Mgcl2 Concentration And Annealing Temperature Of Primers Biology Essay

Toxoplasma gondii is a one-celled eucaryotic protozoon parasite capable of infecting all warm-blooded animate beings including worlds, avian, farm animal and aquatic mammals ( Dubey et al. , 2007a, Dubey et al. , 2007b, Nissapatorn et al. , 2004 ) . Felids play the function of the unequivocal host for the parasite as merely they can bring forth the environmentally immune oocytes which become extremely infective when it sporulates ( Herrmann et al. , 2010 ) . Infection happens when a warm-blooded being comes into direct contact with corrupt fecal matters or tail. An infection besides takes topographic point when one unwarily ingests H2O or undercooked meat laced with T. gondii ( Petersen, 2007 ) . The other tract that has been identified for transmittal is through pregnant female parents go throughing on the infection to their foetus congenitally ( Jones et al. , 2003 ) .

Although about tierce of the universe human population is inveterate infected with T. gondii, it is normally symptomless in healthy persons ( Quan et al. , 2008 ) . However, in an immunocompromised person, complications due to the infection can be fatal as it can do cervical or occipital lymphadenopathy, optic toxoplasmosis, inborn toxoplasmosis, phrenitis and even schizophrenic disorder ( Petersen, 2007, Jones-Brando et al. , 2003 ) . It is besides a proven cause abortion, spontaneous abortion, sterility and neonatal mortality in farm animate beings global ensuing in immense loss of gross ( Rajamanickam et al. , 1990 ) .

Therefore it is of import to be cognizant of the dangers of the parasite and seek to understand it farther by analyzing it extensively. To transport out a survey and detect strains of T. gondii, assorted methods are available such as PCR, DNA sequencing, ASO investigations, DNA microarrays and hybridisation. But for this survey, the chosen method is conventional PCR, as it is proven to hold greater sensitiveness, ability to analyse multiple samples quickly, comparatively low cost and its ability to be discriminate between species and strains given that suited primers are selected for the analysis ( Rochelle et al. , 1997 ) . Therefore, for this research intent, eight different markers that are up to the undertaking have been identified and optimized consequently.

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Materials and Method

Deoxyribonucleic acid Fragment Template

The RH strain of T. gondii which were used in this optimisation was obtained as a gift from Prof. Rahmah Noordin ( INFORMM, Penang ) . The parasite ‘s DNA was isolated from pellets, which were ab initio stored in -80 & A ; deg ; C deep-freeze. Isolation of the DNA templet from the pellets was done by utilizing the QIAamp DNA Mini Kit ( QIAGEN, Hilden, Germany ) , harmonizing to the protocol suggested by the maker. The elution was done by utilizing 100 µl of AE Buffer. The merchandises were tested for quality by utilizing the NanoPhotometer ( Implen, Munich, Germany ) as suggested in the maker ‘s protocol and besides by running them on 1 % agarose gel stained with ethidium bromide. The samples are rejected if RNA sets were seeable in the cataphoresis consequences.

Primer Analysis

The chosen markers for the undertaking are as listed in Table 1. The particular instance here is the marker SAG2 whereby the venue has two polymorphous sites at 3? and 5? terminals for Type II and Type III of the parasite ( Howe et al. , 1997 ) . So the elaboration of this peculiar venue was performed individually at either stop ( Behzadi et al. , 2003, Ferreira et al. , 2008 ) . All the other markers were chosen as they are normally used for placing T. gondii from assorted isolates ( de Melo Ferreira et al. , 2006, Khan et al. , 2005, Su et al. , 2006 ) . The sequence of each primer was reconfirmed by mentioning to Toxoplasma Genome Map Database. The PCR primers were synthesized by a commercial research lab and were of PCR class ( 1st Base, Shah Alam, Malaysia ) .

Deoxyribonucleic acid Amplification

The variables investigated for the optimisation of the eight markers includes Mg chloride ( MgCl2 ) concentration, tempering temperature, PCR additives and sensitiveness ( Rochelle et al. , 1997 ) . Theoretical analysis of each forward and change by reversal primer was carried out utilizing a primer analyzing and planing package ( PearlPrimer, v1.1.19 ) . With the package a theoretical tempering temperature was obtained for each primer and the trial to make up one’s mind on the optimum temperature was carried out within a ±5 & A ; deg ; C scope of the theoretical temperature. If the consequences were non fulfilling than the temperature scope was shifted consequently. The initial tempering temperature scope for each marker optimisation is shown in Table 2. From analyzing old literatures, the tendency for the optimal concentration of MgCl2 used was identified as 1.5 millimeter. Baring that in head, each marker was optimized for MgCl2 concentration between 1.5 millimeters and 2.0 millimeter scope.

The basic content of the PCR tubing was ever ; 2.0 µl of 10 X Taq buffer, 0.4 µl of dNTP, 0.2 µl of each forward and change by reversal primer every bit good as the Taq DNA Polymerase. Each tubing besides contained a changeless sum of DNA templet, which was set at 1 µl. The MgCl2 concentration varied between 1.20 – 1.60 µl. The PCR grade Milli-Q H2O ‘s ( Millipore Corp. , Massachusetts, USA ) volume, ranged between 14.40 – 14.80 µl per tubing depending on the MgCl2 concentration. The pick of utilizing the Milli-Q H2O was made after comparing consequences with commercially available PCR class H2O. Each PCR tubing used in this experiment had a concluding volume of 20 µl and was given a quick-spin in microcentrifuge prior to elaboration.

