质粒提取与酶切电泳实验报告

1 分子实验报告 2013030020华天瑞

Preparation of Plasmid DNA, Restriction Enzyme Digestion, and

Agarose Gel Electrophoresis

2014/10/14-21

1 Intro

1.1 Objective

To learn

? The characteristics of plasmid DNA

? The method of plasmid DNA mini-preparation by alkaline lysis and the measurement of

DNA concentration by spectrophotometer ? The characteristics of restriction endonuclease

? How to use agarose gel electrophoresis to separate DNAs To understand: The principles of purification and quantification of plasmid DNA

1.2 Principle

1.2.1 Plasmid and Vector

Plasmid is a small, independently replicating, piece of extrachromosomal cytoplasmic DNA( double stranded and usually circular ) that is capable of autonomous replication and can be transferred from one organism to another.

Vector serve as carriers to allow replication of recombinant DNA in the host cell, usually a vector covers

? Antibiotic resistance gene: such as ampicillin resistant gene, kanamycine resistant gene,

and etc.

? Origin of replication (ori ).

? Multiple cloning site (MSC) or polylinker ? Marker genes: such as LacZ gene. 1.2.2 Alkaline Lysis ( 0.2molNaOH + 1%SDS )

SDS is a kind of anionic detergent. It can break bacterial cells and denature proteins. When bacterial cell wall is broken, the plasmid DNA and genomic DNA will be released out and be denatured in alkali environment. When the solution is neutralized by acidic reagent (such as KAc) , the plasmid DNA will be renatured rapidly due to its smaller size. After centrifugation, the plasmid DNA will be in supernatant, while the genomic DNA will stay in the sediment at the bottom of the tubes together with other cell debris. 1.2.3 DNA Concentration Measurement

Based on the strong absorbance of base pairs (A-T, G-C) at 260nm UV, the concentration of DNA can be measured by spectrophotometry. When detected under neutral condition, A260 is used to calculate the nucleic acid concentration where as the ratio of A260/A280 can be used to estimate the purity of nucleic acid (1.8 for pure DNA). 1.2.4 Restriction Endonuclease

TypeII RE cuts dsDNA at specific restriction sites on specific sequence, producing restriction fragments.

1.2.5 Gel Electrophoresis

2 分子实验报告 2013030020华天瑞

Solidified agarose solution has certain size of small pores of which the size is decided by concentration. In the electric field and buffer in neutral pH, negatively charged nucleic acid will migrate toward the positive pole. DNA fragments can be separated by different mobility in gel electrophoresis.

1.2.6 EB ( Ethidium bromide )

EB can bind with DNA through inserting into the base pairs of DNA molecule. Excited by UV, the DNA bands in gel electrophoresis will emit red fluorescence which can be detected easily. The minimal DNA quantity that can be tested by this method is about 10ng.

2 Materials and Reagents

? E.coli DH5 harboring pCMV-Myc-T10(SIPAR) ? TIANprep Mini Plasmid Kit

P1: (1％Glucose, 50mM/L EDTA pH8.0, 25mM/L Tris-HCl pH8.0) P2: 0.2 mM/L NaOH, 1％ SDS P3: 5 mol/L Kac, pH4.8 ? plasmid pCMV-Myc-SIPAR ? NEB 1kb DNA Ladder ? EcoRI, XhoI（Takara） ? 10×H buffer ? agarose

? TBE/TAE buffer(1×) ? EB (10mg/ml)

? Loading buffer(3×):

0.25% Bromophenol blue

40％(W/V) sucrose or 30％glycerol

3 Procedures

3.1 Preparation of Plasmid DNA

a. Add 500μl Buffer BL to spin column CP3. Centrifuge for 1 min at 12,000 rpm in a table-top microcentrifuge. Discard the flow-throw, and place Spin Column CP3 into the collection tube. b. Harvest 1.4 ml bacterial cells in a microcentifuge tube by centrifuge for 1 min at 12,000 rpm for 1 min at 20℃, then remove all the traces of supernatant. Then redo with 1.4ml bacterial cells in another microcentifuge tube.

