heliX®
General Questions
switchSENSE® is a biophysical research technology to investigate molecular interactions. The core of this technology are DNA nanolevers attached to gold microelectrodes. These DNA nanolevers can easily be customized with any ligand of choice. The orientation of the nanolevers can be controlled by applying voltage to the microelectrodes. We differentiate two measurement modes in switchSENSE® experiments, the dynamic mode and the static mode. In dynamic mode, an alternating voltage is applied, causing the negatively charged DNA nanolevers to oscillate at high frequencies. In static mode, a negative voltage is applied to hold the nanolevers in a static, upright orientation. The nanolevers are additionally equipped with a fluorescent dye. The readout signal of a switchSENSE® experiment is a change in fluorescence intensity. This can be caused by multiple events. For example, the local environment of the dye can change due to e.g. binding of an analyte to the ligand. Furthermore, the gold electrode surface quenches the dye, thus changes in the distance between the dye and the sensor surface will affect the fluorescence intensity. Some assays also include a second fluorescent dye and changes in intensity are caused by Förster resonance energy transfer (FRET) between the two dyes (see Which options do I have for dual-color assays? for details). Based on these measurement modes you can characterize your molecular interactions in great detail, ranging from kinetic rates to conformational changes of binding partners. Find out more about the technical details of switchSENSE® here.
The heliX+ is equipped with 2 lasers and 4 single-photon counters. This allows to collect signals from two different fluorescent dyes for each of the two measurement spots. You have many options to use this for your specific assay requirements:
- Multiplex and measure 4 different binding events in parallel
- Measure 2 different binding events at the same time and at the same sensor spots, e.g. for avidity analyses of bispecific binders
- You can functionalize one measurement spot with two different ligands and additionally adjust the specific density for each of them to mimic the ligand density on the cell surface. This is especially helpful when analyzing for example bispecific antibodies to differentiate between the affinity of the two antibody epitopes and the avidity
- Measure ternary complex formation
- Using the specialized Y-structure DNA nanolevers you can investigate any kind of ternary binding, e.g. PROTACs or molecular glues.
- Measure specific induced conformational changes
- You can exploit the FRET effect to investigate for example aptamer folding or RNA loop formation or any conformational changes with site-specific labels
switchSENSE® is a very versatile technology and offers comprehensive biophysical information. You can measure the following parameters:
Kinetics (association rate kon, dissociation rate koff)
Affinity, Avidity (Kd)
Dose response (EC, IC50)
Multispecific interactions (e.g. bispecific antibodies)
Ternary complex formation / proximity induced binding (e.g. PROTACs)
Conformational changes
Relative changes in protein size
Nucleic acid enzyme binding and activity (kcat, KM)
Your analyte of interest can be anything ranging from small molecules to peptides and proteins and even multispecific binders like antibodies or PROTACs. If you have questions concerning the applicability of your specific analyte, contact our specialists!
Your ligand of interest can be a single-strand RNA or DNA sequence, a double-strand RNA or DNA sequence, an aptamer, a small molecule, a protein or peptide of any desired size, a liposome, a virus-like particle, or whatever else you can think of. If you have questions concerning the applicability of your specific ligand, contact our specialists!
During a measurement in dynamic mode, the DNA nanolevers are switched by applying an alternating voltage to the gold electrode, whereas in static mode they are kept in an upright orientation by a constant negative potential.
- The dynamic mode is usually used to investigate conformational changes.
- The static mode can be used for kinetic measurements as well as the investigation of bispecific binders, protein-protein interactions or enzymatic activity measurements.