WELCOME TO

PG DEPARTMENT OF CHEMISTRY

RESHMA RAJANM. Sc. Chemistry (S4)

N. S. S. College, Pandalam

PREPARATION AND PHOTOPHYSICAL STUDIES OF

MODEL ORGANIC COMPOUNDS

P-nitro aniline (PNA) and m-nitro benzoic acid (MNBA) are two important organic members of the organic family.

PNA is a solvatochromic dye which changes the absorption peak with the nature of the solvent.

These organic compounds used as a precursors for many organic reactions and intermeadiate in the synthesis of dyes.

Both PNA and MNBA are used as a corrosion inhibitor.

INTRODUCTION

Serum albumins plays an important role in the transport and deposition of a variety of molecules.

Function of a protein depends on its conformation and protein folding studies have gained much significance.

Binding of probes to proteins can provide useful information of the structural features that determines the effectiveness of proteins.

The studies on the interaction between PNA and MNBA with BSA have been monitored with an aim to understand the change in the micro structure of proteins as a result of ligand interaction.

SCOPE OF THE PRESENT INVESTIGATION

Two model organic compounds – p-nitro aniline and m-nitro benzoic acid have been synthesized from multi-step process.

P-nitro aniline is prepared from acetylation of aniline and m-nitro benzoic acid is prepared in a multi-step process starting from methyl benzoate.

Compounds have been synthesized and characterized by UV-VIS Absorption spectroscopy.

To investigate photo physical properties by using steady state fluorescence measurements.

OBJECTIVES OF THE WORK

Acetanilide Glacial acetic acid Methyl benzoate con. H2SO4 con. HNO3, Con.HCl NaOH

CHARACTERIZATION METHODS

Fluorescence spectroscopy UV-Visible spectroscopy

REAGENTS:

SYNTHESIS OF ORGANIC COMPOUNDS

UV-VIS Absorption spectra

UV Visible absorption spectra of p-nitro aniline and m-nitro benzoic acid in

different solvents. 

The absorption spectra of BSA in the presence of PNA and MNBA

respectively

Synchronous fluorescence spectra of BSA in the presence of different concentrations of PNA and MNBA

respectively

Synchronous fluorescence spectra

Fluorescence spectra

Effect of PNA MNBA on the fluorescence spectrum of BSA

Stern-volmer plot of F0/F versus PNA and MNBA at 298 K

Stern-volmer plot

Plot of log [(F0 −F)/F] vs log [PNA] and log [MNBA] respectively.

log plot

Overlap of the absorption spectrum PNA and emission spectrum of BSA

FRET

Overlap of the absorption spectrum MNBA and emission spectrum of BSA

Overlap Forster Transfer Molar absorption

Protein Ligand Intergral, J Distance Efficiency coefficient(cm6) (A0) (%) e(l)

BSA p nitroaniline 8.41 × 10-12 78.61 49.99 942250

The values of overlap integral and Forster distance for BSA-PNA energy transfer.

The Quenching parameters for BSA-PNA and BSA MNBA systems.

Ligand KSV (M-1) Kq (M-1 s-1) n Kb (M-1)

PNA 3.82 × 104 3.82 × 1012 1.09 1.16 × 105

MNBA 2.21 × 104 2.21 × 1012 1.11 8.34 × 104

CONCLUSIONS From synchronous spectra, interaction of PNA with BSA

results in the change of tryptophan microenvironment to a hydrophobic one, whereas for MNBA the change in conformation provides a polar micro environment for the tryptophan residue.

Form Stern-Volmer analysis, a combined static and dynamic mechanism of interaction is suggested for PNA and BSA. MNBA - BSA system suggests a static quenching procedure through the formation of 1:1 complex.

From FRET, a combined static and dynamic mechanism of interaction is confirmed for PNA – BSA with a non-radiative energy transfer process.

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