Photothermal studies of pH induced unfolding of apomyoglobin |
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Authors: | Miksovská Jaroslava Larsen Randy W |
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Affiliation: | (1) Department of Chemistry, University of South Florida, Tampa, Florida |
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Abstract: | Conformational dynamic and enthalpy changes associated with pH induced unfolding of apomyoglobin were studied using photoacoustic calorimetry and photothermal beam deflection methods. The transition between the native state and the I intermediate was induced by a nanosecond pH jump from o-nitrobenzaldehyde photolysis. Deconvolution of photoacoustic waves indicates two kinetic processes. The fast phase ( < 50ns) is characterized by a volume expansion of 8.8 ml mol–1. This process is followed by a volume contraction of about –22 ml mol–1 ( 500 ns). Photothermal beam deflection measurements do not reveal any volume changes on the time scale between 100 s and 5 ms. We associate the volume contraction with structural changes occurring during the transition between the native state and the I intermediate. The lack of any processes on the ms time scale may indicate the absence of structural events involving larger conformational changes of apomyoglobin after the pH jump. |
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Keywords: | Apomyoglobin protein folding photoacoustic calorimetry photothermal beam deflection |
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