Cell Disruption: Getting the RNA Out - Technical Bulletin #183
Description: Complete Disruption –A Critical Step Cellular disruption is the first step in RNA isolation and one of the most critical steps affecting yield and quality of the isolated RNA.
DNase I Demystified
Description: Answers to some of the questions surrounding this commonly used enzyme
Does Fractionation of Blood Samples Affect mRNA Expression Levels?
Description: An experiment is described that addresses whether blood cell fractionation affects the levels of several key mRNAs expressed in leukocytes.
Getting Intact RNA From LCM Samples
Description: Ambion has optimized the processing and staining of tissues for LCM and offers these suggestions for avoiding pitfalls and obtaining high quality RNA from LCM samples.
High Throughput miRNA Isolation
Description: The MagMAX™-96 for Microarrays Total RNA Isolation Kit combines TRI Reagent® Solution and the Ambion® MagMAX bead-based technology to recover high-quality RNA ideal for use on microarrays. Now, with a minor protocol modification, miRNAs can be isolated using this kit as well.
Organisms Compatible with the MICROBExpress™ Bacterial mRNA Isolation Kit
Description: A continually updated list of bacteria that can be used with the MICROBExpress™ Kit.
Practical Tips for Handling RNA
Description: Useful tips on phenol extraction, ethanol precipitation, and resolubilization of RNA.
Ribosomal RNA Sizes
Description: A chart of rRNA sizes for human, mouse, xenopus, drosophila, yeast, and tobacco leaf.
RNA Isolation: The Basics
Description: Learn about the many different approaches to RNA isolation in "RNA Isolation: The Basics." This article discusses isolation procedures for both total and poly(A) RNA. It also covers the treatment and handling of tissues or cells prior to RNA isolation and storage of purified RNA, which are also critical for obtaining high-quality RNA.
RNA Yields from Tissues and Cells
Description: RNA content can vary widely between tissues, cell-types, physiological state, etc. This webpage provides general guidelines for estimating RNA yields from a variety of cells and tissues.
The Do's and Don'ts of Total RNA Isolation
Description: Tips from the Bench
The Optimal Thickness of FFPE Sections for miRNA Isolation
Description: Our scientists examine the effect of section thickness (5–40 µm) on miRNA isolation from FFPE tissues.
Tips from the Bench
Does Fractionation of Blood Samples Affect mRNA Expression Levels?
Description: An experiment is described that addresses whether blood cell fractionation affects the levels of several key mRNAs expressed in leukocytes
Tips for Optimizing Bacterial Array Analysis
Description: Advice on the isolation of RNA from bacteria for array analysis, including the use of Ambion's RNAlater™ storage solution, RiboPure™ Bacteria RNA Isolation Kit, MicrobEnrich™ and MicrobExpress™ Kits.
The Use of LiCl Precipitation for RNA Purification - Technical Bulletin #160
Tips from the Bench 7(4)
Description: Is Your DNase RNase-Free?
Top Ten Ways to Improve Your RNA Isolation
Working with RNA - Technical Bulletin #159
Description: A protocol for denaturing gel electrophoresis of RNA for Northern blot or quality assessment. Native gel electrophoresis is also described.
Alternative Protocol for Extraction of RNA from Cells Captured on LeukoLOCK™ Filters Using TRI Reagent®
Blood Fractionation Protocol for Collection of White Blood Cells
Description: This protocol describes the fractionation of 2.5-10 ml blood samples for the collection of WBCs for subsequent storage and/or RNA isolation.
Isolating Small RNAs Using the MagMAX™-96 for Microarrays Kit
Description: With very slight modifications, the MagMAX-96 for Microarrays Kit can be used to isolate total RNA that includes the small RNA fraction (miRNA, tRNA, 5S/5.8S rRNA, and other small RNA species).
Isolation of Small RNAs Using the RiboPure™-Blood Kit
Description: With a few additional reagents and significant protocol modifications, the RiboPure™-Blood Kit can be used to isolate total RNA that includes the small RNA fraction from RNAlater® Solution-treated human blood samples.
RNAqueous™-96 RNA Isolation Kit Automation Protocol
Description: An automated RNAqueous-96 protocol developed for the MultiPROBE® II HT Liquid Handling System with a Gripper Integration Platform. The protocol should be adaptable to other liquid handling systems.
