# SELEX Prez

version from 2015-04-12 16:30

## Math/Formulas

Coulombs law (applied to electric fields)F = qE
electrophoretic velocity of a particle in Ev_(ep) = u_(e)*E
electrophoretic mobility of an ion (u_e)directly proportional to the ion charge, inversely proportional to ion size and solvent viscosity
Describe the significance of silonyl groups in CE
Advantages of CE of HPLC1) no peak broadening 2) no stationary phase
Motion of ions inside EOF, do negative ions move towards - electrode too?
Explain why a specific wavelength of light is needed to detect molecules using UV absorbance (UV Vis)exciting electrons (pi & non-bonding electrons) with the correct wavelength of light allows them to jump to a higher energy orbital, these orbitals have energy differences that are discrete and can be related to the wavelength of light through the equation: E = hc/λ which means that the wavelengths (λ) of light too are discrete!
Beer-Lambert LawA=(ɛ)(l)(c) where A = absorbance, ɛ = constant representing pressure temp etc, l = path length (distance light must travel) and c = concentration.

## Presentation - Slide Figures

starts with a large random-sequence DNA pool, this is incubated with the target which is fixed in place

## Chromatography Basics

stationary phasethe (immobile) solid particles in the column through which we pass our mobile phase (solvent) and sample through
mobile phasethe solvent we drip on top of the column (on top of sample) helps to drive the separation process
HPLC vs standard Column Chromatographythe solid particles used are much smaller, this increases the overall surface area available for absorption of the sample

## Detection Methods

difference between fluorescence and UV absorbanceThis technique is complementary to fluorescence spectroscopy, in that fluorescence deals with transitions from the excited state to the ground state, while absorption measures transitions from the ground state to the excited state

## Random Questions

What are the disadvantages of aptamers
What is a proteins isoelectric point - how does this relate to past work on Chromeo P503?
Electrolyte? a liquid (such as the liquid in a battery) through which electricity can pass
can path length of UV absorbance be increased?yes can use bubble or z-cells at detection point, but there is a tradeof increasing path length decreases resolution
Kdis the equilibrium binding (dissociation) constant, in Molar, computed as Koff/Kon
Koffthe dissociation rate constant in min^-1
Konthe association rate constant, in units of M-1 min-1.
Why are aptamers lost through heterogenous phase methods?
Summarize the Beer-Lambert Law as it applies to UV AbsorbanceAbsorbance is propotional to path length * concentration of the analyte, this creates issues for protein detection in CE experiments because the path length = capillary's diameter (~0.1mm) and the protein concentrations present after purification are usually quite low so limits of detection are quite narrow
How is it that DNA will migrate as a single electrophoretic zoneDNA molecules have similar electrophoretic mobilities regardless of sequence
How do certain EOF conditions effect the mobility of protein relative to DNA?in the presence of EOF (bare silica capillaries, positive electrode at injection end of capillary) protein mobility will be higher than that of DNA
If positive polarity is located near the injection end what EOF-related method considerations should be made?under such conditions bare silica capillaries should be used to ensure EOF propels then negatively charged protein/DNA towards the opposite capillary outlet.
If negative polarity is located near the injection end what EOF-related method considerations should be made?under such conditions coated silica capillaries should be used to suppress reverse-EOF and ensure negatively charged DNA and protein reach the capillary outlet
how many rounds of NECEEM-based selection have been sufficient to reach a level of affinity that cannot be improved upon?Three rounds