After the initial characterization, it is possible to purify further some or all of the plasmid DNAs by RNase digestion and extraction with organic solvents. This further purified DNA is suitable for techniques such as DNA sequencing, subcloning or the production of gene probes. In order to purify plasmid DNA after the isolation process, any residual RNA and contaminating protein are removed. This purification step involves two main steps, which are, first, removing residual RNA by using RNase in order to digest RNA and, second, extract contaminating protein using organic solvents, phenol-chloroform.
Materials:
RNase A: Make up as a solution in water at 10 mg/mL, Heat for 10 min in a boiling water bath or heating block to eliminate any DNase activity. Aliquot and store at -20oC.
0.4 M Ammonium acetate.
Chloroform= A 24: 1 mix of chloroform and isoamyl alcohol. Store at 4oC.
Phenol/chloroform= 25:24: 1 mix of TE-equilibrated phenol, chloroform, and isoamyl alcohol. Store at 4oC.
100% Ethanol.
Sterile wooden toothpicks.
Methods:
Add 50 microliters of 4 M ammonium acetate containing 200 micrograms/mL RNase A to each miniprep and incubate it at room temperature for 20 min.
Add 100 microliters of phenol/chloroform to each DNA preparation.
Vortex briefly and centrifuge at high speed for 2 min in a microfuge. Remove the top layer containing the DNA and place it in a new sterile tube.
Add 100 microliters of chloroform to each tube.
Vortex briefly and centrifuge at high speed in a microfuge for 2 min. Remove the DNA in the top layer and place it in a second sterile tube.
For phenol/chloroform extractions avoid removing material from the interface.
Add 200 microliters of 100% ethanol to each tube.
Shake briefly to precipitate the DNA and centrifuge at high speed for 5 min at room temperature.
Done. Now you can extract, isolate, and purify Plasmid DNA using methods which I had described in this blog. Hopefully those can be useful for you.
By the year 2050, nearly 80% of the earth's population will reside in urban centers. Applying the most conservative estimates to current demographic trends, the human population will increase by about 3 billion people during the interim. An estimated 109 hectares of new land (about 20% more land than is represented by the country of Brazil) will be needed to grow enough food to feed them, if traditional farming practices continue as they are practiced today. At present, throughout the world, over 80% of the land that is suitable for raising crops is in use (sources: FAO and NASA). Historically, some 15% of that has been laid waste by poor management practices. What can be done to avoid this impending disaster?
A Potential Solution: Farm Vertically
The concept of indoor farming is not new, since hothouse production of tomatoes, a wide variety of herbs, and other produce has been in vogue for some time. What is new is the urgent need to scale up this technology to accommodate another 3 billion people. An entirely new approach to indoor farming must be invented, employing cutting edge technologies. The Vertical Farm must be efficient (cheap to construct and safe to operate). Vertical farms, many stories high, will be situated in the heart of the world's urban centers. If successfully implemented, they offer the promise of urban renewal, sustainable production of a safe and varied food supply (year-round crop production), and the eventual repair of ecosystems that have been sacrificed for horizontal farming.
It took humans 10,000 years to learn how to grow most of the crops we now take for granted. Along the way, we despoiled most of the land we worked, often turning verdant, natural ecozones into semi-arid deserts. Within that same time frame, we evolved into an urban species, in which 60% of the human population now lives vertically in cities. This means that, for the majority, we humans are protected against the elements, yet we subject our food-bearing plants to the rigors of the great outdoors and can do no more than hope for a good weather year. However, more often than not now, due to a rapidly changing climate regime, that is not what follows. Massive floods, protracted droughts, class 4-5 hurricanes, and severe monsoons take their toll each year, destroying millions of tons of valuable crops. Don't our harvestable plants deserve the same level of comfort and protection that we now enjoy? The time is at hand for us to learn how to safely grow our food inside environmentally controlled multistory buildings within urban centers. If we do not, then in just another 50 years, the next 3 billion people will surely go hungry, and the world will become a much more unpleasant place in which to live.
