This document discusses chemical modifications of proteins. Chemical modifications can be done intentionally to study structure-function relationships, develop new products, or improve existing ones. Modifications are used in fields like pharmacology, food production, and industry. Specific modifications discussed include sulfhydryl and disulfide modifications by oxidation, and reduction of disulfide bonds. Applications mentioned are in basic protein chemistry, food and nutrition to prevent deterioration or alter properties, and pharmaceuticals to alter biological properties, target drug delivery, or influence drug lifetime in the body.

1. Chemical Modifications of
Protein
Presented To: Dr. Rafiq Ahmed
Presented By: Zohaib Hussain
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2. Protein Engineering
Problem
Solving
Technique
Technology Research
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3. Chemical Modifications
Modification
Reactive
Side Chains
Oxidation Reduction Nucleophilic Electrophilic
Natural
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4. Deteriorations
Peptide bond scissions
Racemizations
β-eliminations
Formation of products
Reaction of proteins with added chemicals.
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5. Why chemical modifications?
• Modified intentionally
• Structure-function relationship
• Studies or for development of new products
• Improved products
• The techniques used in pharmacological, food and feed, or other
industrial areas
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6. Sulfhydryl and disulfide
• Catalytic sites of a wide variety of enzymes
• Maintenance
• Inactivation of SH enzymes by iodine
• Modify cysteinyl, tyrosinyl, tryptophanyl
resiudes
• Acidic pH, low temp, and excess of reagent
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7. Mechanism
• Human serum albumin and tobacco mosaic
virus
• Ovalbumin ,8-lactoglobulin, dihydrofolate
reductase, and papain
• Oxidation with iodine will led to the formation
of suIfenyl iodide derivatives.
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8. Recovery
Sulfenyl derivatives
sulfhydryl
• On addition of thiols
• Recovery of enzymatic activity,
• With the reduction, ranges from 50-100%.
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9. Reduction of Protein Disulfide
Bonds
WITH PARTIAL OR TOTAL RETENTION OF BIOLOGICALACTIVITY9

10. Application in Basic Protein
Chemistry
• Reactive and Active site modifications
• To alter physical and biological properties
• Radio-isotopic labeling
• Modifications for analytical proposes
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11. Applications For Food and
Nutritional Purposes
• Blocking of deteriorative reactions
• Physical properties
• Flavor and color
• Nutritional properties
• Aid the physical separation form crude
• Inactivate/remove undesirable substances
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12. Blocking of deteriorative
reactions
• Stages harvesting, processing, cooking, storage
• Brown color of bread crust
• Millard reaction (non-enzymatic browning)
• In-solubilize, colored, off-flavours
• Nutritive loss and possibility of toxicity
• Acetylation, methylation, isopropylation
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13. Texturization
• Protein rich products-Structure, Shape, texture
• Resemble those of conventional food products
• Meat Like materials from plant proteins-fillers
• Textured proteins- High pH, Substances-
Neutralization-desired physical property
• Recemization-serine
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14. Functional Properties
• Gelling ability, solubility, viscosity
• Contribution to nature of food product
• Baking industry-Proteins modified chemically
• Oxidants- Consistency and strength
• Enhance mechanical strength-disulfide
interchanges
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15. Application in Pharmaceuticals
• Interaction of proteins-Chemical reagents
• Drug act by direct inactivation of a target
molecule
• Covalent combination with the drug
• Naturally occurring toxins results in the body
• Chemical warfare
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16. Life time of drug
• Protein hormones
• Lower their rate of removal from the
bloodstream
• Efficiency/Frequency of admnistration
• Animal insulin by coupling to protamine-zinc
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17. Target Specific Transport
• To transport the substances to targets site
• Radioactive iodine or toxic substances attached to
antibodies in attempts to kill cancer cell
• Drugs-irreversible enzyme inhibitors
• Modifications for altering biological properties
• Glutaraldehyde's cross-linking effect on proteins is in
the preparation of prostheses for internal organs, e.g.
heart valves
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18. Every Ending is Just a Really New Beginning
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