Notes Schedule updated: tomorrow Exp.2 pre-lab Lab report Citations: Think about intellectual contribution Lab notebook definitely needs cited Henderson-Hasselbalch I owe you some additional practice problems To be added to website soon Chapter 3 Reading Wont cover details of Edman degradation- mediated protein sequencing (part of 3.4) Wont cover Chapter 3.5 (yet) Suggested HW 2, 3, 4, 5, 7, 8, 9, 10, 12, 13, 14, 18 Condensation of two amino acids to form a peptide bond -COOH +NH 2 - C O N H H2OH2O + Peptide bond: amide Large positive G: amino acids need to be activated Amino terminus N-terminus Carboxyl terminus C-terminus Peptide bond Proteins/polypeptides are polymers of amino acids N-terminus C-terminus -carbon amino group (basic) carboxylic group (acidic) R group (gives the amino acid its identity) Generic -amino acid (Most) amino acids have a stereocenter L isomer: L for life 20 common amino acids Make up vast majority of amino acids in natural proteins Coded for in the genetic code Other amino acids: Posttranslational modifications Intermediates in metabolic pathways Two main groups of side chains (plus subgroups) Nonpolar (hydrophobic) Aliphatic (non-aromatic, mostly straight chains) Aromatic (conjugated ring structures) Polar (hydrophilic) Uncharged Hydrogen bonds Positively charged basic Negatively charged acidic At physiologic pH (~7) Things to know about amino acids 1.Name 2.R-group structure 3.R-group classification 4.Three-letter abbreviations 5.One-letter abbreviations Two cysteine residues oxidize to form a disulfide bond -Covalent bond: stronger than a hydrogen bond -Reversible: readily reduced back to free sulfhydryls Free amino acid: acid & base pI: isoelectric point pH at which the species has no net charge No net mvmt within electric gradient +1 Uncharged side chain: pI = (pK (NH3+) + pK (COOH) ) pI between pK R and pK 2 Free amino acid vs. polymers Terminology Dipeptide (two amino acids) Tri-, tetra-, penta-peptide (etc) Oligopeptide (several a.a. ~3-30?) Polypeptide (multiple a.a.) Protein (multiple a.a.) Free amino acid vs. polymers Pentapeptide (five carbons!) Whats the charge at pH=7?