Solution macromolecules

At any point within the boundary layer, the convective flux of the macromolecule solute to the membrane surface is given by the volume flux,/ of the solution multipfled by the concentration of retained solute, c. At steady state, this convective flux within the laminar boundary layer is balanced by the diffusive flux of retained solute in the opposite direction. This balance can be expressed by equation 1 ... 

Sample preparation for AFM analysis is relatively simple. Generally, a desired amount of sample is absorbed onto a smooth and clean substrate surface, for example, a freshly cleaved mica surface. For example, to prepare a food macromolecule sample for AFM imaging in air, the diluted macromolecule solution is disrupted by vortexing. Then, a small aliquot (tens of microliters) of vortexed solution is deposited onto a surface of freshly cleaved mica sheet by pipette. The mica surface is air dried before the AFM scan. A clean surrounding is required to avoid the interference of dust in the air. Molecular combing or fluid fixation may be applied to manipulate the molecule to get more information. 

Add 10 pi of 5 M sodium cyanoborohydride in 1N NaOH (Aldrich) per ml of the macromolecule solution volume prepared in (1). Caution Highly toxic compound. Use a fume hood and be careful to avoid skin contact with this reagent. 

Expressions (9) - (12) are initial for analysis of osmotic pressure of macromolecules solution into further presented partial variants. 

The choice of carrier liquid is primarily based on the suspension stability for colloids or solvent goodness for macromolecule solutions. Moreover, surface-charged colloidal particles are also sensitive to ionic strength and addition of surfactants. 

Salts of low molecular mass (or any small molecule) can be removed from solutions of large molecules by gel filtration because the large molecules are eluted first. This technique, called desalting, is useful for changing the buffer composition of a macromolecule solution. 

As in Equation 14 for the density increment, the right side of Equation 13a is equal to (dn/dg2)T,m,ns, i-e., the refractive index increment measured by using a dialyzed macromolecule solution and the dialyzate as reference solvent.)... 

Dissolve SFB or SFPA (Molecular Probes) in DMF. The concentration should be such that a small aliquot can be added to the reaction medium to obtain about a 10-fold excess of modifying reagent over the amount of amines to be modified. Add no more than 100 pi of the modifier/DMF solution to each milliliter of the macromolecule solution prepared in (1). 

When a monochromatic, coherent light is incident into a dilute macromolecule solution, if solvent molecules and macromolecules have different refractive index, the incident light is scattered by each illuminated macromolecule to all directions [9, 10]. The scattered light waves from different macromolecules mutually interfere, or combine, at a distant, fast photomultiplier tube detector and produce a net scattering intensity I(t) or photon counts n(t) which is not uniform on the detection plane. If all macromolecules are stationary, the scattered light intensity at each direction would be a constant, i.e. independent of time. 

Equilibrium dialysis is an analytical technique which is usually performed with commercial apparatus. In this technique, the two dialysis chambers, separated by a membrane, are filled respectively with macromolecule solution and with ligand, which is usually radioactively labelled. After equilibrium has been reached, samples are removed from the two chambers the concentration of free ligand is determined from one sample, and free plus bound ligand from the other. Parameters characterising the binding equilibrium can be determined by appropriate analysis of the data. 

Complex fluids such as electrolyte solutions, polymer solutions, and biological macromolecule solutions pose significant obstacles to molecular... 

The simplest technique for biological macromolecule crystallisation is batch crystallisation. This is the simple binary combination of biological macromolecule solution and precipitant to create an instantaneous state of high supersaturation. This minimal process can give diffraction quality crystals under some circumstances but many other techniques... 

Figure 6.8 Liquid-liquid diffusion Saturated solution of biological macromolecule (e.g. protein) is placed in a sealed capillary environment in contact with precipitant solution. Slow mixing and liquid diffusion creates sufficient precipitant gradient in the macromolecule solution to "seed" crystallisation.

The densities of liquids and liquid mixtures are conventionally measured using pYcniinietcr or hydroiiielermethods (Figure 4.2), but these are rarely accurate enough for the dilute macromolecule solutions normally encountered in biophysical studies. 

G.D.J. Phillies, G.S. Ullmann, K. Ullmann and T.-H. Lin, "Phenomenological Scaling Laws for Semidilute Macromolecule Solutions From Light Scattering by Optical Probe Particles, J. Chem. Phvs.. 82, 5242-5246 (1985). 

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