Amino acids and Peptides - Biochemistry - Lecture Slides, Slides of Biochemistry

Download Amino acids and Peptides - Biochemistry - Lecture Slides and more Slides Biochemistry in PDF only on Docsity! Amino acids and peptides The ―Lego‖ of proteins Docsity.com Amino Acids • Same general structure • Called alpha amino acids • L- isomer is physiologically active • Side chain or R group determines other properties • Acid-base properties H 3 N+ R O O Docsity.com Aromatic Amino Acids H 3 N+ O O H 3 N+ O N O H 3 N+ O OH O phenylalanine (F) tyrosine (Y) pKr = 10 . 07 tryptophan (W) Docsity.com Polar Amino Acids, alcohols H 3 N+ OH O O H3N+ CH 3 OH O O Serine (S) Threonine (T) Docsity.com Polar Amino Acids (sulfur containing) H 3 N+ O SH O N 3 N+ O S CH 3 O Cysteine (C) Methionine (M) Docsity.com Charged Amino Acids (Basic) H 3 N+ O NH NH 2 + NH 2 O H 3 N+ O N NH O H 3 N+ O NH 3 + O Arginie (R) pKr = 12 . 48 Histidine (H) pKr = 6 . 0 Lysine (K) pKr = 10 . 53 Docsity.com Titration of Amino acids ¢ Titration of glycine 12 GLYCINE (0.1 M) TITRATION T T T T T T T T T T T T o 1 2 3 4 5 6 7 & Q 10 ll 12 13 1 N NaOH (ml) Docsity.com Titration of Glutamate H 3 N+ O O O O Glutamate (E) pKr = 4 . 25 pK = 2 . 19 pK = 9 . 67 Docsity.com Peptides • Peptide bond is amide linkage between amino acids • No free rotation about C-N bond due to partial double bond character of bond – resonance N H O R2 H 3 N+ O R1 O N O R2 H 3 N+ O R1 O - peptide bond + Docsity.com Tetrapeptide ¢ Note planes of peptide bonds o N+ c—wN <> c= N Docsity.com Peptides • Peptides are vectorial – Have N and C termini • Sequences read H3N +---COO- P-I-G N H O H 2 N+ O N H O O Docsity.com Other small interesting peptides • Enkephalins Y-G-G-F-L Y-G-G-F-M • Oxytocin C-Y-I-Q-N-C-P-L-G-NH2 • Has C—C disulfide • Vasopressin C-Y-F-Q-N-C-P-R-G-NH2 • Also disulfide Docsity.com Chemical Synthesis of Peptides • Why? • Done solid phase – Problem with in solution • Hard to make pure desired sequence – Purify by filtration • Side chains blocked • Made backwards ( C---N) Docsity.com Scheme for peptide synthesis Solid-phase Peptide synthesis OQ m9 @RNH-CH-CNH-CHEC-O mo Deprotection @=nH-cH- oH promod aming acid TT A" & AO Actiostion I uN i 1 NH, CH © NH CHOCO ff deprotected peptide soli wn ppesrt — sesien highlights newly formed peptide bond Docsity.com