Structure of DNA hydration shells studied by Raman spectroscopy

✍ Scribed by N. J. Tao; S. M. Lindsay; A. Rupprecht

• Publisher: Wiley (John Wiley & Sons)
• Year: 1989
• Tongue: English
• Weight: 702 KB
• Volume: 28
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360280509

✦ Synopsis

Synopsis

We have used Raman scattering to study the water 0-H stretching modes at -3450 and -3220 cm-' in DNA films as a function of relative humidity (r.h.). The intensity of the 3220-cm-' band vanishes 88 the r.h. is decreased from 98% to around 80%, which indicates that the hydrogen-bond network of water is disrupted in the primary hydration shell (which therefore cannot have an "ice-like" structure). The number of water molecules in the primary hydration shell wa8 determined from the intensity of the -3200-cm-' band as about 30 water molecules per nucleotide pair. The -3400-cm-' 0-H stretch band was used for determining the total water content, and this band persists at 0% r.h., implying that 5-6 tightly bound water molecules per nucleotide pair remain. The frequency of the -3400-m-' 0-H stretch mode is lower by 30 to 45 ax-' in the primary hydration shell compared to free water. The water content as a function of r.h. obtained from these experiments agrees with gravimetric measurements. The h p p e r a n c e of the -3200-cm-' band and the shift of the -3400-cn-' 0-H stretch band provide a reliable way of measuring the hydration number of DNA.