Hyperkromisena

Hyperkromisena is a term used in biochemistry and molecular biology to describe an abnormal increase in the absorption of ultraviolet light by a nucleic acid solution, typically DNA or RNA, relative to its expected or normal absorbance. This phenomenon is usually observed when DNA or RNA denatures, meaning its double-stranded helical structure unfolds into a single-stranded form. The unfolding exposes the bases, which were previously partially shielded within the double helix, allowing them to interact more readily with UV light.

The most common wavelength at which hyperchromicity is measured is 260 nanometers, as the purine and pyrimidine bases of nucleic acids have a strong absorption peak at this wavelength. When DNA or RNA denatures, the absorbance at 260 nm increases significantly. This increase is quantified as the hyperchromic effect and is often expressed as a percentage relative to the absorbance of the native, double-stranded molecule.

The hyperchromic effect is a valuable tool in molecular biology. It is frequently used to assess the purity of nucleic acid samples, as denatured DNA or RNA will exhibit a higher absorbance than native DNA or RNA of the same concentration. It is also employed to monitor the melting or denaturation process of DNA, often referred to as the melting temperature (Tm), which is the temperature at which half of the DNA molecules have denatured. Changes in Tm can indicate variations in base composition or the presence of stabilizing or destabilizing agents. Furthermore, hyperchromicity can be used to determine the concentration of nucleic acids in solution, although other methods are often preferred for greater accuracy.