protein structures
Page 1: Introduction
Title: Structure of the Protein
Presenter: Dr. Zeba un Naher, MBBS MD (Clinical Biochemistry)
Affiliation: Assistant Professor, Maldives School of Medicine, Maldives National University
Page 2: Objectives
Describe: Chemical and physical properties of proteins and their functions.
Classifications: Different classes of proteins in relation to their functions.
Explain Structures: Primary, secondary, tertiary, and quaternary structures of proteins.
Separation Principles: Principles of separation for proteins.
Page 3: Physical Properties of Proteins
Taste and Odor: Pure proteins are generally tasteless and odourless, though hydrolysates can taste bitter.
Colloidal Nature: Proteins exhibit properties due to their large molecular size, behaving as colloids.
Amphoteric Nature: Proteins contain both acidic and basic groups.
Page 4: Further Properties of Proteins
Electric Mobility: Proteins possess electrically charged groups, allowing them to migrate in an electric field.
Labile Characteristics: Many proteins can be modified by pH changes, UV radiation, heat, and organic solvents.
Absorption Spectrum: Absorption maximum at 280 nm due to tyrosine and tryptophan.
Page 5: Chemical Properties of Proteins
Colour Reactions of Proteins
Importance: Used for qualitative and quantitative detection of proteins.
Biuret Test: Violet color indicates multiple peptide bonds; involves a copper coordination complex.
Page 6: Additional Chemical Properties
Xanthoproteic Reaction
Chemistry: Yellow color with nitric acid but changes to orange when alkaline due to phenyl ring nitration.
Hopkins-Cole Reaction
Process: Reaction of indole ring of tryptophan with glacial acetic acid forms a purple product.
Page 7: Classes of Proteins by Function
Structural: Provide components (e.g., collagen, keratin).
Contractile: Movement of muscles (e.g., myosin, actin).
Transport: Carry substances (e.g., hemoglobin, lipoproteins).
Storage: Store nutrients (e.g., casein, ferritin).
Hormonal: Regulate metabolism (e.g., insulin, growth hormone).
Enzymatic: Catalyze reactions (e.g., sucrase, trypsin).
Protection: Immune response (e.g., immunoglobulins).
Page 8: Four Levels of Protein Structure
Primary Structure: Linear sequence of amino acids.
Secondary Structure: Stable configurations due to hydrogen bonding.
Tertiary Structure: 3D conformation due to folding.
Quaternary Structure: Assembly of subunits.
Page 9: Primary Structure and Folding
Definition: Sequence of amino acids specifying protein structure.
N-terminus and C-terminus: Ends of the polypeptide chain.
Page 10: General Characteristics of 3D Structure
Conformation: Determines protein function.
Types of Proteins: Globular, fibrous, transmembrane.
Requirements for Shape: Specific binding and flexibility.
Page 11: Peptide Backbone Structure
Composition: Joined by peptide bonds with limited bending.
Importance: Dictates secondary and tertiary structure.
Page 12: Arrangements of Molecules
Conformation: Various spatial arrangements due to single bond rotations.
Page 13: Peptide Backbone
Structure: Sequential links through peptide bonds, influencing protein function.
Page 14: Additional Insights on Primary Structure
Importance: Encodes information crucial for higher structure folding.
Detection: Mass determined by spectrometry (sequencing).
Page 15: Secondary Structure
Metaphor: Similar to folding a paper airplane; structure affects function.
Recurring Structures: α-helix and β-sheet, stabilized by hydrogen bonds.
Page 16: Key Types of Secondary Structure
Patterns: Two main folding patterns—α-helix and β-sheet.
Stability: Hydrogen bonds contribute stability.
Page 17: More on Secondary Structure
Characteristics: Description of α-helix and its arrangements.
Proline Positions: Affects structure; not favored in the middle.
Page 18: Tertiary Structure
Maintaining Forces: Hydrogen bonds, ionic bonds, disulfide bonds, and hydrophobic interactions.
Domains: Independent structural regions within proteins.
Page 19: Tertiary Structure Dynamics
Hydrophilic and Hydrophobic Regions: Importance in 3D arrangement and protein solubility.
Page 20: Quaternary Structure
Definition: Formation of a functional protein complex from subunits.
Metaphor: Like building with Lego blocks; specific arrangement is key.
Example: Hemoglobin with four subunits.
Page 21: Visualization of Protein Structure
Illustration: Different protein structures and their organization from primary to quaternary.
Page 22: Functions of Quaternary Structure
Advantages: Increases protein stability, reduces genetic coding requirements, and enhances reaction speed.
Page 23: Protein Separation Techniques
Role: Crucial for protein study and clinical applications.
Methods: Based on properties like solubility, size, charge.
Page 24: Purification Methods Recap
Significance: Essential for identifying abnormal samples in labs.
Page 25: Characteristics of Proteins
Molecular Weight: Sum of amino acid masses in daltons or kilodaltons.
Importance of Assays: Critical for protein location post-fractionation.
Page 26: Types of Assays
Spectroscopic Assays: Color change indicates protein presence.
Immunological Assays: Use antibodies as a detection system.
Page 27: Centrifugation Basics
Process Explanation: Uses centrifugal force to separate components based on density.
Page 28: Dialysis in Medicine
Methods: Hemodialysis vs. peritoneal dialysis, both maintain body balance and remove waste.
Page 29: Column Chromatography Overview
Separation Strategies: Sizes, charge, and affinity determine how proteins are separated.
Page 30: Gel Filtration Chromatography
Explanatory Mechanism: Small molecules traverse resin longer than larger ones.
Page 31: Ion Exchange Chromatography
Separation Based on Charge: Differentiating anions and cations using buffers for protein loading.
Page 32: Electrophoresis Overview
Motion under Electric Field: Separates based on size and charge; anionic and cationic movement.
Page 33: SDS-PAGE Details
Methodology: Denatures proteins to linear forms for size-based separation.
Page 34: Role of Antibodies
Function: Attack antigens, critical for immune defense.
Epitopes: Specific binding sites crucial for antibody recognition.
Page 35: Antibody Development
Process: Injection into animals to trigger immune response and produce polyclonal antibodies.
Page 36: Western Blotting Technique
Importance: Separates and analyzes low-abundance proteins through gel transfer.
Page 37: Post-Electrophoresis Protocols
Membrane Binding and Blocking: Prevents non-specific antibody binding after protein transfer.
Page 38: Gel Electrophoresis Functionality
Separation Properties: Molecules move through gel based on size, charge, and composition.
Page 39: ELISA Overview
Method Introduction: A precise immunoassay technique highlighting molecular presence and quantity.
Page 40: ELISA Steps
Process Sequence: From antibody coating to color change detection signifying target presence.
Page 41: References
Bibliography for Further Study: Essential texts and resources in biochemistry.