Is the definition of Taq enzyme units the same for different brands? Is a 1U/25 μ L system sufficient?

Most mainstream manufacturers generally adopt the standard definition for enzyme activity units, but differences in buffer composition, pH, and substrate conditions can lead to slight variations in actual usage. In a 25 μL system, adding 1 U corresponds to approximately 0.04 U/μL, which is usually sufficient for bacterial colony PCR and plasmid templates within 500 bp. If inhibitors are introduced by the colony template, it is recommended to reduce the template amount or add BSA rather than blindly increasing the enzyme. When switching to a new brand, first perform an enzyme titration to confirm the optimal amount.

PCR of bacterial colonies within 500bp using 1U/25 μ L is generally sufficient, and some systems can also be expanded with 0.5U. When the copy number of plasmid template is low, it can still maintain 1U, and the key is primer quality and annealing temperature. It is recommended to run a gradient of 0.5U, 1U, and 1.5U after the arrival of the new enzyme, observe the band brightness and non-specific properties, and not use it in large quantities according to the recommended amount in the instructions.

When purchasing 5000U large packaging, it is necessary to distinguish between pure enzyme value and buffer containing solution dNTP、 The total price of the reference primer. Different brands have different concentrations, which need to be converted into per reaction cost. Especially for colony PCR, the enzyme requirements are not high, and domestic large packaging is usually sufficient. Request the agent to provide samples and inter batch quality inspection reports, and clarify whether cold chain shipping, delivery time, and return/exchange conditions are available. Local agent packaging can shorten the waiting time.

After aliquoting the 5000U bulk package, store at -20°C. Ordinary Taq is generally stable, but the specific shelf life is affected by glycerol concentration, buffer, freezer temperature fluctuations, and repeated freeze-thaw cycles. It is recommended to aliquot into 50-100 μL/tube, use a non-frost-free freezer or place on an inner shelf, avoid frequent opening and closing near the door, use one tube at a time, and perform a positive control at least every six months. It cannot be promised that "it will be fine for one to two years"; actual testing shall prevail.