Filament formation

Permanent chemical crimp can be obtained by creating an asymmetric arrangement of the skin and the core parts of the fiber cross section. Skin cellulose is more highly ordered than core cellulose and shrinks more on drying. If, during filament formation in the spin bath, the skin can be forced to burst open to expose fresh viscose to the acid, a fiber with differing shrinkage potential from side-to-side is made, and crimp should be obtained (Fig. 5a). 

Although most /3- lactam antibiotics bind covalently to some or all of the same six proteins, there are decided differences among them in terms of their relative affinities. For example, cefoxitin (see Table 1 for structures) fails to bind to protein 2 while cephacetrile binds very slowly to proteins 5 and 6. Cephaloridine binds most avidly to protein 1, the transpeptidase, and inhibits cell elongation and causes lysis at its minimum inhibitory concentration. On the other hand, cephalexin binds preferentially to protein 3 and causes inhibition of cell division and filament formation (75PNA2999, 77MI51002). 

Myosin-II phosphorylation is also an important mechanism for regulating myosin assembly in nonmuscle and smooth muscle cells (Kom and Hammer, 1988). For example, myosin-II ixomAcanthamoeba is more soluble when the heavy chain is phosphorylated compared to the unphosphorylated species. Similarly, phosphorylation of the light chains of vertebrate smooth muscle and nonmuscle myosin-II affects filament formation by these myosins. These myosins undergo a... 

Keratins are made of filaments, approximately 10 nm in diameter and hundreds of nanometers in length, via assembly of rod-shaped, coiled-coil proteins. Filament formation is initiated by the creation of a dimer comprising monomeric units 44-54 nm in length. Such dimers may form three types of lateral interactions leading to filament formation from equimolar amounts of acidic and basic dimers. In vitro assembly involves the correct alignment of two, three, or four dimers into a nucleus for further, rapid filament assembly [6]. 

The activity and stability of catalysts for methane-carbon dioxide reforming depend subtly upon the support and the active metal. Methane decomposes to carbon and hydrogen, forming carbon on the oxide support and the metal. Carbon on the metal is reactive and can be oxidized to CO by oxygen from dissociatively adsorbed COj. For noble metals this reaction is fast, leading to low coke accumulation on the metal particles The rate of carbon formation on the support is proportional to the concentration of Lewis acid sites. This carbon is non reactive and may cover the Pt particles causing catalyst deactivation. Hence, the combination of Pt with a support low in acid sites, such as ZrO, is well suited for long term stable operation. For non-noble metals such as Ni, the rate of CH4 dissociation exceeds the rate of oxidation drastically and carbon forms rapidly on the metal in the form of filaments. The rate of carbon filament formation is proportional to the particle size of Ni Below a critical Ni particle size (d<2 nm), formation of carbon slowed down dramatically Well dispersed Ni supported on ZrO is thus a viable alternative to the noble metal based materials. 

As the metal particle size decreases the filament diameter should also decrease. It has been shown that the surface energy of thirmer filaments is larger and hence the filaments are less stable (11,17-18). Also the proportion of the Ni(l 11) planes, which readily cause carbon formation, is lower in smaller Ni particles (19). Therefore, even though the reasons are diverse, in practice the carbon filament formation ceases with catalysts containing smaller Ni particles. Consequently, well dispersed Ni catalysts prepared by deposition precipitation of Ni (average metal particle size below 2-3 nm) were stable for 50 hours on stream and exhibited no filamentous coke [16]. 

Zemlan, F., Thienhaus, O.J. and Bosmann, H.B. (1989). Superoxide dismutase activity in Alzheimer s disease possible mechanism for paired helical filament formation. Brain Res. 476, 160-162. 

Filament Formation. Cells that reproduce and divide in a normal manner may be induced to grow in filaments by changing the... 

Variation in the magnesium (Mg) content of the medium may exert a marked effect on cell division of some bacteria. In a Mg-deficient medium, Gram-positive rods grow in the form of long filaments. Such filaments revert to normal forms when transferred to the same medium supplemented with suitable concentrations of Mg. Filament formation is enhanced by the addition of zinc and cobalt. Inhibition of cell division occurs also in media supplemented with an excess of Mg. 

A series of kinetic studies on the carbon filament formation by methane decomposition over Ni catalysts was reported by Snoeck et al. [116]. The authors derived a rigorous kinetic model for the formation of the filamentous carbon and hydrogen by methane cracking. The model includes the following steps ... 

Snoeck, J., Froment, G., and Fowles, M., Kinetic study of the carbon filament formation by methane cracking on a nickel catalyst, /. Catal., 169, 250,1997. 

Richard Williams, Injection by Internal Photoemission Allen M. Barnett, Current Filament Formation R. Baron and J.W. Mayer, Double Injection in Semiconductors W. Ruppel, The Photoconductor-Metal Contact... 

IV. Filament Formation and Prion Conversion Are Based on Amyloidosis... 

F. Filament Formation Depends Mostly on Amino Acid Composition,... 

III. Filament Formation In Vivo and In Vitro A. Filament Formation In Vivo... 

All fungal prion proteins readily form filaments in vitro (Dos Reis et al., 2002 Glover et al., 1997 Sondheimer and Lindquist, 2000 Taylor et al., 1999). In near-native buffer conditions, filament formation typically occurs in hours to days. Ure2p filaments assembled in vitro have a diameter of —20 nm and like the filaments observed in situ (Section III.A Fig. 4), they are not hollow. 

Taken together, these observations establish that it is the prion domain alone that is responsible for filament formation. 

F. Filament Formation Is Not Based on Interactions Between the N- and C-Domains... 

Constructs of Sup35p (Sup35pN and Sup35pNM) have been investigated by CD spectroscopy and in both cases an increase of /(-structure on filament formation was reported (Glover et al., 1997 King et al., 1997). No attempt was made to quantitate secondary structure. 

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