15 Circular Dichroism and Related Spectroscopic Techniques
Sophia C. Goodchild Krishanthi Jayasundera and Alison Rodger
Department of Molecular Sciences, Macquarie University, NSW, 2109, Australia
15.1 Significance and Background
Humans navigate the world in which we live largely by vision. Our photoreceptors are able to detect light mainly between 390 and 720 nm. Along with the use of infra‐red (IR) light (which we refer to as heat), sound waves and contact, this means our spatial resolution can range from hundreds of micrometres to of the order of a kilometre. Our spatial resolution is thus about seven orders of magnitude, but we use only a small part of the electromagnetic spectrum and despite our dynamic range we do not approach the molecular level. If we could see the molecular level, we would be overwhelmed by data but would be able intuitively to grasp how biological and other molecular systems work.
We can use different microscopy techniques to improve the dynamic range of our vision. Classical optical microscopy takes our resolution to about half the wavelength of the light used. When one uses electron rather than light microscopy, has ideal samples, low temperature, and quite a lot of computing power, it is now possible to ‘see’ subnanometre structures. The various forms of probe microscopy are also in the same regime, with scanning tunnelling microscopy having lateral resolution of down to ∼0.1 nm and atomic force microscopy a bit higher. These techniques ...