Scatchard analysis

Using cultured mammalian sarcoma cells, it has been found that transferrin is necessary in the growth medium for galllum-67 uptake to occur (95,96.97). A transferrin receptor on EMT-6 sarcoma cells for 25i iabeled transferrin was characterized by Scatchard analysis to have an average association constant K = 4.54 X 10 1/mole and approximately (with variation) 500,000 receptors per cell ( ). It was proposed that tumor accumulation of galllum-67 can occur only if the metal is complexed with transferrin so that it can interact with the receptors of tumor, as well as non-mallgnant cells (.33). The complex then enters the cell via an adsorptive endocytosis process (95.96.97.98.99) similar to the manner in which iron is taken up by reticulocytes and bone marrow cells (100.101). These transferrin receptors are saturable (that is, a plot of 125i transferrin uptake versus extracellular transferrin concentration reaches a peak ( at about 200 u g/ml) as more carrier transferrin is added to the medium) (95). Since uptake is also proportional to the fraction of 

ACS Symposium Series American Chemical Society Washington, DC, 1980. 

It has been further shown that a majority (approximately 60jt) of the extractable Qa (about 70 of the cellular gallium) from tumor and liver cells of the rat is associated with two macromolecular fractions of molar weight 1-1.2 x 105 Daltons and 4-5 X 10 Daltons (64) The 1-1.2 x 1o5 D band is found in both liver and tumor cells, whereas the 4-5 x 10 D band is found 

Lactoferrin, with a molecular weight of 8.5-9.0 x 10 and a structure similar to transferrin (112) has been suggested as an alternative intracellular gallium-binding agent (113). 

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Scatchard analysis Scattering studies Scavenger model Scav-Ox... 

Size Isomers. In solution, hGH is a mixture of monomer, dimer, and higher molecular weight oligomers. Furthermore, there are aggregated forms of hGH found in both the pituitary and in the circulation (16,17). The dimeric forms of hGH have been the most carefully studied and there appear to be at least three distinct types of dimer a disulfide dimer connected through interchain disulfide bonds (8) a covalent or irreversible dimer that is detected on sodium dodecylsulfate- (SDS-)polyacrylamide gels (see Electroseparations, Electrophoresis) and is not a disulfide dimer (19,20) and a noncovalent dimer which is easily dissociated into monomeric hGH by treatment with agents that dismpt hydrophobic interactions in proteins (21). In addition, hGH forms a dimeric complex with ( 2). Scatchard analysis has revealed that two ions associate per hGH dimer in a cooperative... 

Scatchard analysis, a common linear transformation of saturation binding data used prevalently before the widespread availability of nonlinear fitting software. The Scatchard transformation (see Chapter 4.2.1), while easy to perform, can be misleading and lead to errors. 

Inhibition of EGF binding by palytoxin could be due to a decrease in receptor affinity, as in the case of TPA-type tumor promoters, and/or a decrease in receptor number. In Swiss 3T3 cells there are two classes of EGF receptors. The dissociation constants for the two EGF receptor classes were determined to be approximately 2 X 10 M and 2 x 10" M, corresponding to approximately 1 x 10 and 1 X 10 receptor molecules per cell, respectively (33). Scatchard analysis revealed that treatment of Swiss 3T3 cells with palytoxin, like PDBu, caused an apparent loss in high-affinity binding (Figure 2). However, in contrast to PDBu, palytoxin also caused a significant (approximately 50%) loss of low affinity EGF binding. 

Figure 2. Scatchard analysis of I-EGF binding to Swiss 3T3 cells treated with PDBu or palytoxin. Confluent quiescent Swiss 3T3 cells were treated at 37 C with solvent (o) or 200 nM PDBu ( ) for 15 min (Upper panel) or with solvent (o) or 11 pM palytoxin ( ) for 60 min (Lower panel). Cells were assayed as in Figure 1. (Reproduced with permission from Ref. 33. Copyright 1987 Cancer Research, Inc.)...

Fig. 3 Scatchard analysis of inmiune complex binding to the macrophages incubated with bupleuran 2IIb...

NMDA on the affinity and binding site density by Scatchard analysis, as described in the note with table 4. 

Scatchard analysis is very useful in certain therapeutic situations. For example, this type of analysis is used to determine the number of estrogen receptors present in a biopsy of breast tissue prior to developing a drug treatment regimen for breast cancer in a patient. 

FIG. 4. Scatchard analysis of specific 3H-LSD binding to crude homogenates of cortex from rats treated with either 200 9 intraventricular 5,7-DHT, 20 mg/kg i.p. PCA, or saline 45 days prior to assay. Specific binding of 3H-LSD (final concentrations from 1-100 nm) was defined as the difference between 3H-LSD binding in the absence and presence of 10 jim 5-HT. Each point represents the mean of three rats. The dissociation constants (KD) of 5,7-DHT- and saline-treated rats were significantly different (p < 0.05 f-test). (From ref. 16, with the permission of ANKO International Inc. for Neuroscience and Biobehavioral Reviews.)... 

Scatchard Analysis Quantifies the Receptor-Ligand Interaction... 

Scatchard analysis is reliable for the simplest cases, but as with Lineweaver-Burk plots for enzymes, when the receptor is an allosteric protein, the plots deviate from linearity. 

Terms in bold are defined i neuroendocrine system 882 radioimmunoassay (RIA) 884 Scatchard analysis 884 endocrine glands 886 paracrine 886 autocrine 886 insulin 887 epinephrine 888 norepinephrine 888 catecholamines 888 eicosanoid... 

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