Unit 4- Analytical Techniques Flashcards
Define isoelectric point.
pH at which the amino acid has a net charge of zero (aka as a zwitterion).
Describe three features of the structure of DNA that X- ray crystallography helped Rosalind Franklin identify.
Any of: DNA forms a double helix, DNA is double stranded, Twists very 3.4 nm, 10 basepairs/twist. phosphate grps on the outside of double helix
Gel electrophoresis separates proteins on the basis of what two factors?
Size and charge
A hexagon shape present in X-ray crystallography indicates?
Benzene ring
Identify two factors that affect the overall charge on a protein
The type of amino acids in the polypeptide chain and the pH of the chemical environment
In chromatography, what is the mobile phase?
A liquid or gas that carries the sample molecules along the column or TLC plate
In chromatography, what is the stationary phase?
Solid particles to which the sample molecules adsorb
In mass spectroscopy, what does the M+1 peak indicate?
The presence of carbon 13 isotopes.
In mass spectroscopy, what does the M+2 peak indicate?
The presence of a halogen.
In mass spectroscopy, what does the M peak indicate?
Molecular mass of the molecular ion.
The key information gained from IR spectroscopy is?
Functional groups present
Name the two types of stretching vibration modes in IR spectroscopy
Symmetric and antisymmetric stretching
True or false? A cationic exchange column has a negatively charged stationary phase (solid support)
TRUE
True or False? All bond types, polar and non-polar, will give
rise to a band in an IR
FALSE. IR active bonds must be polar
True or FALSE? A substance to be
separated by TLC that is strongly attracted to the stationary phase will travel more slowely than a substance that is not strongly attracted.
TRUE
True or False? Electron density maps can not be created from X-ray diffraction patterns.
FALSE
True or False? Strongly polar bonds produce weak bands in an IR spectrum
FALSE
TRUE or FALSE? The longer the protein sample is in the chromatography column the higher the retention time.
TRUE
True or False? The strength with which proteins bind to the solid support in a cationic exchange column is determined by the relative degree of negative surface charge on each different protein.
TRUE
True or False? Weakly polar bonds produce weak bands in an IR spectrum.
TRUE
What does a peak at 15m/z in mass spectroscopy indicate?
Methyl fragment CH3+
What does a peak at 29 m/z in mass spectroscopy indicate?
Ethyl fragment CH3CH2+ or aldehyde CHO+
What is the amino acid charge if the pH<pI?
Negative
What is the amino acid charge if the pH>pI
Positive
