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protein preparations Flashcards

1
Q

What are proteins composed of?

A

amino acids (base) linked by amide bonds

fibrous and globular

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2
Q

examples of fibrous proteins

A

mechanical functions

  • hair
  • skin
  • bones
  • connective tissue
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3
Q

examples of globular proteins

A

enzymes
antibodies
inhibitors

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4
Q

How many AA does insulin have?

A

55 AA (peptide)

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5
Q

What formulations are proteins given in?

A

injection

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6
Q

How are therapeutic proteins formed?

A

extracted from natural sources

OR

engineered in a lab
- recombinant deoxyribonucleic acid (rDNA) technology or gene cloning

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7
Q

examples of biopharmaceutical proteins

A 
vaccines
recombinant proteins
blood products
enzymes
mAb
nucleic acid-based therapeutics
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8
Q

Brand name for recombinant human insulin

A

Humulin

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9
Q

What challenges are there with proteins/insulin?

A

producing stable and biological active therapeutic protein for LT storage

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10
Q

When AA join what do they form?

A

proteins

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11
Q

How do AA join?

A

by formation of a peptide bond

1 molecule of water is released (condensation)

COOH—NH2

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12
Q

What are peptide bonds susceptible to?

A

hydrolysis

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13
Q

What is primary structure of a protein?

A

linear sequence of AA

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14
Q

What is secondary structure of proteins?

A

polypeptide chain folds and turns by H bonding

-> gives alpha helices and beta sheets

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15
Q

What is tertiary structure of proteins?

A

folded, native or 3D structure

  • biologically active in this shape
  • protein can have biological effect
  • polypeptide chains become functional
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16
Q

What is quaternary protein structure?

A

Ig or antibody structures (large molecules)

several protein chains packed together

held together by H bonds, van der Waals forces

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17
Q

chemical instability of folded/native proteins

A

deamidation (Glu, Asp)
oxidation (His, Met, Cys)
peptide bond hydrolysis
disulfide exchange

-> leads to irreversible denaturation

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18
Q

physical instability of folded/native proteins

A 
temperature
pressure
pH (ionisation)
surface adsorption (contsiner/package)
aggregation

-> reversible denaturation

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19
Q

challenge with proteins - aggregation

A

aggregation is a problem in high conc formulations

may lead to loss of efficacy/safety

based on surrounding environmnt (pH, ionic strength, temp, excipients, stress)

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20
Q

deatured proteins

A

unfolded

not active

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21
Q

What happens if you remove water from proteins?

A

forms dry proteins

inaccurate native structure due to protein protein interactions

-> not active if dry, need water (reconstitute back to native structure)

22
Q

Why are surfactants used in protein formulations?

A

act as a stabiliser during processing to prevent destruvtive effect of heat/shear

23
Q

Whay are sugars added as an excipient?

A

sugars prevent interactions between protein molecules

help proteins stay in native structure

24
Q

2 excipients used to protect proteins from air-liquid interface effect

A

sugars

surfactants

25
preferential hydration of proteins
water molecules have higher affinity for protein than excipients
26
What is preferential binding of proteins?
excipients have higher binding to the surface of the protein excludes water
27
How to make proteins stable?
co-solute omitted from surface of protein interactions with water molecules more desirable than interactions with additive formation of a 'hydration shell' around protein required for protein activity
28
What is a 'hydration shell'?
water molecules interact with protein surface and bind more desirable than interaction with additive shell required for protein activity
29
How are proteins in liquid form given?
injections solutions for nebulisation
30
What maintains protein stability in liquid form?
additives
31
examples of additives
``` sugars polymers cyclodextrins salts (pH, ionic strength) non-ionic surfactants ```
32
examples of sugars used as additives
trehalose mannitol sucrose
33
What pH is insulin soluble at?
pH < 5
34
What form of proteins is more stable for LT storge?
solid forms
35
excipients in powder protein formulations
bulking agents (trehalose, lactose) salt (NaCl)
36
properties of injection formulations
sterile isotonic clear after reconstitution low viscosity
37
What techniques are used to produce proetins in dried powder forms?
freeze drying spray freeze drying spray drying supercritical fluid technology
38
difference between freeze drying and spray freeze/spray/supercritical fluid tech
freeze drying - cannot produce dried protein particles with controlled particle size the others - can produce protein particles with controlled particle size (< 5 micro m)
39
What can spray drying modify?
particle size and shape particle surface texture
40
What does spray drying do?
- particles dissolved/suspended in a liquid | - converts contents of solution/suspension into powder in 1 step
41
steps of the spray drying process
1. atomisation of the liquid as fine droplets into a hot air stream by spray nozzle 2. atomisation creates a large SA and rapid evaporation of the solvent 3. after droplets dry, the powder is separated from the air stream by cyclone separator
42
What properties of the drying chamber affect droplet stability?
protein denaturation water content hot gas in contact with protein droplets
43
What properties of the air intake affect droplet stability?
pH, protein, additives concs flow rate temperature
44
What properties of the dry product affect droplet stability?
LT stability packaging storage conditions particle shape
45
What spray drying variables affect the resulting particle size?
1. spray pattern 2. conc of solute 3. air flow system
46
Why is protein denaturation minimal?
cold water is circulating around the protein solution AND presence of protein solution droplets in drying chamber is for a short time
47
What types of particles can spray drying produce?
solid particle hollow particle cenosphere
48
What additives are good/bad to stabilise proteins?
good - poly vinyl pyrrolidone bad - methacrylic acid (destabilises freeze dried proteins)
48
What additives are good/bad to stabilise proteins?
good - poly vinyl pyrrolidone bad - methacrylic acid (destabilises freeze dried proteins)
49
What is Circular Dichroism used for?
characterises secondary and tertiary structure of proteins in solutions

PHA223 (43 decks)

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