Sodium Acetate Precipitation of Small Nucleic Acids
Description: This precipitation protocol can be used to concentrate small nucleic acids from dilute solutions.
TRI Reagent® DNA/Protein Isolation Protocol
Description: Describes the isolation of DNA and protein from the interphase and organic/phenol phase produced during the lysate extraction step of the TRI Reagent® RNA isolation protocol.
An Alternative to Deep Freezing of Aquatic Ecological Samples - TechNotes 13(4)
Description: The study described here demonstrated that RNAlater® Solution successfully preserves microcrustacean RNA and DNA for up to one month at room temperature, and for up to four months at 5°C.
A Better Way to Isolate RNA AND Protein from the Same Sample - TechNotes 10(3)
Description: Ambion introduces the PARIS Kit for the isolation of both RNA and native protein from the same experimental sample.
An Optimized Gene Expression Workflow for Single Cells - TechNotes 16(1)
Description: Applied Biosystems scientists have improved the reliability of gene expression analysis in single cells by optimizing the protocol for the TaqMan® PreAmp Cells-to-CT™ Kit to prepare single cells for preamplification and real-time PCR analysis.
Assessing RNA Quality - TechNotes 11(1)
Description: Is a 28S:18S ratio of "2" really important? Find out in the first in a series of articles discussing RNA quality from the experts at The RNA Company.
Automate and Accelerate Nucleic Acid Purification - TechNotes 15(2)
Description: The MagMAX™ Express Magnetic Particle Processor is the premier platform for automation of high-throughput nucleic acid isolation and purification using the proven magnetic bead-based MagMAX technology.
Automated Workflow for High Quality, High Throughput Viral RNA - TechNotes 15(1)
Description: This article describes how the Ambion® MagMAX™ magnetic bead-based technology has been successfully adapted for automated sample processing on the Caliper Life Sciences Sciclone® ALH 3000 Workstation.
Automating RNA Isolation - TechNotes 9(3)
Description: Data from 48 samples processed using a 96 well plate-based RNA isolation protocol adapted for a robotic liquid handling system.
Bacterial RNA Isolation from Infected Eukaryotic Hosts - TechNotes 9(6)
Description: Remove >90% of mammalian RNA from complex mixtures of host-bacterial samples using Ambion's new MICROBEnrich™ Kit.
Broad Spectrum Pathogen Detection Using Microarray Technology - TechNotes 13(3)
Description: An overview of a recent publication reporting on the feasibility of using microarray technology for surveillance and diagnosis of respiratory pathogens from clinical samples. Ambion’s MICROBEnrich™ technology was used to enrich samples for the pathogen-derived RNA.
Coprecipitants for Demanding Molecular Biology Applications - TechNotes 10(2)
Description: An overview of Ambion's coprecipitant products for use during the precipitation of small amounts of nucleic acids.
Detect and Quantitate MicroRNA in Laser Capture Microdissection Samples - TechNotes 13(1)
Description: This article describes how three Ambion kits were used for the quantitation of specific miRNAs and detection of differential miRNA expression in laser capture microdissected mouse brain samples.
DNA-free™ - A New Method to Remove DNA - TechNotes 8(3)
Description: Treat RNA preps prior to RT-PCR
Don’t Bother Quantitating RNA for Gene Expression Analysis - TechNotes 15(3)
Description: This article demonstrates that relative gene expression data obtained from real-time PCR using the Cells-to-CT™ workflow is equivalent to that obtained using purified RNA quantitated by spectrophotometry, but with significantly less time and effort required and greater sensitivity.
Effect of Freeze-Thawing of Tissue on RNA Integrity - TechNotes 9(3)
Description: Tips from the Bench
Efficient Cellular Fractionation for RNA and Protein Isolation - TechNotes 11(1)
Description: This article discusses Ambion's Protein And RNA Isolation System (PARIS™) which employs a rapid and simple procedure to isolate both total RNA and native protein from the same sample. Examples of data from downstream applications are included.
Examine microRNA Profiles from Archived Formalin-fixed, Paraffin-embedded (FFPE) Tissue - TechNotes 12(3)
Description: Use Ambion's new RecoverAll™ Kit for the quantitative recovery of RNA, including microRNA, from FFPE samples. The isolated miRNAs can then be used for miRNA expression profiling.
