RNA quantification for appropriate concentration and quality (260/280 ratio) is an important step before downstream analysis (including sequencing, RT-qPCR, etc.). Having insufficient RNA quantities or a high salt or phenol in the RNA product can lead to variable or irreproducible downstream results. The various methods used for RNA quantification include: 1. UV spectrophotometric (challenges include: low sensitivity, cannot distinguish between nucleic acid species), 2. Fluorescence-based (challenges include: requires standards, cannot measure amplifiability, not sequence-specific), and 3. RT-PCR (challenges include: requires standards, time-intensive, costly). In order to overcome these challenges, and also to ensure the proper quantification and quality control for RNA product, it is important to use at least two or more methods in order to discard any inconsistencies. Using standards for calibrations increases the sensitivity range for RNA detention (fluorescence- and RT-PCR-based methods). When using RT- PCR, it is important to choose correct primers, aligning to the desired site on the template and of appropriate product length, along with positive, negative and loading controls. It is also important to have at least two primer pairs in order to confirm results.
RNA quantification for appropriate concentration and quality (260/280 ratio) is an important step before downstream analysis (including sequencing, RT-qPCR, etc.). Having insufficient RNA quantities or a high salt or phenol in the RNA product can lead to variable or irreproducible downstream results. The various methods used for RNA quantification include: 1. UV spectrophotometric (challenges include: low sensitivity, cannot distinguish between nucleic acid species), 2. Fluorescence-based (challenges include: requires standards, cannot measure amplifiability, not sequence-specific), and 3. RT-PCR (challenges include: requires standards, time-intensive, costly). In order to overcome these challenges, and also to ensure the proper quantification and quality control for RNA product, it is important to use at least two or more methods in order to discard any inconsistencies. Using standards for calibrations increases the sensitivity range for RNA detention (fluorescence- and RT-PCR-based methods). When using RT- PCR, it is important to choose correct primers, aligning to the desired site on the template and of appropriate product length, along with positive, negative and loading controls. It is also important to have at least two primer pairs in order to confirm results.
Protein expression refers to the techniques in which a protein of interest is synthesized, modified or regulated in cells. The blueprints for proteins are stored in DNA which is then transcribed to produce messenger RNA (mRNA). mRNA is then translated into protein. In prokaryotes, this process of mRNA translation occurs simultaneously with mRNA transcription. In eukaryotes, these two processes occur at separate times and in separate cellular regions (transcription in nucleus and translation in the cytoplasm). Recombinant protein expression utilizes cellular machinery to generate proteins, instead of chemical synthesis of proteins as it is very complex. Proteins produced from such DNA templates are called recombinant proteins and DNA templates are simple to construct. Recombinant protein expression involves transfecting cells with a DNA vector that contains the template. The cultured cells can then transcribe and translate the desired protein. The cells can be lysed to extract the expressed protein for subsequent purification. Both prokaryotic and eukaryotic protein expression systems are widely used. The selection of the system depends on the type of protein, the requirements for functional activity and the desired yield. These expression systems include mammalian, insect, yeast, bacterial, algal and cell-free. Each of these has pros and cons. Mammalian expression systems can be used for transient or stable expression, with ultra high-yield protein expression. However, high yields are only possible in suspension cultures and more demanding culture conditions. Insect cultures are the same as mammalian, except that they can be used as both static and suspension cultures. These cultures also have demanding culture conditions and may also be time-consuming. Yeast cultures can produce eukaryotic proteins and are scalable, with minimum culture requirements. Yeast cultures may require growth culture optimization. Bacterial cultures are simple, scalable and low cost, but these may require protein-specific optimization and are not suitable for all mammalian proteins. Algal cultures are optimized for robust selection and expression, but these are less developed than other host platforms. Cell-free systems are open, free of any unnatural compounds, fast and simple. This system is, however, not optimal for scaling up.
