Biomolecular Structure and Interactions

• QUANTUM THEORY

  • Explains atomic structure, chemical bonding, chemical reactions, spectral colors in absorption and emission, excitation states, and all other properties
  • Theoretical basis of modern physics that explains how matter behaves on the atomic and subatomic level
• • Interaction Principle: To know something, interaction is necessary – every aspect of quantum theory involves interactions
• • Probabilistic Nature: Predicting individual processes is impossible; only probabilities can be determined
  • Instead of exact predictions, measurements yield 'mean data' or the most probable outcomes
• • Particle Representation: Each particle can be represented by a complex wave function
• • Wave-Particle Duality: Quantum wave equation determines whether something behaves as a particle or wave
• • Wave Function in Confinement: Electrons confined in a space exhibit exponential tails within the walls of their confinement
• • Characteristics of Stable Mass: A stable, localizable mass has fixed mass and quantized spin
• Max Planck

  • German Scientist involved in quantum theory
  • Received a Nobel Prize for his discovery of energy quanta
  • Challenged classical mechanics
• Scanning Tunneling Microscopy

  • Works on the principle of the tunneling effect, a quantum phenomenon where particles can pass through barriers
  • Uses a sharp tip that gets very close to the sample
  • Applies voltage between tip and sample, causing electrons to tunnel from sample to tip
  • Tunneling current measured, with higher current indicating a smaller tip-sample distance
  • Provides high resolution (0.1 nm) images of surfaces at the atomic level
  • Invented in 1986, winning a Nobel Prize that same year
• Atomic Force Microscopy

  • Invented as a modification of STM
  • Works by detecting forces between the tip and atoms on the sample's surface
  • Uses a sharp tip that can be attracted or repelled by the sample's atoms
  • Provides information about surface topography and can be used on various materials, including insulators unlike STM
• • AFM operates in three modes:
  • Contact mode: High resolution but risk of damaging the sample due to close tip-sample distance.
  • Non-contact mode: Protects the sample but has lower resolution.
  • Tapping mode: Offers a balance between resolution and minimizing damage.