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Dear all,
Can anyone exactly define and differentiate the terms selectivity and
specificity.
Thanks in advance.
With Regards,
Veeravalli Vijaya Bhaskar,
Research Associate,
Aurigene Discovery Technologies Limited,
Bioanalytical Division,
Bangalore,
Email: vijay_b.aaa.aurigene.com
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Sure Vijay,
Selectivity depicts a molecule with greater affinity for one receptor
(or
any process for that matter) over another. The key is that implicit
in this
definition (or rather characterization), is that the selectivity can be
"overcome" by overloading the system, and the "other" receptor
experiences
binding and/or activation.
Specificity takes selectivity one step further, where no increase in the
ligand or molecule of interest can activate the other receptor(s).
Hope that helps.
Cheers
SHAWN SPENCER, PhD.
Assistant Professor of Biopharmaceutics
Dyson Bldg., Rm 227
College of Pharmacy and Pharmaceutical Sciences
Florida A&M University
Tallahassee, FL 32307
shawn.spencer.aaa.famu.edu
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Hi Veeravalli,
Here are my two cents:
The words selectivity, specificity, and sensitivity (derived from
Latin seligere, specificus, sensitivus), can be confusing terms as
they are often used synonymously in the medical literature. However,
they should not be used interchangeably as each represents a different
phenomenon:
The word selectivity describes a drug's ability to affect a particular
cell populationin preference to others. Selectivity is generally a
worthy property in a drug because a drug having high selectivity may
have a dramatic effect when there is a single agent that can be
targeted against the appropriate molecular-driver involved in the
pathogenesis of a disease. Selectivity is used to describe the
ability of a drug to affect a particular population, i.e., gene,
protein, signaling pathway, or cell, in preference to others. For
example a selective drug would have the ability to discriminate
between cell or receptor populations, and so affect only one cell
population, and thereby produce an event.
Specificity, a term most often confused with selectivity, is used to
describe the capacity of a drug to cause a particular action in a
population. For example, a drug of absolute specificity of action
might decrease or increase, a specific function of a given gene or
protein or cell type, but it must do either, not both.
Sensitivity is used to describe the capacity of a population, to
respond to a drug's ability, to stimulate that entity at a specified
dose. The smaller the dose required producing an effect, the more
sensitive is the responding system. (The word used to describe this
activity in the drug which is the cause of the population sensitivity,
is potency).
I hope this helps.
Murad
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I don't know if I'm thinking right, but there probably will be someone =20=
correcting me.
In chemistry reactions i think that if you have compounds "A", "B" and =20=
"C", "A" is selective to "B", if it reacts preferable with it, but =20
there would also be a marginally reaction to "C", like 5% of reaction. =20=
"A" would have a 95% selectivity to compound "B". I think that =20
specificity is when "A" only reacts with "B". "A" would have =20
specificity to "B".
Please someone correct me if I'm wrong.
Perhaps you were talking about specificity and sensibility of a =20
method, in statistic terms?
Andr=E9 Mateus
andrenmateus.at.gmail.com=
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Yes Andre that is basically a correct description.
For example, organic chemists regularly use the term "stereoselective"
to refer to a reaction that produces a preponderance of one isomer
(more "B" than "C"). Rarely does one encounter the term
"stereospecific" in the purely small molecule synthetic organic realm
(only product/isomer "B" with no "C"). Of course, Mother Nature has
us chemists beat hands down when it comes to doing stereospecific
chemical reactions.
Mark M. McPhee, Ph.D.
Director of Pharmaceutical Development
PrincetonOne, LLC
Mark.McPhee.-at-.PrincetonOne.com
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Dear Sir
I guess you are asking about analytical parts like chromatography or so.
When the sample of drug contains a drug along with some impurities and
it is separated using chromatographic method,
if the chromatographic method is able to separate the drug and
impurities from each other but not the individual impurities, then the
method is said to be Specific. if the chromatographic method is able
to separate the drug along with individual impurities, then the method
is said to be Selective.
Hope this help
Regards
Sachin Ramrao Patil
Dept. of Pharm..Tech. Formulations
Block-E, NIPER,
Sec-67, S.A.S. Nagar
Mohali, Punjab-160062
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Dear Sachin,
A method is specific if it produces a response for only one single
analyte. Since it is almost impossible to develop a chromatographic
assay for a drug in a biological matrix that will respond to only the
compound of interest, the term selectivity is more appropriate.
Selectivity of a method is its ability to produce a response for the
target analyte which is distinguishable from all other responses (e.g.
endogenous compounds).
J. LIQ. CHROM. & REL TECHNOL., 23(3), 329-354 (2000).
You can also find the cross references in the same article.
Hope this helps.
Regards
Sivacharan Kollipara
Metabolism & Pharmacokinetics Department
Ranbaxy Research Laboratories
Plot-20, Sector-18
Gurgaon, Haryana
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Apparently the definition depends on the context.
Molecular
Receptor for ligand
Enzyme for substrate
Antibody for antigen
Analytical
Response when the analyte is missing
Response to similar analytes present
ROC
Ability to detect a disease when it is present
Ability to detect the absence of disease.
Ed F. O'Connor,PhD
78 Marbern Drive
Suffield, CT 06078-1533
email: efoconnor.-a-.cox.net
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