Peptide Structure Modifications: Effect of Radical Species Generated by Controlled Gamma Ray Irradiation Approach

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概要

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• The present work aimed at evaluating the radiolysis effect upon a set of peptides, most of them involved in physiological functions. To generate reactive radical species, a Co60 source (up to 15 kGy) was used for controlled gamma irradiation of some peptide solutions including derivatives attaching the stable free radical Toac (2,2,6,6-tetramethypiperidine-1-oxyl-4-amino-4-carboxylic acid). Regardless of the peptide sequence, a nonlinear and progressive degradation of a total of nine peptides was detected. The results were interpreted in the light of the half-life dose (D1/2) parameter which represents the dose necessary for 50% peptide structure degradation. The vasoactive angiotensin II (AngII)'s analogue Ang-(1–7) showed greater stability towards gamma ray radiation than bradykinin (BK), Toac0-BK, Pro4-BK (D1/2 around 4 and 2 kGy, respectively) which decreased to about 0.5–1.0 kGy in the case of acetyl-α-melanocyte-stimulating hormone (Ac-α-MSH) and substance P (SP). In terms of peptide structural modifications, the data acquired from different analytical methods suggested a Phe to Tyr (or its ortho and/or meta isomers) transformation as a consequence of the hydroxyl moiety insertion. Noteworthy, this effect seemed to be position-dependent as only Phe located at or near the C-terminal portion seemed to display this transformation. In contrast, Met is comparatively more easily oxidized, thus allowing to conclude that gamma irradiation may induce a complex position and/or sequence-dependent effect on peptides. As previously applied for BK, some irradiated peptides were submitted to their by-products purification, indeed a complementary target of the present approach for development of uncommon analogues for further structure–function investigation.

著者

• Nakaie Clovis

  Department Of Biophysics Universidade Federal De Sao Paulo

• Vieira Renata

  Department of Biophysics, Paulista Medical School, Federal University of Sao Paulo

• Rosa José

  Protein Chemistry Center and Department of Molecular and Cell Biology, Ribeirao Preto Medical School, University of Sao Paulo (USP)

• Nardi Daniela

  Department of Biophysics, Paulista Medical School, Federal University of Sao Paulo

• Nascimento Nanci

  Nuclear and Energy Research Institute (IPEN), University of Sao Paulo (USP)

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• Peptide Structure Modifications: Effect of Radical Species Generated by Controlled Gamma Ray Irradiation Approach

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