PCR Beginner's Guide: Selection criteria for optimal re-temperature
The selection criteria for the optimum anneal temperature should be the intermediate temperature of the amplifiable range.
When using the temperature gradient method to find the optimal re-ature temperature, novices often choose the temperature conditions with the most amplification products, but the amplification effect is not ideal after the non-gradient amplification. The main reason for this phenomenon is that the selection criteria for the optimum re-temperature are not correct. I have done thousands of gene amplifications more than 10 years ago. Through temperature gradient experiments, the temperature range that can be amplified is generally 3-30 degrees. The criteria chosen should be the intermediate temperature of the amplifiable range.
because:
1. There are many factors affecting the amount of amplified products, some of which are random. It can be seen from the irregularity of the platform period of quantitative PCR.
2. The temperature and temperature curves of different instruments and different locations are different. According to the factory standard of the instrument manufacturer, the accuracy is also +-0.3 degrees and the uniformity is +-0.3 degrees.
3. The temperature accuracy of the PCR instrument will be worse when it is subjected to gradient amplification.
Selecting the intermediate temperature eliminates the effects of instrument temperature differences.
In addition, the choice of the amount of the template when performing the temperature gradient is also very important.
Although there are many types of tapping screws, they all have the following similarities:
(1) are generally made of carbonized carbon steel (accounting for 99% of total production). It can also be made of stainless steel or non-ferrous metals.
(2) The product must be heat treated. Carbon steel tapping screws must be carbonized and stainless steel tapping screws must be solution hardened. In order to make tapping screws to meet the requirements of the standard of mechanical properties and performance.
(3) The product surface hardness is high, the core toughness is good. That is, "soft inside strong outside". This is a major feature of tapping Screw performance requirements. If the surface hardness is low, it can not be screwed into the matrix; If the core toughness is poor, a twist will break, can not be used. So "inside soft outside steel" is self-tapping screw to meet the use of performance, very important requirements.
(4) The surface of the product needs surface protection treatment, generally electroplating treatment. Some product surface must be treated by phosphate (photostatting), such as wall panel self - tapping screws for photostatting.
(5) Production by cold heading process. It is recommended to use high-speed cold heading machine and high-speed wire rolling machine or high-speed planetary wire rolling machine. High speed is emphasized here to ensure product quality. Only the head of tapping screw produced by high-speed machine is well formed and the thread quality is high.
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