Question

describe two (2) experimental techniques that can be used to study the interactions of biological molecules such as peptides with lipids and/or membranes at the cell surface

Answer 1

There are several techniques to study the interaction between peptides and lipids. For example,

• Fluorescence spectroscopy
• NMR spectroscopy
• Infrared spectroscopy
• Surface plasmon resonance
• Electron paramagnetic resonance spectroscopy

1. Fluorescence microscopy:

• This comes under electromagnetic spectroscopy. We are able to arrive at decisions based on the fluorescence of given samples.
• Here basically a source of ultraviolet light is used that excites the electrons present in certain molecules. On excitement, these molecules give out light energy at, lower energy, called the Stokes shift.
• We are able to study the position of proteins and lipids or membrane affinities. A fluorescence tag is given to both the protein and lipid. By doing this, we can figure out the fast kinetics mechanics by which protein gets inserted into the membranes of the cell. The peptides which are bound to the membranes have tryptophan residues that have fluorescence properties. This tryptophan is highly sensitive to the surrounding polarity. So these tryptophan are capable of emitting shorter wavelengths, as a result, intensity also decreases.
• It is a very sensitive technique but not useful for compounds that don't have fluorescence.

2. NMR spectroscopy:

• Also called Nuclear Magnetic Resonance Spectroscopy.
• It involves the absorption of electromagnetic radiation by nuclei of atoms at 9 to 400 MHz radio frequencies.
• It basically works on the principle of creating a magnetic field by the spinning of the electrons. When the molecules move from the excited state to the ground state the emitted radio frequency will be at the same level as the absorbed frequency. This emitted frequency will be read in NMR spectroscopy.
• Solid-state NMR is being used specifically for studying peptide membrane interaction.