Chemistry Reference
In-Depth Information
1
0.8
2
A
0.0
45
000
36
000
∼
ν
, cm
−
1
Figure 2.7
UV spectra of polynucleotide poly(G-C).poly(G-C) in 25% ethanol solution
(10
−
2
M NaCl) without (1) and with (2) Ni
2+
ions; concentration is 0.75 Ni/P
5
4
3
1000
2
0
1
−
1000
6
7
−
2000
45 000
40 000
35 000
∼
, cm
−
1
ν
Figure 2.8
UDS of polynucleotide poly(G-C).poly(G-C) in 25% ethanol solution at different
concentrations of Ni
2+
: (1) 0.1 Ni/P, (2) 0.25 Ni/P, (3) 0.3 Ni/P, (4) 0.4 Ni/P, (5) 0.5 Ni/P,
(6) 0.75 Ni/P, (7) 1 Ni/P
concentrations of 0.75 Ni
2+
per nucleotide (P)). Ni
2+
ions cause a signifi cant red shift
of 700 cm
− 1
and strong hypochromic effect (25%). Figure 2.8 shows the UDS of
poly(dG - dC) ·poly(dG-dC) in 0.25% ethanol solution with Ni
2+
/P ratios in the range
0.1 to 1.0. Figure 2.9 demonstrates a large difference between the UDS of Ni
2+
/
poly(dG - dC) ·poly(dG-dC) recorded in water (1) and in 25% ethanol solution (2).
In the fi rst case a typical saturation line is shown while in the second case an S
shape curve characteristic of conformational change is observed, e.g. B
→
A or
B
Z transition. The CD spectra (Figure 2.10) recorded under the same conditions
as for UDS show that at concentration Ni/P = 0.2 the polynucleotide is in the C
conformation (commonly observed as a low humidity form of the lithium salt). At
higher concentrations of Ni
+2
, the double helix is shown to undergo transition to the
→