Protein expression refers to the techniques in which a protein of interest is synthesized, modified or regulated in cells. The blueprints for proteins are stored in DNA which is then transcribed to produce messenger RNA (mRNA). mRNA is then translated into protein. In prokaryotes, this process of mRNA translation occurs simultaneously with mRNA transcription. In eukaryotes, these two processes occur at separate times and in separate cellular regions (transcription in nucleus and translation in the cytoplasm). Recombinant protein expression utilizes cellular machinery to generate proteins, instead of chemical synthesis of proteins as it is very complex. Proteins produced from such DNA templates are called recombinant proteins and DNA templates are simple to construct. Recombinant protein expression involves transfecting cells with a DNA vector that contains the template. The cultured cells can then transcribe and translate the desired protein. The cells can be lysed to extract the expressed protein for subsequent purification. Both prokaryotic and eukaryotic protein expression systems are widely used. The selection of the system depends on the type of protein, the requirements for functional activity and the desired yield. These expression systems include mammalian, insect, yeast, bacterial, algal and cell-free. Each of these has pros and cons. Mammalian expression systems can be used for transient or stable expression, with ultra high-yield protein expression. However, high yields are only possible in suspension cultures and more demanding culture conditions. Insect cultures are the same as mammalian, except that they can be used as both static and suspension cultures. These cultures also have demanding culture conditions and may also be time-consuming. Yeast cultures can produce eukaryotic proteins and are scalable, with minimum culture requirements. Yeast cultures may require growth culture optimization. Bacterial cultures are simple, scalable and low cost, but these may require protein-specific optimization and are not suitable for all mammalian proteins. Algal cultures are optimized for robust selection and expression, but these are less developed than other host platforms. Cell-free systems are open, free of any unnatural compounds, fast and simple. This system is, however, not optimal for scaling up.
Human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) have been greatly used for studies on embryonic development and cell differentiation.iPSCs provide a stable source for either self-renewal or differentiation into suitable cells when cultured in a particular environment. Pluripotent cell culture was originally started by deriving cells from inner cell mass (ICM) from pre-implanted blastocysts, these were called embryonic stem cells. These cells after isolation can be grown on traditional extracellular matrices (like mouse embryonic fibroblasts, MEFs) or feeder-free culture systems. DMEM/F12 has been the most commonly used basal media in the culture of pluripotent cells. These cells are cultured at normal atmospheric oxygen levels, 21%, however, some studies have proposed that 4% oxygen tension may be better for hESC growth. Higher D-glucose concentration (4.2g/l) and osmolarity (320mOsm) that mimics the natural environment of embryonic tissue are optimal for the growth of hESCs. Supplements like N2 and/or B-27, in the presence of growth factors like bFGF, have been shown to increase pluripotency of these cells. bFGF, FGF2 and other ligands of receptor tyrosine kinases like IGF are also required or maintain self-renewal ability of these cells. TGF𝛃1, by its activation of SMAD2/3 signalling, also represses differentiation of iPSCs. Other compounds like ROCK inhibitors reduce blebbing and apoptosis in these cells to maintain their clonogenicity. However, an inhibitor for LIF (leukaemia inhibitory factor, which is one of the pluripotent genes) has an opposing effect. Therefore, it is important to understand the culture conditions and media composition that affect downstream signalling in hESCs or iPSCs that may lead to their differentiation.
