KD

KD=[A][R][AR]

From Radioligand Binding Assays to a Scatchard Plot

  1. Perform Total Binding ( Curve 1 )

    • Use only radiolabeled ligand ( "hot" ligand )

    • This includes both specific and non-specific binding.

    • Incubate receptor preparation with increasing concentrations of radioligand

    • Measure total bound radioactivity at each concentration

    • Total Binding Btotal is a combination of :

      • Specific binding ( to actual receptors )

        • Non-specific binding ( to membranes , non-receptor sites )

  2. Measure Non-Specific Binding ( Curve 2 ) :

    • Add an excess of non-radioactive ligand ( "cold" ligand )

    • This competes with the radioligand for receptor sites , preventing it from binding specifically

    • What remains bound is only non-specific binding

    • Measure bound radioactivity at each radioligand concentration

    • This curve represents non-specific binding ( BNSB )

  3. Calculate Specific Binding ( Curve 3 ) :

    • Subtract non-specific binding from total binding

      • Bspecific=BtotalBNSB

    • This isolates only the radioligand bound to receptors.

    • curve represents specific binding , which follows saturation kinetics and is used for Scatchard analysis.

    https://www.sygnaturediscovery.com/wp-content/uploads/2018/03/binding1.jpg

  4. Generate a Scatchard Plot :

    • Use specific binding ( Bspecific ) and free ligand concentration ( [L] ) to construct the Scatchard plot

    • Plot:

      Bspecific[L] (y-axis) vs. Bspecific (x-axis)
      B[L]=BmaxBKd
    • Where:

      • B = bound ligand (pmol/mg protein)

      • [L] = free ligand concentration (nM)

      • Bmax = maximum number of binding sites

      • Kd = dissociation constant (affinity, nM)

    • Rearrange into a linear equation :

     

    • Scatchard Plot Equation for Single Binding System :

    [B][F]=( 1KD[B] )+BmaxKD
    • The slope gives 1/Kd ( binding affinity ) , and the x-intercept gives Bmax ( total receptor density )


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Define pA2

pA2=log( KB )

Define the Difference Between Affinity and Efficacy

Affinity = how well a ligand fits and binds

Efficacy = how effectively that ligand activates the receptor once bound

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Give Examples of 4 Different Receptor Transduction Mechanisms

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Ligand-Gated Ion Channels

G-Protein Coupled Receptors ( GPCR )

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Kinase Coupled Receptors

Nuclear Receptors


Describe 5 Routes of Drug Administration

  1. Oral : Drugs are taken through the mouth and absorbed via the gastrointestinal tract

  2. Rectal : Administered through the rectum , useful when oral administration is not feasible

  3. Topical : Applied to the skin or mucous membranes , such as creams or eye drops

  4. Injection : Includes intravenous ( IV ) , intramuscular ( IM ) , and subcutaneous ( SC ) methods for direct delivery into blood or tissue

  5. Respiratory : Inhaled drugs ( e.g., nasal sprays, inhalers ) absorbed through the respiratory tract

O - R - T - I -R


Identify the 3 Compartments of Body Water

  1. Intervascular = blood plasma within blood vessels

    • 3 Liters = 4%

  2. Interstitial = fluid surrounding the cells in tissues

    • 9 Liters = 13%

  3. Intracellular = fluid inside cells ( cytosol )

    • 28 Liters = 41%

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Identify 3 Things that Will Affect Drug Bioavailability

  1. Absorption : Passage through membranes , impacted by drug solubility and ionization

  2. First-Pass Metabolism : Degradation in the gut wall or liver before reaching systemic circulation

  3. Chemical Stability : Destruction of the drug in the gastrointestinal tract ( e.g., stomach acid )


Describe the 2 Phases of Metabolism

  1. Phase I :

    • Convert parent compound into a more polar / hydrophilic metabolite

    • Involves oxidation, reduction, or hydrolysis to add or unmask functional groups ( e.g., -OH , -NH2 ) , often preparing the drug for Phase II

  2. Phase II : Conjugation reactions with endogenous substrates to further increase water solubility for excretion.

    • conjugation with glucoronide , sulfate , acetate , amino acid

    • try to make them even more polar , to get them out of the body and into the urine

    • Phase II is the true “detoxification” step in the metabolism process

image-20250125072058579


Describe the 3 Ways that the Body Excretes Drugs

  1. Renal Excretion : Through urine , involving filtration , secretion , and reabsorption in the kidneys

  2. Biliary Excretion : Through bile , often leading to fecal elimination

  3. Respiratory Excretion : Drugs exhaled through the lungs , especially volatile compounds


Cytokines Effects on Nervous System

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Misc