Formulation of DNA and proteins MCQs With Answer

Formulation of DNA and proteins MCQs With Answer

Introduction: This quiz collection focuses on formulation principles for proteins and DNA relevant to M.Pharm students. It covers molecular stability, degradation pathways, excipient selection, delivery strategies, analytical techniques and process considerations such as lyophilization, buffer choice, surfactant use and metal ion control. Questions aim to deepen understanding of how formulation science preserves biological activity, minimizes aggregation and nuclease degradation, and optimizes delivery for therapeutics and vaccines. Answers include concise rationales embedded in option phrasing to aid learning. Use these MCQs for exam preparation, classroom review and practical formulation problem-solving to reinforce critical design choices used in modern biopharmaceutical development.

Q1. Which level of protein structure is defined directly by the linear sequence of amino acids?

• Primary structure (amino acid sequence)
• Secondary structure (α-helix, β-sheet)
• Tertiary structure (3D folding)
• Quaternary structure (subunit assembly)

Correct Answer: Primary structure (amino acid sequence)

Q2. What is the most common molecular driving force for non-native protein aggregation in therapeutic formulations?

• Hydrophobic interactions between partially unfolded molecules
• Enzymatic proteolysis by residual proteases
• Covalent glycation with excipients
• Reversible ionic pairing with buffer ions

Correct Answer: Hydrophobic interactions between partially unfolded molecules

Q3. What is the primary purpose of lyophilization (freeze-drying) for protein and DNA therapeutics?

• Remove water to stabilize labile biomolecules for long-term storage
• Sterilize the product by heat-induced denaturation
• Concentrate the formulation by removing salts
• Induce controlled aggregation to improve immunogenicity

Correct Answer: Remove water to stabilize labile biomolecules for long-term storage

Q4. Which excipient is widely used as a non-reducing disaccharide lyoprotectant to stabilize proteins during drying?

• Trehalose (non-reducing disaccharide)
• Sodium chloride (tonicity agent)
• EDTA (metal chelator)
• Polysorbate 80 (surfactant)

Correct Answer: Trehalose (non-reducing disaccharide)

Q5. What is the principal role of nonionic surfactants such as polysorbate 20 or 80 in protein formulations?

• Prevent surface adsorption and reduce agitation-induced aggregation
• Adjust solution pH to the protein’s stability range
• Act as primary antimicrobial preservatives
• Increase osmolarity to isotonic levels

Correct Answer: Prevent surface adsorption and reduce agitation-induced aggregation

Q6. Why is PEGylation commonly applied to therapeutic proteins?

• Increase circulation half-life and reduce immunogenicity
• Increase enzymatic activity by exposing active sites
• Promote rapid renal clearance for safety
• Enhance covalent aggregation for depot effect

Correct Answer: Increase circulation half-life and reduce immunogenicity

Q7. Which formulation strategy helps protect DNA from nuclease degradation during storage?

• Inclusion of chelators (e.g., EDTA) to remove divalent cations required by DNases
• Raising ionic strength with high concentrations of NaCl
• Adding protease inhibitors to the buffer
• Using methanol as a cosolvent to denature nucleases

Correct Answer: Inclusion of chelators (e.g., EDTA) to remove divalent cations required by DNases

Q8. Which criterion is most important when selecting a buffer system for a protein formulation?

• Buffer pKa within ~1 unit of target formulation pH to minimize pH shifts
• Maximum ionic strength to stabilize all proteins
• Use of organic buffers exclusively to prevent microbial growth
• Always choose phosphate buffers regardless of protein

Correct Answer: Buffer pKa within ~1 unit of target formulation pH to minimize pH shifts

Q9. How does trehalose stabilize proteins in a lyophilized (dry) cake?

• By forming a vitrified glass matrix that immobilizes protein and preserves native structure
• By acting as a strong reducing agent to prevent oxidation
• By donating protons to buffer pH changes during storage
• By chelating metal ions that catalyze aggregation

Correct Answer: By forming a vitrified glass matrix that immobilizes protein and preserves native structure

Q10. Which description best matches a nucleation-dependent aggregation mechanism for proteins?

• Nucleation followed by growth of aggregates (nucleation-dependent polymerization)
• Single-step reversible unfolding without aggregate growth
• Proteolytic fragmentation producing increased monomer population
• Covalent cross-linking exclusively by disulfide bonds from the native state

Correct Answer: Nucleation followed by growth of aggregates (nucleation-dependent polymerization)

Q11. Which analytical technique is preferred for quantifying soluble protein aggregates and oligomers in formulation development?

