Biomolecular Interaction Technologies Center: www.bitc.unh.edu at /

Word	Symbol	Definition
Chromophore		A group of atoms and electrons which form part of an organic molecule and cause it to be colored.
Diffusion Coefficient (Diffusivity)	D	Proportionality constant between the mass flux due to diffusion and the concentration gradient of the species. The higher the diffusion coefficient the faster the components diffuse into each other.
Electroosmotic flow		Often abbreviated as EOF, this is the motion of ions in a solvent through a narrow channel caused by an applied electric potential.
Ellipticity	Q	The angle of polarization in degrees or millidegrees resulting from plane-polarized light passing thorough an optically active substance.
Evanescent Wave		Standing waves formed when sinusoidal waves are internally reflected off an interface at an angle greater than the critical angle, causing internal reflection. Their intensity decays exponentially with the distance from the interface.
dn/dc		Also referred to as the specific refractive index increment, it describes how much the refractive index of a polymer solution changes with respect to the concentration of the solute.
Flourescence Anisotropy	r	Method for measuring the binding interaction between two molecules.
Frictional Coefficient	f	This factor, which depends on the size and shape of the particle being analyzed, contributes, along with the velocity, to the drag force experienced by the particle during a sedimentation run in analytical ultracentrifugation.
Incident Plane of Polarization		For a polarized incident beam, the incident plane of polarization is the plane along which the incident beam waves are polarized.
Joule heating		Process by which the passage of an electric current through a conductor releases heat. Also known as Ohmic or resistive heating.
Mobility		The rate at which a substance moves in electrophoresis. Ion charge, field strength, ion shape, and the coefficient of friction all factor into this rate.
Multi-photon Excitation		Multi-photon excitation, or MPE, is a fluorescence detection method by which high-intensity laser pulses cause the excitation of two or more photons in a fluorophore , which creates a much stronger signal for detection, allowing greater sensitivity or smaller sample volumes.
Optically Asymmetric Environment		Microenvironment, such as that found in a folded protein, which causes an otherwise achiral chromophore to absorb left- and right- circularly polarized light differently
Partial Specific Volume	vbar	This is a measure of the change in the volume (ml) of the solution per gram solute. This value is used in analytical ultracentrifugation analysis and often calculated using programs such as Sednterp but can be measured, although this requires a fair amount of material. For calculated estimates, the amino acid compostion is needed. A 1% error in vbar will propagate to a 3% error in molecular weight determinations by AUC.
Pegylated		Addition of polyethylene gylcol polymers.
Photobleaching		Photobleaching is the process by which fluorophores are destroyed photochemically over time. FRET uses this phenomonon by detecting energy transfers among molecules to determine molecular confirmation, association, and separation distances.
Plane Polarized		Plane polarized light occurs where the light waves have been synchronized to oscillate along a single plane.
Quantum Dots		Quantum dots are semiconductor nanostructures that confine the movement of their valance electrons resulting in a discrete quantized energy spectrum. Their photostability allows much greater sensitivity when used in fluorescence applications than typical organic fluorophores.
Refractive Index		The refractive index is a ratio that compares the speed of light in a vacuum to the speed of light though a substance. In SPR, molecules bound to the surface of a chip change this property measurably, thus providing information about the molecules.
RMS radius		The RMS radius, or root mean squared radius, is a method of mathematically compensating for the constructive and destructive phase interactions of the laser when measuring the radius of larger molecules.
S_(20,w) Values		While AUC results may yeid S values as S_(xp) dependant on the actual conditions of the experiement, they can often be corrected to S_(20,w) standard conditions - as if the experiment had been performed at 20°C in water - for ease of comparison.
Sauerbry Relation		This is a relationship between mass on the surface of a quartz crystal, and the resonance frequency of the quartz. Thus, the quartz can be used as a microbalance.
Sedimentation Coefficient	S	Ratio of velocity of sedimentation of a molecule to the centrifugal force required to produce this sedimentation.
Stokes-Einstein Relation	Df=K_bT	Relates the translational diffusion coefficient to the frictional coefficient, assuming globular molecular shape.
Virial Coefficient	B_i	In a multi-particle system, the virial expansion can be used to express the pressure in equilibrium. The virial coefficients relate to the interactions between the particles of the system.

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