Biology Reference
In-Depth Information
Figure 16.9.
DNA denaturation and renaturation.
helix in exactly the same configuration is one of the most important
features of DNA. Unwinding of the double helix to form two single
strands occurs by disruption of base stacking and hydrogen bonds
betweenpairedbases.Duringthisdenaturationprocess,nocovalent
bonds in DNA gets broken (Fig. 16.9). Heat and extreme pH features
cancausedenaturationofdouble-strandedDNA.Whentemperature
or pH is returned to the physiological range unwound strands
rewind or anneal to yield intact double helix, therefore this seper-
ation of DNA strands is reversible. Each DNA molecule has a charac-
teristic denaturation temperature or melting point (
T
m
). Since there
arethreehydrogenbondsbetweenGandCandtwohydrogenbonds
between A and T, separation of paired DNA strands is more di
cult
when GC ratio is higher than AT ratio. The transition from double
helix to the single-stranded denaturated form can be detected by
monitoring the absorption of UV light at A260. Denaturation of
double-stranded nucleic acid causes an increase in absorption.
16.4 DNA in Electrochemical DNA-Based Biosensors
DNA-based biosensors are mainly based on hybridization, which
consists of DNA base pairing between two complementary nucleic
