Spectrophotometric studies on the interaction between nevadensin and lysozyme

Interaction between nevadensin and lysozyme (Lys) was studied using spectrophotometric techniques such as steady fluorescence, synchronous fluorescence, circular dichroism (CD) and UV–vis absorption. The fluorescence emission intensity of Lys was strongly quenched by the addition of nevadensin. Spectrophotometric observations are rationalized in terms of a static quenching process at lower concentration of nevadensin (less than 8 μM) and a combined quenching process at higher concentration of nevadensin (8–20 μM). Binding constants and binding sites for the nevadensin–Lys system were evaluated. The distance of 2.28 nm and the energy transfer efficiency of 0.586 between nevadensin and Lys, evaluated from the Förster non-radioactive resonance energy transfer theory, indicated that the energy transfer from Lys to nevadensin occurred with higher possibility. Thermodynamic data showed that nevadensin was included in the hydrophobic cavity of Lys via hydrophobic interactions. UV/vis measurements on the enzymatic activity of Lys in the absence and presence of nevadensin indicated that the interaction between nevadensin and Lys led to a reduction in the activity of Lys. Furthermore, nevadensin binding to Lys had no influence on the molecular conformation of Lys.