Fold & Function
Hemoglobin’s quaternary structure consists of these subunits
What are 2 α-globin + 2 β-globin (a heterotetramer)?
Protein concentration is commonly measured by absorbance at this UV wavelength
What is 280 nm?
SDS coats polypeptides so they all carry this charge in proportion to their mass, which lets the gel separate them by size alone
What is a negative charge?
Solved 3D protein structures are deposited in this public database
What is the Protein Data Bank (PDB)?
This glowing fusion tag was used as a proof of concept for transferring genes into cats
What is GFP (green fluorescent protein)?
This iron-containing porphyrin ring is hemoglobin’s prosthetic group
What is heme?
In size-exclusion (gel filtration) chromatography, these proteins come off the column first
What are the largest proteins?
In a Western blot, incubating the membrane with milk or BSA before adding antibodies is called this step
What is blocking?
A CD spectrum with negative bands at 222 nm and 208 nm and a positive band at 195 nm indicates this secondary structure
What is an α-helix?
In a pull-down where protein X is the bait, you probe the Western blot with an antibody against this
What is protein Y (the prey), not X?
This single amino acid substitution in β-globin causes sickle-cell anemia
What is Glu6Val (E6V)?
Your POI has a pI of 6.5 and sits in pH 7.4 buffer. Name the column type it binds and a pH buffer that would elute it
What is an anion exchanger (DEAE), eluted with a pH 6.0 buffer?
Trypsin cleaves after these two residues, unless the next residue is proline
What are lysine (K) and arginine (R)?
This technique was used to solve the SARS-CoV-2 spike in weeks. It needs no crystals, uses tiny sample amounts and suits complexes over 100 kDa
What is cryo-EM?
Formaldehyde is a non-specific example of this technique, which traps weak or transient interactions with covalent bonds
What is chemical cross-linking?
The normal prion PrPC is mostly α-helical, but the misfolded, infectious PrPSc is mostly this
What are β-strands / β-sheets?
His-tagged proteins bound to a Ni²⁺-NTA resin are eluted with this free molecule
What is imidazole?
Edman degradation removes residues one at a time from this end of a polypeptide, and it is limited to roughly this many residues
What is the N-terminus, ~100 residues?
An IR amide I band between 1620 and 1640 cm⁻¹ points to this secondary structure, as seen when a prion misfolds
What is β-sheet?
In this method, the biotin ligase BirA is fused to a POI and biotinylates any protein within ~10 nm. Streptavidin beads then pull those proteins out
What is BioID?
Your body makes many different IgG antibodies, and they are told apart mainly by this
What are differences in primary sequence?
A casein drink claims 10 g/L. A280 = 0.823, ε = 11,000 M⁻¹cm⁻¹, l = 1 cm and MW = 25,000 g/mol. The actual concentration is in g/L.
What is ≈ 1.87 g/L?
In mass spec, a serine-containing fragment shows a mass jump from 87 to 167 amu (+80). This explains it
What is phosphorylation (phosphoserine)?
RNase (a cytoplasmic globular protein with buried Trp) is treated with urea + BME. Predict the change in Trp fluorescence.
What is a red shift (longer wavelength, lower intensity)?
Unlike FRET, this distance-dependent assay needs no external light source, because its donor is an enzyme reaction that makes light
What is BRET (bioluminescence resonance energy transfer)?