Proteins and its subunits, Slides of Chemistry

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AMINO ACIDS, PEPTIDES AND PROTEINS TOPIC OULINE — Amino acids — Proteins — Levels of Protein Structure — Examples of Proteins — Keratin, Collagen, Silk Fibroin — Myoglobin, Hemoglobin, Immunoglobulins — Protein Purification & Characterization Techniques AMINO ACIDS —~ — The amino residues in proteins are L stereoisomers L-alanine D-olonine wv © CHg Chg + o % | + HsN—C— CO —C—NHs AMINO ACIDS — Amino acids can be classified by R group — Nonpolar, Aliphatic R groups — Aromatic R groups — Polar, Uncharged R groups — Positively Charged (Basic) R groups — Negatively Charged (Acidic) R groups AMINO ACIDS — Nonpolar, Aliphatic R groups — tend to cluster together within the proteins, stabilizing protein structure by means of hydrophobic interactions Coo" coo" COO” COO" _ . 7 H 4 bw sl Vu ao HN ¢ H HN—¢-H 3N H;N—C—H we H;N—C CH, H—C—CH, ee eee SS HC—cH, of, CHs “CH cH, 3 Glycine Alanine Proline Valine Leucine Isoleucine AMINO ACIDS — Aromatic R, groups — Accounts for the characteristic strong absorbance of light by most proteins at a wavelength of 280 nm Goo coo” ¢oo HsN—C—H HN—C— —H H,N—C —H CHoe 5 6 & NH Phenylalanine Tyrosine Tryptophan AMINO ACIDS — Polar, Uncharged R Groups — More soluble in water than nonpolar amino acids coo- coo coo . 9°" . foo . | . | . | HN-G—H HN Hi H3N—C—H H,N—C—H H,N~ 0-H CH CHs CH,OH H—C—OH CH, As ve | | HN oO é CH, SH H.N~ “oO Serine Threonine Cysteine Asparagine Glutamine AMINO ACIDS — Uncommon amino acids also have an important functions H HO—C——CH, ] H,N—CH,—CH—CH—CH,—CH—COO- HC, _CH—COO- ba oe, 5-Hydroxylysi H H yeroxylysine 4-Hydroxyproline AMINO ACIDS — Amino acids can act as acids and bases i H i H i H H OH or _} H—C—H — H-—C—H H —H 7 ( s i o Pe ao Oo” O-H ” ‘o® o ‘o® ton atlow pH zwitterion ton at high pH neutral pil AMINO ACIDS — Amino acids can act as acids and bases / H H. | JH H.. | UH “Ne : “Ne | OH | H—tC—H —=| H—U—H + | H I 1. o” “on d’ *o® fon af tow publ nwhthertove mental pil OH down at fidget) pu - AMINO ACIDS Yj, — Characteristic titration curves Wy — predict the electric charge of amino acids  Classification of proteins (Based on chemical composition) — Simple proteins — Also known as homoproteins, they are made up of only amino acids. — Examples are plasma albumin, collagen, and keratin. Human Serum Albumin Classification of proteins (Based on chemical composition) — Conjugate Proteins — Sometimes also called heteroproteins, they contain in their structure a non-protein portion. Carbohydrate chain — Glycoproteins - Protein Glycoprotein + Glycolipid b chotesteryl Esters ™~ ATARI; =— Chromoproteins IULUUL UU LULU UU — 7 Cholesterol — Lipoproteins — Phosphoproteins Classification of proteins (Based on shaped) — Fibrous proteins — They have primarily mechanical and structural functions, providing support to the cells as well as the whole organism — insoluble in water as they contain, both internally and on their surface, many hydrophobic amino acids — polypeptide chains form long filaments or sheets — e.g. Fibroin, Collagen, a-Keratins, Elastins, Classification of proteins (Based on biological functions) — Transport proteins — Many small molecules, organic and inorganic, are transported in the bloodstream and extracellular Hemoglobin Molecule fo in ff tachsin ann. % fluids, across the cell membranes, and inside the cells from one compartment to another, by specific proteins Classification of proteins (Based on biological functions) — Storage proteins — ferritin, that stores iron intracellularly in a non-toxic form — milk caseins, that act as a reserve of amino acids for the milk; — egg yolk phosvitin, that contains high amounts of phosphorus; — prolamins and glutelins, the storage proteins of cereals Classification of proteins (Based on biological functions) — Hormones — Contractile and motor proteins — Defense proteins — Receptor proteins — Structural proteins — Storage of energy LEVELS OF PROTEIN STRUCTURE (Primary Structure) — Polypeptide Chains Are Flexible Yet conformationally Restricted — the peptide bond is essentially planar and has a partial double-bond character Peptide-bond resonance structures LEVELS OF PROTEIN STRUCTURE (Primary Structure) — All most peptide bonds in proteins are trans LEVELS OF PROTEIN STRUCTURE (Primary Structure) R : N . < N c yn A? iy H | O — This freedom of rotation about two bonds of each amino acid allows proteins to fold in many different ways. SEQUENCING   NEXT MEETING NA LANG    LEVELS OF PROTEIN STRUCTURE (Secondary Structure) —Spatial arrangement of amino acid residues —Polypeptide Chains Can Fold into Regular Structures — Alpha Helix — Beta Sheet — Turns and Loops  LEVELS OF PROTEIN STRUCTURE (Secondary Structure) —Alpha Helix — Stabilized by hydrogen bonds between the NH and CO groups of the main chain — Translation of 1.5A — 3.6 amino acid per turn (5.4 A) LEVELS OF PROTEIN STRUCTURE (Secondary Structure) —Beta Pleated Sheet — B sheet can run in opposite directions (antiparallel B sheet) or in the same direction (parallel B sheet) LEVELS OF PROTEIN STRUCTURE (Secondary Structure) —Turns and Loops — Hairpin turns/ B turns — Q-loops LEVELS OF PROTEIN STRUCTURE (Secondary Structure) —Special Type of Helices —a-keratin — collagen —Special Type of B-sheets —Silk Fibroin LEVELS OF PROTEIN STRUCTURE (Secondary Structure) —Collagen * 2 — most abundant protein of mammals @ 0s, ' — main f ibrous component of skin, bone, tendon, of. cartilage, and teeth oe.” wie, 3 _ Rod-shaped molecule (3000 A by 15 A) w — Glv-Pro-Hvp LEVELS OF PROTEIN STRUCTURE (Tertiary Structure) TERTIARY STRUCTURE —The overall 3-D james: arrangement of all atoms in a protein Polypeptide Backbone — Motifs — combinations of secondary structure Disultide bridge oO i ch, -RHIEOI-<—cx, tonic bond — supersecondary structure LEVELS OF PROTEIN STRUCTURE (Tertiary Structure) B-a-B Helix-turn-helix Greek key motif all\,, B-barrel B-meander