Patent Application
20130071917
The present invention relates to an apparatus for insulated isothermal polymerase chain reaction and particularly to a capillary adopted for an apparatus of insulated isothermal polymerase chain reaction.
Using polymerase chain reaction (PCR) to amplify selective DNA nucleic acid sequence is a well-developed and important medical and bio technology at present. It mainly includes three steps: denaturation, annealing of primers and extension of primers. These three steps require different reaction temperatures. The present PCR reaction requires reactants including template DNA to be amplified, oligonucleotide primer pairs complementary to selected sequence of each strand of the template DNA, thermostable DNA polymerase and deoxynucleoside triphosphate (dNTP). The reactants are repeatedly heated and cooled in the PCR reaction to be circulated at three different temperatures to amplify selected portions of the template DNA nucleic acid sequence.
The first process of denaturation in PCR is to heat the reactants to a high temperature to separate double-strand template DNA into single-strand DNA. A typical denaturation temperature is ranged between 90 and 95° C.
The second process of annealing of primers in PCR is to cool the reactants with the separated single-strand DNA to a lower temperature, so that the primer bind the single-strand DNA to form a complex thereof. A typical annealing temperature is selected according to melting temperature (Tm) of the primer, and usually is ranged between 35 and 65° C.
The third process of extension of primers in PCR is to maintain the reactants at a suitable temperature. Through action of DNA polymerase, the primer is extended to form a new single-strand DNA complementary to each strand of the template DNA. A typical extension temperature is 72° C.
The aforesaid three processes form a cycle and two times of the template DNA can be replicated in each cycle. By repeating the three processes of denaturation, annealing of primers and extension of primers in PCR at three different temperatures cyclically for twenty to forty times, millions of targeted replicates of nucleic acid sequence can be produced.
The conventional PCR machine (i.e. thermal cycler) controls the temperature of reactants via thermal conduction. The reaction container holding the PCR reactants is in contact with a solid metal member with a high thermal conductivity. The metal member is connected to a heating and cooling device, and its temperature is changed via the heating and cooling device. Hence the conventional thermal cycling PCR needs to spend extra time and use additional resources to heat and cool other substances in addition to the PCR reactants. Due to the characteristic of precision of the PCR machine, it is usually very expensive.
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As the conventional capillary 1 is formed in a circular shape and arranged in an upright manner and the convection is characterized in a phenomenon of heat flow rising and cool flow falling, the flowing speed in the capillary 1 is fast enough to easily result in mixing of the heat flow and cool flow without obvious separation. This causes decrease of reaction efficiency.
Therefore, the primary object of the present invention is to provide a capillary structure to increases cycling duration of convection.
The invention provides a capillary adopted for an apparatus of insulated isothermal polymerase chain reaction that is mounted onto a test tube holder. The capillary includes a tube which has an elongated tubular housing space with an axial direction forming an inclined angle against the plane of the test tube holder. The elongated tubular housing space is cut to form an axial cross section with a distance between left and right edges greater than that between front and rear edges.
Thus, when reactants are filled in the elongated tubular housing space and heated to generate convection, due to the distance between the left and right edges of the axial cross section thereof is greater than that between the front and rear edges, the left and right edges of the axial cross section form a narrower passage, hence can reduce the flowing speed of the heat flow in the convection and increase the cycling duration thereof, i.e. increase the reaction duration of the reactants, thus can increase the reaction efficiency of the apparatus of insulated isothermal polymerase chain reaction.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
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The tube 11 can be coupled with a high thermal conductive ring 30 which can be made of metal such as copper at a position close to the bottom of the elongated tubular housing space 12. The tube 11 also can be coupled with a cap 40. The bottom of the elongated tubular housing space 12 can also be gradually shrunk to form an elongated narrow space 121 to improve identification.
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As a conclusion, the present invention provides a non-circular capillary to reduce flowing speed of the convection 51 and increase the reaction duration of the reactants 50, thus can increase the reaction efficiency of the apparatus of insulated isothermal polymerase chain reaction to meet use requirements.
