'Biological Circuit' Components Developed; New Microscope Technique for Measuring Them

The research was conducted by Dawn Bonnell, Trustee Chair Professor and director of the Nano/Bio Interface Center, graduate students Kendra Kathan-Galipeau and Maxim Nikiforov and postdoctoral fellow Sanjini Nanayakkara, all of the Department of Materials Science and Engineering in Penn's School of Engineering and Applied Science. They collaborated with assistant professor Bohdana Discher of the Department of Biophysics and Biochemistry at Penn's Perelman School of Medicine and Paul A. O'Brien, a graduate student in Penn's Biotechnology Masters Program.

Their work was published in the journal ACS Nano.

The development involves artificial proteins, bundles of peptide helices with a photoactive molecule inside. These proteins are arranged on electrodes, which are common feature of circuits that transmit electrical charges between metallic and non-metallic elements. When light is shined on the proteins, they convert photons into electrons and pass them to the electrode.

"It's a similar mechanism to what happens when plants absorb light, except in that case the electron is used for some chemistry that creates energy for the plant," Bonnell said. "In this case, we want to use the electron in electrical circuits."

Similar peptide assemblies had been studied in solution before by several groups and had been tested to show that they indeed react to light. But there was no way to quantify their ambient electrical properties, particularly capacitance, the amount of electrical charge the assembly holds.

"It's necessary to understand these kinds of properties in the molecules in order to make devices out of them. We've been studying silicon for 40 years, so we know what happens to electrons there," Bonnell said. "We didn't know what happens to electrons on dry electrodes with these proteins; we didn't even know if they would remain photoactive when attached to an electrode."

Designing circuits and devices with silicon is inherently easier than with proteins. The electrical properties of a large chunk of a single element can be measured and then scaled down, but complex molecules like these proteins cannot be scaled up. Diagnostic systems that could measure their properties with nanometer sensitivity simply did not exist.

The researchers therefore needed to invent both a new way of a measuring these properties and a controlled way of making the photovoltaic proteins that would resemble how they might eventually be incorporated into devices in open-air, everyday environments, rather than swimming in a chemical solution.

To solve the first problem, the team developed a new kind of atomic force microscope technique, known as torsional resonance nanoimpedance microscopy. Atomic force microscopes operate by bringing an extremely narrow silicon tip very close to a surface and measuring how the tip reacts, providing a spatial sensitivity of a few nanometers down to individual atoms.
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How To Use a CB Radio System

The Citizens Band or CB radio system is used for short distance communications. It is often used in business operations where the base of operations can communicate with employees who are in the field. A CB radio can be used in a vehicle and communicate with other people on a given frequency. On shared frequencies you have to follow a set of rules before jumping into a conversation. If you are going to use the CB radio system for the first time the information below will help you get started.

          Get familiar with the CB radio controls. Before you start up the CB radio system you have to learn a few things about the controls. You’ll be talking on the CB radio in no time as soon as you learn what some of the controls are for and how to use them.
          The Squelch – Use this to control the noise on the radio. Adjusting the squelch control can reduce the noise level and enable strong signals to get through. If you adjust it high enough you can eliminate the sound but you will also cut low and distant signals.
          The Mic Gain – The mic gain increases or decreases your voice volume over the air. You want to leave it at the highest setting so you can be heard by everyone.
          Volume – This only controls the volume of the sound output on your speakers.
          RF Gain – This lessens the strength of the signals coming into your CB radio. Using it will affect both high and low frequencies.
          CH19 – This is the emergency channel on the CB radio. You should remember this in times of emergency.
          PA/CB – When this is switched to PA your voice will only be heard over the speakers.
          ANL and NB – If you pass through areas that have frequencies that can interfere with your CB radio you will get a lot of noise. This will put more focus on communication signals and reduce interference.
Turning on the CB Radio. Plug the power cable into a wall outlet and turn on the power switch on the CB radio. Adjust the controls to reduce noise so you can hear incoming voice signals.
Communicating with others. Make sure your mic gain control is in the highest position and listen in on a frequency. If you hear a conversation going on between two or more people wait until you they are finished or call in a break. Saying “break” over the air will notify those who are talking that you need to call out to someone in particular or just want to send a message to everyone who can hear. Push the mic button to speak and talk into the mic. Say break a couple of times and then wait for your turn. The people on the frequency will let you know when it’s your turn when they say “Go ahead break”.

There are a lot of communication codes that are used on the CB radio. You have to learn all of them to properly communicate with others over the air.
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