1 / 23

Amino acids and peptides

Amino acids and peptides. The “Lego” of proteins. 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. Amino Acids, General. pK of carboxyl group around 2.3

Faraday
Download Presentation

Amino acids and peptides

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Amino acids and peptides The “Lego” of proteins

  2. 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

  3. Amino Acids, General • pK of carboxyl group around 2.3 • Deprotonated at physiological pH • R – COO- • pK of amino group around 9.5 • Protonated at physiological pH • H3N+-R • Some R-groups are acidic or basic

  4. Nonpolar amino acids

  5. Aromatic Amino Acids

  6. Polar Amino Acids, alcohols

  7. Polar Amino Acids(sulfur containing)

  8. Polar amino acids (amides)

  9. Charged Amino Acids (Acidic)

  10. Charged Amino Acids (Basic)

  11. Titration of Amino acids • Titration of glycine

  12. Titration of Glutamate

  13. Purification of amino acids • Chromatography • Various types • Ion exchange • Uses net charge or can change with pH • Separate K, D and A • HPLC

  14. Electrophoresis • Using electricity to move particles through a gelatinous matrix • Isoelectric point • IEF

  15. 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

  16. Tetrapeptide • Note planes of peptide bonds

  17. Peptides • Peptides are vectorial • Have N and C termini • Sequences read H3N+---COO- P-I-G

  18. Draw a tetrapeptide of L-A-R-D at physiological pH • Answer

  19. Biologically Interesting Peptides • Aspartame • L-aspartyl-Lphenylalanine methyl ester

  20. 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

  21. 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)

  22. Scheme for peptide synthesis

  23. Tetrapeptide answer • Back

More Related