c. Resuspend pelleted bacterial cells in 250μl Buffer P1

d. Add 250μl Buffer P2 and mix thoroughly by inverting the tube 6-8 times

e. Add 350μl Buffer P3 and mix immediately and thoroughly by inverting the tube 6-8 times f. Centrifuge for 10min at 12,000 rpm

g. Apply the supernatants to the Spin Column CP3, centrifuge for 1min at 12,000 rpm

h. Wash the Spin Column CP3 by adding 700μl Buffer PW and centrifuge for 1min at 12,000 rpm. Discard the flow-through, wash again with 500μl Buffer PW and centrifuge for 1min at 12,000 rpm.

i. Discard the flow-through and centrifuge for 2min at 12,000 rpm

j. Place the Spin Column CP3 in a clean 1.5ml microcentrifuge tube. Add 50μl EB, let stand for 4min, and centrifuge for 2 min at 12,000 rpm.

3 分子实验报告 2013030020华天瑞

3.2 Restriction Enzyme Digestion and Agarose Gel Electrophoresis

a. Enzyme digestion of plasmid DNA（pCMV-Myc-SIPAR）

Table 1 Plamid(ng) Buffer(μl)* EcoR1(μl) Xho1(μl) H2O(μl) Ⅰ Ⅱ Ⅲ 201 201 201 2 2 2 0 0.5 0.5 0 0 0.5 16.5 16.0 15.5 Total volumn(μl) 20 20 20 Digestion at 37 °C water bath for 1 hour.

Add 10 μl 3x loading buffer to each tube, load 15 μl sample for gel electrophoresis. b. Add 0.8 g agarose and 100 ml 1X TAEinto a flask, microwave agarose melts c. Insert comb into the mold. Position the comb 0.5-1.0 mm above the plate d. Pour the warm agarose solution(65℃) into the mold, avoid air bubbles

e. Solify the gel under room temperature for 45 min, then carefully remove the comb f. Place the gel into electrophoresis chamber full with 0.5×TAE/TBE

g. Load sample 15μl mixture with disposable micropipette. Change the micropipette every time. Add 4 μl 1 kb DNA ladder (50ng/μl) as reference.

h. Electrophoresis at 100V, stop electrophoresis when the band of bromophenol blue is of 4 strings away from bottom of the gel

i. Place the gel into EB working solution (0.5 g/ml) to stain the gel for 3min j. Observation and photography

4 Results and Discussions

4.1 Spectrophotometry of DNA extraction

Table 2 : Spectrophotometry results of DNA extraction A260 0.405 A280 0.214 A260/A280 1.904 DNA concentration 201 ng/μl Generally the ratio A260/A280 of pure DNA is 1.8, smaller than the result. Meanwhile, the ratio of A260/A230 is relatively high(2.783), suggesting that the amount of RNA is small. Analysing by synthesis these two facts, the extraction of DNA may

1 2 3 Laddecontain certain amount of oligonucleotides which can cause A260/A280

r to be higher than reference level.

4.2 Photograph of stained gel

After exposure under UV light, photograph was taken and is shown

below.

Well 1 contains untreated plasmid, 2 bands are present on the lane. The fastest and brightest band locates at the length of around 3.0-4.0 kb. Because of the fact that plasmid DNA in supercoiled form moves faster in electrophoresis, bright band at 3-4 kb indicates that most of plasmids collected are in their natural supercoiled form. The other dimmer band at around 6 kb suggests that other conformation of the plasmid DNA also appears in the extraction( DNA with open strand ). Usually, the dimmer band is brighter than shown in our case.

6.0 4.0 3.0 2.0 4 分子实验报告 2013030020华天瑞

One possible explanation is that in procedure c of 3.1, pelleted bacterial cells were not resuspended sufficiently, causing a lose of open strand( as well as some supercoiled form DNA). This can also exlpain the relatively low concentration of DNA(201ng/μl).

