Creative Biolabs offers dual-polarization interferometry (DPI) services, which provide exquisite sensitivity to give previously unavailable insights into the structural changes taking place in molecular systems as they function and interact. DPI resolves protein structure to subatomic dimensions in real time and is typically used to characterize biochemical interactions by quantifying any conformational change at the same time as measuring reaction rates, affinities and thermodynamics.

Introduction

DPI measures the structure of a protein in one dimension (i.e. its diameter or size) and the density (i.e. its mass per unit volume or how tightly folded it is) by coupling the protein to a glass slide and probing its structure using non-diffractive optics. DPI offers the ability to quantify changes in the thickness and density on the chip surface, shape orientation, binding & conformational changes, membrane behavior and interactions, etc.

Data generated from our DPI quantitative structural measurements can be compared directly with complimentary techniques such as X-ray crystallography, NMR and neutron reflection, whilst also being capable of functional measurement at far higher sensitivity and with less ambiguity than classical optical and acoustic biosensor technologies.

Other optional antibody analysis services:

• Antibody Characterization
• Antibody Affinity Measurement
• Hybridoma Sequencing Service
• De Novo Antibody Sequencing Services
• Precision Paratope Mapping Service
• Monoclonal Antibody Epitope Binning
• SPR Services
• Isothermal Titration Calorimetry (ITC) Services
• Differential Scanning Calorimetry (DSC) Services

Published Data

• The Lipid and Membrane Recognition by OSBP and Its Phosphomimetic Mutant Using DPI

Fig. 2 Interaction of OSBP with immobilized DOPC bilayer on DPI sensor. (Parthajit Mukherjee, 2018)

Oxysterol binding protein (OSBP) can bind, extract, and transfer sterols and phosphatidylinositol-4-phosphate (PI(4)P) between liposomes. Here, the researchers used double polarization interferometry (DPI) to characterize the interaction of OSBP flowing through immobilized dioleoyl-phosphatidylcholine (DOPC) bilayers containing PI(4)P, cholesterol, or 25-hydroxycholesterol. They analyzed the kinetics of membrane interaction between phosphorylated mutant OSBP and PI(4)P binding.

FAQ

1. What is dual-polarization interferometry and how does it work in protein analysis?

   DPI is an analytical technique used to measure the molecular size, shape, and conformational changes of proteins in real-time. It involves the use of two polarized light waves passing through a sample, allowing for precise measurements of changes in the optical properties of the layer where the protein is immobilized. DPI provides detailed insights into protein interactions, binding kinetics, and structural dynamics.

2. What are the advantages of using DPI for protein analysis?

   DPI offers several advantages including label-free detection, which means that proteins do not need to be modified with fluorescent or radioactive labels. This preserves the natural state of the protein, providing more accurate data on its behavior and interactions. DPI can also simultaneously measure multiple parameters such as thickness, density, and mass, providing comprehensive information about the protein under study.

3. What type of samples can be analyzed using DPI?

   DPI can analyze a wide range of biological samples including pure protein solutions, complex biological mixtures, and even intact cells. The technique is highly versatile and can be used to study proteins in various environments, such as in solution, attached to surfaces, or within lipid bilayers. It is particularly useful for studying membrane proteins and protein-protein interactions.

4. How sensitive is DPI in detecting protein interactions and changes?

   DPI is highly sensitive and capable of detecting very small changes in protein structure and interactions. It can measure layer thickness changes as small as a fraction of a nanometer, making it suitable for detecting subtle conformational changes that occur during protein binding events. This sensitivity makes DPI an excellent tool for detailed studies of protein function and interaction dynamics.

5. Can DPI measure protein interactions with small molecules and ions?

   DPI is effective in measuring interactions between proteins and small molecules or ions. This capability allows researchers to study how proteins bind with ligands, drugs, or metal ions, which is crucial for drug discovery and understanding enzymatic mechanisms. DPI provides insights into the kinetics and affinity of these interactions, helping in the identification and optimization of potential drug candidates.

6. What are the limitations of using DPI for protein analysis?

   One key limitation is the requirement for immobilization of the protein on a sensor surface, which can potentially alter its natural behavior or activity. Additionally, DPI requires relatively large amounts of sample compared to other techniques like surface plasmon resonance (SPR), and the setup and analysis can be complex, requiring skilled operation and interpretation.

7. How does DPI compare to other biophysical techniques like SPR or ELISA?

   DPI provides more comprehensive data than techniques like SPR or ELISA because it can simultaneously measure multiple biophysical properties such as mass, thickness, and refractive index. Unlike ELISA, DPI is label-free, which avoids potential issues with label interference. Compared to SPR, DPI offers higher resolution in the measurement of layer properties, though SPR may be more sensitive in detecting very low-affinity interactions.

8. What kind of data analysis is required for DPI measurements?

   Data analysis for DPI involves interpreting interference patterns generated by the interaction of polarized light with the protein layer. This analysis can be complex, requiring software that can model the refractive index and thickness of the layer to quantify molecular interactions and changes. The data provide insights into molecular mass, structural alterations, and binding kinetics, requiring careful analysis to ensure accuracy and relevance to the biological questions being investigated.

Resources

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