Video transcript we've already talked about how to write an equilibrium expression so if we have some generic acid H a that donates a proton to h2o h2o becomes h3o plus and H turns into the conjugate base which is a minus and so here's our equilibrium expression and the ionization constant ka for a weak acid we already talked about the fact that it's going to be less than 1 so here we have three weak acids so hydrofluoric acid acetic acid and methanol and over here are the KA values so you can see that hydrofluoric acid has the largest KA value so even though they're all considered to be weak acids all right 3.
Ka and acid strength. Using a pKa table. Up Next. It is the pH at which a protein or another molecule is electrically neutral has no net electrical charge. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile.
Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Anne Marie Helmenstine, Ph. Chemistry Expert.
Helmenstine holds a Ph. If you already know the pKa value for an acid and you need the Ka value, you find it by taking the antilog. In practice, this means raising both sides of the equality to exponents of In the Bronsted-Lowry formulation of acids in solution, the acid donates a proton and the solution accepts one. The solution becomes one containing a conjugate base — which is the product of the acid having lost a proton — and a conjugate acid. Theoretically, this reaction can happen in both directions.
When the solvent is water, this is written as:. It's possible to determine this strength of the original acid by dividing the concentrations of the conjugate acid and base by the concentrations of the original acid and base.
When the solvent is water, it's left out of the equation. This operation gives you the dissociation constant Ka:. The equilibrium concentrations of reactants and products could also be characterized by an equilibrium association constant Ka which is simply the reciprocal of Kd.
Kd is the inverse of the equilibrium association constant, Ka, i. The smaller the KD value, the greater the binding affinity of the ligand for its target. The larger the KD value, the more weakly the target molecule and ligand are attracted to and bind to one another. Ka is a measure of the affinity of the drug for the receptor.
A drug with a low Kd value has a high Ka value and therefore high affinity for the receptor. What would one expect to be a good KD value? Most antibodies have KD values in the low micromolar to nanomolar to range.
High affinity antibodies generally considered to be in the low nanomolar range with very high affinity antibodies being in the picomolar range. Bmax is the total number of receptors expressed in the same units as the Y values i.
The KD is a useful way to present the affinity of a drug for its biological target. This is because the number KD quickly tells us the concentration of drug that is required to yield a significant amount of interaction with the target protein. Thus, a Kd of 1 microM can be considered as high affinity in metabolism regulation, while it can be considered a low affinity in antibody design.
And this is related to another way to judge the strength of an interaction which takes into account the potential concentrations of the interacting molecules. Almost any street drug with these chemicals added are named KD. Typically, the chemicals from the bug spray give users a minute high that leaves them in a zombie-like state. Begin typing your search term above and press enter to search.
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