PMID- 16920828
OWN - NLM
STAT- MEDLINE
DCOM- 20061213
LR  - 20240413
IS  - 0006-3495 (Print)
IS  - 1542-0086 (Electronic)
IS  - 0006-3495 (Linking)
VI  - 91
IP  - 9
DP  - 2006 Nov 1
TI  - Enthalpy of the B-to-Z conformational transition of a DNA oligonucleotide 
      determined by isothermal titration calorimetry.
PG  - 3383-9
AB  - The influence of high concentrations of Na(+) or [Co(NH(3))(6)](3+) on the 
      conformation of two related DNA oligomers was investigated by circular dichroism 
      spectropolarimetry (CD), isothermal titration calorimetry (ITC), and differential 
      scanning calorimetry (DSC). As revealed by CD, DNA oligomers, (dC-dG)(4) and 
      (dm(5)C-dG)(4), both form right-handed double helical structures (B-DNA) in 
      standard phosphate buffer with 115 mM Na(+) at 25 degrees C. However, at 2.0 M 
      Na(+) or 200 microM [Co(NH(3))(6)](3+), (dm(5)C-dG)(4) assumes a left-handed 
      double helical structure (Z-DNA), whereas the unmethylated (dC-dG)(4) analog 
      remains right-handed under those conditions. ITC was then used to determine the 
      enthalpy change upon increasing the concentration of either Na(+) or 
      [Co(NH(3))(6)](3+) for both DNA oligomers at 25 degrees C. The titration with 
      Na(+) resulted in endothermic isotherms with (dm(5)C-dG)(4) being more 
      endothermic than (dC-dG)(4) by 700 cal/mol basepair. In contrast, titration with 
      [Co(NH(3))(6)](3+) resulted in exothermic isotherms with (dC-dG)(4) being more 
      exothermic than (dm(5)C-dG)(4) by 720 cal/mol basepair. We attribute the enthalpy 
      difference to the conformational transition from B-form DNA to Z-form DNA for 
      (dm(5)C-dG)(4), a transition which does not occur for the unmethylated 
      (dC-dG)(4). The value of approximately 700 cal/mol basepair for the enthalpy of 
      the B-Z transition compares favorably with previously published results obtained 
      by different techniques. DSC was used to monitor the duplex to single strand 
      transitions for both oligomers under the different concentrations. These results 
      indicated that methylation of the cytidine destabilizes (dm(5)C-dG)(4) relative 
      to (dC-dG)(4). Coupling the DSC data with the ITC data allowed construction of a 
      thermodynamic cycle which gives insight into the influence of both temperature 
      and ionic strength on the heat content of the two DNA systems studied. Further, 
      this study reveals the utility of using ITC for determinations of transition 
      enthalpies with the appropriate choice of control.
FAU - Ferreira, Jaime M
AU  - Ferreira JM
AD  - Department of Chemistry and Biochemistry, Seton Hall University, South Orange, 
      New Jersey 07079, USA.
FAU - Sheardy, Richard D
AU  - Sheardy RD
LA  - eng
PT  - Journal Article
DEP - 20060818
PL  - United States
TA  - Biophys J
JT  - Biophysical journal
JID - 0370626
RN  - 0 (Oligonucleotides)
RN  - 9007-49-2 (DNA)
SB  - IM
MH  - Calorimetry/methods
MH  - Computer Simulation
MH  - DNA/*chemistry/*ultrastructure
MH  - Energy Transfer
MH  - *Models, Chemical
MH  - *Models, Molecular
MH  - Motion
MH  - Oligonucleotides/*chemistry
MH  - Protein Conformation
MH  - Temperature
MH  - Thermodynamics
MH  - Titrimetry/methods
PMC - PMC1614508
EDAT- 2006/08/22 09:00
MHDA- 2006/12/14 09:00
PMCR- 2007/11/01
CRDT- 2006/08/22 09:00
PHST- 2006/08/22 09:00 [pubmed]
PHST- 2006/12/14 09:00 [medline]
PHST- 2006/08/22 09:00 [entrez]
PHST- 2007/11/01 00:00 [pmc-release]
AID - S0006-3495(06)72049-5 [pii]
AID - 84145 [pii]
AID - 10.1529/biophysj.106.084145 [doi]
PST - ppublish
SO  - Biophys J. 2006 Nov 1;91(9):3383-9. doi: 10.1529/biophysj.106.084145. Epub 2006 
      Aug 18.