Low-angle X-ray diffraction

Herbette and co-workers [425-428,445] studied the structures of drugs bound to liposomes using a low-angle X-ray diffraction technique. Although the structural... 

With these factors in mind, a new method to evaluate the conformation of an amphiphilic molecule at the site of interest was Introduced. The method is built on the fact that the determination of Interlayer spacings of a lamellar liquid crystal using low angle X-ray diffraction methods in combination with density measurements will provide sufficient information to calculate the cross-sectional areas occupied by each amphiphlle (19). 

This material may be removed by reheating the sample to 850°, followed by the same annealing procedure outlined above. The X-ray diffraction pattern for 2H(a)-TaS2 may be used for identification. The following d values have been obtained for major low angle X-ray diffraction lines (and intensities) 6.05 (1) 3.025 (0.06) 2.8709 (0.32) 2.7933 (0.07) 2.3937 (0.80) and 2.3389 (0.04) A. Note that it is difficult to obtain the ideal intensities because of preferred orientation of the crystallites. This material is a superconducting metal with Te = 0.8 0.05°K.2... 

The pyridine intercalate is blue-black. Examination of the individual platelets under a microscope reveals a characteristic exfoliated appearance. Hexagonal symmetry is retained with a = 3.325 A and c/2 = 12.03 A. Comparison with the slab thickness for the parent 2H(a)-TaS2 shows a c-axis expansion, 8, of 5.99 A. The following d values have been obtained for low-angle X-ray diffraction lines 12.03, 6.015,4.010,3.008, 2.880, and 2.859 A. 2TaS2 C5HsN is also super conducting with a transition temperature of 3.5 0.3°K2,3... 

Langmuir-Blodgett (LB) films prepared from N-docosylpyridinium and TCNQ, transferred to substrates, and exposed to iodine vapor Visible and infrared spectra and low-angle X-ray diffraction Lateral d.c, conductivity was about lO- Scm 1 726, 729... 

The low angle X-ray diffraction patterns were recorded either at LURE, the French synchrotron facility, with a wavelength of X = 1.2836 A in a transmission mode, or with a Philips diffractometer using the Cu K wavelength in a reflection mode. 

In the ideal situation any supposed LB layer structure would be examined by low angle X-ray diffraction, electron diffraction and by the polarising optical microscope. It is unfortunate that this procedure is rarely carried out. Thus in this chapter only those cases have been discussed where at least some effort has been made to determine the structure and degree of order of the film. 

Recently Japanese workers have succeeded in forming well ordered LB films from single compounds which show a high in-plane conductivity and whose layer structure has been characterised by low angle X-ray diffraction [351, 352]. 

Ronziere, M-C., Berthet-Colominas, C., and Herbage, D. (1987). Comparative structural studies of reconstituted and native type I and type II collagen fibrils by low angle X-ray diffraction. Biochim. Biophys. Acta 916, 381-387. 

One of the tasks of structural biologists studying muscle contraction is to determine the organization and shapes of the myosin head in muscle under different physiological conditions. The technique of low-angle X-ray diffraction has unique advantages in this process, particularly since it can be applied to living muscle, which can be stimulated to produce active force or can be studied under a variety of different steady-state conditions. The main problem with X-ray fiber diffraction, as detailed in Squire and... 

Fig. 18. (A) Observed top half of the low-angle X-ray diffraction pattern from...

Al-Khayat, H. A., Yagi, N., and Squire, J. M. (1995). Structural changes in actin-tropomy-osin during muscle regulation Computer modelling of low-angle X-ray diffraction data. / Mol. Biol. 252, 611-632. 

Fig. 13. Illustrations of the possible arrangement of C-protein (MyBP-C) on the myosin filament backbone in projection down the axis (A) and in axial view (B). Of particular importance here is the possibility that the N-terminal half of C-protein extends out and binds to actin in relaxed muscle. (C) Simulation of the possible interactions of C-protein with binding sites on actin generated using the program MusLABEL (Squire and Knupp, 2004). (D) Left left half of the low-angle X-ray diffraction pattern from bony fish muscle (as in Fig. 11C), showing (right) the possible positions where the C-protein array in (D) might contribute. (From Squire elal, 2003d.)...

Fig. 15. Intensity profiles along the equator of the bony fish muscle low angle X-ray diffraction pattern from muscles at rest (A), fully active (B), and in rigor (C). The indexing in (A) is based on the hexagonal A-band lattice, and the arrows indicate peaks that come from the Z-band. (C) to (F) are computed electron density maps based on the amplitudes of the A-band peaks in (A) to (A), respectively. The simple lattice unit cell is outlined in (D). (From Harford and Squire, 1997.)...

In active or rigor muscle, heads that do not overlap actin filaments become disordered (Cantino et al, 2002 Padron and Craig, 1989). They therefore contribute little to the observed low-angle X-ray diffraction patterns. This population increases with increasing sarcomere length (reduced filament overlap). 

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