Extract MicroRNA from Blood Samples - TechNotes 13(1)
Description: Ambion's LeukoLOCK™ Total RNA Isolation System provides researchers with a fast way to isolate nucleic acids (including miRNA) from the leukocyte fraction (WBCs) of whole blood.
Faster Nucleic Acid Isolation From FFPE Tissues - TechNotes 16(1)
Description: Applied Biosystems has improved the protocol for the Ambion® RecoverAll™ Total Nucleic Acid Isolation Kit for FFPE Tissues, resulting in significantly reduced processing time.
Get the miRNA Out—Plant Applications - TechNotes 11(5)
Description: The mirVana™ miRNA isolation Kit is shown to be a useful tool for small RNA isolation from plant tissues.
Go from Cells in Culture to Real-Time PCR Data Even Faster - TechNotes 15(2)
Description: The new TaqMan® Fast Cells-to-CT Kit combines the advantages of Cells-to-CT sample preparation with the reduced thermal cycling times offered by TaqMan Fast Universal Master Mix to further expedite gene expression analysis for researchers using cells in culture.
Got Small RNA? - TechNotes 12(1)
Description: An overview (with data) of Ambion's mirVana™ PARIS™ Kit and mirVana™ miRNA Isolation Kit for the isolation of total RNA without loss of small RNA species.
Hands-free Tissue Disruption with MELT™ System - TechNotes 12(4)
Description: Ambion’s Multi-Enzymatic Liquefaction of Tissue (MELT™) Total Nucleic Acid Isolation System is a simpler and safer alternative to traditional RNA and genomic DNA isolation procedures.
High Throughput RNA Recovery from Mammalian, Plant, and Viral Samples - TechNotes 13(1)
Description: Ambion's MagMAX™ magnetic bead-based kits enable the isolation of RNA from diverse sample types and a broad range of sample sizes.
Ideal Control for PCR Inhibition and Cell Input - TechNotes 15(2)
Description: The TaqMan® Cells-to-CT™ Control Kit includes Xeno RNA™ Control, a synthetic RNA transcript with a unique sequence that lacks homology to current annotated biological sequences, making it an ideal control for any experiment.
Improve RNA Isolation for Array Analysis and More - TechNotes 10(3)
Description: An overview of Ambion's RiboPure™ RNA Isolations Kits, including kits specifically designed for isolation from bacteria and yeast.
Improved Gene Expression Profiling With Mouse Blood Samples - TechNotes 13(4)
Description: Use of the Mouse RiboPure™-Blood RNA isolation Kit and GLOBINclear™ Mouse/Rat Globin mRNA depletion technology for gene expression analysis resulted in increased sensitivity and reproducibility on Affymetrix GeneChip® microarrays.
Improved Methods for Gene Expression Profiling from Blood Samples - TechNotes 13(3)
Description: Ambion offers integrated solutions for gene expression profiling from whole blood, including products for sample collection and stabilization, blood cell fractionation, RNA isolation, and globin mRNA removal.
Improved Microarray Sensitivity using Whole Blood RNA Samples - TechNotes 12(3)
Description: Improve your array analysis results by removing up to 95% of the globin transcripts from human, mouse, or rat whole blood total RNA samples using our GLOBINclear™ Kits.
Is Your RNA Intact? - TechNotes 8(3)
Description: Methods to check RNA integrity
Isolate and Quantitate miRNA from Plants - TechNotes 14(4)
Description: This article describes successful results obtained with Arabidopsis thaliana miRNA isolated using the Ambion® Plant RNA Isolation Aid in conjunction with the mirVana™ miRNA Isolation Kit. The resulting miRNA was quantitatively analyzed using TaqMan® MicroRNA Assays.
Isolate High Quality Total RNA from LCM Samples Suitable for Microarray and qRT-PCR Analysis - TechNotes 12(1)
Description: Using several of Ambion's new/improved products, it is now possible to carry out microarray expression profiling and qRT-PCR with RNA recovered from LCM samples.
Isolate RNA for Global Transcriptome Analysis - TechNotes 13(3)
Description: Recently, Ambion scientists collaborated with researchers at Beth Israel Deaconess Medical Center, Harvard Medical School, and Illumina, Inc. to assess global gene expression profiles in a mouse xenograft model for prostate cancer. An overview of their results is presented here.