Well 2 contains the sample digested by EcoR I alone and single band with the size of approx. 6 kb is presented. Note that total length of recombined pMCV-Myc-SIPAR is 5.7 kb, the observation of single band near 6 kb suggests a total digestion, which match the expectation of a single incision site. Well 3 contains sample digested by EcoR I and Xho I. Lane 3 has two bands with length slightly shorter than 4 kb and 2 kb, respectively. The lagging band is brighter than the leading band, which is reasonable since the two bands have the same molecular number. Ladder Well 200ng DNA was added into ladder well, which gives a total mass of 50ng to 3.0 kb fragment. Brightness of leading band in lane 3 is somewhat equal to that of 3.0 kb, suggesting that the sample added contains approximately (50 + 50 * 2 =) 150ng plasmid DNA (note that theoretical length of leading band DNA is 1.9kb and lagging band is 3.8kb). When this value is doubled (recall that we loaded 15μl out of 30), the experimental mass of plasmid (around 300ng) is, more or less, close to the DNA that was added to the mixture( 1.5μl * 201 ng/μl = 302ng ).

Reference

A. Files of experimental outlines provided by teacher on online.

B.http://zhidao.http://www.wodefanwen.com//link?url=l0MyBERohqsqDHawmUf0nLMlQVggyW87Qpd8bHsgMLfZDkwrVbPp_i9BCILbmr40s5ZlyIT6Z5MwaGhP7l5G0a

Questions

1. Difference between preparation of plasmid and genome DNA. Plasmids are small, supercoiled DNA which can be easily renatured by adjusting pH( such as using alkaline lysis). This make the preparation for plasmid easy. While genome DNA is linear and huge in length and always combined with proteins, the preparation is complicated for protein needs to be degraded and the activity of DNase must be low to avoid the degradation of DNA itself.

2. Analysis of African green monkey small polydisperse circular DNA junction region, clone pDM-r1 by BioEdit ? After installation of BioEdit 7.2.5, run the program and create a new alignment (Ctrl + N). ? Choose Sequence ? New Sequence, and paste the sequence of African green monkey small polydisperse circular DNA junction region, clone pDM-r1 from database in GenBank. ? Choose Sequence ? Nucleic Acid ? Restriction Map, default setting is to detect restriction sites for restriction enzymes that recognize a 6-bp fragment. Mapping outcome is listed below:

BioEdit version 7.2.5 (12/11/2013) Restriction Mapping Utility (c)1998, Tom Hall

5 分子实验报告 2013030020华天瑞

Restriction Map 2014/10/23 1:40:55 100 base pairs

Translations: none

Restriction Enzyme Map:

1

AAAGCTTATCCACCCATGATCAAGTGGGCTTTATCCCTGGGATGCAAGGCTCCAGAATTTCATATTCAGCCAAACTAAGT 80 1

TTTCGAATAGGTGGGTACTAGTTCACCCGAAATAGGGACCCTACGTTCCGAGGTCTTAAAGTATAAGTCGGTTTGATTCA 80

HindIII BclI TaqII BpmI BstF5I ApoI TspDTI

SfaNI TspDTI Eco57MI NlaIV BsaJI Hpy188III BsaJI FokI

81 TTCATAAGTGAAGGAGAAAT 100 81 AAGTATTCACTTCCTCTTTA 100

Restriction table:

Enzyme Recognition frequency Positions __________________________________________________________________________

ApoI r'AATT_y 1 56 BclI T'GATC_A 1 18 BpmI CTGGAGnnnnnnnnnnnnnn_nn' 1 36

BsaJI C'CnnG_G 2 36, 37 BstF5I GGATG_nn' 1 47 Eco57MI CTGrAGnnnnnnnnnnnnnn_nn' 1 36 FokI GGATGnnnnnnnnn'nnnn_ 1 54 HindIII A'AGCT_T 1 3 Hpy188III TC'nn_GA 1 53 NlaIV GGn'nCC 1 51 SfaNI GCATCnnnnn'nnnn_ 1 32 TaqII CACCCAnnnnnnnnn_nn' 1 28

TspDTI ATGAAnnnnnnnnn_nn' 2 50, 72

本文来源：https://www.bwwdw.com/article/igoh.html