LECTURE 11: Protein sequencing and evolution/ Secondary structure

Ion Exchange Chromatography

A technique that separates proteins based on their charge; cation exchange uses negatively charged columns to bind positively charged protein groups.

Cation Exchange Chromatography

A form of ion exchange chromatography where the column is negatively charged and attracts positively charged proteins.

Gel Filtration Chromatography

A method that separates molecules based on size; larger molecules elute from the column faster than smaller ones.

Hydrophobic Interaction Chromatography

A technique that separates proteins based on their hydrophobic regions, targeting the protein's nonpolar surfaces.

Affinity Chromatography

A method that purifies proteins by using a ligand specific to the target protein to allow binding and separation.

Disulfide Bonds

Covalent bonds formed between cysteine residues in proteins, important for maintaining tertiary and quaternary structure.

SDS (Sodium Dodecyl Sulfate)

A detergent used in gel electrophoresis to impart a negative charge to proteins and denature them by disrupting hydrophobic interactions.

Beta-Mercaptoethanol

A chemical reagent that reduces disulfide bonds in proteins, aiding in their denaturation.

Isoelectric Focusing

A technique that separates proteins based on their isoelectric point, where proteins are focused in a pH gradient until they reach their neutral charge.

Peptide Sequencing

A process of identifying the sequence of amino acids in a peptide by removing and analyzing one amino acid at a time.

Invariant Residue

An amino acid residue that remains constant across different species due to its critical role in protein function.

Conservative Substitution

The replacement of an amino acid in a protein with another that possesses similar chemical properties.

Hydrophobic Interactions

Forces that stabilize protein structure, involving the clustering of nonpolar amino acid side chains away from water.

Primary Structure

The linear sequence of amino acids in a polypeptide chain.

Secondary Structure

The local folded structures that form within a polypeptide due to hydrogen bonding, including alpha-helices and beta-sheets.

Tertiary Structure

The overall three-dimensional shape of a polypeptide chain, determined by interactions between side chains.

Quaternary Structure

The structure formed when two or more polypeptide chains assemble into a multi-subunit complex.