Advantages of Vertical Farming
Year-round crop production; 1 indoor acre is equivalent to 4-6 outdoor acres or more, depending upon the crop (e.g., strawberries: 1 indoor acre = 30 outdoor acres)
No weather-related crop failures due to droughts, floods, pests
All VF food is grown organically: no herbicides, pesticides, or fertilizers
VF virtually eliminates agricultural runoff by recycling black water
VF returns farmland to nature, restoring ecosystem functions and services
VF greatly reduces the incidence of many infectious diseases that are acquired at the agricultural interface
VF converts black and gray water into potable water by collecting the water of
evapotranspiration
VF adds energy back to the grid via methane generation from composting non-edible
parts of plants and animals
VF dramatically reduces fossil fuel use (no tractors, plows, shipping.)
VF converts abandoned urban properties into food production centers
VF creates sustainable environments for urban centers
VF creates new employment opportunities
We cannot go to the moon, Mars, or beyond without first learning to farm indoors on
earth
VF may prove to be useful for integrating into refugee camps
VF offers the promise of measurable economic improvement for tropical and subtropical
LDCs. If this should prove to be the case, then VF may be a catalyst in helping to reduce or even reverse the population growth of LDCs as they adopt urban agriculture as a strategy for sustainable food production.
VF could reduce the incidence of armed conflict over natural resources, such as water
and land for agriculture
Urban Farming’s mission is to create an abundance of food for people in need by planting, supporting and encouraging the establishment of gardens on unused land and space while increasing diversity, raising awareness for health and wellness, inspiring and educating youth, adults and seniors to create an economically sustainable system to uplift communities around the globe.
INDIRECT ELISA The indirect ELISA utilizes an unlabeled primary antibody in conjunction with a labeled secondary antibody. Since the labeled secondary antibody is directed against all antibodies of a given species (e.g. anti-mouse), it can be used with a wide variety of primary antibodies (e.g. all mouse monoclonal antibodies).
INDIRECT ELISA :
INDIRECT ELISA Advantages of indirect detection Wide variety of labeled secondary antibodies are available commercially. Versatile, since many primary antibodies can be made in one species and the same labeled secondary antibody can be used for detection. Immunoreactivity of the primary antibody is not affected by labeling. Sensitivity is increased because each primary antibody contains several epitopes that can be bound by the labeled secondary antibody, allowing for signal amplification.
DIRECT ELISA The direct ELISA uses the method of directly labeling the antibody itself. Microwell plates are coated with a sample containing the target antigen, and the binding of labeled antibody is quantitated by a colorimetric, chemiluminescent, or fluorescent end-point.
DIRECT ELISA :
DIRECT ELISA Advantages of Direct Detection Quick methodology since only one antibody is used. Cross-reactivity of secondary antibody is eliminated. Disadvantages of Direct Detection Immunoreactivity of the primary antibody may be reduced as a result of labeling. Labeling of every primary antibody is time-consuming and expensive. No flexibility in choice of primary antibody label from one experiment to another. Little signal amplification.
COMPETITIVE ELISA : COMPETITIVE ELISA In this Unlabeled antibody is incubated in the presence of its antigen. These bound antibody/antigen complexes are then added to an antigen coated well. The plate is washed unbound antibody is removed. The secondary antibody, specific to the primary antibody is added. This second antibody is coupled to the enzyme. A substrate is added, and remaining enzymes elicit a chromogenic or fluorescent signal. For competitive ELISA, the higher the original antigen concentration, the weaker the eventual signal.
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood. Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding. In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding. The sample is sent to a laboratory where the targeted antibody (or antigen) is linked to an enzyme. If the target substance is in the sample, the test solution turns a different color.
How to Prepare for the Test
No special preparation is needed.
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
This test is often used to see if you have been exposed to viruses or other substances that cause infection. It is often used to screen for current or past infections.
Normal Results
Normal values depend on the type of substance being identified. Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
Abnormal values depend on the type of substance being identified. In some people, a positive result may be normal.
Risks
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. Other risks associated with having blood drawn are slight but may include:
Excessive bleeding
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Alternative Names
Enzyme-linked immunoassay; EIA
References
Ashihara Y, Kasahara Y, Nakamura RM. Immunoassay and immunochemistry. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: Saunders Elsevier; 2006:chap 43.
