Signal Patch clamp details

Patch clamp electrophysiology

The latest version of Signal for Windows incorporates many powerful new features for whole cell and single channel experiments that make Signal ideal for electrophysiological recording. The use of familiar terms and easy set up protocols for standard requirements enable the experimenter to get started quickly. Signal also incorporates an import function allowing you to analyse data from other recording systems.

Stimulus generation

Generate stimuli on up to 8 DACs and 8 TTL lines.
Define as many as 256 sets of up to 500 pulses.
Set stimuli at a fixed level or relative to an adjustable holding potential or current.
Output multiple sets of arbitrary waveforms per sweep. Waveforms are held in 1401 memory for very accurate timing.
Sequence through sets of pulses manually, cyclically, randomly or by user-defined protocol.
Interactively edit, add and remove stimuli while recording.
Define pulses with fixed or stepping amplitudes and durations.
Pulse types include square waves, ramp, sinusoid, pulse trains and pre-recorded or user-generated waveforms, for example, recorded action potentials.

Clamp specific sampling support

Set up a particular recording state to be used for seal and membrane resistance measurements.
Easy adjustment of holding potentials.
Dynamic readout of seal resistance.
Support for dynamic clamp studies with up to 15 selectable conductance models. Update rates of up to 100kHz glitch free.
Membrane analysis option displays measurements of total resistance, access and membrane conductance, capacitive transient decay time constant and membrane capacitance.
Display selected measurements as a graph against time.

Amplifier communication

Telegraph communication to set channel scales based on voltages supplied from a wide range of patch clamp amplifiers.
Direct software communication with Axon Instruments MultiClamp 700A/B. Reads values for gains, filter settings, membrane capacitance, series resistance and external command sensitivity. The values read are stored in the Signal data file.

Leak subtraction

3 methods of defining leak data.
Multiple on-line model methods for leak subtraction when using dynamic clamp
On-line and off-line subtraction of scaled leak trace, including capacitive transients.

Single channel analysis
Idealised trace generation converts the waveform to a set of events describing the state of the channel(s) at the time of each transition point. Details include time, duration, mean amplitude and flags for open/closed, first latency and level.

View details of individual events. Edit events by dragging times and levels or setting values in a dialog.
Superior detection of short events with SCAN analysis.
Interactively insert and remove events.
Open/closed time and amplitude histograms from idealised traces.
Amplitude histograms produced from original data.
Include/exclude events based on associated flags.
Idealised trace generation and analysis are available on-line as well as off-line.

Curve fits
Fit mathematical functions to original or leak subtracted data and trend plots.

Fit types include:
- Exponential, first or second order
- Gaussian, one or two
- Polynomials from first to fifth order
- Sigmoid (Boltzmann) curve
Gives best fit coefficients and an estimate of confidence.
Display fit coefficients in trend plots.

Trend plots
The trend plot function in Signal generates a graph of measurements taken from the recorded data both on-line and off-line. For each frame selected, measurements are taken and plotted as X and Y coordinates. A typical example would be the generation of an IV curve.

Identify positions for measurements either manually or by setting 'active cursors' to seek for data features.
Extensive range of available measurements including levels, times, fit coefficients, areas, means, slopes, RMS amplitudes and standard deviations.
Plot up to 32 independent sets of measurements with optional log axes.
Easy export of results to spreadsheet.

Advanced features

The output sequencer provides advanced control functions including fast access to incoming data. This can be used in many ways, for example, to generate a stimulus ramp and halt ramping immediately upon detection of an action potential.
The script language provides the user with the ability to customise the system for particular requirements. This is used for automation and to add specific functions not available through the menus, for example non-standard leak subtraction routines. Script control can also enhance standard functions including the option of higher order curve fits.