Bead-string structure

Fig. 4. Scanning electron microscope (SEM) image of FeCl3-intercalated CNTs assuming a bead-string structure with partially intercalated and swelled portions.

Fig. 4.12 Illustration of the cascading collapse transition of a charged polymer in a poor solvent, with a bead-string structure that eventually collapses into a single sphere...

Why does the collapse transition of a polyelectrolyte chain show the bead-string structure ... 

Biochemical reconstitution of the 30 nm fiber has recently been succeeded by using a salt-dialysis procedure with a long DNA template (>100 kb) (Hizume et al, 2005). AFM imaging of the reconstituted chromatin has shown that the beads-on-a-string structure of the nucleosomes ( 400 nucleosomes on 100 kb DNA) are converted to a thicker fiber in the presence of histone HI. The thickness of the fiber changes reversibly between 20 nm and 30 nm, depending on the salt environment (in 50 mM and 100 mM NaCl, respectively) (Fig. 4) namely, the linker histone directly promotes a thicker fiber formation in a salt-dependent manner. 

The genome of the eukaryotic cell is packaged in a topologically complex, fibrous superstructure known as chromatin. The nucleosome core particle is the fundamental building block of chromatin and contains 146 bp of DNA wrapped in roughly two super helical turns around an octamer of four core histones (H3, H2B, H2A and H4) resulting in a beads on a string structure. This 10 nm structure further folds and... 

As already noted above, AFM imaging and quantitations on LH-stripped chromatin fibers revealed extended beads-on-a-string structures, in agreement with early EM results [17]. Nucleosomal arrays reconstituted from naked DNA fragments and histone octamers had similar appearance [36 2]. 

Several reports have used AFM imaging, in conjunction with traditional biochemical methods, to address this question (it must be noted that an in-depth AFM study of this issue is still to be performed). The AFM data suggest thus far that hyperacetylated histones isolated from cells treated with histone deacetylase inhibitors produce beads-on-a string structures somewhat more extended than those obtained using histones purified from control cells [37,38], in agreement with EM imaging results obtained on circular chromatin templates [49]. In addition, acetylation seems to enhance the non-random nucleosome-loading behavior seen in subsaturated nucleosomal arrays (see above, and Table 1). 

Calis HP, Takacs K, Gerritsen AW, Bleek CMvd. Bead-string reactor. In Cybulski A, Moulijn JA, eds. Structured Catalysts and Reactors. New York Marcel Dekker, 1998 355-392. 

Beads on a string structure positively charged liposomes adhere as an intact bead on a negatively charged DNA strand. 

H.P.A. Calis, Development of Dustproof Low Pressure Drop Reactors with Structured Catalyst Packings—The Bead String Reactor and the Zeolite-Covered Screen Reactor, Ph.D. dissertation. Delft University, Delft, The Netherlands. 1995. 

In addition to and as an alternative for the existing concepts of low-pressure-drop reactors with structured catalyst packings, discussed in the previous chapters, a new concept is proposed in this chapter the bead-string reactor (BSR). The BSR was invented [1] as an alternative for a parallel-passage reactor (PPR) with extremely thin catalyst beds, viz. beds of only one catalyst-particle-diameter width. 

K. Rehme, Convective heat transfer over rod bundles. Handbook of Single-Phase Convective Heat Transfer (S. Kaka9, R.K. Shah, and W. Aung, eds.), Wiley, New York, 1987, p. 7-1. H.P. Calls, Development of Dustproof Low-Pressure-Drop Reactors with Structured Catalyst Packings—The Bead String Reactor and the Zeolite-Covered Screen Reactor, Eburon P L Press, Delft, The Netherlands, 1995. 

Y arin et al. [29, 111] gave a theory of the capillary breakup of thin jets of dilute polymer solutions and formation of the bead-OTi-the-string structure (some additional later results can be foimd in [90]). The basic quasi-one-dimensional equations of capillary jets (1.49) and (1.50) are supplemented with an appropriate viscoelastic model for the longitudinal stress. Yarin et al. [29, 111] used the Hinch rheological constitutive model, which yields the following expression... 

Oliveira, M. S. N., Yeh, R., McKinley, G. H. (2006). Iterated stretching, extensional rheology and formation of beads-on-a-string structures in polymer solutions. Journal of... 

Li, J., Fontelos, M. A. (2003). Drop dynamics on the beads-on-string structure for viscoelastic jets A numerical study. Physics of Fluids, 15, 922-937. 

Fig. 18.13 The high-adhesive superhydrophobic FPI mat with high thermal stability, (a, b) Bead-on-string-structured FPI electrospun nanofibers film that shows superhydrophobic property, (c) An annealing comparison of the thermal stability of two polymers, FPI and PS. The samples were heated at 150 °C. After heating, the PS sample turned into transparent, which means the micro structures of the PS film have been destroyed, while the FPI sample has no change, (d) Adhesion curve of FPI superhydrophobic electrospim film it means that the film is high adhesive to water (Reproduced from Ref. [49] by permission of The Royal Society of Chemistry)...

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