cDNA Library

A cDNA library is a collection of reverse-transcribed mRNA, which means it only contains the expressed gene of an organism. The information in the cDNA library is a powerful and useful tool to study the expression of genes. Compared with genomic library, the cDNA library is obviously much smaller, and it is easier to screen clones from it to obtain specifically expressed genes. According to different applications, different categories of cDNA library have been developed these years, such as Normalized cDNA library, Subtractive cDNA library, SSH cDNA library, and Yeast two-hybrid cDNA library, used in different fields.

The normal process of gene expression is consist of transcription and translation. During transcription, the mRNA produced with DNA sequences as templates can be translated into protein in the organism, which indicates the mRNA contains the complete information of expressed genes in a single organism. Therefore, the complementary DNA (cDNA) is produced by reverse transcription of mRNA with reverse transcriptase, which contains only all expressed genes, excluding other noncoding genes such as introns and exons.

Fig.1 Construction of cDNA library.

• Isolation and purification of mRNA
  Since the construction of the cDNA library starts from mRNA, the first step is to collect total mRNA from the interest sample such as bacteria, viruses, plants, or animals. The common methods for the isolation of mRNA include column chromatography methods and magnetic capture methods.
• Synthesis of the first strand of cDNA
  Single-strand RNA needs to be converted into DNA by reverse transcriptase first for amplification in the next step.
• Amplification and synthesis of the double-stranded cDNA
  The single-strand DNA is converted into double-strand DNA by DNA polymerase and amplificated to collect sufficient materials for up-follow steps. To be attention, the amount of amplification needs to be controlled to avoid over-amplification of the library.
• Insertion of cDNA into a vector and transfection into host cells
  Trim the DNA with nuclease to obtain blunt ends, and ligate it into a vector by adding terminal transferase. These recombinant molecules are taken up in a host bacterium by transfection, creating a cDNA library.
• Screening library
  In order to isolate clones that contain regions of interest from a library, the library must first be screened. The methods of screening include hybridization and PCR.

• Enriched with fragments from actively transcribing genes
• Devoid of Introns that interrupt the cloned sequences
• Smaller than genomic library
• Can be directly expressed in prokaryotic organisms
• Lack of the non-coding and regulatory elements in genomic DNA

• Study of mRNA expression
• Helpful in the expression of eukaryotic genes in prokaryotes
• Isolation of gene that codes for particular mRNA
• Study of reverse genetics
• Screening genomic libraries to isolate specific cDNA
• Helpful in the generation of antibodies and monoclonal antibodies

Hybridization Ovens

Hybridization ovens are instruments used in molecular biology labs to prehybridize or hybridize the membranes used in blotting techniques. Modern designs combine a hybridization station, active mixing capability, accurate temperature control, and a fluorescent reader into one compact bench top unit.

Lab Automated Extraction Workcells

Extraction Workcells extremely simplify the process of separating pure nucleic acids and/or proteins from various natural resources. It is a reliable, automated system to automate the tedious, error-prone tasks in your protocols, with the flexibility to support frequent changes in your process

Digesters

Digesters break down samples into their basic constituents for analysis. Digestion is the process of breaking down substances into their basic constituents, typically by using reagents such as strong acids, alkalis, or enzymes. It causes the complex matrices of compounds to gradually decompose and separate into distinct elements of interest.

DNA/RNA/Protein Purification Systems

DNA/RNA/Protein Purification System is a compact automated nucleic acid extraction and purification platform that can process up to several samples simultaneously. The instrument can purify DNA or RNA from various sample types in the same consistent and reliable manner with higher throughput.

Electroporators

Electroporators increase membrane permeability so that new substances can be properly introduced. Offered in typical parameters of voltage, the appliances create an electrostatic field in solutions to allow macromolecule movement through provisional porous cell membranes.

DNA Sequencing Equipment

A DNA sequencer is a scientific instrument used to automate the DNA sequencing process. Given a sample of DNA, a DNA sequencer is used to determine the order of the four bases: G (guanine), C (cytosine), A (adenine) and T (thymine). This is then reported as a text string, called a read.

Laboratory Incubators

An incubator is a device used to grow and micro biological cultures or cell cultures. It is made up of a chamber with a regulated temperature. Some incubators also regulate humidity, gas composition, or ventilation within that chamber. An incubator maintains optimal temperature, humidity, and other conditions such as the oxygen content of the atmosphere inside.

Electrophoresis Systems

Electrophoresis equipment applies an electric charge to molecules, causing them to migrate towards their oppositely charged electrode. The technique is found in all research and clinical laboratories utilizing DNA and protein applications, and is divided into gel and capillary techniques. Choice of electrophoresis equipment depends on the molecule of study, appropriate method of separation and downstream application.

Centrifuges

A centrifuge is a device that uses centrifugal force to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby separating fluids of different densities. It works by causing denser substances and particles to move outward in the radial direction. At the same time, objects that are less dense are displaced and moved to the center.

Digital Gel Imaging Systems

Digital gel imaging system enables quick and easy visualization, documentation, and analysis of nucleic acid and protein gels, blots. An automatic gel imaging system works on the principle that when ultraviolet light is directed towards a stained gel, the dye gets excited, and emits fluorescent light. This phenomenon can be observed and recorded in the visible range using a digital camera.

PCR Workstation / PCR Hood

A PCR workstation, also called a PCR hood, is a work space, enclosed on three sides, that provides a space for doing amplification of DNA and/or RNA. PCR hoods are used in biology and genetic labs so that there isn’t any cross contamination between samples. PCR workstations have no circulation, which helps to prevent contamination, and UV lights for sterilization.

Real-time PCR System

Real-Time PCR, also called Quantitative PCR, was developed as a precise, efficient and rapid method for nucleic acid detection. Real-time PCR Detection System is mainly composed of control system, power supply system, photoelectric system, module components, hot lid, shell parts and software etc. Flexible choices of sample capacity with different layers of detection systems can be achieved.

Pipettes

A pipette is a laboratory tool commonly used in chemistry, biology and medicine to transport a measured volume of liquid, often as a media dispenser. Pipettes come in several designs for various purposes with differing levels of accuracy and precision, from single piece glass pipettes to more complex adjustable or electronic pipettes.

Steam Sterilizers

Steam Sterilizers are also known as autoclaves, is a machine that uses steam under pressure to kill harmful bacteria, viruses, fungi, and spores on items that are placed inside a pressure vessel. The basic principle of steam sterilization is to expose each item to direct steam contact at the required temperature and pressure for the specified time.

STEMart offers complete instruments and equipment used in the research of genomic library to facilitate your study. If you want to learn more detail about our devices, or would like to consult with the experts at STEMart, please feel free to contact us.