• Size-exclusion chromatography (SEC) for soluble aggregates and oligomers
• SDS-PAGE under reducing conditions only
• ELISA for total protein content
• Mass spectrometry for aggregate size distribution

Correct Answer: Size-exclusion chromatography (SEC) for soluble aggregates and oligomers

Q12. Which preservative is commonly used in multidose parenteral protein formulations to prevent microbial growth?

• Benzyl alcohol used as a preservative in multidose parenteral formulations
• EDTA as the primary antimicrobial preservative
• Trehalose as an antimicrobial agent
• Glycerol as the sole preservative for injectable proteins

Correct Answer: Benzyl alcohol used as a preservative in multidose parenteral formulations

Q13. How does proximity to a protein’s isoelectric point (pI) typically affect its solubility and formulation stability?

• Proteins are least soluble and more prone to aggregation near their isoelectric point (pI)
• Proteins are most soluble near the pI due to increased charge repulsion
• There is no effect of pI on solubility in buffered systems
• Proteins only aggregate at pH values far from their pI

Correct Answer: Proteins are least soluble and more prone to aggregation near their isoelectric point (pI)

Q14. Which delivery strategy is commonly used to increase cellular uptake of plasmid DNA in vaccine formulations?

• Use of cationic lipids/nanoparticles to complex DNA and enhance cellular uptake
• Formulation with high concentrations of anionic polysaccharides
• Simple dilution in saline without carriers
• Encapsulation in hydrophobic oils only

Correct Answer: Use of cationic lipids/nanoparticles to complex DNA and enhance cellular uptake

Q15. What is the primary destabilizing effect of trace transition metal ions in protein formulations?

• They catalyze oxidative degradation (e.g., via Fenton-type chemistry)
• They act as cryoprotectants during freeze–thaw
• They significantly increase solution viscosity
• They always stabilize tertiary structure through coordination

Correct Answer: They catalyze oxidative degradation (e.g., via Fenton-type chemistry)

Q16. Which excipient is commonly used as a cryoprotectant to reduce freeze–thaw damage to proteins in aqueous formulations?

• Glycerol (cryoprotectant reducing ice-induced damage during freeze–thaw cycles)
• Polysorbate 80 to lower melting point of ice
• EDTA as primary cryoprotectant
• Sodium chloride for cryoprotection

Correct Answer: Glycerol (cryoprotectant reducing ice-induced damage during freeze–thaw cycles)

Q17. What osmolarity is generally targeted for parenteral protein formulations to match physiological conditions?

• Approximately 300 mOsm/kg (isotonic with plasma)
• Less than 50 mOsm/kg to avoid cell swelling
• Over 1000 mOsm/kg to ensure protein stability
• Osmolarity is irrelevant for parenteral formulations

Correct Answer: Approximately 300 mOsm/kg (isotonic with plasma)

Q18. Which technique is commonly employed to remove bacterial endotoxins (LPS) from protein or DNA preparations?

• Ion-exchange and affinity chromatographic methods (e.g., polymyxin B) are commonly used for endotoxin removal
• Simple filtration through 0.22 µm sterile filter removes endotoxin completely
• Heat sterilization at 100°C eliminates endotoxin activity without affecting biomolecules
• Dialysis against water removes endotoxin quantitatively

Correct Answer: Ion-exchange and affinity chromatographic methods (e.g., polymyxin B) are commonly used for endotoxin removal

Q19. During primary drying in freeze-drying, what critical parameter must be controlled to prevent collapse of a protein cake?

• Maintain product temperature below the collapse temperature (Tc) and control chamber pressure to sublimate ice efficiently
• Increase product temperature above Tg to speed drying
• Use the highest possible chamber pressure to avoid sublimation
• Eliminate annealing steps to preserve structure

Correct Answer: Maintain product temperature below the collapse temperature (Tc) and control chamber pressure to sublimate ice efficiently

Q20. Which spectroscopic technique is most widely used to monitor changes in protein secondary structure (α-helix vs β-sheet) during formulation studies?

• Circular dichroism (CD) spectroscopy for monitoring protein secondary structure (α-helix, β-sheet)
• Reversed-phase HPLC to resolve secondary structure elements
• Size-exclusion chromatography to detect α-helix content
• Ion mobility mass spectrometry for routine secondary structure quantitation

Correct Answer: Circular dichroism (CD) spectroscopy for monitoring protein secondary structure (α-helix, β-sheet)

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