<s>
The	O
Tsou	B-Application
plot	I-Application
is	O
a	O
graphical	O
method	O
of	O
determining	O
the	O
number	O
and	O
nature	O
of	O
the	O
functional	O
groups	O
on	O
an	O
enzyme	O
that	O
are	O
necessary	O
for	O
its	O
catalytic	O
activity	O
.	O
</s>
<s>
Despite	O
the	O
possible	O
objections	O
,	O
the	O
Tsou	B-Application
plot	I-Application
gave	O
clear	O
results	O
when	O
applied	O
by	O
Paterson	O
and	O
Knowles	O
to	O
inactivation	O
of	O
pepsin	O
by	O
trimethyloxonium	O
tetrafluoroborate	O
(	O
Meerwein	O
's	O
reagent	O
)	O
,	O
a	O
reagent	O
that	O
modifies	O
carboxyl	O
residues	O
in	O
proteins	O
.	O
</s>