Protein expression refers to the techniques in which a protein of interest is synthesized, modified or regulated in cells. The blueprints for proteins are stored in DNA which is then transcribed to produce messenger RNA (mRNA). mRNA is then translated into protein. In prokaryotes, this process of mRNA translation occurs simultaneously with mRNA transcription. In eukaryotes, these two processes occur at separate times and in separate cellular regions (transcription in nucleus and translation in the cytoplasm). Recombinant protein expression utilizes cellular machinery to generate proteins, instead of chemical synthesis of proteins as it is very complex. Proteins produced from such DNA templates are called recombinant proteins and DNA templates are simple to construct. Recombinant protein expression involves transfecting cells with a DNA vector that contains the template. The cultured cells can then transcribe and translate the desired protein. The cells can be lysed to extract the expressed protein for subsequent purification. Both prokaryotic and eukaryotic protein expression systems are widely used. The selection of the system depends on the type of protein, the requirements for functional activity and the desired yield. These expression systems include mammalian, insect, yeast, bacterial, algal and cell-free. Each of these has pros and cons. Mammalian expression systems can be used for transient or stable expression, with ultra high-yield protein expression. However, high yields are only possible in suspension cultures and more demanding culture conditions. Insect cultures are the same as mammalian, except that they can be used as both static and suspension cultures. These cultures also have demanding culture conditions and may also be time-consuming. Yeast cultures can produce eukaryotic proteins and are scalable, with minimum culture requirements. Yeast cultures may require growth culture optimization. Bacterial cultures are simple, scalable and low cost, but these may require protein-specific optimization and are not suitable for all mammalian proteins. Algal cultures are optimized for robust selection and expression, but these are less developed than other host platforms. Cell-free systems are open, free of any unnatural compounds, fast and simple. This system is, however, not optimal for scaling up.
Contamination can affect cell characteristics, i.e., growth, metabolism, and morphology leading to unreliable and erroneous experimental data. Depending on the source of contaminants, one can detect contamination by using a light microscope, gram stain, isothermal amplification, or PCR. Bacteria and fungi can usually be identified by optical microscopy. Mycoplasma in cell cultures cannot be detected visually. Hence, these microbes can go unnoticed for long periods and are determined using dedicated assays. Early and rapid identification of contaminants is vital to detect, handle and prevent contamination for good cell-culture practices. However, detection and identification can be challenging and tricky based on usual visual identifications. Hence it is essential to use a standard contamination detection kit to detect and maintain best practices.
Contamination can affect cell characteristics, i.e., growth, metabolism, and morphology leading to unreliable and erroneous experimental data. Depending on the source of contaminants, one can detect contamination by using a light microscope, gram stain, isothermal amplification, or PCR. Bacteria and fungi can usually be identified by optical microscopy. Mycoplasma in cell cultures cannot be detected visually. Hence, these microbes can go unnoticed for long periods and are determined using dedicated assays. Early and rapid identification of contaminants is vital to detect, handle and prevent contamination for good cell-culture practices. However, detection and identification can be challenging and tricky based on usual visual identifications. Hence it is essential to use a standard contamination detection kit to detect and maintain best practices.
Contamination can affect cell characteristics, i.e., growth, metabolism, and morphology leading to unreliable and erroneous experimental data. Depending on the source of contaminants, one can detect contamination by using a light microscope, gram stain, isothermal amplification, or PCR. Bacteria and fungi can usually be identified by optical microscopy. Mycoplasma in cell cultures cannot be detected visually. Hence, these microbes can go unnoticed for long periods and are determined using dedicated assays. Early and rapid identification of contaminants is vital to detect, handle and prevent contamination for good cell-culture practices. However, detection and identification can be challenging and tricky based on usual visual identifications. Hence it is essential to use a standard contamination detection kit to detect and maintain best practices.
Contamination can affect cell characteristics, i.e., growth, metabolism, and morphology leading to unreliable and erroneous experimental data. Depending on the source of contaminants, one can detect contamination by using a light microscope, gram stain, isothermal amplification, or PCR. Bacteria and fungi can usually be identified by optical microscopy. Mycoplasma in cell cultures cannot be detected visually. Hence, these microbes can go unnoticed for long periods and are determined using dedicated assays. Early and rapid identification of contaminants is vital to detect, handle and prevent contamination for good cell-culture practices. However, detection and identification can be challenging and tricky based on usual visual identifications. Hence it is essential to use a standard contamination detection kit to detect and maintain best practices.
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