Proteins Flashcards
(31 cards)
What are proteins made up of
Amino acid, joined by peptide bonds
3 special cases of amino acids
Proline, Cysteine, Glycine
Types of intramolecular forces
Covalent bond, ionic bond
Types of intermolecular forces
Hydrogen bond, Dipole-dipole, Dispersion
Chemical stability depends on _____ structure of the protein
Primary
Length of oligo peptide (units: amino acids)
n < 20
Length of polypeptide (units: amino acids)
20-50
Two types of secondary structure
alpha-helix, beta-pleated sheet
How does protein secondary structure arise
Hydrogen bonding between amino hydrogen and carboxyl oxygen in the peptide backbone (not from R groups)
Name the covalent bond used in protein tertiary structure
Disulfide bond
How are protein quarternary structures formed
Interactions between separate tertiary structures
Same types of bonds, just between chains rather than within a chain
Protein shapes and their respective functions
Globular - catalyze reactions
Fibrillar - provide structure
Common proteins + what are they made up of
Collagen - alpha-chains
Elastin - major component of tissue, arteries, elastic ligaments, skin, bladder
What is fibronectin? What is is important for?
ECM non-collagenous adhesive proteins
Organizes matrix and enables cell attachment
Very important for endothelial cell function and viability
What is topography
Surface roughness
3 cases of protein - surface interactions
- In vitro, single (component/protein), low concentration
- In vitro, single (component/protein), high concentration
- In vivo, multi (component/protein), high total protein concentration
Which case is adsorption?
Singe component, low concentration
What factor dominates protein-surface interaction?
Opposite charge attraction and hydrophobic/hydrophilic interactions to drive the initial adhesion event
Steps of time-dependent spreading
- Protein sticks to random areas of surface, possibly in reversible fashion
- Previously adsorbed proteins begin reorienting + spreading out on the surface. Then, they become irreversibly adsorbed. New proteins continue to adsorb to open surface areas.
- Process continues until most of the available surface area is covered with irreversibly adsorbed proteins.
- When surface is exposed to buffer solutions, the reversibly adsorbed proteins desorbs.
- irreversibly adsorbed proteins remain
Keep in mind
- Proteins are not rigid structures
- They can undergo structural alterations with the surface
- Microenvironment of the protein (pH, ionic strength) can further alter a protein’s conformation
- Even though conformation changes upon adhesion to a surface, the protein retains some biological activity
What are immuno globins (Ig)?
Antibodies
Process of competitive protein adsorption to a surface
- Low mw proteins come in first, binds to surface
- Low mw proteins are replaced by less mobile, bigger proteins that have a higher affinity for the surface
Which have bigger size (low mobility/high mobility)?
Low mobility proteins are bigger in size compared to high mobility proteins
What is the name of effect in which protein adsorption is based on size and mobility?
Vroman effect
