As a domain expert in molecular biology and biochemistry, I often encounter various measurements and ratios that are crucial for assessing the purity and integrity of biological samples. One such important ratio is the A260/A230 ratio, which is particularly useful when dealing with nucleic acids like DNA and RNA.
The A260/A230 ratio is a secondary measure of nucleic acid purity, complementing the more commonly known A260/A280 ratio. This ratio is derived from the absorbance readings taken at 260 nm and 230 nm wavelengths using a spectrophotometer. The absorbance at 260 nm is characteristic of nucleic acids due to the presence of their aromatic bases, which absorb light at this wavelength. On the other hand, absorbance at 230 nm is not specific to nucleic acids and can be influenced by various other compounds.
When evaluating the purity of a sample, a higher A260/A230 ratio is generally indicative of a purer sample. This is because a high ratio suggests that there is minimal contamination from other organic compounds or salts that might absorb light at 230 nm. The ideal A260/A230 ratio for pure nucleic acids is typically above 2.0, although this can vary slightly depending on the specific sample and the presence of any contaminants.
Strong absorbance around 230 nm can be a cause for concern, as it may indicate the presence of organic compounds or chaotropic salts in the sample. Chaotropic salts, such as sodium perchlorate or guanidine hydrochloride, are known to disrupt the structure of proteins and can interfere with the purification process of nucleic acids. The presence of such compounds can lead to inaccurate measurements and affect the integrity of the nucleic acids.
It is important to note that while the A260/A230 ratio is a helpful tool, it should not be used in isolation. It is often used in conjunction with the A260/A280 ratio to get a more comprehensive understanding of sample purity. The A260/A280 ratio is more commonly used because proteins also absorb light at 280 nm due to the presence of aromatic amino acids like tryptophan and tyrosine. A ratio within the range of 1.8 to 2.2 for DNA and 2.0 to 2.2 for RNA is generally considered acceptable for most applications.
In summary, the A260/A230 ratio is a valuable parameter for assessing the purity of nucleic acid samples. A high ratio suggests minimal contamination, while strong absorbance at 230 nm may indicate the presence of interfering compounds. It is essential to use this ratio in conjunction with the A260/A280 ratio and other purity assessments to ensure the accuracy and reliability of nucleic acid analysis.

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A260/A230 ratio. This ratio is used as a secondary measure of nucleic acid purity. The A260/A230 ratio values for pure samples are often higher than the respective A260/A280 ratio values. Strong absorbance around 230nm can indicate that organic compounds or chaotropic salts are present in the purified DNA.Aug 23, 2011read more >>