Biophysics Expert

Before Starting

1. Which biological system? (protein, membrane, cell, tissue)
2. Structural, mechanical, or dynamic properties?
3. Experimental or theoretical approach?

Core Expertise Areas

Single Molecule Techniques

Optical tweezers: laser trap applies piconewton forces, measures nm displacements. Magnetic tweezers: magnetic bead manipulation, torque and force measurements. AFM force spectroscopy: unfold proteins and measure force-extension curves. FRET: fluorescence resonance energy transfer, measures nanometer-scale distances. Single molecule fluorescence: track individual molecules in living cells.

Membrane Biophysics

Lipid bilayer: two leaflet structure, fluid mosaic model, selective permeability. Membrane tension: controls cell shape, migration, and mechanosensing. Patch clamp: measure single ion channel currents in picoampere range. Lipid rafts: cholesterol-rich ordered domains, organize signaling proteins. Vesicle mechanics: osmotic pressure, Helfrich elasticity, flickering spectroscopy.

Protein Mechanics

Protein folding: hydrophobic collapse, hydrogen bond formation, funnel energy landscape. Mechanical unfolding: stepwise unfolding domains detected by AFM or optical tweezers. Motor proteins: myosin, kinesin, dynein convert chemical energy to mechanical work. Worm-like chain: polymer model for DNA and unfolded proteins, persistence length.

Biological Imaging

Confocal microscopy: optical sectioning, fluorescence, subcellular resolution. TIRF: total internal reflection fluorescence, single molecule sensitivity at surface. STORM and PALM: super-resolution beyond diffraction limit, 20nm resolution. Cryo-EM: near-atomic resolution protein structures, complement to X-ray crystallography.

Best Practices

• Always include appropriate controls for fluorescence experiments
• Correct for photobleaching in long single molecule recordings
• Validate single molecule observations with ensemble measurements
• Consider thermal fluctuations in all nanoscale measurements

Common Pitfalls

Pitfall	Fix
Ignoring thermal noise at nanoscale	kBT = 4 pN nm, comparable to biological forces
Fluorescent label affecting protein function	Test labeled vs unlabeled activity
Surface effects in single molecule assays	Use appropriate blocking and surface chemistry
Confusing correlation with mechanism	Mechanistic interpretation needs additional experiments

Related Skills

• cell-biology-expert
• molecular-biology-expert
• physics/quantum-mechanics-expert