Isolate RNA from White Blood Cells Captured by a Novel Filter System - TechNotes 12(4)
Description: Introducing the LeukoLOCK™ Total RNA Isolation System for the cellular fractionation of whole blood and total RNA stabilization/extraction from the leukocyte population.
Isolating miRNA for Profiling Studies - TechNotes 13(2)
Description: Ambion has developed a complete line of kits and reagents for isolating miRNAs from a wide range of cell and tissue types, as well as from blood and FFPE samples.
Isolation to Detection: RNA Analysis with Low Copy Number Templates - TechNotes 13(3)
Description: Together, Ambion and Applied Biosystems provide researchers with a complete family of products that takes experiments from sample preparation through target detection and analysis.
Isolation of Total RNA from Difficult Tissues - Technical Bulletin #177
Magnetic Bead-based Viral RNA Isolation from Diverse Biological Samples - TechNotes 13(2)
Description: Ambion's MagMAX™ technology has been used successfully for viral RNA/DNA purification from a variety of animal tissues, as well as from blood, serum, plasma, milk, swabs, and feces.
Make Time Stand Still with RNAlater™ - TechNotes 10(1)
Description: A description of Ambion's RNAlater™ Tissue Collection: RNA Stabilization Solution that makes it possible for researchers to postpone RNA isolation for days, weeks, or even months after tissue collection without sacrificing RNA integrity.
Making the Most of Limited Samples: Skip RNA Isolation and PreAmplify Cell Lysates Directly - TechNotes 14(4)
Description: The new TaqMan® PreAmp Cells-to-CT™ Kit combines the convenient Cells-to-CT lysis and reverse transcription (RT) reagents with TaqMan PreAmp Master Mix for cDNA pre-amplification.
Maximize Viral RNA Yield from Biological Fluid - TechNotes 11(5)
Description: Efficient viral RNA isolation from cell-free samples using our new MagMAX™ Viral RNA Isolation Kit.
Maximize Your RNA Yield - TechNotes 8(3)
Description: What Yield to Expect
miRNA Expression in White Blood Cells - TechNotes 11(3)
Description: Several of Ambion's miRNA analysis products were used to analyze miRNA expression in human white blood cells.
Obtaining the Highest Quality RNA from Blood Samples - TechNotes 16(1)
Description: In this article we discuss these challenges and the methods available for isolating high quality RNA from blood.
Optimized Biopsy Preservation for Clinical Gene Expression and Profiling - TechNotes 13(4)
Description: In the studies described here, RNAlater® Solution was used to store and stabilize clinical skin biopsy samples for gene expression analysis via real time RT-PCR and array analysis.
Optimized Gene Expression Analysis from FFPE Samples - TechNotes 14(3)
Description: The optimized protocol presented here can be used to reliably quantify mRNA expression levels using RNA isolated from FFPE samples and real-time RT-PCR.
Preserve RNA in the Tissue Before RNA Isolation - TechNotes 8(2)
Description: RNAlater™ will preserve RNA in tissues to be used for histology.
Protect RNA and Improve Target Cell Identification - TechNotes 12(1)
Description: Ambion's new LCM Staining Kit enables scientists to obtain high quality RNA from frozen, OCT-embedded tissues.
Purify Bacterial mRNA - TechNotes 9(1)
Description: Finally a kit for isolating bacterial mRNA from total RNA samples
Purify RNA Directly from Whole Blood - TechNotes 11(4)
Description: Ambion's RiboPure™-Blood Kit procedure overcomes the challenges involved in isolating intact RNA from whole blood.
Quantitate and Profile miRNA without RNA Isolation - TechNotes 15(1)
Description: miRNA expression profiling directly from cultured cells without RNA purification is quick, easy, and sensitive with the TaqMan® MicroRNA Cells-to-CT™ Kit.
Quantitate miRNA from a Few Drops of Mouse Blood - TechNotes 14(4)
Description: The Mouse RiboPure™-Blood Kit can be used to isolate high-quality total RNA, including miRNA, from mouse tail vein bleeds in time course studies. MicroRNA can then be quantitated using TaqMan® MicroRNA Assays.
