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Questions and Answers
The method is based on the rate of disappearance of ______ from a dialysis cell.
The method is based on the rate of disappearance of ______ from a dialysis cell.
drug
A ______ dialysis bag containing the drug-protein solution is suspended in the buffer solution.
A ______ dialysis bag containing the drug-protein solution is suspended in the buffer solution.
cellophane
The dialysis process follows the rate law: -d[Dt]/dt = k______.
The dialysis process follows the rate law: -d[Dt]/dt = k______.
Df
______ bonding is actually not bond formation at all, but rather the tendency of hydrophobic molecules or hydrophobic parts of molecules to avoid water.
______ bonding is actually not bond formation at all, but rather the tendency of hydrophobic molecules or hydrophobic parts of molecules to avoid water.
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Large hydrophobic species such as proteins avoid the water molecules in an ______ solution by associating into micelle-like structures.
Large hydrophobic species such as proteins avoid the water molecules in an ______ solution by associating into micelle-like structures.
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Both the solutions are stirred continuously and are periodically removed from outside the dialysis bag and analyzed ______.
Both the solutions are stirred continuously and are periodically removed from outside the dialysis bag and analyzed ______.
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Albumin is the most important plasma protein due to its _______________ concentration relative to other proteins.
Albumin is the most important plasma protein due to its _______________ concentration relative to other proteins.
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The interaction between a protein and a drug molecule can be represented as P + D → _______________.
The interaction between a protein and a drug molecule can be represented as P + D → _______________.
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The association constant 'k' is the ratio of the concentration of _______________ to the product of the concentrations of unbound protein and unbound drug.
The association constant 'k' is the ratio of the concentration of _______________ to the product of the concentrations of unbound protein and unbound drug.
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α1-acid glycoprotein is a plasma protein that has a greater affinity for _______________ drugs.
α1-acid glycoprotein is a plasma protein that has a greater affinity for _______________ drugs.
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Protein binding can _______________ the distribution of the drug throughout the body.
Protein binding can _______________ the distribution of the drug throughout the body.
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One of the experimental methods for determining protein binding is _______________.
One of the experimental methods for determining protein binding is _______________.
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Protein binding can also _______________ the excretion of a drug which may accumulate in the body.
Protein binding can also _______________ the excretion of a drug which may accumulate in the body.
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Protein binding can lead to a _______________ change in the protein which may become capable of binding other agents.
Protein binding can lead to a _______________ change in the protein which may become capable of binding other agents.
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The solubility behavior of a drug is studied in the ______________ of a protein.
The solubility behavior of a drug is studied in the ______________ of a protein.
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The effect of protein on the partitioning behavior of drug molecules between an aqueous and an organic solvent that are ______________.
The effect of protein on the partitioning behavior of drug molecules between an aqueous and an organic solvent that are ______________.
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In equilibrium dialysis method, the protein solution is enclosed within a ______________ membrane.
In equilibrium dialysis method, the protein solution is enclosed within a ______________ membrane.
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The ultrafiltration method is similar to equilibrium dialysis method, but uses ______________ to force the solvent and the free drug across the membrane.
The ultrafiltration method is similar to equilibrium dialysis method, but uses ______________ to force the solvent and the free drug across the membrane.
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Dynamic dialysis is a ______________ method for studying the concentration of bound drug in protein solution.
Dynamic dialysis is a ______________ method for studying the concentration of bound drug in protein solution.
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Equilibrium dialysis method is used to assess the degree of binding by measuring the conc. of free and ______________ drug.
Equilibrium dialysis method is used to assess the degree of binding by measuring the conc. of free and ______________ drug.
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In equilibrium dialysis method, the solution is agitated slightly until ______________ has been achieved.
In equilibrium dialysis method, the solution is agitated slightly until ______________ has been achieved.
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Ultrafiltration method is more convenient than other methods for routine determinations because it is less ______________ consuming.
Ultrafiltration method is more convenient than other methods for routine determinations because it is less ______________ consuming.
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Study Notes
Equilibrium Dialysis Method
- The method is based on the rate of disappearance of a drug from a dialysis cell, which is proportional to the concentration of unbound drug.
- The apparatus consists of a jacketed (temperature-controlled) beaker with a buffer solution, a cellophane dialysis bag containing a drug-protein solution, and continuous stirring.
- The dialysis process follows the rate law: -d[Dt]/dt = k[Df], where [Dt] is the total drug concentration, [Df] is the concentration of free or unbound drug, and k is the first-order rate constant representative of the diffusion process.
Hydrophobic Interaction
- Hydrophobic bonding is not a bond formation, but rather the tendency of hydrophobic molecules or hydrophobic parts of molecules to avoid water.
- Large hydrophobic species, such as proteins, avoid water molecules in an aqueous solution by associating into micelle-like structures with non-polar portions in contact in the inner regions and polar ends facing the water molecules.
Protein Binding
- Plasma proteins, such as albumin, globulin, and lipoproteins, can bind with a large number of drug molecules, altering the biological properties of the drug.
- Protein binding can:
- Facilitate the distribution of the drug throughout the body
- Inactivate a drug by reducing the concentration of free drug at the receptor site
- Retard the excretion of a drug, leading to accumulation in the body
- Alter the duration of action of a drug
- Displace body hormones or co-administered agents
- Bring about a configurational change in the protein, which may bind other agents
- Alter the therapeutic effect by forming a drug-protein complex that is biologically active
Albumin Binding
- Albumin is the most important plasma protein due to its high concentration and ability to bind both acidic and basic drugs.
Tetracycline-Albumin Binding
- Another plasma protein is α1-acid glycoprotein, which binds to numerous drugs, with a greater affinity for basic than acidic drugs.
Binding Equilibria
- The interaction between a protein (P) and a drug molecule (D) can be represented as: P + Df ⇌ PD
- The association constant (K) is: K = [PD] / [P] [Df]
- [PD] is the concentration of the protein-drug complex, [P] is the concentration of unbound protein, and [Df] is the concentration of unbound drug.
Experimental Methods for Determining Protein Binding
- Equilibrium dialysis method
- Ultrafiltration method
- Dynamic dialysis method
- Other methods: electrophoresis, gel filtration, and NMR
- These methods can be used to:
- Study the solubility behavior of a drug in the presence and absence of a protein
- Investigate the effect of protein on the partitioning behavior of drug molecules between an aqueous and an organic solvent
- Analyze the change in spectral characteristics of drug molecules for assessing the degree of binding
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Description
This method determines the rate of drug-protein binding through a dialysis process. It involves a jacketed beaker with a buffer solution and a cellophane dialysis bag containing the drug-protein solution.
