Interaction of cetyltrimethylammonium bromide with nucleic acids and determination of nucleic acids at nanogram levels based on the measurement of light scattering

After the addition of cetyltrimethylammonium bromide to DNA, the of DNA inc reased and changed from -70.2 to +21.6 mV, and the absorbance at 260.0 nm i ncreased. This indicates that DNA is partly denatured and a large new ion a ssociation complex formed. The formation of the new associate can result in very strong light scattering at 414.0 ran, which is in proportion to the c oncentration of nucleic acids in the range 2.5 x 10(-8) to 2.0 x 10(-5) g m l(-1) for calf thymus (ct)DNA, 2.5 x 10(-8) to 2.0 x 10(-5) g ml(-1) for fi sh sperm (fs)DNA, and 5.0 x 10(-8) to 5.0 x 10(-5) g ml(-1) for yeast (y)RN A. The detection limits (3 sigma) are 8.3, 2.4, and 23.4 ng ml(-1), respect ively. Synthetic samples were determined satisfactorily. (C) 2001 Elsevier Science B.V. All rights reserved.