Chemical Modification kinectics

[deits at deits]

In Article <35s6ja$i4l at news.duke.edu> "lees at acpub.duke.edu (Steve Lee)" says:
> 
> i'm currently modifying the reactive site of a serpin with
> phenylglyoxal.  and i come up with some very odd modification kinetics
> that i have never seen before and i was wonderinf if anyone else has
> seen anything like this before..  the graph looks like this...
> 
> the y axis is %inhibitory activity on a log scale and the x axis is the
> time of the modification reaction.. as the reaction proceeds, the
> inhibityory activity of the serpin should decrease..
> 
> 
> 100  -|*
>       |
>       | *
>       | 
>       |   *
> 10   -|
>       |       *
>       |
>       |   	 	*
>       |					*
> 1    ---------------------------------------------
>       0		30	    60		90
> 
> 
> the graph should be linear on this plot denoteing a pseudo first order
> reaction but it's not....
> 
> if you have any idea at all as to why it looks like this or if you've
> seen reaction kinetics like this before please email me and let me
> know..
> 
> thanks alot.
> 
> steve
> 
You might want to look at an article by E.T. Rakitizis, Biochemical Journal,
Vol. 217 pp. 341-351 (1984) for a detailed review of the kinetics of protein
modification by chemical reagents.  It includes analysis of cases where 
multiple sites are modified.
					Tom Deits
					Michigan State University
					deits at pilot.msu.edu