Protein Interaction Coupling (PICO)
Our proprietary Protein Interaction Coupling (PICO) technology enables the high-throughput analysis and absolute quantification of proteins, protein interactions, and post-translational modifications using digital PCR technology. To learn more, read our PICO Handbook for a comprehensive overview.
The unique features of PICO:
- Ultra-high sensitivity (upper femtomolar with ordinary antibodies)
- Absolute quantification (quantifying molar amounts without an external standard)
- Small sample input (down to 0.5 µL or a few hundred cells)
- Zero background
- Easy multiplexing (measure up to three targets simultaenously)
- Digital assay (counting individual molecules)
- Homogeneous (workflow without washing steps)
Watch our technology explainer video below to learn about the basic principles of PICO:
The PICO Workflow
Antibody selection and labeling
After the selection of target-specific antibodies (1), the antibodies are conjugated with unique DNA oligonucleotides (PICOglue Labels) to form ready-to-use binding agents (2) for the PICO assay.
Lysis, mixing & incubation
The biological sample is lysed (1), mixed, and incubated with the labeled antibodies (2). During the incubation, 'couplexes', targets bound by two different labeled antibodies, are formed (3).
Sample dilution and partitioning
The sample is highly diluted (1), loaded onto a dPCR plate, and partitioned into thousands of partitions. The high dilution ensures single molecules per partitions (2).
Digital PCR reaction
During the dPCR reaction thousands of partitions are simultaneously amplified and specific fluorescent signals are generated (1). Couplex-containing partitions are detected and counted as double positive partitions, here labeled with green color (2).
Data analysis with AMULATOR
The raw dPCR data is uploaded to AMULATOR, Actome‘s online data analysis software (1). AMULATOR converts the couplex count into molar concentration (2).
What can PICO measure?
In a PICO Assay you can use a total of four different labeled antibodies. Using two labeled antibodies allow the detection of a single target (e.g. a single protein, a protein interaction, or a post-translational modification). Using three or four labeled antibodies opens up the possibilities to detect up to three targets simultaneously. Check out all the possibilities below!
Two-color PICO Assays
Single protein quantification
Protein interaction quantification
Post-translational modification quantification
1. Single proteins - by using two antibodies recognizing different accessible epitopes of the same protein
2. Protein interactions - by using two antibodies, each targeting one of the interacting proteins
3. Post-translational modifications (PTM) - by using one antibody targeting the protein and one antibody targeting the PTM of the same protein
Three- or four-color PICO Assays
Multiplex PICO Assay
Triangular PICO Assay
Quadratic PICO Assay
1. Two individual targets - all combinations of a 2-color PICO Assay are possible
2. 'Triangular measurement' - quantify the total amount of a protein and its modification simultaneously (phosphorylation, methylation, acetylation, etc...)
3. 'Quadratic measurement' - allowing to quantify an interaction and both interaction partners
Compatible digital PCR devices for PICO
PICO is compatible with both QIAGEN and Stilla digital PCR systems. If you are a digital PCR company and would like employ PICO on your instrument let's get in touch.
QIAcuity Digital PCR System - QIAGEN
The QIAcuity is a nanoplate-based digital PCR instrument that comes in 1-, 4-, or 8-plate format. It can detect five different fluorescent dyes that are fully compatible with the PICO Probes and the entire PICO workflow.
Nio™ Digital PCR - Stilla Technologies
The Nio™ digital PCR instruments employ the proprietary Crystal Digital PCR® technology for partitioning the samples into a large array of thousands of individual droplet crystals. The instrument is available in three different configurations and its fluorescent channels are compatible with the PICO Probes and the entire PICO workflow.
naica® system - Stilla Technologies
The naica® dPCR instrument, simillarly to the Nio™, employs the proprietary Crystal Digital PCR® technology for partitioning the samples into a large array of thousands of individual droplet crystals. Its fluorescent channels are compatible with the PICO Probes and the entire PICO workflow.
