 Overview
About IGOR Pro
Versions:
What's New
Features
Force
Acquisition
Analysis
Modification
Help
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Force Acquisition
The MFP1D software interface allows up to four data channels to be collected in a single pull. Data can be collected at a sampling rate up to 20 kHz, meaning that a one second force plot will have 20,000 data points in it. Also built into the force acquisition interface is the ability to pause in mid pull, which we have called "dwell". You can dwell for a set period of time, and then continue on the pull. In addition, there is an ability to do reverse pulls in that the piezo first retracts and then goes forward. In this manner, you can leave the tip in contact with the surface for an extended period time, allowing slower kinetic interactions to occur, and then separate the tip and surface to monitor the forced separation.
There is also no need to maintain the same velocity (non-synched velocities) of the tip for the approach and retract portions. This allows you to approach the surface quickly, collecting fewer data points, while moving away from the surface slowly, or vice-versa. This way you can keep the data points where you need them most.
The 1D system has more specific types of force plots, mostly due to customer request. One example of such is "Dual Pulls", pulls within pulls. A Dual pull may move towards the surface, then move a shorter distance away, switch directions again, and move back towards the surface, and finally move back to where the tip started. This way you can move the tip into the surface, and move it back (hopefully with molecular chains attached). Then you can relax those chains, and then finally stretch those chains until they rupture. This allows you to study relaxation events of the molecular chains on the second time scale.
Additionally there is a data acquisition mode we have termed "Fly-Fishing". Here the Piezo is driven directly by the hamster knob on the controller. This enables you to drive any molecular chains attached to the tip in whatever fashion you feel like, and with a simple way to change the rate at which those chains are driven at. Fly-fishing is an extremely flexible interface for you to perform the custom experiments your studies require.
Force Analysis
A flexible interface has been provided to display any collected or calculated data type vs. any other data type. You can plot time on the Y axis and Force on the X. The interface treats calculated data types the same as any collected data type so that you can plot Force, Tip-Sample Separation, Loading Rate, etc. It is also very easy to display only certain sections of the data. For example, you can show only the dwell data; or both the trace and retrace, but hide the dwell. We have also included a few WLC models in the force analysis software. For example, you can fit multiple stretching events to a single chain model with multiple attachments, such as domain unfolding, or to a multi-chain model each with a single attachment. You can also hold any parameter constant, or constrain it to remain within a given range. Additionally, the multiple responses can be fit with the same persistence length (see Fig 1).
Force Modifications
It is quite easy to recalibrate the optical lever sensitivity in the off-line software. It is then just one more click to apply that value to all the force plots in the directory, and just one more click to save them all again. You have enough to do without having to go through repetitive mind-less hoops that other software packages force you to jump through. An easy to use interface is provided to offset the data in the X and Y axes. Also, extensive help files are provided to help guide you in creating your own custom modifications to the data. |
