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EQUILIBRIUM AND KINETICS STUDIES OF THE REACTION OF
PIGEON CARBOXYHAEMOGLOBIN WITH 5-5’-DITHIOBIS (2-NITROBENZOIC ACID) (DTNB)
Akpoveta, O.V and Osakwe, S.A
1Department of Chemistry,
College of Education, Agbor, Nigeria.
2 Department of Chemistry, Delta
State University, Abraka, Nigeria.
saosakwe@yahoo.com
ABSTRACT
Equilibrium and kinetic
parameters keq and KI were determined as a
function of Ph for the reaction of the free sulphydryl groups present in
the cycsteine residues of the carboxyhaemoglobin derivative of pigeon
with 5,5’-dithiobis (2 – nitrobenzoic acid) (DTNB). Much difficulty had
been experienced from kinetic experiment in determining KI by
carrying out a concentration dependence of Kobs. The
pseudo-first order rate constant, hence the determination of KI
has not been experimentally feasible. This study highlights the
importance of determining Keq from he reaction as it serves
as a breakthrough and complementary step towards the understanding of
the kinetic (KI) of carboxyhaemoglobin reactions. The
absorbance of the species involved in the reaction was obtained from a
UV-visible spectrophotometer, and the equilibrium constant (Keq)
was calculated on the basis of an equation relating the concentration of
the species involved in the reaction. Kr was consequently calculated
from the results of Keq obtained. The results show that the
apparent second order reverse rate constant (Kr) is higher for
CysF9(93)B than for CysB5(23)B over the entire pH range indicating
higher reactivity for CysF9(93)B sulphydryl group. It could then be
inferred that CysF9(93)b corresponds to the fast phase while CysB5(23)B
corresponds to the slow phase. Kr increased by almost three orders of
magnitude for CysF9 (93)B and by two orders of magnitude for CysB5(23)B
reaction. From this study the dependence of the apparent reverse second
order rate constants on pH for the reactions of CYSF9(93)B
and CYSB5 (23)B sulphuryl grous of pigeon
carbonmonoxyhaemoglobin with 5-5 – dithiobis (2-nitrobenzoic acid) DTNB
were established.
KEYWORDS:
Equilibrium, Kinetics, Reactions, Carboxyhaemoglobin, Pigeon |
