We would like to talk about QCM today. QCM is a molecular interaction analyzer based on a very simple principle using the vibration of a quartz crystal plate at a constant speed.

Vibrations are very small amplitudes at the nanometer level, so you can't see them with your eyes. The reason that molecular interactions can be analyzed at a vibrating quartz crystal plate, or more precisely, the electrode (sensor) part of a quartz crystal plate is that frequency decreases as the thickness of the quartz crystal plate changes (sauerbrey equation). When the changed thickness, in other words, molecules bond on the quartz crystal plate, the average film thickness changes slightly according to the number of molecules.

As a result, the weight of the bond is proportional to the amount of frequency change so that you can see the bonding amount of molecules. Our device is, computationally, sensitive enough to detect hydrogen molecules if they bond tightly to the sensor.


QCM is like a precise balance.
So how small molecules can QCM measure?


We have confirmed that a one-amino-acid-sized molecule called cysteine with a molecular weight of about 120 can bind to the gold electrode.

However, as mentioned earlier, we should be able to detect hydrogen with a molecular weight of 1. Why is there no report on the application example? In reality, when you analyze interactions, you need to analyze the interactions between two kinds of molecules.

In this case, the size of the immobilized molecule (host molecule) and the size of the additive (analyte) that reacts with it are important. For example, the binding of a drug (molecular weight of about 300) to an IgG antibody molecule (molecular weight 1.5 million) is difficult to detect. That is because the number of analyte molecular bonds per unit sensor area is small. It is necessary to make adjustments to measure these combinations.

One of our achievements is a measurement system of deoxynivalenol, a well-known toxin in foods, using a competitive reaction with antibodies (May 2011 Japanese Society for Food Hygiene and Safety). In short, if you make the weight of the analyte to be detected relatively large, the experiment will work.


QCM can measure quite complicated systems.
How is the sensitivity of QCM determined?


If a quartz crystal plate is sliced thin, the frequency increases. The higher the frequency, the higher the detection sensitivity.

However, If the quartz crystal plate is cut thin, it will be easy to break and make it difficult to use it. Our sensors use a 27 MHz crystal resonator, and the thickness of the quartz crystal plate is about 60 μm.

In some way, when the sensitivity of the quartz crystal plate (vibration frequency) increases, nonspecific signals also increase, so the most important thing is to establish an experimental method to reduce nonspecific reactions.


QCM has Flow and Batch types.
Why does Initium stick to batch measurement systems?


In the hope of making experiments of molecular interaction accessible to many researchers, we aimed to develop equipment that is inexpensive and easy to use.

We have been manufacturing batch type measurement system for ten years. Although the advantage of the flow system equipment was that it could directly observe the dissociation reaction, and it was easy to automate, we first pursued the advantage of cuvettes (Batch). Everybody wanted a flow system. ( or still wants to a flow system), but the benefits of batch systems have become clear.
From the point of equipment system ① ready-to-use system, ②simple equipment and rarely fails(only two motors were worn out in 10 years), ③The consumables are just sensors, and there are few other maintenance replacements, so there will be no running costs.

From the point of the experiment, ① it can measure for a long time, ② measurement environment can be arranged such as light irradiation. It is also advantageous to observe the state of the reaction liquid during the reaction and to sample the solution during measurement.

Also, from the point of data reliability, ① physical cleaning can be performed ② high stirring efficiency. In many cases, just running the solution through the sensor doesn't make the sensor clean enough.


Easy maintenance and low sunning cost are very attractive.
But isn't it hard to build an experimental system?


Do not worry!

In the QCM industry, we are confident that we have a complete support system.
We will continue to support our customers by providing consultations of measurement protocols and other things after purchase.



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