Immunofluorscence  53BP1 [H-300] Rabbit Human

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.

Protein isolation is a technique that involves isolation and/ or purification of protein from cells or tissues via chromatography or electrophoresis. The major challenges in protein isolation include: 1. The concentration of proteins in cells is variable and tends to be small for some intracellular proteins. Unlike nucleic acids, proteins cannot be amplified. 2. Proteins are more unstable than nucleic acids. They are easily denatured under suboptimal temperature, pH or salt concentrations. 3. Finally, no generalized technique/protocol can be applied for protein isolation. Proteins may have different electrostatic (number of positively or negatively charged amino acids) or hydrophobic properties. Therefore, protein purification requires multiple steps depending on their charge (a negatively charged resin/column for positively charged proteins and vice-versa), dissolution (using detergents) and unlike in the case of DNA and RNA, instead of using salts, proteins should be isolated by isoelectric precipitation.

Stem cells have the unique ability to self-renew or differentiate themselves into various cell types in response to appropriate signals. These cells are especially important for tissue repair, regeneration, replacement, or in the case of hematopoietic stem cells (HSCs) to differentiate into various myeloid populations. Appropriate signals refer to the growth factor supplements or cytokines that mediate differentiation of various stem cells into the required differentiated form. For instance, HSCs can be differentiated into dendritic cells (with IL-4 and GM-CSF), macrophages (with m-CSF) and MDSCs (with IL-6 and GM-CSF). Human pluripotent stem cells (hPSCs) and induced pluripotent stem cells (iPSCs) can be first cultured in neural differentiation media (GSK3𝛃-i, TGF𝛃-i, AMPK-i, hLIF) to form neural rosettes, which can be differentiated into neural or glial progenitors (finally differentiated into oligodendrocytes). Neural progenitors can be finally differentiated into glutaminergic (dibytyryl cAMP, ascorbic acid) and dopaminergic (SHH, FGF-8, BDNF, GDNF, TGF-𝛃3) neurons. Thus, it is important to first identify the self-renewing cell line: its source and its final differentiation state, followed by the supplements and cytokines required for the differentiation, and final use. Timelines are another thing that is considered. For instance, it takes 7-10 days to form neural rosettes from iPSCs and 3 days to differentiate neural progenitors to neurons. Finally, the stability for stem cell culture media varies. It is advised to make fresh media every time when differentiating HSCs to myeloid populations, whereas neural differentiation media may remain stable for two weeks when stored in dark between 2-8C.

The formation of DNA from an RNA template using reverse transcription leads to the formation of double-stranded complementary DNA or cDNA. The challenges with this process include 1. Maintaining the integrity of RNA, 2. Hairpin loops or other secondary structures formed by single-stranded RNA can also affect cDNA synthesis, and 3. DNA-RNA hybrids, which may result when the first strand of cDNA is formed. For the first challenge, using workflows that involve proper isolation and storage of RNA, and maintaining a nuclease-free environment helps obtain RNA with ideal 260/230 ratios. Using a reverse transcriptase that can tolerate high temperatures (50-55oC), overcomes obstacles imposed by secondary RNA structures. Finally, RNase H has the ability to hydrolyze RNA before the formation of a second cDNA strand. It is important to ensure that RNase H activity is optimal because higher RNase H activity leads to premature degradation of the RNA template. Many reverse transcriptases offer built-in RNase H activity.

The formation of DNA from an RNA template using reverse transcription leads to the formation of double-stranded complementary DNA or cDNA. The challenges with this process include 1. Maintaining the integrity of RNA, 2. Hairpin loops or other secondary structures formed by single-stranded RNA can also affect cDNA synthesis, and 3. DNA-RNA hybrids, which may result when the first strand of cDNA is formed. For the first challenge, using workflows that involve proper isolation and storage of RNA, and maintaining a nuclease-free environment helps obtain RNA with ideal 260/230 ratios. Using a reverse transcriptase that can tolerate high temperatures (50-55oC), overcomes obstacles imposed by secondary RNA structures. Finally, RNase H has the ability to hydrolyze RNA before the formation of a second cDNA strand. It is important to ensure that RNase H activity is optimal because higher RNase H activity leads to premature degradation of the RNA template. Many reverse transcriptases offer built-in RNase H activity.

