Dialysis constant

Table 10. Dependence of the dialysis constant for the permeability of urea (P) on the composition of the polyelectrolyte complex membrane115 ...

Equilibrium dialysis was used to measure a binding constant of 103 m 1 between 87 and DNA. They interpreted these results as being consistent with intercalation of DNA by 77, indicating that azinomycin B itself may also intercalate. 

The affinity and cross-reactivity of the whole serum and Fab fragments were determined using equilibrium dialysis for the affinity determination and RIA for the cross-reactivity studies. The average intrinsic affinity constant (Ko) of the antibody (Nisonoff and Pressman 1958) changed very little throughout the... 

Preventive measures for patients who may be prone to hypotension include accurate determination of the dry weight and maintaining a constant ultrafiltration rate. Midodrine is an a-adrenergic agonist that is effective in reducing hypotension in patients with autonomic dysfunction that is taken with each dialysis session or as chronic therapy. Midodrine can be administered at doses of 2.5 to 10 mg prior to HD or 5 mg twice daily for chronic hypotension. Side effects of midodrine include pruritus and paresthesias. 

The very slow dissociation rates for tight binding inhibitors offer some potential clinical advantages for such compounds, as described in detail in Chapter 6. Experimental determination of the value of k, can be quite challenging for these inhibitors. We have detailed in Chapters 5 and 6 several kinetic methods for estimating the value of the dissociation rate constant. When the value of kofS is extremely low, however, alternative methods may be required to estimate this kinetic constant. For example, equilibrium dialysis over the course of hours, or even days, may be required to achieve sufficient inhibitor release from the El complex for measurement. A significant issue with approaches like this is that the enzyme may not remain stable over the extended time course of such experiments. In some cases of extremely slow inhibitor dissociation, the limits of enzyme stability will preclude accurate determination of koff the best that one can do in these cases is to provide an upper limit on the value of this rate constant. 

In a dialysis experiment, a dialysis bag containing the dissolved humic materials is placed in a solution of a pollutant (preferably radiolabeled). The dialysis tubing is chosen so the pollutant is free to diffuse through the bag while the humic materials are retained inside the bag. The solution is shaken at constant temperature until it comes to an equilibrium point. At equilibrium, the pollutant inside the dialysis bag consists of two fractions that truly dissolved and the bound to the humic materials. The concentration of pollutant on the outside of the dialysis bag consists only of the free, truly dissolved fraction. Any increase of the pollutant concentration on the inside of the dialysis bag is due to binding by dissolved humic materials. A series of dialysis experiments, therefore, can measure the bound fraction concentration as a function of the free concentration. 

The binding constants of a number of compounds were measured using dialysis, solubility and sorption techniques. The solubility technique was used for compounds which were not radiolabeled. All data was collected at pH = 8.3. The binding constants were then compared to the octanol/water partition coefficients for the compounds and the molar solubilities of the compounds. The data is presented in Table II. The Kow values were taken from the literature.18 22-2 The solubility values were determined in this research with the exception of DDT and Lindane, which were taken from the literature. A plot of log Kc vs. log Kow is presented in Figure 5. The slope of this line is 0.71, the intercept is 0.75 and the value of the correlation coefficient is 0.9258. The regression is highly significant... 

The chilled azide solution is added slowly, dropwise with constant vigorous stirring into a solution of bovine-serum albumin. The pH is maintained at 8.0 to 8.7 by the careful addition of NaOH solution. The resulting pale-yellow solution is kept at 4°C for a duration of 36 hours and then dialysed against trimethamine buffer. After further dialysis for two days against distilled water, the immunogen is isolated by lyophilization. 

Meadows et al. (1998) conducted a 28 d exposure of brown trout (Salmo trutta), standard SPMDs and hexane fllled dialysis bags (Sodergren, 1987) to spring water (total organic carbon < 1 mg L ) contaminated with PCBs. Trout were not fed during the exposure, and temperature and flow conditions remained constant throughout the exposure. A good correlation (r = 0.89) was found between the uptake rate constants ( u,fs) for whole body trout and the uptake rate constants... 

Responses in the dopamine system are more complex (see chapter by Balfour, this volume). Repeated nicotine injections resulted in enhanced extracellular DA levels in the NAc (Benwell and Balfour 1992, 1997), but not in the striatum (Benwell and Balfour 1997). Analysis of the precise placement of dialysis probes has revealed differential responses to drugs of abuse, including nicotine, between the NAc core (ventral striatum) and shell (Di Chiara 2002 Balfour 2004 Wonnacott et al. 2005 see chapter by Balfour, this volume). Moreover, the sensitised neurotransmitter responses observed in the hippocampus and NAc were markedly attenuated if rats received a constant infusion of a low level of nicotine (Benwell and Balfour 1997). Thus, transient peaks of nicotine appear capable of sensitising some brain pathways with respect to catecholamine release, but the responses may be mitigated by lower sustained plasma concentrations, possibly due to desensitisation. The extent that presynaptic nAChRs contribute to this process in vivo is unclear presynaptic a7 nAChRs on glutamatergic afferents to the VTA merit attention as potential mediators of sensitisation (see Sect. 2.2.2). 

In the absence of crystallographic data, there exist many other experimental criteria that allow the determination of the binding mode [30,38]. They can be classified into two categories the measurement of physical effects on DNA and spectroscopic studies (Table 1, first column, C and A respectively). Irrespective of the binding mode, the binding parameters (the affinity constant and the number n of occupied base pairs per molecule) can be determined from equilibrium dialysis and Scatchard plots [43 46]... 

Next, the RBDCL was screened against the TAMRA-labeled DNA sequences. As seen in Fig. 3.11, only one pool of resin showed significant fluorescence. This pool contained the monomer Cys-Ser-Ser-Quin, and as such the homodisulfide (Cys-Ser-Ser-Quin) was selected as the best binder. Equilibrium dialysis experiments confirmed that (Cys-Ser-Ser-Quin) bound the target DNA Sequence 2 with a dissociation constant of 2.8 tM. While it is certainly true that identification of amplified compounds from large solution-phase DCLs is possible, given sufficiently... 

The equilibrium dialysis experiment revealed that histidine-substituted salicylamide was selected as an RNA ligand. Subsequent binding analysis by UV titrations and Job plot revealed the histidine-substituted salicylamide Cu + complex bound the target RNA hairpin with an apparent dissociation constant of 150 nM. This binding constant likely reflects more complex binding processes than a simple 1 1 interaction, as the observed binding curve saturates well below the concentration of the histidine-substituted salicylamide, and thus the actual affinity of the complex for targeted RNA is probably lower. Importantly, however, titrations with the... 

COOPERATIVE LIGAND BINDING EQUILIBRIUM CONSTANT EQUILIBRIUM DIALYSIS HUMMEL-DREYER METHQD LINKED EUNCTIQN THEQRY KLQTZ PLQT... 

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