Cell cytotoxicity assays measure the ability of certain compounds or chemical mediators to reduce the viability of the cells. The term cell cytotoxicity assay can sometimes be used interchangeably with cell proliferation assay. Healthy living cells can be identified by the use of formazan dyes, protease biomarkers or by measuring ATP content. The formazan dyes are chromogenic products formed by the reduction of tetrazolium salts by dehydrogenases, such as lactate dehydrogenase (LDH) and reductases that are released during cell death. Common tetrazolium salts include INT, MTT, MTS and XTT. Cell cytotoxicity can also be measured by using the SRB and WST-1 assays. These assays can usually be used in a high-throughput fashion and can be quantitated by measuring absorbance, colorimetry or luminescence. All these assays require similar numbers of cell plating at the initiation, a time course of treatment with the cytotoxic agent and at least triplicates for each condition at every point of analysis. Cell shrinkage, plasma membrane blebbing, cell detachment, externalization of phosphatidylserine, nuclear condensation and ultimately DNA fragmentation are well-described features of apoptosis. The assays that rely on cell membrane integrity for their function, may not be able to quantify early apoptosis. Therefore, in order to distinguish early apoptotic vs. late apoptotic or necrotic cells, additional flow cytometry techniques can be used. A combination of Annexin V and PI (propidium iodide) can be used to distinguish early (Annexin V+/PI-) and late apoptotic (Annexin V+/PI+) cells. Sometimes, caspase assays are used in order to differentiate the stages of apoptosis.
Cell cytotoxicity assays measure the ability of certain compounds or chemical mediators to reduce the viability of the cells. The term cell cytotoxicity assay can sometimes be used interchangeably with cell proliferation assay. Healthy living cells can be identified by the use of formazan dyes, protease biomarkers or by measuring ATP content. The formazan dyes are chromogenic products formed by the reduction of tetrazolium salts by dehydrogenases, such as lactate dehydrogenase (LDH) and reductases that are released during cell death. Common tetrazolium salts include INT, MTT, MTS and XTT. Cell cytotoxicity can also be measured by using the SRB and WST-1 assays. These assays can usually be used in a high-throughput fashion and can be quantitated by measuring absorbance, colorimetry or luminescence. All these assays require similar numbers of cell plating at the initiation, a time course of treatment with the cytotoxic agent and at least triplicates for each condition at every point of analysis. Cell shrinkage, plasma membrane blebbing, cell detachment, externalization of phosphatidylserine, nuclear condensation and ultimately DNA fragmentation are well-described features of apoptosis. The assays that rely on cell membrane integrity for their function, may not be able to quantify early apoptosis. Therefore, in order to distinguish early apoptotic vs. late apoptotic or necrotic cells, additional flow cytometry techniques can be used. A combination of Annexin V and PI (propidium iodide) can be used to distinguish early (Annexin V+/PI-) and late apoptotic (Annexin V+/PI+) cells. Sometimes, caspase assays are used in order to differentiate the stages of apoptosis.
ELISA is the most commonly used method of detecting and quantifying the concentration of an antigen in an unknown sample. During the experiment, If you get a weak signal, then make sure reagents are at room temperature before starting the assay. Try increasing incubation times to ensure maximal antibody binding and amplify the signal. Secondly, if you get values above 0 in the negative control indicates a high background signal. Try to consider reducing your antibody concentration and prevent non-specific binding of antibodies by using affinity-purified antibody and suitable blocking buffers. To avoid high well to well variation, do not stack plates during incubation, no bubbles in the plate and wash wells thoroughly to avoid variation.
ELISA is the most commonly used method of detecting and quantifying the concentration of an antigen in an unknown sample. During the experiment, If you get a weak signal, then make sure reagents are at room temperature before starting the assay. Try increasing incubation times to ensure maximal antibody binding and amplify the signal. Secondly, if you get values above 0 in the negative control indicates a high background signal. Try to consider reducing your antibody concentration and prevent non-specific binding of antibodies by using affinity-purified antibody and suitable blocking buffers. To avoid high well to well variation, do not stack plates during incubation, no bubbles in the plate and wash wells thoroughly to avoid variation.
ELISA is the most commonly used method of detecting and quantifying the concentration of an antigen in an unknown sample. During the experiment, If you get a weak signal, then make sure reagents are at room temperature before starting the assay. Try increasing incubation times to ensure maximal antibody binding and amplify the signal. Secondly, if you get values above 0 in the negative control indicates a high background signal. Try to consider reducing your antibody concentration and prevent non-specific binding of antibodies by using affinity-purified antibody and suitable blocking buffers. To avoid high well to well variation, do not stack plates during incubation, no bubbles in the plate and wash wells thoroughly to avoid variation.
Get tips on using IGF-IRα/β siRNA (r) to perform siRNA / miRNA gene silencing Rat - RGC-5 IGF1R
Bacterial culture is a process of letting bacteria multiply in a controlled fashion (temperature, humidity, oxygen content or shaking), in a predetermined culture medium (antibiotic resistance to obtain homogenous clones). It is an important step, especially during cloning, as a single cell can be grown homogeneously (on semi-solid or in liquid conditions) to obtain colonies. As mentioned, bacteria can be cultured in broth cultures (Luria broth or LB) or Petri dishes (Agar plates). A specific antibiotic can be added to the broth or agar plates in order to grow bacteria which have the gene insert conferring its resistance to that antibiotic. Following points are necessary to consider for optimal growth conditions: 1. In general, most bacteria grow well at 37C, but there are some strains which require growth temperatures between 25-30C. 2. It is ideal in broth cultures to fill the flask to ⅓ or less of the total flask volume for optimal aerobic growth. 3. Shaking speeds between 140-180 rpm are appropriate to ensure aeration and that the cells are surrounded by fresh media, and do not settle.
Bacterial culture is a process of letting bacteria multiply in a controlled fashion (temperature, humidity, oxygen content or shaking), in a predetermined culture medium (antibiotic resistance to obtain homogenous clones). It is an important step, especially during cloning, as a single cell can be grown homogeneously (on semi-solid or in liquid conditions) to obtain colonies. As mentioned, bacteria can be cultured in broth cultures (Luria broth or LB) or Petri dishes (Agar plates). A specific antibiotic can be added to the broth or agar plates in order to grow bacteria which have the gene insert conferring its resistance to that antibiotic. Following points are necessary to consider for optimal growth conditions: 1. In general, most bacteria grow well at 37C, but there are some strains which require growth temperatures between 25-30C. 2. It is ideal in broth cultures to fill the flask to ⅓ or less of the total flask volume for optimal aerobic growth. 3. Shaking speeds between 140-180 rpm are appropriate to ensure aeration and that the cells are surrounded by fresh media, and do not settle.
Gene silencing through the use of small interfering RNA (siRNA) has become a primary tool for identifying disease-causing genes. There are several aspects for preparing and delivering effective siRNA to knockdown a target gene. The length of siRNA should be 21–23nt long with G/C content 30–50%. If a validated siRNA sequence for your target gene is not available, use siRNA generated against the entire target gene ORF. Always work with two or three different siRNA constructs to get reliable results. If you are not sure how much siRNA to use for a given experiment, start with a transfection concentration of 10-50 nM and use siRNA-specific transfection reagent to ensure efficient siRNA delivery in a wide range of cells.
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