Book contents
- Frontmatter
- Contents
- Preface
- 1 Once upon a (length and) time (scale). . .
- 2 The molecules of life – an idiot’s guide
- 3 Making the invisible visible: part 1 – methods that use visible light
- 4 Making the invisible visible: part 2 – without visible light
- 5 Measuring forces and manipulating single molecules
- 6 Single-molecule biophysics: the case studies that piece together the hidden machinery of the cell
- 7 Molecules from beyond the cell
- 8 Into the membrane
- 9 Inside cells
- 10 Single-molecule biophysics beyond single cells and beyond the single molecule
- Index
3 - Making the invisible visible: part 1 – methods that use visible light
Published online by Cambridge University Press: 05 February 2013
- Frontmatter
- Contents
- Preface
- 1 Once upon a (length and) time (scale). . .
- 2 The molecules of life – an idiot’s guide
- 3 Making the invisible visible: part 1 – methods that use visible light
- 4 Making the invisible visible: part 2 – without visible light
- 5 Measuring forces and manipulating single molecules
- 6 Single-molecule biophysics: the case studies that piece together the hidden machinery of the cell
- 7 Molecules from beyond the cell
- 8 Into the membrane
- 9 Inside cells
- 10 Single-molecule biophysics beyond single cells and beyond the single molecule
- Index
Summary
It is very easy to answer many of these fundamental biological questions; you just look at the thing! . . . Unfortunately, the present microscope sees at a scale which is just a bit too crude.
(Feynman, 1959)GENERAL IDEA
In this chapter we discuss the techniques which are available to the experimental scientist who wishes to visualize or detect single biological molecules primarily using visible light, both in the test tube and in the living cell.
Introduction
How can we ‘see’ something like a single biological molecule, which is of the order of a thousand million times smaller than a typical object in the macroscopic world that we visualize with our naked eyes? The region of the human eye responsible for detecting light, the retina, consists of two types of cells called rods and cones (rods differ by being 100 times more sensitive than cones but they respond more slowly, have less spatial resolution and do not discriminate colour), both of which can convert detected photons of light into electrical signals, conveyed via ion channels and nerve fibres into the brain. The resolving power of the human eye, the visual acuity, is a measure of the smallest angular separation that the eye can resolve, which for humans has a theoretical limit equivalent to ~0.01°, about 20 milliradians, determined by the limit of optical diffraction set by the wavelength of the incident light and the diameter of the aperture in front of the ‘imaging device’ (here set by the pupil of the eye), as shown in Figure 3.1A.
- Type
- Chapter
- Information
- Single-Molecule Cellular Biophysics , pp. 60 - 101Publisher: Cambridge University PressPrint publication year: 2013