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Interaction between Soluble and Membrane-Embedded Potassium Channel Peptides Monitored by Fourier Transform Infrared Spectroscopy

Figure 4

Effects of low salt and ID pre-oxidation on KV1-ID interaction.

A. Amide I regions of deconvolved spectra of KV1 polypeptide (10 mg/ml) reconstituted by thin-film method into DMPC vesicles (100 mg/ml) in the presence of 1 mg/ml wild-type ID peptide in 1/10 deuterated PBS (‘low salt’) with 40% v/v TFE at a range of temperatures during cooling from 20°C to 5°C (blue lines) and heating from 5°C to 30°C (red lines). B. Comparison of absorbance of infrared light at 1633 cm−1 relative to absorbance at 1652 cm−1, calculated from deconvoluted spectra, of KV1 polypeptide reconstituted in DMPC vesicles at a range of temperatures during cooling from 20°C to 5°C (blue lines), heating from 5°C to up to 80°C (red lines) and re-cooling from to 5°C (blue lines), for the following: KV1+ wild-type ID peptide in low salt (open square); KV1 in DBS in the absence of ID peptide (triangle); KV1+ wild-type ID (filled square); KV1+ pre-oxidized wild-type ID (filled circle); KV1+ pre-oxidized wild-type ID in low salt (open circle). Dashed lines: values taken from earlier figures herein for comparison. C. Amide I regions of deconvolved spectra of KV1 polypeptide (10 mg/ml) reconstituted by thin-film method into DMPC vesicles (100 mg/ml) in the presence of pre-oxidized 1 mg/ml wild-type ID peptide in deuterated PBS with 40% v/v TFE at a range of temperatures during cooling from 20°C to 5°C (blue lines), heating from 5°C to 80°C (red lines) and re-cooling from 80°C to 5°C (blue lines). The initial 1651 cm−1 absorbance peak and the emerging 1633 cm−1 peak (*) are indicated. D. Amide I regions of deconvolved spectra of KV1 polypeptide (10 mg/ml) reconstituted by thin-film method into DMPC vesicles (100 mg/ml) in the presence of pre-oxidized 1 mg/ml wild-type ID peptide in 1/10 deuterated PBS (‘low salt’) with 40% v/v TFE at a range of temperatures during cooling from 20°C to 5°C (blue lines), heating from 5°C to 80°C (red lines) and re-cooling from 80°C to 5°C (blue lines). The initial 1651 cm−1 absorbance peak and the emerging 1633 cm−1 peak (*) are indicated.

Figure 4

doi: https://doi.org/10.1371/journal.pone.0049070.g004