Diffraction small angle

In order to learn about the phase states adopted by LPS and lipid A, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and X-ray small-angle diffraction with CuXa or synchrotron radiation have been applied. In the following section, some recent results are summarized. 

SAXS Small angle diffraction patterns were obtained a room temperature using a "Searle" X-ray camera with Cu Ka (1.54A) radiation (35 kV, 25 mA). The exposure times were about 65 hours. 

Small Angle Diffraction from Contracting Muscle. 130... 

Bouwstra, J.A., et al. 1994. The lipid and protein structure of mouse stratum corneum A wide and small angle diffraction study. Biochim Biophys Acta 1212 183. 

Holland, H.E., et al. 1995. Interactions between liposomes and human stratum corneum in vitro Freeze fracture electron microscopical visualization and small angle diffraction scattering studies. Br J Dermatol 132 853. 

Fig. 3.21 Electron density profiles obtained by Fourier transformation of the small-angle diffraction intensities for DMPC at 22°C. A molecular graphic representation of a DMPC...

Burmester A, Geil PH (1972) Small angle diffraction from crystalline polymers. In Pae RD, Morrow DR, Chen Y (eds) Advances in polymer science and engineering. Plenum, New York, pp 42-100... 

Above 110 °C, this arrangement becomes mobile, and a smectic C liquid-crystalline phase is entered. Samples cooled down from the isotropic melt (140 °C) show Schlieren and banded textures when viewed under crossed polarizers (Figure 8). These textures look similar to nematic Schlieren textures, but from the X-ray diffraction data it is clear that 12c forms a homeotropically oriented smectic C phase. In a nematic phase, the small-angle diffraction peak would be absent, and a broad scattering feature, a nematic streak , would be observed. Polymer 12c was the first example of a PPE derivative for which three states of matter, i.e. crystalline, thermotropic liquid crystalline, and a highly viscous isotropic liquid, were accessible [46]. 

Bouwstra, J. A., Gooris, G. S., Van der Spek, J. A., Lavrijsen, S. and Bras, W. (1994). The lipid and protein stmcture of mouse stratum comeum A wide- and small-angle diffraction study. Biochim. Biophys. Acta /2/2 183. 

Investigations on the same mats were performed also by Spells, Barham, and Keller . In this case the recrystallization took place at 116 °C and 120 °C and the heating time was slower than in the first case (40 °C per min). It was observed that under these conditions the small angle diffraction maximum shifts gradually to smaller angles. The increase of the long period takes place logarithmically with time at 120 °C while a discontinuity occurs at 116 °C. The absolute intensity of the diffraction maximum first increases and remains constant afterwards. There is no indication of a decrease. From these results one can not conclude that no... 

Results of small-angle meridional measurements (Figure 1.5. ) show the absence of small-angle diffraction maximum and this shows the absence of large-period stmcture, that is in this case there is no regular alternation of crystalline and amorphous sections along the axis of the fibre. 

Non-lamellar lipid mesophases (Fig. 4) may also be identified by their characteristic small-angle diffraction pattern. The structure of the inverse hexagonal lipid-water mesophase (denoted as Hu) is based on cylindrical water rods, which are surrounded by lipid monolayers. The rods are packed in a two-dimensional hexagonal lattice with Bragg peaks positioned at... 

Small-Angle Diffraction from Stacked Membranes.181... 

Fig. 7 a. Time-resolved small-angle diffraction from a multi-lamellar aqueous dispersion (c p 0.2) of dipalmitoyl-phos-phatidylcholine (DPPC) during a temperature-jump and -drop experiment. The respective temperature courses are shown in the inserts, b Contour-line plot of the intensities obtained in the heating-experiment, c Temperature-dependence of the recovery rates of the phase, on the equilibration temperature, upon cooling from 37 °C. (From Ref. 74, with permission)... 

Fig. 9. Time-resolved small-angle diffraction from a mixture of l-palmitoyl-2-6leoyl-phosphatidyl-choline and l-hexadecyl-2-oleoyl-phosphatidylethanolamine. Two minutes after mixing of the aqueous dispersions (c,p 0.2) the temperature was raised from 10 to 70 °C, where the latter lipid species forms a hexagonal H phase, while the former stays lamellar. Fusion ofThe two phases and reformation of a lamellar phase is evident from the decay of the hexagonal 1120 reflection. (From Ref. 74, with permission)...

ATPase (MW 10 ) which is responsible for the active transport function of Ca ions across the membrane about 40% of the total membrane dry mass is lipid, mainly phosphatidylcholine, in a typical bilayer arrangement, as has been confirmed by static X-ray small-angle diffraction of stacked vesicle preparations... 

Fig. 10a and b. Small-angle diffraction pattern from an oriented, stacked sample of sarcoplasmic reticulum vesicles, obtained in 1 s with synchrotron radiation at Stanford Synchrotron Radiation Laboratory. The peaks correspond to the first seven orders of a lamellar diffraction pattern with a lattice periodicity of 200 A and exhibit the significant effects of lattice disorder of the second kind. The intensity distribution in (b) was obtained by integration of the two-dimensional pattern (a) between the limits indicated in (a). (From Ref. 85, with permission)... 

Fig. lla-c. Left. Small-angle diffraction patterns of sarcoplasmic reticulum membranes before (al) and immediately after flash photolysis (0.25-s UV flash) of caged ATP (bl) with a 0.5-s exposure pattern (cl) shows the result of a 0.5-s exposure 1 min or more after the UV flash. 

There is now a considerable number of SR instruments which have been or are being used for protein crystallography at various SR sources around the world (table 5.5 documents the existing ones). In this section a survey is made of the various instruments. An extensive discussion of mirror-monochromator cameras used for small angle diffraction at DESY, NINA, SPEAR, VEPP-3 and DORIS has been given by Rosenbaum and Holmes (1980). 

A mirror-monochromator camera was established on the DESY synchrotron for small angle diffraction experiments by Rosenbaum et al (1971) and Barrington-Leigh and Rosenbaum (1974). The instrument was used at a fixed wavelength of 1.5 A. The system was used to evaluate the synchrotron as an X-ray source for SR protein crystallography by Harmsen et al (1976). Their work encouraged the use of DORIS as a source for protein crystallography (see sections 5.6.4 and 10.1). 

Encouraged by the success on DESY, Harmsen and Rosenbaum (described in Rosenbaum and Holmes (1980) and Rosenbaum (1980)) established a mirror-monochromator camera on DORIS which was used for small angle diffraction and protein crystallography. 

The Biology Department beam line includes a station for protein crystallography (with Supper oscillation camera and FAST TV diffractometer) and a station for small angle diffraction (with a three-circle goniostat and MWPC electronic area detector). The latter station may be available for optimised anomalous dispersion crystallographic studies. The optical design for each consists of a bent pre-mirror, double crystal monochromator and bent post-mirror the mirrors have rhodium coatings (Wise and Schoenborn 1982). 

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