Quantitating RNA - TechNotes 9(4)
Description: Tips for optimizing RNA quantitation
Real-Time RT-PCR Directly from Cell Lysates: A Complete Workflow without RNA Purification - TechNotes 14(3)
Description: For investigators evaluating gene expression in cultured cells, RNA isolation can be a bottleneck. With our new TaqMan® Gene Expression Cells-to-CT Kit, however, RNA purification from cultured mammalian cells is no longer necessary.
Recover High Yields of Total Nucleic Acid from Formalin-fixed, Paraffin-embedded (FFPE) Tissue - TechNotes 12(3)
Description: Ambion's new RecoverAll™ Kit enables researchers to isolate DNA and/or RNA (including microRNA) from FFPE samples. The nucleic acids recovered are ideal for various downstream applications such as microarray analysis, qRT-PCR, and mutation screening.
Recovering RNA from Small Samples - TechNotes 9(6)
Description: Ambion's RNAqueous™-Micro Kit allows for quantitative recovery of concentrated RNA from 4 - 400,000 cells ready for immediate use in downstream applications.
Research Highlight: Superior Microarray Data from Blood Samples - TechNotes 14(4)
Description: Array analysis using total RNA with a high percentage of globin mRNA reduces signal-to-noise ratios, while increasing signal variation. Our GLOBINclear™ Whole Blood Globin Reduction Kits solve this problem.
RNA Extraction from Blood: Choosing the Best System for Your Gene Expression Studies - TechNotes 14(2)
Description: Applied Biosystems/Ambion has developed multiple approaches for extracting RNA from blood, allowing researchers to choose the system that most closely meets the needs of their specific projects.
RNA from LCM Samples - TechNotes 11(3)
Description: RT-PCR analysis of RNA isolated from laser capture microdissected samples using Ambion's RNAqueous®-Micro Kit.
RNA from Mouse Whole Blood for Expression Profiling - TechNotes 13(3)
Description: Ambion’s Mouse RiboPure™-Blood RNA Isolation Kit is optimized for maximum yield of high quality total RNA directly from up to 0.5 ml samples of mouse or rat whole blood.
RNA Isolation for RT-PCR - TechNotes 8(1)
Description: An overview of Ambion's RNA isolation kits developed specifically for RT-PCR analysis
RNA Isolation for RT-PCR - TechNotes 9(5)
Description: A method for RNA isolation and DNA removal
RNA, DNA, and Protein from a Single Sample - TechNotes 12(3)
Description: TRI Reagent®--Now available from Ambion. Isolate DNA-free RNA, RNA-free DNA, and/or protein from diverse biological samples. Fast, simple, scalable.
RNA Remains Stable During Long-term Tissue Storage in RNAlater® - TechNotes 12(4)
Description: Tissues stored in RNAlater® or flash-frozen and stored at -80°C... How does the RNA compare after 2.5 years?
RNAlater® Around the World: Preserve Prognostic Gene Expression Signatures for Microarray Analyses - TechNotes 13(3)
Description: Scientists at Veridex LLC designed a study to assess gene expression profiling from paired tumor samples. They found no significant differences in RNA yield and quality with RNAlater-preserved vs snap-frozen tissues.
RNAlater® FAQs - Preserving RNA Before Isolation - TechNotes 11(4)
Description: Some commonly asked questions about RNAlater, an aqueous solution designed to maintain RNA integrity during storage of fresh tissue and cell samples.
RNAlater® for RNA and Protein Stabilization - TechNotes 11(3)
Description: Intact protein can be recovered from RNAlater-stabilized samples for use in downstream applications such as Western blotting or 2D gel analysis.
RNAlater™ Preserves Bacterial Gene Expression Profiles for Array Analysis - TechNotes 9(5)
Description: Arresting gene expression patterns during sample processing
RNAlater® Solution Around the World: FACS Into RNAlater® Solution for Gene Profiling - TechNotes 14(4)
Description: Researchers from the University of California, Irvine, describe a method utilizing RNAlater® Solution for FACS that minimizes downstream perturbation of gene expression profiles in sorted cells.
RNAlater® Solution Around the World: Preserving RNA Quality for Transcriptome Analysis - TechNotes 14(3)
Description: A comparison of different tissue storage methods led researchers at the National Institute of Biomedical Innovation in Osaka, Japan to recommend RNAlater® Solution as one way to preserve tissues for gene profiling.
RNAlater® Solution Around the World: Stabilizing Expression Profiles - TechNotes 14(2)
Description: Here we describe how three different research groups used RNAlater Solution to preserve samples for microarray and RT-PCR studies.
