Table 1. Identification of the platinum chelates formed by reaction of cis-[Pt(NH₃)₂(H₂O)₂]²⁺ 1 with AG₃(T₂AG₃)₃ I and (T₂AG₃)₄ II^a.

Analysis of the platinated fragments from gel bands 1.1 and 1.2 (Fig. 2)		Platinated sitesb
		A1	G10	A13	G22
% Platinated G	1.1 (I)		80		80
(DMS)	1.2 (I/IIb)		80		80
% Platinated A–	1.1 (I)	<15		<15
N7 (DEPC)c	1.2 (I/IIb)	<15		<15
3′-Exonuclease	1.1 (I)	A1 and G2d	G10	A13 and G14d	G22
stopd	1.2 (I/IIb)	A1 and G2d	G10	A13 and G14d	G22
‘n-mer like’ migration of the platinated fragment after digestion	1.1 (I) 1.2 (I/IIb)	9 9/11	9–10e 9–10e/12	17 16/18	20 21/23
Base position in	1.1 (I)	5′	3′	5′	3′
the chelate	1.2 (I/IIb)	5′	3′	5′	3′
Conclusion	1.1 (I)	One bis-chelate A1–G10/A13–G22
	1.2 (I/IIb)	Two chelates A1–G10 or A13–G22

^aSee text for step-by-step analysis.

^bII is a 24mer but for the sake of comparison we have adopted the same base numbering as that of the 22mer I (Fig. 1). However, the size of the fragments is the actual one.

^cDEPC/piperidine treatment does not detect A–N1 binding. The lower limit of reliable quantification by gel analysis is 15%.

^dFor some adducts, the 3′-exonuclease digestion exhibits a 1 nt premature arrest. This is easily detected thanks to the assignment of the platination sites by chemical digestion.

^eThe two values result from the non-identity of the migration scales of the free and platinated fragments.