Kinetic Aspects of Recognition

The kinetics of the binding of 2 -deoxyadcnosine 5 -monophosphate (dAMP) to H2(TMpyP) 52 was studied via the laser Raman temperature jump method. The association- and dissociation-rate constants at 25 C in pH 6.9 aqueous solution were 1.9 x 10 M s and 

9 X 10 s, respectively. For complexation, a slacking-lype interaction between the 7r-syslem of the porphyrin and the aromatic moiety of the guest was operating. 

Conformational dynamics in molecular recognition has been studied for several systems involving porphyrins. Atropisomerization of porphyrin 111 was controlled by adding quinones.- In the absence of quinones, the ratio of atropi.somers was ot,o(.a,a a.a,a,/f z,a,/) ,/( a,/f,a./f=l.() 4.4 2.2 0.8. which is close to the statistical ratio of I 4 2 I. By adding 2.3.5,6-(etramethoxy-p-benzoqui-none, induced-fit-type binding occurred and the proportion of i.somer a.a.of.a was increased up (o 80%. 

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