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Amino acids and peptides The “Lego” of proteins www.freelivedoctor.com.

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Presentation on theme: "Amino acids and peptides The “Lego” of proteins www.freelivedoctor.com."— Presentation transcript:

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

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 www.freelivedoctor.com

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 H 3 N + -R Some R-groups are acidic or basic www.freelivedoctor.com

4 Nonpolar amino acids www.freelivedoctor.com

5 Aromatic Amino Acids www.freelivedoctor.com

6 Polar Amino Acids, alcohols www.freelivedoctor.com

7 Polar Amino Acids (sulfur containing) www.freelivedoctor.com

8 Polar amino acids (amides) www.freelivedoctor.com

9 Charged Amino Acids (Acidic) www.freelivedoctor.com

10 Charged Amino Acids (Basic) www.freelivedoctor.com

11 Titration of Amino acids Titration of glycine www.freelivedoctor.com

12 Titration of Glutamate www.freelivedoctor.com

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

14 Electrophoresis Using electricity to move particles through a gelatinous matrix Isoelectric point IEF www.freelivedoctor.com

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 www.freelivedoctor.com

16 Tetrapeptide Note planes of peptide bonds www.freelivedoctor.com

17 Peptides Peptides are vectorial –Have N and C termini Sequences read H 3 N + ---COO - P-I-G www.freelivedoctor.com

18 Draw a tetrapeptide of L-A-R-D at physiological pH Answer www.freelivedoctor.com

19 Biologically Interesting Peptides Aspartame –L-aspartyl-Lphenylalanine methyl ester www.freelivedoctor.com

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-NH 2 Has C—C disulfide Vasopressin C-Y-F-Q-N-C-P-R-G-NH 2 Also disulfide www.freelivedoctor.com

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) www.freelivedoctor.com

22 Scheme for peptide synthesis www.freelivedoctor.com

23 Tetrapeptide answer www.freelivedoctor.com

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