Protein Analysis FAQ

• • How to Determine Protein Size Based on the Gel

  During SDS-PAGE, a molecular weight marker—comprising a set of proteins with known molecular weights—is typically loaded into one lane of the gel. After electrophoresis, these standard proteins produce a series of bands, each corresponding to a specific molecular weight. The sample and the molecular weight marker are run simultaneously in SDS-PAGE. Upon completion of electrophoresis, the migration position of the sample band on the gel is observed and compared with the bands of the adjacent molecular.......

• • Why Does the Protein Band Broaden After Moving from Stacking to Separating Gel in SDS-PAGE

  In the process of SDS-PAGE electrophoresis, protein samples are first loaded onto the stacking gel and then migrate into the separating gel. These two types of gels serve different functions and possess distinct physicochemical properties: 1. Stacking Gel This gel is characterized by a low polyacrylamide concentration and relatively large pore size. It does not separate proteins based on molecular weight. Instead, its primary function is to concentrate all proteins into a sharply focused zone, thereby......

• • Classification of Serotonylated Histones Within Post-Translational Modification Types

  5-hydroxytryptamine (5-HT, also known as serotonin) modification of histones is classified as serotonylation, a distinct form of post-translational modification (PTM) that has gained increasing attention in recent years. Serotonylation involves the covalent attachment of serotonin molecules to specific amino acid residues on proteins, such as the formation of an amide bond with glutamate residues. This type of modification plays a role in regulating various physiological processes in living organisms.......

• • What Is Species Variation in Proteins

  Species variation in proteins refers to differences in protein sequences, structures, and functions across different species or populations. These variations arise through evolutionary processes and reflect both the phylogenetic relationships among species and their adaptive strategies to distinct environments. Species Variation in Protein Sequences Each species possesses a unique genome, and the proteins encoded by these genes often differ in their amino acid sequences from those of other species.

• • Desalting Following Protein Separation and Purification: Where Do These Salts Originate

  Desalting is frequently required following protein separation and purification. The salts present at this stage primarily originate from endogenous ions within biological systems (e.g., Na⁺, K⁺, Cl⁻), buffer salts used in extraction solutions, salts contained in elution buffers, and ionic components introduced by certain denaturants. Elevated salt concentrations can adversely impact protein activity, stability, and interactions with other molecules. Moreover, residual salts may interfere with downstream....

• • How to Analyze Differential Proteins Obtained from Proteomics

  When investigating specific biological processes, diseases, or therapeutic interventions, it is often essential to analyze proteins that are differentially expressed under varying conditions. Once these differential proteins are identified—commonly through techniques such as mass spectrometry or two-dimensional electrophoresis—the subsequent step involves their in-depth analysis and interpretation to elucidate their roles and biological significance: Functional Annotation 1. Utilize databases such as.......

• • What Is the Principle of Tandem Mass Spectrometry

  Tandem mass spectrometry (commonly referred to as MS/MS or MS²) enables the detailed characterization of molecules by sequentially separating and detecting ions through two or more stages of mass spectrometric analysis. This approach is particularly effective for identifying molecular components within complex samples—such as proteins, peptides, and various organic compounds—and is extensively utilized in biochemistry, pharmaceutical research, environmental science, and related fields. The fundamental......

• • Is There a Specific Experimental Method for Cross-Linking Protein Interaction Analysis? How to Select a Cross-Linking Agent

  Cross-linking protein interaction analysis generally consists of three major steps: the cross-linking reaction, protein separation, and detection. For example, in an in vitro cross-linking experiment: 1. Cross-Linking Reaction The target protein solution is mixed with a selected cross-linking agent, allowing the reaction to proceed under appropriate conditions. Cross-linking agents can be broadly classified into chemical cross-linkers and photo-cross-linkers. Commonly used chemical cross-linkers include....

• • How to Convert the Results, Content, and Proportion of Monosaccharide Composition Determination

  Monosaccharides are carbohydrates that cannot be further hydrolyzed into simpler molecules. Many complex polysaccharides, including cellulose and starch, can be hydrolyzed to monosaccharides through acid treatment. By analyzing the hydrolysis products, the types and relative proportions of monosaccharides present in the original polysaccharides can be determined. The conversion process is as follows: 1. Experimental Results First, determine the total concentration of all monosaccharides in the sample.

• • What Should Be Done When SDS-PAGE Bands Contain Multiple Protein Bands in Protein Sequencing?

  When a section of an SDS gel contains more than one protein band, these bands may correspond to distinct proteins or various isoforms, including alternative translation products or forms modified post-translationally. To accurately identify the amino acid sequence of each protein individually, it is necessary to further separate and purify these proteins. The following methods are typically employed to address SDS gels with multiple protein bands:   1. SDS-PAGE Optimization Initially, perform a second......