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Flash photolysis study of insulin
Scientia Sinica. Series B, Chemical, Biological, Agricultural, Medical & Earth Sciences
|April 1, 1984
Summary
UV photolysis of insulin and DPI reveals key radicals, correlating with tyrosine exposure. This study quantifies accessible tyrosine residues in these proteins.
Area of Science:
- Photochemistry
- Protein Science
- Spectroscopy
Background:
- Tyrosine residues in proteins are susceptible to UV-induced photodamage.
- Understanding tyrosine photolysis is crucial for protein stability and function studies.
- Insulin and des-pentapeptide (B26-30)-insulin (DPI) are important protein models.
Purpose of the Study:
- To determine and compare transient absorption spectra of UV-photolysis products of insulin and DPI.
- To identify initial photoproducts and their formation mechanisms.
- To quantify the number of light-accessible tyrosine residues in insulin and DPI.
Main Methods:
- Transient absorption spectroscopy was used to analyze UV-photolysis products.
- Photolysis quantum yields were measured for insulin, DPI, and free tyrosine.
- Spectra were analyzed to identify radical species and their absorption maxima.
Main Results:
- The far-UV absorption band (<300 nm) of photolysis products was reported for the first time.
- Key photoproducts identified include p-alanylphenoxyl radical (λmax = 410, 390 nm) and an unidentified radical (λmax = 270 nm).
- Photolysis yields correlate with the dissociation rate of tyrosine hydroxyl groups, indicating residue exposure.
Conclusions:
- The study provides quantitative data on light-accessible tyrosine residues in insulin and DPI.
- Tyrosine residue exposure significantly influences UV-photolysis product formation.
- This research offers deeper insights into protein photodegradation mechanisms.