Ligands concentration, fluctuation

For simplicity, we will examine only the effect of these fluctuations on the equilibrium number of bound receptors. Consider the equilibrium solution of the kinetic equation for simple ligand binding to cell surface receptors [Eq. (7)]. If there are random, thermal fluctuations SL of ligand concentration in the volume of medium accessible to receptor binding, these will lead to corresponding fluctuations in the equilibrium number of complexes Ceq according to... 

Equation (15) dictates, for example, that at a mean or bulk ligand concentration of L = KD, a 10% fluctuation in local ligand concentration... 

In order to use Eq. (15) to calculate the expected effect of fluctuations in ligand concentration on equilibrium receptor binding, we need to estimate a value for the term 8L/L. Estimates for thermal fluctuations in local ligand concentration can be easily obtained (Tranquillo and Lauffenburger, 1987a). The magnitude of 8L/L is approximately... 

The second and more likely source of deviations in the number of bound receptors from the mean behavior predicted by deterministic models is fluctuating reaction kinetics. Stated another way, the signal of ligand concentration analyzed earlier may be relatively constant, but the detector of surface receptors may contribute random errors caused by the probabilistic nature of the binding event. The rate constant for a... 

More recently, Noda has proposed the use of infrared two-dimensional correlation spectroscopy (2D-IR) to increase the information that can be extracted from a spectrum. This approach, essentially different from 2D-NMR spectroscopy, uses correlation analysis of the dynamic fluctuations caused by an external perturbation to enhance spectral resolution without assuming any line shape model for the bands. The technique was intended for the study of polymers and liquid crystals, and it has recently been applied to proteins. In the latter case, the perturbation can be achieved through changes in temperature, pH, ligand concentration and lipid-to-protein ratio. 

River inputs. The riverine endmember is most often highly variable. Fluctuations of the chemical signature of river water discharging into an estuary are clearly critical to determine the effects of estuarine mixing. The characteristics of U- and Th-series nuclides in rivers are reviewed most recently by Chabaux et al. (2003). Important factors include the major element composition, the characteristics and concentrations of particular constituents that can complex or adsorb U- and Th-series nuclides, such as organic ligands, particles or colloids. River flow rates clearly will also have an effect on the rates and patterns of mixing in the estuary (Ponter et al. 1990 Shiller and Boyle 1991). 

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