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Enthalpy
Arrays
Detecting Molecular Interactions
Enthalpy Arrays enable faster,
more cost-efficient biological
research
and
drug discovery
through direct measurement of molecular interaction.
Direct measurement and thorough characterization
of molecular interactions, such as protein-ligand
binding, enzymatic turnover, and protein-protein,
could open up a wide range of possibilities in
proteomics research and pharmaceutical development.
Performing these measurements on a large scale
can enable researchers to accurately, efficiently,
and cost effectively characterize specific interactions-such
as the thermodynamic nature of a drug-target interaction
or screening for proteins that react with a drug
candidate-which can boost productivity and significantly
reduce product development time.
Through its partnership with the Scripps Research
Institute, PARC has developed a calorimetric based technology
– known as an enthalpy array
– that allows scientists
to analyze and determine molecular interactions,
without tampering with sample reactivity through immobilization or labeling.
Available Technologies
Traditionally, isothermal
titration calorimetry is the method of choice to
characterize the thermodynamics of molecular interactions.
While the approach is widely used in drug discovery
and basic sciences, the level of use is severely
hampered by large sample requirements and long
measurement times.
On the other hand, biochemical
assays, such as fluorescent labeling, were developed
for high-throughput
screening, but these methods do not provide a complete
thermodynamic characterization of the reaction.
What's needed: a nanocalorimetry method that
addresses sample size, improves measurement time,
and provides thermodynamic characterization ability.
PARC Approach
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Enthalpy
Arrays are fabricated in a standard 96-detector
format to
interface with automated laboratory equipment.
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PARC's enthalpy arrays address the key needs of molecular interaction
measurements, including:
- measurement speed;
- small
sample size;
- no modification of reagents; and
- accurate
thermodynamic characterization of fast-reacting
samples.
Fabricated using microscale technology
in a standard 96-detector format, the enthalpy
arrays interface with automated laboratory equipment.
Using these arrays, scientists at PARC and the
Scripps-PARC institute have measured the enthalpies
of reaction for several different types of biological
interactions, including protein-ligand binding
reactions, enzymatic reactions, and organelle activity.
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Sample
and reference specimens are mixed in identical
detector regions,
providing differential temperature measurement.
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How It Works
Each detector cell in the array
consists of two identical
adjacent detector regions that provide a differential
temperature measurement-one for the sample and
one for a reference specimen. Each region is
equipped with two amorphous silicon thermistors
combined in an interconnected Wheatstone bridge,
and each region also has its own isothermal merging
and mixing mechanism that is electrostatically
driven.
After the mixing of two small
(appx. 250 nl) drops, the detector measures the
temperature change relative to a simultaneous merging
of similar but non-reacting materials in the adjacent
detector region. This relative measurement effectively
subtracts out correlated background drifts in temperature
and other factors. When the temperature relative
to the reference cell changes, the voltage output
of the bridge changes proportionally.
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