exchangeable positions. The deuterated histones obtained here are of great value for their possible widespread use for structural studies of chromatin.

Nylon 6-clay hybrid (NCH) is a molecular composite of Nylon 6 and uniformly dispersed silicate monolayers of montmorillonite. In this study the preferred orientation of montmorillonite and Nylon-6 crystallites in a thick (3 mm) injection-molded bar of NCH has been investigated using x-ray diffraction and electron micrography (TEM). It is clear that this bar has a triple layer structure consisting of surface, intermediate, and middle layers which have different preferred orientation. In the surface layer both the silicate monolayers and the chain axes of Nylon-6 crystallites are parallel to the bar surface though the latter are randomly oriented within the plane. In the intermediate layer the silicate monolayers remain parallel to the bar surface but the Nylon-6 crystallites rotate by 90° so that the chain axes would be perpendicular to the bar surface or the silicate monolayers. In the middle layer the silicate monolayers are randomly oriented around the flow axis of the NCH bar while remaining parallel to it, and the Nylon crystallites are randomly oriented around the flow axis while keeping their chain axes perpendicular to the silicate monolayers. It may be concluded that such preferred orientation of Nylon 6 crystallites is induced by the clay because the crystallites in the pure Nylon 6 bar have no preferred orientation. ©1995 John Wiley & Sons, Inc.