Site Directed Mutagenesis (SDM) Human Point mutation HeLa

Get tips on using QuikChange Site-Directed Mutagenesis Kit, 10 Rxn to perform AAA for reviews

DNA-protein interactions are studied by using ChIP. The basic steps in this technique are crosslinking, sonication, immunoprecipitation, and analysis of the immunoprecipitated DNA. During ChIP, if chromatin is under-fragmented or fragments are too large which can lead to the increased background and lower resolution. Shorter cross-linking times (5-10 min) and/or lower formaldehyde concentrations (<1%) may improve shearing efficiency. If Chromatin is over-fragmented, then optimize shearing conditions for each cell type to improve ChIP efficiency. Over-sonication of chromatin may disrupt chromatin integrity and denature antibody epitopes. If you do not see any product or very little product in the input PCR reactions, add 5–10 μg chromatin per IP.

Though DNA quantification is but one small step in the multifaceted DNA sample preparation workflow, it can have large implications on the performance and validity of conclusions drawn from downstream assays. Major challenges include accuracy, precision, reproducibility, and detection of present contamination. Among UV spectrophotometry, fluorescence and real-time PCR based methods, the quantification method should be chosen based on the requirement of the downstream assay.

The RNA interference (RNAi) is used to inhibit gene expression or translation, by neutralizing targeted mRNA molecules. Two types of RNA molecules such as microRNA (miRNA) and small interfering RNA (siRNA) play a central role in RNAi. Few points have to be considered to increase the transfection efficiency of siRNA. Always use healthy, actively dividing cells to maximize transfection efficiency. The confluency of cells should be between 50-70%. Always use the most appropriate siRNA concentration to avoid off-target effects and unwanted toxic side effects. Positive and negative controls should be used for each and every experiment to determine transfection efficiency.

RNA-Seq is a method to sequence RNA by applying Next Generation Sequencing (NGS). The quality of RNA is critical for the success of RNA-Seq. The integrity of RNA is measured by the RNA integrity number (RIN). RIN is computed from RNA electrophoresis and electropherogram profiles (the peak area of the 28S rRNA should be approximately twice the peak area of the 18S rRNA). If you get the RIN value lower than 7, the possibility of getting the low quality of RNA-seq data is high. To get a high quality RNA, it is better to work with fresh samples or snap-freeze the tissues in liquid nitrogen as quickly as possible and store them at -80°C until further use. Make sure designated areas and all your filter tips, microfuge tubes, plastic, and glassware are RNase-free.

Cell cycle can be challenging due to difference introduced by sample handling, timing, and difference within the sample. Downstream instriuments to analyse cell cycle (Multicolor flow cytometry and multicolor imaging) can answer these challenges. Relevant markers can be combined with cell phenotyping markers to look at events within subpopulations of cells.

DNA microarrays enable researchers to monitor the expression of thousands of genes simultaneously. However, the sensitivity, accuracy, specificity, and reproducibility are major challenges for this technology. Cross-hybridization, combination with splice variants, is a prime source for the discrepancies in differential gene expression calls among various microarray platforms. Removing (either from production or downstream bioinformatic analysis) and/or redesigning the microarray probes prone to cross-hybridization is a reasonable strategy to increase the hybridization specificity and hence, the accuracy of the microarray measurements.

miRNA is the inherent gene silencing machinery which can have more than one mRNA target, whereas siRNA can be designed to target a particular mRNA target. By design, both siRNA and miRNA are 20-25 nucleotides in length. The target sequence for siRNAs is usually located within the open reading frame, between 50 and 100 nucleotides downstream of the start codon. There are two ways in which cells can be transfected with desired RNAi: 1. Direct transfection (with calcium phosphate co-precipitation or cationic lipid mediated transfection using lipofectamine or oligofectamine), and 2. Making RNAi lentiviral constructs (followed by transformation and transduction). Lentiviral constructs are time consuming, but provide a more permanent expression of RNAi in the cells, and consistent gene silencing. Direct transfection of oligonucleotides provides temporary genetic suppression. Traditional methods like calcium phosphate co-precipitation have challenges like low efficiency, poor reproducibility and cell toxicity. Whereas, cationic lipid-based transfection reagents are able to overcome these challenges, along with applicability to a large variety of eukaryotic cell lines. When using oligos, the ideal concentration lies between 10-50nM for effective transfection.

miRNA is the inherent gene silencing machinery which can have more than one mRNA target, whereas siRNA can be designed to target a particular mRNA target. By design, both siRNA and miRNA are 20-25 nucleotides in length. The target sequence for siRNAs is usually located within the open reading frame, between 50 and 100 nucleotides downstream of the start codon. There are two ways in which cells can be transfected with desired RNAi: 1. Direct transfection (with calcium phosphate co-precipitation or cationic lipid mediated transfection using lipofectamine or oligofectamine), and 2. Making RNAi lentiviral constructs (followed by transformation and transduction). Lentiviral constructs are time consuming, but provide a more permanent expression of RNAi in the cells, and consistent gene silencing. Direct transfection of oligonucleotides provides temporary genetic suppression. Traditional methods like calcium phosphate co-precipitation have challenges like low efficiency, poor reproducibility and cell toxicity. Whereas, cationic lipid-based transfection reagents are able to overcome these challenges, along with applicability to a large variety of eukaryotic cell lines. When using oligos, the ideal concentration lies between 10-50nM for effective transfection.

miRNA is the inherent gene silencing machinery which can have more than one mRNA target, whereas siRNA can be designed to target a particular mRNA target. By design, both siRNA and miRNA are 20-25 nucleotides in length. The target sequence for siRNAs is usually located within the open reading frame, between 50 and 100 nucleotides downstream of the start codon. There are two ways in which cells can be transfected with desired RNAi: 1. Direct transfection (with calcium phosphate co-precipitation or cationic lipid mediated transfection using lipofectamine or oligofectamine), and 2. Making RNAi lentiviral constructs (followed by transformation and transduction). Lentiviral constructs are time consuming, but provide a more permanent expression of RNAi in the cells, and consistent gene silencing. Direct transfection of oligonucleotides provides temporary genetic suppression. Traditional methods like calcium phosphate co-precipitation have challenges like low efficiency, poor reproducibility and cell toxicity. Whereas, cationic lipid-based transfection reagents are able to overcome these challenges, along with applicability to a large variety of eukaryotic cell lines. When using oligos, the ideal concentration lies between 10-50nM for effective transfection.