Metabolomics FAQ

• • Is an OPLS-DA Model with a Q2Y Value of Around 0.2 Considered Reliable in the Case of a Small Sample Size?

  Q2Y Value as a Critical Metric for Evaluating the Predictive Performance of OPLS-DA Models 1. Understanding the Q2Y Value The Q2Y value is widely used in OPLS-DA to assess the predictive performance of a model. A higher Q2Y value (close to 1) indicates strong predictive reliability, whereas a lower Q2Y value suggests poor predictive performance. Typically, a Q2Y value above 0.5 is deemed acceptable for model validation.   2. Impact of Small Sample Sizes on Q2Y Values When working with small sample siz......

• • How to Calculate Polysaccharide Purity?

  The purity of polysaccharides is typically determined using analytical techniques such as high-performance liquid chromatography (HPLC) or gel permeation chromatography (GPC). Different analytical methods may employ distinct calculation approaches. Here, we describe a purity calculation method based on chromatographic analysis:   Sample Preparation and Analysis The polysaccharide sample is subjected to analysis using an appropriate chromatographic system.   Peak Area Calculation In the chromatogram, p......

• • What Is the Optimal Concentration Method for High-Volume Solutions in Polysaccharide Extraction and Purification?

  During the extraction and purification of polysaccharides, if the solution volume is large, the following concentration methods can be considered:   Filtration-Based Concentration An appropriate filter membrane or filter paper can be used to remove macromolecules and impurities from the polysaccharide solution, yielding a relatively pure filtrate. The filtrate is then subjected to reduced temperature or vacuum conditions to facilitate solvent evaporation, thereby achieving concentration.   Membrane Se......

• • How to Purify Polysaccharides Using a Sephadex Gel Column After Impurities Remain Following Fibrous Column Chromatography?

  Polysaccharide purification is a multistep process that often requires optimization to achieve high purity. If impurities persist after processing with a fibrous column, further purification using a Sephadex gel filtration column may be necessary. The following steps outline the procedure for gel filtration purification of polysaccharides:   1. Selection of an Appropriate Sephadex Gel Choose a Sephadex gel suitable for the molecular weight range of the polysaccharide to be separated, such as Sepharose......

• • What Are the Common Methods for Polysaccharide Degradation?

  Polysaccharides are biopolymers composed of multiple monosaccharide units linked by glycosidic bonds, including starch, cellulose, and glycogen. Various methods exist for polysaccharide degradation, and the choice of method depends on the polysaccharide type, the intended purpose of degradation, and specific application requirements. Below are some commonly employed degradation strategies:   Enzymatic Hydrolysis Polysaccharides can be hydrolyzed by specific enzymes that catalyze the cleavage of glycos......

• • What Are the Targeted Methods for Detecting Short-Chain Fatty Acids in Fecal Samples?

  Targeted detection of short-chain fatty acids (SCFAs) in fecal samples is commonly conducted using gas chromatography-mass spectrometry (GC-MS), owing to its high suitability for analyzing volatile organic compounds, a category to which SCFAs belong. This technique allows for highly specific and quantitative analysis of SCFAs, including acetic acid, propionic acid, and butyric acid. The overall analytical workflow typically involves the following steps:   Sample Collection and Preparation 1. Collectio......

• • What Are the Effective Strategies for Removing Impurities from Crude Polysaccharide Extracts?

  Polysaccharides are macromolecular compounds composed of multiple monosaccharide units and exhibit a wide range of biological activities and potential applications. Crude extracts of polysaccharides often contain various impurities, including proteins, nucleic acids, pigments, and minerals, among others. The choice of impurity removal strategies typically depends on the source, structural characteristics, and physicochemical properties of the polysaccharide, as well as the nature of the impurities pre......

• • What Analytical Techniques Are Available for the Detection of Bile Acids in Fecal Samples?

  The detection of bile acids in fecal samples primarily relies on advanced biochemical analytical techniques characterized by high sensitivity and efficiency. Commonly employed methods include the following:   Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) LC-MS/MS enables comprehensive structural and quantitative profiling of bile acids. Owing to its high sensitivity and specificity, it is particularly well-suited for analyzing multiple bile acid species in complex biological matrices such ......

• • How Are Lipids Extracted and Exosomes Isolated in Lipidomics Research?

  In lipidomics research, the extraction of lipids and the isolation of exosomes represent two essential procedures. The following summarizes widely adopted techniques for both processes:   Lipid Extraction Two classical protocols are commonly employed: the Folch and Bligh-Dyer methods.   1. Folch Method Samples are mixed with a chloroform–methanol solution at a 2:1 (v/v) ratio, followed by the addition of saline to induce phase separation. This results in a biphasic system: the upper aqueous/methanol p......

• • How Should Non-Normally Distributed Data Be Addressed in Univariate Statistical Analysis?

  In univariate statistical analysis, data normality is typically a key assumption underlying parametric testing. When data deviate from a normal distribution, several strategies can be employed to address this issue:   Applying Data Transformations Transformations such as logarithmic, square root, or Box-Cox can help approximate normality. Following transformation, the data's distribution should be reassessed for normality before proceeding with parametric analyses.   Employing Non-Parametric Tests If ......