The PCR elaboration procedure was carried out in the 96-well MyCycler thermic cycler ( Bio-Rad, California, USA ) . Although the annealing temperature varied for each primer, the other stairss were carried out in changeless conditions. The reaction mixture is denatured at 95 & A ; deg ; C for 5 proceedingss, followed by 35 rhythms of denaturing measure for 30 seconds, tempering for 30 seconds and extension at 72 & A ; deg ; C for 1 minute. Final extension incubation at 72 & A ; deg ; C was carried out for 10 proceedingss before the tubing we incubated in the thermic cycler at 4 & A ; deg ; C boundlessly prior to aggregation.

Merchandise Analysis

The PCR merchandises were observed with 1 % agarose gels, stained with ethidium bromide. The gels were run at 100 V and 400 ma for an hr before being observed under Syngene InGenius L UV transilluminator ( Synoptics, Cambridge, UK ) . Although the optimisation stairss were performed utilizing Taq DNA polymerase, verification measure for each optimized primer was done with Pfu DNA polymerase. So for the verification measure both 10 Ten Taq buffer and Taq DNA polymerase were replaced with its Pfu opposite numbers consequently.


Purity of Deoxyribonucleic acid Fragments

The Deoxyribonucleic acid fragments isolated from the pellets were estimated for their pureness by utilizing the NanoPhotometer. The ratio of A260/A280 is determined for pellets, which recorded a value of 1.865 and 1.814 consequently. The gel image obtained as shown in Figure 1 had no RNA bands on them.

MgCl2 concentration and Annealing Temperature of Primers

The first primer optimized was 3 ‘ SAG2 where the primer was ab initio optimized between 55 – 65 & A ; deg ; C. Unsatisfactory consequences obtained within the scope prompt farther trials at two different temperature ranges ; 45 – 55 & A ; deg ; C and 63 – 68 & A ; deg ; C. The 2nd temperature scope is shown in Figure 2 ( A ) and it clearly indicates that the set is merely present at about 63 & A ; deg ; C, and it was besides best observed at 1.5 millimeter MgCl2 concentration. The following primer, 5 ‘ SAG2 had clearer and more consistent sets with 2.0 millimeters MgCl2 concentration and the set was clear at 59.9 & A ; deg ; C as shown in Figure 2 ( B ) . BTUB was best seeable with 1.5 millimeters MgCl2 concentration and 58.7 & A ; deg ; C tempering temperature as depicted in Figure 2 ( C ) . Similarly, cB21-4, GRA1, GRA6 and SRS1 besides had optimum MgCl2 concentration of 1.5 millimeters. Meanwhile, SAG3 was best observed with 2.0 millimeters MgCl2 concentration. On the other manus, the annealing temperature of cB21-4 was 53.7 & A ; deg ; C, GRA1 was 61.1 & A ; deg ; C, GRA6 was 57.8 & A ; deg ; C, SAG3 was 66 & A ; deg ; C, and eventually SRS1 was 64.2 & A ; deg ; C.


It is an established fact that for finding of nucleic acerb concentration in solutions, the optical density at wavelength 260 nanometer ( A260 ) is typically used. The pureness of nucleic DNA in a solution can be determined by obtaining the ratio of A260/A280, where a pure merchandise will hold a reading between 1.80 – 2.00 A ( Kartha et al. , 2007 ) . The pellets used in this research were purified and had a reading within the given scope, bespeaking the positive quality of the Deoxyribonucleic acid fragments used in this research. Therefore, we can be certain that they were clear of any protein taint every bit good as RNA taint as can be observed in Figure 1. It can be seen that the gel is free of RNA sets.

On the annealing temperature optimisation forepart, 3 ‘ SAG2 marker proved to be the tougher one to optimise as it required trials on three different tempering temperature ranges ( 45 – 55 & A ; deg ; C, 55 – 65 & A ; deg ; C and 63 – 68 & A ; deg ; C ) before the best possible tempering temperature could be decided. The initial temperature scope showed inconclusive consequences, while the lower temperature scope gave a excessively many broad sets. The concluding temperature scope which was tested showed that there would be no set when the temperature exceeds 63.3 & A ; deg ; C. So the annealing temperature of 3 ‘ SAG2 was decided to be 63.0 & A ; deg ; C as it best represented the set at about 222 base brace as good.

Highly thermostable DNA polymerase is used in PCR reactions as it can defy the perennial warming and chilling inherent in PCR and synthesise DNA at high temperatures. Besides, consideration of mistake rate besides of import in choosing the efficient DNA polymerase. The mistake rate of Pfu DNA polymerase in PCR is 2.6 ten 10-6 nucleotides/cycle and lower than Taq DNA polymerase which is 2.0 ten 10-4 nucleotides/cycle. Pfu DNA polymerase is the enzyme that catalyzes the templet dependent polymerisation of bases into duplex Deoxyribonucleic acid in the 5 ‘ to 3 ‘ way. Pfu DNA polymerase besides exhibits 3 ‘ to 5 ‘ exonuclease ( proofreading ) activity that enables the polymerase to rectify nucleotide incorporation mistakes. However, Pfu DNA polymerase is more expensive comparison to Taq DNA polymerase. Therefore, in this experiment we used Taq DNA polymerase for optimisation and reconfirmation of consequences is done with Pfu DNA polymerase.


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