Preparation and photophysical studies of model organic compounds

1. RESHMA RAJAN
M. Sc. Chemistry (S4)
N. S. S. College, Pandalam

3.  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.

4.  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.

5.  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.

6.  Acetanilide
 Glacial acetic acid
 Methyl benzoate
 con. H2SO4
 con. HNO3,
 Con.HCl
 NaOH
CHARACTERIZATION METHODS
 Fluorescence spectroscopy
 UV-Visible spectroscopy

9. UV Visible absorption spectra of p-nitro
aniline and m-nitro benzoic acid in
different solvents.

10. The absorption spectra of BSA in the
presence of PNA and MNBA
respectively

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

12. Fluorescence spectra
Effect of PNA MNBA on the fluorescence
spectrum of BSA

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

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

15. Overlap of the absorption spectrum PNA and
emission spectrum of BSA
FRET

16. Overlap of the absorption spectrum MNBA and emission
spectrum of BSA

17. 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

18. 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.

19. THANK YOU