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Structural modification of proteins by direct electric current from low voltage
Daniela Calzia1, Isabella Panfoli, Silvia Ravera
1Department of Biology, Università di Genova, 16132 Genova, Italy.
Journal of Biochemical and Molecular Toxicology
|October 15, 2009
Summary
Direct electric current (dc) irreversibly inactivates enzymes with high charged-polar amino acid content (CH-PO). This finding offers insights into protein behavior under electrical fields and potential applications in medical devices.
Area of Science:
- Biochemistry
- Electrochemistry
- Protein Science
Background:
- The interaction between direct electric current (dc) and proteins is not well understood.
- Previous research showed dc inactivated specific enzymes in Crotalus atrox venom and caused eukaryote adenylate kinases (AK) to precipitate.
- Adenylate kinase 1 (AK1) has a high percentage difference of charged versus polar amino acid content (CH-PO).
Purpose of the Study:
- To investigate the effect of low-voltage dc on the enzymatic activity of various proteins.
- To determine if the charged-polar amino acid content (CH-PO) influences protein inactivation by dc.
- To explore the potential of CH-PO as a predictive parameter for protein response to electrical fields.
Main Methods:
- Exposure of 18 enzymes, including commercial AK1, to dc (0-0.7 mA, 0-10 V) in solution.
- Assay of enzymatic activity after current exposure.
- Analysis of protein structural modifications using circular dichroic spectroscopy.
- Correlation of inactivation with CH-PO values and ionic strength.
Main Results:
- Enzymes with CH-PO values > 10.0 were irreversibly inactivated by dc exposure.
- Enzymes with CH-PO values between +3 and -5 remained active.
- Inactivation depended on ionic strength, not net protein charge.
- Circular dichroism indicated structural changes in some inactivated enzymes.
Conclusions:
- The CH-PO value is a significant, albeit approximate, predictor of protein inactivation by low-voltage dc.
- Current density appears to be the primary factor driving the observed inactivation.
- Enzymatic activity may be a more sensitive indicator of conformational changes than circular dichroism.
- Findings may enhance understanding of electrical medical devices.
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