Two-dimensional NMR analysis of the conformational and dynamic properties of .alpha.-helical poly(.gamma.-benzyl L-glutamate)

1986 ◽  
Vol 108 (17) ◽  
pp. 5130-5134 ◽  
Author(s):  
Peter A. Mirau ◽  
Frank A. Bovey
2000 ◽  
Vol 149 (4) ◽  
pp. 767-774 ◽  
Author(s):  
Isabelle Arnal ◽  
Eric Karsenti ◽  
Anthony A. Hyman

Microtubules are dynamically unstable polymers that interconvert stochastically between growing and shrinking states by the addition and loss of subunits from their ends. However, there is little experimental data on the relationship between microtubule end structure and the regulation of dynamic instability. To investigate this relationship, we have modulated dynamic instability in Xenopus egg extracts by adding a catastrophe-promoting factor, Op18/stathmin. Using electron cryomicroscopy, we find that microtubules in cytoplasmic extracts grow by the extension of a two- dimensional sheet of protofilaments, which later closes into a tube. Increasing the catastrophe frequency by the addition of Op18/stathmin decreases both the length and frequency of the occurrence of sheets and increases the number of frayed ends. Interestingly, we also find that more dynamic populations contain more blunt ends, suggesting that these are a metastable intermediate between shrinking and growing microtubules. Our results demonstrate for the first time that microtubule assembly in physiological conditions is a two-dimensional process, and they suggest that the two-dimensional sheets stabilize microtubules against catastrophes. We present a model in which the frequency of catastrophes is directly correlated with the structural state of microtubule ends.


1990 ◽  
Vol 68 (9) ◽  
pp. 999-1012 ◽  
Author(s):  
E. Sackmann

The cell plasma is a composite type of material that is made up of a two-dimensional liquid crystal (lipid–protein bilayer) to which a macromolecular network (the cytoskeleton) is loosely coupled. The latter may be approximately two dimensional as in the case of the erythrocytes or may extend throughout the whole cell cytoplasm. Owing to this combination of two states of matter, the membrane combines the dynamics and flexibility of a fluid with the mechanical stability of a solid. Owing to its low dimensionality, the local structure of the bilayer or the global shape of cells may be most effectively controlled and modulated by biochemical signals such as macromolecular adsorption. The present contribution deals with comparative studies of the local and global dynamic properties of biological and artificial membranes. In the first part the question of the physical basis of selective lipid–protein interaction mechanisms is addressed and the outstanding viscoelastic properties of plasma membranes and their role for local instabilities shape fluctuations of cells and the cell–substrate interaction are described. The second part deals with the molecular architecture and dynamics of composite membranes prepared by combining monomeric and macromolecular lipids. These model membranes open new possibilities to mimick complex mechanical processes of cell plasma membranes and to prepare low-dimensionality macromolecular solutions and gels. Finally, the use of such compound systems by nature to prepare the semipermeable protective layers of plant leaves, the so-called cuticle, is discussed. In analogy to plasma membranes, the local transport properties are modulated by variation of the liquid-crystalline state of the monomeric waxes.


FEBS Letters ◽  
1987 ◽  
Vol 219 (1) ◽  
pp. 17-21 ◽  
Author(s):  
Mitsuhiko Ikura ◽  
Osamu Minowa ◽  
Michio Yazawa ◽  
Koichi Yagi ◽  
Kunio Hikichi

Biochemistry ◽  
1985 ◽  
Vol 24 (20) ◽  
pp. 5592-5598 ◽  
Author(s):  
Francis Michon ◽  
Jean Robert Brisson ◽  
Rene Roy ◽  
Fraser E. Ashton ◽  
Harold J. Jennings

1997 ◽  
Vol 55 (1) ◽  
pp. 544-550 ◽  
Author(s):  
R. K. Moudgil ◽  
P. K. Ahluwalia ◽  
K. Tankeshwar ◽  
K. N. Pathak

Author(s):  
Necati OZDEMIR ◽  
Derya AVCI ◽  
Beyza Billur ISKENDER

This paper is concerned with the numerical solutions of a two dimensional space-time fractional differential equation used to model the dynamic properties of complex systems governed by anomalous diffusion. The space-time fractional anomalous diffusion equation is defined by replacing second order space and first order time derivatives with Riesz and Caputo operators, respectively. By using Laplace and Fourier transforms, a general representation of analytical solution is obtained as Mittag-Leffler function. Gr\"{u}nwald-Letnikov (GL) approximation is also used to find numerical solution of the problem. Finally, simulation results for two examples illustrate the comparison of the analytical and numerical solutions and also validity of the GL approach to this problem.


2015 ◽  
pp. 97-116 ◽  
Author(s):  
Yuri Kobljanskyj ◽  
Denys Slobodianiuk ◽  
Gennady Melkov ◽  
Konstantin Guslienko ◽  
Valentyn Novosad ◽  
...  

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