TAILIEUCHUNG - Báo cáo khoa học: Studies on the interaction of Nile red with horseradish peroxidase in solution

The interaction of an extrinsic probe (Nile red) with an enzyme (horse-radish peroxidase) in solution was investigated using fluorescence tech-niques. Nile red fluorescence is very environmentally sensitive and the presence of domains of differing polarity within the enzyme was ascer-tained by the decomposition of the Nile red emission spectrum. | ềFEBS Journal Studies on the interaction of Nile red with horseradish peroxidase in solution Graham Hungerford Ana Rei and M. Isabel C. Ferreira Departamento de Fisica Universidade do Minho Braga Portugal Keywords energy transfer fluorescence molecular modeling spectraldecomposition Correspondence G. Hungerford Departamento de Fisica Universidade do Minho 4710-057 Braga Portugal Fax 351 253678981 E-mail graham@ Received 10 August 2005 revised 7 October 2005 accepted 17 October 2005 doi The interaction of an extrinsic probe Nile red with an enzyme horseradish peroxidase in solution was investigated using fluorescence techniques. Nile red fluorescence is very environmentally sensitive and the presence of domains of differing polarity within the enzyme was ascertained by the decomposition of the Nile red emission spectrum. Further evidence for the position of the probe inside the enzyme was obtained from a molecular modeling study. A decrease in the emission intensity of the dye during incubation with horseradish peroxidase was explained by the occurrence of resonance energy transfer between the Nile red and the heme group in the enzyme. This was supported by a calculation of the critical transfer distance and a comparison of the fluorescence intensity of the dye in both the holo- and apo-enzyme. These data were then applied to the study of the effect of temperature on the structure of the enzyme where changes in conformation were elucidated. It is a well known fact that the biochemical reactivity of biological molecules can to a large extent be controlled by the dynamics of the molecule namely its folding conformational mechanisms 1 . One such case is the ability of hemoproteins to participate in several important biochemical processes such as electron transfer oxygen transfer oxygenation and peroxidation. In particular horseradish peroxidase HRP is well known for its catalysis of the cleavage of H2O2 and studies have

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