Morphology filamentous

Myosin may be extracted via high-ionic-strength buffers and purified. Synthetic thick filaments of myosin spontaneously assemble upon lowering the ionic strength of its solution, exhibiting the morphological characteristics of native thick filaments. This process initiates with myosin monomers assembled into parallel dimers. The dimers assemble into antiparallel tetramers, the tetramers into octamers, and the octamers into minifilaments... 

These changes in morphology induced by chemical substances are usually temporary, since reversion to normal form occurs promptly when the filamentous bacteria are subcultured in the absence of the inhibitory agents. Irradiation, on the other band, may give rise to a temporary or permanent induction of filamentous cells. 

Copolymers (graft or block) made of immiscible sequences give rise to biphasic morphologies depending on the ratio of immiscible sequences (or of their lengths). Such possible microstructures are reported in Figure 33. A minor phase can be dispersed as nodules (spheres) or filaments (cylinders) while, when concentrations of both phases get similar, lamellar (interpenetrated) structures can appear. It should be noted that rather similar morphologies could also be found in (compatibilised) polymer blends. 

At the end of 2003, new research results led to sensational headlines Minerals Cooked Up in the Laboratory Call Ancient Microfossils Into Question was the title chosen by Richard A. Kerr for his article in Science dealing with synthetically prepared silicate carbonates. Their microstructures show morphologies which look exactly like those of filaments which had been assigned as cyanobacterial microfossils of the Precambrian Warrawoona chert formation in western Australia. The synthetic structures consist of silicate-encapsulated carbonate crystals, and in part have a helically twisted morphology reminiscent of biological objects. Simple... 

The importance of the uniformity of structure and morphology for the strength of the fibre is illustrated in Fig. 73. It shows that the observed filament strength of the PpPTA microfilaments is considerably higher than the strength... 

Fig. 77 The fracture morphology of strong and weak filaments taken from a single PpPTA yarn with a relatively low strength due to polymer degradation...

Neuronal and glial intermediate filaments provide support for neuronal and glial morphologies 127... 

Glial cytoplasmic inclusions are strongly immunoreac-tive for a-synuclein and filaments isolated from the brains of patients with multiple system atrophy are labeled by a-synuclein antibodies [10]. As in dementia with Lewy bodies, assembled a-synuclein is nitrated and phosphory-lated at S129, and the number of a-synuclein-positive structures exceeds that stained by anti-ubiquitin antibodies, confirming that the accumulation of a-synuclein precedes ubiquitination. Filament morphologies and their staining characteristics were found to be similar to those of filaments extracted from the brains of patients with Parkinson s disease and dementia with Lewy bodies. 

They have many of the morphological and ultrastructural characteristics of disease filaments [11, 12] (Fig. 45-5). Assembly is a nucleation-dependent process that occurs through its amino-terminal repeats. The carboxy-terminal region, in contrast, is inhibitory. Assembly is accompanied by the transition from random coil to a [3-pleated sheet. By electron diffraction, a-synuclein filaments show a conformation characteristic of amyloid fibers. Under the conditions of these experiments, P- and y-synucleins failed to assemble, consistent with their absence from the filamentous lesions of the human diseases. When incubated with a-synuclein, P- and y-synucleins inhibit the fibrillation of a-synuclein, suggesting that they may indirectly influence the pathogenesis of Lewy body diseases and multiple system atrophy. 

---