TLS Online TPP Program

#Id: 6361


Repressors bind to specific sites on the DNA. In bacterial cells, such binding sites, called operators
Regulation by means of a repressor protein that blocks transcription is referred to as negative regulation. Activators provide a molecular counterpoint to repressors; they bind to DNA and enhance the activity of RNA polymerase at a promoter; this is positive regulation.Repressor binding to DNA is regulated by a molecular signal called effector

#Unit 2. Cellular Organization #CELL CYCLE #Part B Pointers
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TLS Online TPP Program

#Id: 4668

#Unit 13. Methods in Biology

If the antibody preparation is polyclonal and has a range of affinities, Scatchard plot yields a curved line whose slope is constantly changing. The average affinity constant K0 can be calculated by determining the value of Ka when half of the binding sites are occupied (i.e., when r  1 in this example). In this graph, antiserum #3 has a higher affinity (K0  2.4  108) than antiserum #4 (K0  1.25  108)



TLS Online TPP Program

#Id: 4669

#Unit 13. Methods in Biology

The bacterium Streptococcus pyogenes, for example, expresses cell-wall proteins called M antigens. Antibodies produced to streptococcal M antigens have been shown to cross-react with several myocardial and skeletal muscle proteins and have been implicated in heart and kidney damage following streptococcal infections. 




TLS Online TPP Program

#Id: 4670

#Unit 13. Methods in Biology

Glycosphingolipids as determinants of blood groups

TLS Online TPP Program

#Id: 4671

#Unit 13. Methods in Biology

Antibody and soluble antigen interacting in aqueous solution form a lattice that eventually develops into a visible precipitate. Antibodies that aggregate soluble antigens are called precipitins.


TLS Online TPP Program

#Id: 4672

#Unit 13. Methods in Biology

A precipitation curve for a system of one antigen and its antibodies. This plot of the amount of antibody precipitated versus increasing antigen concentrations (at constant total antibody) reveals three zones: 






TLS Online TPP Program

#Id: 4673

#Unit 13. Methods in Biology

A related quantitative technique, rocket electrophoresis, does permit measurement of antigen levels. In rocket electrophoresis, a negatively charged antigen is electrophoresed in a gel containing antibody. The precipitate formed between antigen and antibody has the shape of a rocket, the height of which is proportional to the concentration of antigen in the well.