Isoelectric Point (pI) Analysis Service

What is pI?

The pI refers to the pH value at which a molecule in a certain solution exhibits neither surface charge nor net charge. That is, in a given milieu at a certain pH value, when the positive and negative charges of a molecule are exactly balanced (resulting in a net charge of zero), it will not move towards either the anode or cathode in an electric field. This specific pH value is known as the molecule's pI. Protein is the most important type of biomolecule. There are tens of millions of types of proteins in nature with many structures and functions, but in the final analysis they are determined by the properties of 20 amino acids. Amino acids are amphoteric electrolytes, regardless of the R group, each amino acid molecule has a carboxyl group (-COOH) that can dissociate a proton and an amino group (-NH₂) that can accept a proton. Since different proteins have different amino acid compositions, the pI of a protein only depends on its amino acid composition, which is a physical and chemical constant.

The analysis of pI is an important aspect in proteins or peptides characterization and is often performed to determine the pH at which a protein or peptide has no net charge. Besides, the pI can provide valuable information about a protein's behavior, solubility, stability and function under different pH. In drug development, understanding the pI of a protein can help scientists select the right conditions to purify, stabilize, and store the protein. In addition, the pI of protein can also be used to optimize the separation and purification process to improve purity and yield, which are crucial for comprehending a range of biochemical problems and of great significance for the development and application of biological drugs.

Isoelectric Point (pI) Analysis Service Figure 1. The amphoteric amino acids.

Our Isoelectric Point Analysis Service

In Creative Proteomics, there are primarily four techniques for determining the pI of peptides and proteins.

1) IEF-gel electrophoresis;

2) Capillary isoelectric focusing (cIEF) technology;

3) imaged capillary isoelectric focusing, (icIEF).

Above methods are high-resolution techniques widely employed in pI measurement. The IEF technique is a streamlined and cost-effective solution. In IEF electrophoresis, a protein with a net positive or negative charge migrates through the pH gradient gel until it reaches its pI. The corresponding pH at which the protein remains neutral (or isoelectric) and remains stabilized (halt in movement), is referred to as the protein's pI. The development of IEF has led to the emergence of 2-D polyacrylamide gel electrophoresis (2D-PAGE), cIEF and icIEF. The cIEF and icIEF techniques enable real-time monitoring, prevent sample degradation, offer superior resolution (exhibiting a 10-fold lower limit of detection) and provide faster sample analysis compared to conventional IEF in gels.

Most importantly, all the methods in Creative Proteomics are proficient and precise for measuring the pI of proteins or peptides. In addition, pI assays can also be used in combination with high-throughput liquid chromatography tandem mass spectrometry (LC-MS/MS) techniques. The skills we have mastered notably demonstrate exceptional resolution and accuracy, reproducibility, and high throughput.

Isoelectric Point (pI) Analysis Service Figure 2. The IEF technology.

Applications of pI Analysis

Protein precipitation;
Protein purification, stabilization, and store;
Protein crystallization trials;
Drug development;
Enzyme development;
Antibody research;
Study protein heterogeneity, including isoforms, PTMs, and protein truncations;
Analyze protein folding status;
Predict protein-protein interactions.

How to place an order

The expertise of Creative Proteomics, with over 10 years of experience in proteins and peptides isoelectric point analysis and proteomics profiling, enables us to provide comprehensive support tailored to your specific requirements for pI analysis. Please feel free to contact us via email whenever you need to discuss your specific requirements. Our customer service representatives are available 24 hours a day, from Monday to Sunday.

How to place an order

Proteomics Sample Submission Guidelines

Ensure your samples are prepared and submitted correctly by downloading our comprehensive Proteomics Sample Submission Guidelines. This document provides detailed instructions and essential information to facilitate a smooth submission process. Click the link below to access the PDF and ensure your submission meets all necessary criteria.

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* For Research Use Only. Not for use in diagnostic procedures.

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From Our Clients

"I recently used their proteomics service for a project analyzing protein interactions in yeast models. The team was very responsive and helped clarify the methodology they employed, which made me feel confident in the results. The data quality was solid, with clear identification of several key proteins involved in our study. Their thorough analysis enabled me to pinpoint specific interactions that I hadn't considered before, which significantly improved the direction of my research. I appreciate their professionalism and support throughout the process."

Sarah Thompson, University of California, Berkeley

"Our lab collaborated with them on a project studying cancer biomarkers. The proteomics analysis provided was detailed and focused, specifically highlighting the differential expression of proteins between healthy and tumor samples. Their clear explanations of the data helped my team understand the biological implications. I also appreciated their willingness to revise the reports based on our feedback, ensuring that we had everything we needed for our publication. This collaborative spirit was invaluable."

Emily Rodriguez, Stanford University

"Our lab worked with them on a project studying the effects of diet on gut microbiota using proteomics. They used a label-free quantification method to analyze proteins in fecal samples before and after dietary intervention. The results showed significant changes in protein expression linked to microbial activity. This was pivotal for our hypothesis about diet-microbiota interactions. The clarity of their data presentation made it easy for our team to integrate these findings into our ongoing research."

Dr. Lisa Wong, University of Toronto

"My experience with Creative Proteomics during the mass spectrometry analysis was excellent. We sent in human saliva and mouse brain tissue samples, which they expertly analyzed using both LC-MS and GC-MS techniques. The results were invaluable, revealing key metabolites in the saliva and identifying biomarkers linked to brain function in the brain tissue."

Dr. Emily Carter, Senior Research Scientist

"The overall service from Creative Proteomics was outstanding. They made the entire process seamless and efficient, allowing us to focus on our research. We worked with leaf and root samples from various Arabidopsis genotypes for targeted metabolomics analysis. Their thorough profiling of primary and secondary metabolites gave us important insights into how the plants respond metabolically to environmental stress."

Dr. Laura Henderson, Plant Physiologist

"We had a pleasant collaboration with Creative Proteomics on mass spectrometry analysis of lipids. They conducted a detailed analysis of lipid species, providing us with important insights into lipid metabolism and its relationship with metabolic syndrome disease states."

Dr. Sarah Mitchell, Research Scientist

Online Inquiry

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