Consecutive Antibody Purification for Trace Polypeptide Mass Spectrometry
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Solution Overview
Problem
Current methods for measuring trace polypeptides in biological samples like plasma or serum, which are abundant in impurities, face challenges due to low purification efficiency and ionization suppression, making it difficult to detect polypeptides using mass spectrometry, especially when genetic engineering techniques are not applicable.
Innovation Solution
A method involving consecutive affinity purification using two different antibodies, where a biological sample is first bound to a first antibody-immobilizing carrier, washed, eluted with an acidic solution, neutralized, and then bound to a second antibody-immobilizing carrier for further purification and elution, followed by mass spectrometry detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single affinity purification is used to measure trace polypeptides in biological samples, then the measurement process is simple, but impurity substances remain that suppress ionization and reduce detection sensitivity
Solution Approach 1:
The purification process is divided into multiple sequential affinity purification steps, each using antibody-immobilizing carriers with different specificities. The first purification removes major impurities, and subsequent purifications further reduce remaining contaminants, progressively improving detection sensitivity without requiring a single complex purification step
Solution Approach 2:
Multiple affinity purification steps are performed before mass spectrometry measurement to pre-remove impurity substances that would otherwise suppress ionization. This preliminary removal of contaminants ensures that the subsequent detection can achieve high sensitivity for trace polypeptides
2Measurement precision
If Protein G beads are used to remove impurity substances before affinity purification, then sensitivity of mass spectrometry is improved, but large amounts of plasma (5 mL) are required which limits general applicability
Solution Approach 1:
The method changes the purification parameters by using antibody-immobilizing carriers with high affinity and specificity for the target polypeptide, allowing efficient purification and concentration of the target from smaller sample volumes. This enables high-sensitivity detection without requiring large amounts of plasma
3Reliability
If Tandem Affinity Purification is used to reduce non-specifically adsorbed substances, then contamination is reduced, but the technique requires genetic engineering of tags which is not applicable to plasma or serum samples
Solution Approach 1:
The method uses antibody-immobilizing carriers that can purify various target polypeptides from different biological samples (plasma, serum, cell culture supernatants) without requiring sample-specific genetic engineering. The carriers serve multiple functions across different sample types and target molecules, providing universal applicability
4Reliability
If HA-FLAG-TIN2 is used for TAP with anti-FLAG and anti-HA antibody carriers, then non-specifically adsorbed substances are reduced, but elution efficiency is poor and target protein recovery is insufficient
Solution Approach 1:
The method extracts the target polypeptide from impurity-rich biological samples through multiple affinity purification steps using antibody-immobilizing carriers. Each purification step selectively binds and extracts the target while leaving impurities behind, achieving both contamination reduction and high recovery efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces impurity substances, enhances the binding efficiency of the target polypeptide, and allows for high-sensitivity detection of trace polypeptides even in samples where genetic engineering is not feasible, improving the sensitivity and specificity of mass spectrometry analysis.
Implementation Method 1
a first reaction step of bringing a liquid containing a biological sample into contact with a first antibody-immobilizing carrier that includes a carrier and an antibody bound to the carrier and having an antigen binding site capable of recognizing a target polypeptide, to bind the target polypeptide in the biological sample with the first antibody-immobilizing carrier
Implementation Method 2
a first eluting step of dissociating and eluting the target polypeptide from the first antibody-immobilizing carrier by using an acidic solution to obtain a first eluate
Data Source
AI summary
Provided is a method for measuring a target polypeptide in a biological sample abundantly containing impurities by mass spectrometry. A method for measuring a target polypeptide in a biological sample includes: a first reaction step of bringing a liquid containing a biological sample into contact with a first antibody-immobilizing carrier to bind the target polypeptide in the biological sample with the first carrier; a first washing step of washing the first carrier; a first eluting step of eluting the target polypeptide from the first carrier by using an acidic solution to obtain a first eluate; a neutralizing step of obtaining a first purified solution by adding a neutral buffer to the first eluate; a second reaction step of bringing the first purified solution into contact with a second antibody-immobilizing carrier, to bind the target polypeptide in the first purified solution with the second carrier; a second washing step of washing the second carrier; a second eluting step of eluting the target polypeptide from the second carrier by using an acidic solution to obtain a second purified solution; and a step of detecting the target polypeptide in the second purified solution by mass spectrometry.