It is common knowledge in most laboratories that RNA is more susceptible to degradation than DNA. Unlike Deoxyribonucleases (DNases), which require metal ions for activity (and can therefore easily be inactivated with chelating agents such as EDTA), ribonucleases (RNases) have virtually no cofactor requirements and advantage of the 2 hydroxyl groups adjacent to the phosphodiester linkages in RNA as a reactive species.

Sources for RNase contamination in the Laboratory
It is possible to contaminate samples with RNases during the course of an experiment in various ways:

1. Autoclaving buffers and solutions will not inactivate RNases and may actually introduce them into buffers e.g. by liberating them from contaminating bacteria.
2. Ungloved hands represent a source for introducing bacteria into solutions resulting in RNase contamination and can even contaminate solutions directly with released cellular RNases.
3. Airborne contaminants settling on the surface of a solution of buffer could also carry RNases.

Laboratory precautions
Microbial ribonucleases share many properties with bovine pancreatic RNase A. The pancreatic ribonucleases are small enzymes (15 kd) and consist of a single polypeptide chain with four disulfide bridges. RNase A is a single-strand specific endoribonuclease that is active over a wide pH range, is resistant to metal chelating agents and can survive prolonged boiling or autoclaving (1). RNase A-type enzymes rely on histidine residues within the active site for catalytic activity and can be inactivated by the alkylating agent diethyl pyrocarbonate (DEPC) which modifies these residues. RN
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