PubMed · 10794872
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J M Thijssen. 2000. Spectroscopy and image texture analysis.. https://doi.org/10.1016/s0301-5629(00)00161-7
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This paper reports the results of applying a computational method called the quantized elastic deformational model, to the determination of conformational flexibility of the supermolecular complex of human fatty acid synthase. The essence of this method is the ability to model large-scale conformational changes such as domain movements by treating the protein as an elastic object without the knowledge of protein primary sequence and atomic coordinates. The calculation was based on the electron density maps of the synthase at 19 A. The results suggest that the synthase is a very flexible molecule. Two types of flexible hinges in the structure were identified. One is an intersubunit hinge formed by the intersubunit connection and the other is an intrasubunit hinge located between domains I and II. Despite the fact that the dimeric synthase has a chemically symmetric structure, large domain movements around the hinge region occur in various directions and allow the molecule to adopt a wide range of conformations. These domain movements are likely to be important in facilitating and regulating the entire palmitate synthesis by coordinating the communication between components of the molecule, for instance, adjusting the distance between various active sites inside the catalytic reaction center. Finally, the ability to describe protein motions of a supermolecular complex, without the information of protein sequence and atomic coordinates, is a major advance in computational modeling of protein dynamics. The method provides an unprecedented ability to model protein motions at such a low resolution of structure.
The mechanical properties of films formed from an aqueous dispersion of polymethlymethacrylate (Eudragit NE30D) and as mixture with an aqueous dispersion of ethylcellulose (Aquacoat ECD30), have been assessed by applying creep tests at different temperatures, using a dynamic mechanical analyser. In the region of linear creep, the film prepared from 100% Eudragit was far less elastic than when 60% Aquacoat was present. In this region, when the applied stress was doubled, the strain response was doubled. In the non-linear region of behaviour, there is clear evidence that the mixed film is more elastic than the film containing only Eudragit.
We characterize vesicle adhesion onto homogeneous substrates by means of a perturbative expansion around the infinite adhesion limit, where curvature elasticity effects are absent. At first order in curvature elasticity, we determine analytically various global physical quantities associated with adhering vesicles: height, adhesion radius, etc. Our results are valid for adhesion energies above a certain threshold, that we determine numerically. We discuss the haptotactic force acting on a vesicle in the limit of weak adhesion gradients. We also propose a few methods for measuring adhesion energies and we suggest a possible way of determining the size of suboptical vesicles using controlled adhesion gradients.