RNAlater® Solution Around the World: The First Step in Cervical Histology and Cytology - TechNotes 15(3)
Description: In this article we describe the successful use of RNAlater® Solution for the storage of cervical samples in preparation for human papilloma virus (HPV) nucleic acid analysis.
RNAlater® Solution—Don't Leave Earth Without It - TechNotes 14(1)
Description: Here we reprint our 2001 article on extraterrestrial use of RNAlater Solution next to a brief synopsis of a recent paper describing how RNAlater Solution facilitated scientific experiments on the International Space Station.
RNAi for High Throughput Analysis - TechNotes 9(5)
Description: Use MEGAscript and MEGAclear for the synthesis and purification of high quality RNA from a large number of samples
RNAi: Get the Whole Story - TechNotes 11(3)
Description: Fully understand the results of siRNA experiments by analyzing the kockdown of both the target mRNA and the corresponding protein.
RNase Activity in Mouse Tissue: Classification, Hierarchy, and Methods for Control - TechNotes 12(3)
Description: A comparison of total RNase activities in 8 different mouse tissues, with recommendations for the best RNA isolation methods.
Robust High Throughput RNA Isolation from Blood Samples - TechNotes 12(3)
Description: Easily isolate viral or total RNA from whole blood or milk samples using Ambion's new MagMAX™-96 Blood RNA Isolation Kit.
Sample Preservation Methods Affect Telomere Length - TechNotes 13(2)
Description: Researchers studying telomeric DNA found that tissues processed immediately or treated with RNAlater® yielded similar relative telomere lengths, while formaldehyde-fixed tissue yielded inconsistent measurements of telomere length.
Simultaneous Extraction of RNA and DNA - Technical Bulletin #161
Superior Gene Expression Profiling with Human Whole Blood Samples - TechNotes 14(3)
Description: This article describes an integrated workflow for gene expression profiling from human whole blood using a selection of Applied Biosystems products.
Thaw Frozen Tissues without Damaging RNA - TechNotes 10(2)
Description: RNAlater-ICE is a unique RNA stabilizing solution - simply drop frozen tissues into RNAlater-ICE and walk away! The tissues thaw without risk of RNA degradation. Once thawed the tissues can be processed like fresh tissues.
The Art of Processing Difficult Samples — RNAlater® Around the World - TechNotes 11(6)
Description: A snapshot of how researchers have used RNAlater in exciting discoveries around the world.
Tips from the Bench
Increasing Your RNA Recovery During Tissue or Cell Extraction
Description: Here we compare three methods for processing frozen tissues in a side-by-side test for quantity of mRNA recovered.
Total RNA from Whole Blood for Expression Profiling - TechNotes 12(2)
Description: Microarray studies were performed to compare the benefits of RiboPure™-Blood Kit–RNAlater® with the market leader's system for isolating blood RNA.
Using SYBR® Green for Real-Time RT-PCR? Try SYBR Green Cells-to-CT™ Kits - TechNotes 15(3)
Description: Learn more about our new Power SYBR Green and Fast SYBR® Green Cells-to-CT™ Kits that take you from cells in culture to real-time RT-PCR analysis without RNA purification.
Watch Your Tissue MELT into High Quality Total RNA - TechNotes 12(3)
Description: With our Multi-Enzymatic Liquefaction of Tissue (MELT™) Total RNA Isolation System, the first step is a rapid enzymatic digestion of the fresh or frozen tissue samples—no homogenization required!
Your Data: Identifying Cancer-Related mRNA Signatures in FFPE Patient Samples
Description: The Yeatman laboratory at the H. Lee Moffitt Cancer Center and Research Institute (Tampa, FL) investigates the gene expression signatures that define colon, breast, and other cancers.
Your Data: Stabilize Difficult-to-work-with RNA Transcripts
Description: RNAlater® Solution provides a method for preserving RNA in tissue samples for large-scale experiments, such as examining the effects of cigarette smoke on tracheal gene expression.
Your Data: LCM Staining Effects on Real-Time RT-PCR
Description: Research is described demonstrating that the Ambion® LCM Staining Kit can be successfully used on formalin-fixed and paraffin-embedded (FFPE) tissues without compromising either the yield or the quality of RNA extracted.