Ultra-weak interactions (K(d)>100μM) between proteins have in the last decade become an increasing focus of attention in cell biology, especially in relation to cell-cell interactions and signalling processes. Methods for their quantitative definition are reviewed. NMR spectroscopy plays a major role in this area, as it not only can define interactions as weak or weaker than 3mM, but in favourable cases structural information concerning the complex can be yielded. Free solution technologies mostly fail when addressed to such systems. The AUC has the highest practical capability, but evaluation of the data to yield K(a) values is complicated by the presence of thermodynamic/hydrodynamic effects of a comparable order of magnitude. These effects can however be computationally removed by means of suitable algorithms, and K(d) values of up to 50mM can be characterised. The relative merits of velocity and equilibrium approaches are discussed, and both are shown to have particular advantages.
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http://dx.doi.org/10.1016/j.ymeth.2011.02.006 | DOI Listing |
J Am Chem Soc
February 2019
Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics , National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda , Maryland 20892 , United States.
Ultra-weak self-association can govern the macroscopic solution behavior of concentrated macromolecular solutions ranging from food products to pharmaceutical formulations and the cytosol. For example, it can promote dynamic assembly of multi-protein signaling complexes, lead to intracellular liquid-liquid phase transitions, and seed crystallization or pathological aggregates. Unfortunately, weak self-association is technically extremely difficult to study, as it requires very high protein concentrations where short intermolecular distances cause strongly correlated particle motion.
View Article and Find Full Text PDFPhys Chem Chem Phys
November 2018
Center for Molecular Modeling, OIR/CIT, National Institutes of Health, U.S. DHHS, USA.
A method is described for the efficient simulation of multiprotein systems in crowded environments. It is based on an adaptive, reversible structural coarsening algorithm that preserves relevant physical features of the proteins across scales. Water is treated implicitly whereas all the other components of the aqueous solution, such as ions, cosolutes, or osmolytes, are treated in atomic detail.
View Article and Find Full Text PDFPLoS One
July 2012
Experimental Zoology, Wageningen University, Wageningen, The Netherlands.
Catfish detect and identify invisible prey by sensing their ultra-weak electric fields with electroreceptors. Any neuron that deals with small-amplitude input has to overcome sensitivity limitations arising from inherent threshold non-linearities in spike-generation mechanisms. Many sensory cells solve this issue with stochastic resonance, in which a moderate amount of intrinsic noise causes irregular spontaneous spiking activity with a probability that is modulated by the input signal.
View Article and Find Full Text PDFMethods
May 2011
University of Nottingham, NCMH, School of Biosciences, Sutton Bonington, Leicestershire LE12 5RD, UK.
Ultra-weak interactions (K(d)>100μM) between proteins have in the last decade become an increasing focus of attention in cell biology, especially in relation to cell-cell interactions and signalling processes. Methods for their quantitative definition are reviewed. NMR spectroscopy plays a major role in this area, as it not only can define interactions as weak or weaker than 3mM, but in favourable cases structural information concerning the complex can be yielded.
View Article and Find Full Text PDFIEEE Trans Ultrason Ferroelectr Freq Control
March 2009
Laboratoire de Génie Electrique et Ferroélectricité, Institut National des Sciences Appliquées de Lyon, Lyon, France.
Polarization phenomena in ferroelectric materials are frequency-dependent, and the present article describes the use of a fractional derivative for the understanding of these phenomena as well as modeling them as functions of frequency and electric field amplitude. The focus was first directed toward the definition and validation of the proposed model through comparisons between simulations and measurements for high electrical field excitation amplitudes on a large frequency bandwidth (major hysteresis loops, measured over 4 decades). Subsequently, the same comparisons were made under ultra-weak as well as weak electric fields.
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