Model answers – lecture 11a – 11b
1. The two main elements for electronic sensing of chemical effects are: recognition of chemical and signal transduction
3. Electrochemical transduction relies on:
flow of electric current or change in potential during electrochemical reactions
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4. One of the essential elements for designing a pregnancy test is:
5. Blood glucose detectors measure the amount of sugar in blood by using a multistage chemical process.
The glucose reacts with glucose oxidase in the strip to make gluconic acid.
Gluconic acid reacts with ferricyanide to produce ferrocyanide. This process results
in a current flow that can be detected by an electrode.
The recognition and transduction methods used in this sensor are:
Quiz 2: (Covid-19 lateral flow test)
Covid-19 lateral flow test is designed to detect SARS-CoV-2 antigens using chromatography in a way similar to the pregnancy test discussed earlier.
What are the key requirements for the design of this test?
A sensor is designed to detect a chemical target (A) by selecting a recognition element
(R). For this sensor to be reliable:
D: option (B and C) are the two essential considerations
Note: It should recognise A with high specificity and selectivity and also the product of
the interaction should be stable
all of the above
Note: a reliable test has a self-check mechanism. It is highly specific and selective to the
target as well as being low cost and easy to use.
enzyme recognition (i.e glucose oxidase reaction with glucose to produce gluconic acid)
and electrochemical transduction (the redox reactions of Ferricyanide )
Reliability – the test is designed to be highly selective to SARS-CoV-2 antigens to
minimize false positive and should also be equipped with a self-check mechanism
to ensure that antibodies are working properly
2. It can detect SARS-CoV-2 antigens with adequate sensitivity
Quiz 3- (MRI):
1. One of the inventors of MRI is: Sir Peter Mansfield
2. The precession rate of a proton depends on:
3. Spatial information in MRI is obtained by: frequency encoding using gradient coils
4. Contrast in MRI is obtained from: relaxation times after applying RF pulse
5. Dynamic information (e.g. brain activity) in MRI is obtained by measuring blood oxygenation levels
All of the above
Note: it depends on the type of the atom, the chemical environment and the externally
applied static magnetisation
How can we obtain magnetic resonance spectrum of ethanol?
Using NMR spectroscopy, an RF pulse is applied to the ethanol sample targeting
hydrogen atoms and RF coil then detects the signal emitted due to the relaxation to
the initial longitudinal magnetisation. The resulting time domain signal is analysed
using fast Fourier transform to identify the peaks in the frequency spectrum that are
indicative to the different covalent bonds between hydrogen and oxygen as well as
hydrogen and carbon. The obtained signal is very weak and therefore averaging after
multiple repeats is required to increase signal-to-noise ratio.
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