Related Experiment Videos
Temperature and pH dependent changes of immunoglobulin G structure
Biochimica Et Biophysica Acta
|March 28, 1975
Summary
Myeloma immunoglobulin G kappa (IgG(K)) undergoes reversible structural changes influenced by pH and temperature. These conformational shifts impact chromophore exposure and tyrosine residue accessibility, affecting protein stability.
Area of Science:
- Biochemistry
- Structural Biology
- Immunology
Background:
- Immunoglobulin G (IgG) is a crucial antibody.
- Understanding IgG conformation is vital for its function.
- Myeloma IgG(K) provides a model for studying IgG structural dynamics.
Purpose of the Study:
- To investigate the temperature and pH-dependent conformational changes of myeloma IgG(K).
- To elucidate the structural transitions and their impact on protein properties.
Main Methods:
- Optical rotatory dispersion
- Circular dichroism
- Thermal perturbation difference spectroscopy
- Solvent perturbation difference spectroscopy
- Electrochemical iodination
- Difference adiabatic scanning microcalorimetry
Main Results:
- A reversible structural change in IgG(K) occurs between pH 6.5 and 6.0, increasing chromophore exposure.
- The 'alkaline state' exhibits a reversible transition (25-35°C) involving tyrosine residue screening and potential helicity increase, with denaturation at 64°C.
- The 'acid state' shows no transition in the 25-35°C range and denatures at 54°C.
Conclusions:
- The pH transition is likely caused by histidine ionization between IgG domains.
- Temperature-induced changes are attributed to altered domain interactions.
- These findings offer insights into IgG structural dynamics relevant to antigen-antibody interactions.