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Conformational changes of polypeptides in intense electric fields
Author(s) -
Bean C. P.,
Bennett A. J.
Publication year - 1973
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1973.360120410
Subject(s) - chemistry , electric field , helix (gastropod) , isothermal process , electromagnetic coil , phase transition , field (mathematics) , phase diagram , globular protein , molecule , transition state theory , crystallography , chemical physics , condensed matter physics , thermodynamics , phase (matter) , physics , kinetics , classical mechanics , reaction rate constant , quantum mechanics , ecology , mathematics , organic chemistry , snail , pure mathematics , biology
Employing a simple “all or none” statistical theory, a calculation is given of the phase diagram in electric field–temperature space for the helix–coil transition of a polypeptide with nonpolar residues but charged end groups. The principal results are (i) the transition field extrapolated to absolute zero is on the order of millions of volts per centimeter, (ii) the normal transition temperature of large molecules is predicted to be significantly affected by fields as low as 30,000 V/cm, and (iii) for temperatures just above the helix‐coil transition temperature, the application of a field to a large molecule causes an initial transition to the helix state and with a further isothermal increase of field the coil state returns. The theory is extended to the case of the unfolding of a globular protein in an electric field. The fields are somewhat lower than those for the helix‐coil transition and are always single‐valued at a given temperature. Lastly the effect of including the presence of charged residues is shown to decrease the estimated critical fields but keep them of the same order of magnitude as those given for the case of nonpolar residues.