Vol.:(0123456789) 1 3 J Fluoresc DOI 10.1007/s10895-017-2171-6 ORIGINAL ARTICLE Fluorescence Behavior of Schif Base-N, N′-bis(salicylidene) Trans 1, 2-Diaminocyclohexane in Proteinous and Micellar Environments Nayan Roy 1  · Surjatapa Nath 1  · Pradip C. Paul 1  · T. Sanjoy Singh 1   Received: 28 June 2017 / Accepted: 10 August 2017 © Springer Science+Business Media, LLC 2017 Keywords Surfactants · Proteins · Binding constant · Fluorescence quenching · Stern–Volmer constant · Fluorescence decay Introduction Over the past few decades, research on micellar media is very important and has been extensively studied as elemen- tary models for biological systems [1] due to their micro- environmental similarity with proteins, enzymes etc., their biomimicking nature and capability of some of them to ef- ciently accommodate and transport of drugs [2–6]. The most signifcant property of an organized assembly is their ability to stabilize and bind probe molecules that are typically insol- uble or sparingly soluble in aqueous solvents. Upon binding a molecule will experience a diferent environment inside the microheterogeneous structure of micelle than that of the bulk solvents. Properties like polarity, viscosity and difu- sion of water molecules towards the core of the micelle are diferent from the bulk phase [7]. Micelles are characterized by two diferent regions, a hydrophobic core and a hydro- philic surface that may be cationic, anionic and nonionic. All these three types of micelles consist of a dry hydrocarbon core surrounded by a wet spherical shell called the Stern layer, a difuse layer called the Gouy Chapman layer and the bulk water [8]. The ionic micelle consists of a micelle-water interface and the charge of this interface can be probed by using a sensor molecules or ions. With the introduction of a proper fuorescent probe that is very sensitive to environ- mental polarity and viscosity, one can follow the process of micellization and also the efect of interface electric feld on the probe where the probe faces various constraints on the free movements. Therefore, several structural studies of diferent micelles and their infuence on photophysical and Abstract Fluorescence properties of N, N′-bis(salicylidene) trans 1, 2-diaminocyclohexane (H 2 L) is used to probe the anionic (SDS), cationic (CTAB) and nonionic (TX-100) micelles as well as in serum albumins (BSA and HSA) and chicken egg white lysozyme (LYZ) by steady state and pico- second time-resolved fuorescence spectroscopy. The fuo- rescence band intensity was found to increase with concomi- tant blue-shift with gradual addition of diferent surfactants. All the experimental results suggest that the probe molecule resides in the micelle-water interface rather than going into the micellar core. However, the penetration is more towards the micellar hydrocarbon core in nonionic surfactant (TX- 100) while comparing with ionic surfactants (SDS and CTAB). Several mean microscopic properties such as criti- cal micelle concentration, polarity parameters and binding constant were calculated in presence of diferent surfactants. The decrease in nonradiative decay rate constants in micellar environments indicates restricted motion of the probe inside the micellar nanocages with increasing fuorescence emis- sion intensity and quantum yields. Further in this work, we also investigated the interaction behavior of the probe with diferent proteins at low concentrations under physiological conditions (pH = 7.4). Stern–Volmer analysis of the trypto- phan (Trp) fuorescence quenching data in presence of probe reveals Stern–Volmer constant (K sv ) as well as bimolecular quenching rate constant (K q ). The binding constant as well as the number of binding sites of the probe with proteins were also monitored and found to be 1:1 stoichiometry ratio. * T. Sanjoy Singh takhelsingh@gmail.com; singhsanjoy2002@yahoo.co.in 1 Department of Chemistry, Assam University, Silchar, Assam 788 011, India