LAUSR

Abstract In this work we have examined the photophysics and binding interaction of a red emitting molecule nile blue A (NBA) with bovine serum albumin (BSA) and human serum albumin (HSA) along with gradual addition of cucurbit[7]uril (CB7) by employing various spectroscopic methods. The change in absorption and emission maxima position of NBA in presence of BSA or HSA as well as in the presence and absence of CB7 strongly suggest strong interaction between the species in the solution. The binding constant as calculated for NBA-HSA and NBA-BSA indicates that NBA prefers binding to HSA than BSA. From the lifetime and rotational relaxation data, it is evident that NBA experiences more restrained environment with HSA compared to BSA with addition of CB7 in the solution. Circular dichroism study indicates that both BSA and HSA, experiences a perturbation in their secondary structures in the presence of NBA and CB7. However, secondary structure of BSA is stabilized whereas, HSA is destabilized in the presence of NBA. From this study, it is evident that there is two types of interaction takes place in these systems. NBA in NBA-BSA-CB7 system undergoes competitive interaction whereas, in NBA-HSA-CB7 system, NBA undergoes cooperative interaction.