The formation of DNA from an RNA template using reverse transcription leads to the formation of double-stranded complementary DNA or cDNA. The challenges with this process include 1. Maintaining the integrity of RNA, 2. Hairpin loops or other secondary structures formed by single-stranded RNA can also affect cDNA synthesis, and 3. DNA-RNA hybrids, which may result when the first strand of cDNA is formed. For the first challenge, using workflows that involve proper isolation and storage of RNA, and maintaining a nuclease-free environment helps obtain RNA with ideal 260/230 ratios. Using a reverse transcriptase that can tolerate high temperatures (50-55oC), overcomes obstacles imposed by secondary RNA structures. Finally, RNase H has the ability to hydrolyze RNA before the formation of a second cDNA strand. It is important to ensure that RNase H activity is optimal because higher RNase H activity leads to premature degradation of the RNA template. Many reverse transcriptases offer built-in RNase H activity.

The process of RNA extraction from bacteria, in general, involves an RNA-protective, effective lysis of bacterial cell wall (which may pose difficulties). EDTA promotes loss of outer membrane to provide lysozyme with access to peptidoglycan. Another common method for cell wall lysis is mechanical disruption using a homogenizer (applied for gram-positive bacteria and some strains of gram-negative bacteria). Following lysis, it is necessary to disrupt protein-nucleic acid interactions, which can be achieved by adding sodium dodecyl sulfate (SDS). Next step involves using phenol-chloroform-isoamyl alcohol extraction, where RNA can be obtained from the bottom organic phase, the top phase consists of DNA and the interphase contains proteins. Isoamyl alcohol is an inert and optional addition to this mixture and is added as an anti-foaming reagent to reduce the interphase. Following RNA extraction, the samples should be checked for its quality by gel electrophoresis (23S and 16S rRNAs and 5s rRNA and tRNA bands) or UV spectrophotometric or fluorescence methods.

Get tips on using Monoclonal Mouse Anti-Human p53 Protein (Dako Omnis) Clone DO-7 to perform Immunohistochemistry Human - p53

Short hairpin or small hairpin RNA (shRNA) is artificial RNA, which has a hairpin loop structure, and uses inherent microRNA (miRNA) machinery to silence target gene expression. This is called RNA interference (RNAi). These can be delivered via plasmids or viral/bacterial vectors. Challenges in shRNA-mediated gene silencing include 1. Off-target silencing, 2. Packaging shRNA encoding lentivirus, and 3. Stable transduction in cells. RNAi has been designed to have anywhere from 19-27 bs, but the most effective design has 19 bp. In case commercial shRNAs are not available, potential target sites can be chosen within exon, 5’- or 3’ UTR, depending on which splice variants of the gene are desired. One should use the latest algorithms and choose at least two different sequences, targeting different regions, in order to have confidence in overcoming off-target effects. A BLAST search after selecting potential design will eliminate potential off-target sequences. For the second challenge, sequencing the vector using primers for either strand (50-100 bp upstream) is suggested, along with using enzymatic digestion on agarose gel for the vector. Next, once the shRNA-containing vector is packaged in a virus, it is important to check the viral titer before transduction. Finally, using a marker in the lentiviral vector (fluorescent protein or antibiotic resistance), along with qPCR for target gene expression can help in determining the efficacy of transduction and shRNA on its target site.

Flow cytometry is an immunophenotyping technique whereby sing cell suspensions are stained for either cell surface markers or intracellular proteins by fluorescently-labelled antibodies and analyzed with a flow cytometer, where fluorescently-labelled molecules are excited by the laser to emit light at varying wavelengths, which is then detected by the instrument. There are several key criteria which are required to be kept in mind while designing a flow experiment- 1. Antibody titration (optimal dilution of antibodies should be calculated in order to avoid over- or under- saturated signals for proper detection of surface and intracellular markers), 2. Precision (3 or more replicates of the sample should be used per experiment), 3. Specificity (proper isotype controls should be included in the experiment), 4. Day-to-day variability (experiments should be repeated 3 or more times to ensure consistency and avoid variability due to flow cytometer settings), 5. Antibody interaction (Fluorescence minus one or FMO should be used, which is the comparison of signals from panel minus one antibody vs. the full panel), and 6. Antibody stability (fluorescently-labelled antibodies should be stored at 4C).